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sqlite/src/btree.c
drh d3d39e939d Add internal support for collating sequences. This breaks 244 tests. (CVS 1420) 
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2004-05-20 22:16:29 +00:00

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/*
** 2004 April 6
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.145 2004/05/20 22:16:29 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
** Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
** "Sorting And Searching", pages 473-480. Addison-Wesley
** Publishing Company, Reading, Massachusetts.
**
** The basic idea is that each page of the file contains N database
** entries and N+1 pointers to subpages.
**
** ----------------------------------------------------------------
** | Ptr(0) | Key(0) | Ptr(1) | Key(1) | ... | Key(N) | Ptr(N+1) |
** ----------------------------------------------------------------
**
** All of the keys on the page that Ptr(0) points to have values less
** than Key(0). All of the keys on page Ptr(1) and its subpages have
** values greater than Key(0) and less than Key(1). All of the keys
** on Ptr(N+1) and its subpages have values greater than Key(N). And
** so forth.
**
** Finding a particular key requires reading O(log(M)) pages from the
** disk where M is the number of entries in the tree.
**
** In this implementation, a single file can hold one or more separate
** BTrees. Each BTree is identified by the index of its root page. The
** key and data for any entry are combined to form the "payload". A
** fixed amount of payload can be carried directly on the database
** page. If the payload is larger than the preset amount then surplus
** bytes are stored on overflow pages. The payload for an entry
** and the preceding pointer are combined to form a "Cell". Each
** page has a small header which contains the Ptr(N+1) pointer and other
** information such as the size of key and data.
**
** FORMAT DETAILS
**
** The file is divided into pages. The first page is called page 1,
** the second is page 2, and so forth. A page number of zero indicates
** "no such page". The page size can be anything between 512 and 65536.
** Each page can be either a btree page, a freelist page or an overflow
** page.
**
** The first page is always a btree page. The first 100 bytes of the first
** page contain a special header that describes the file. The format
** of that header is as follows:
**
** OFFSET SIZE DESCRIPTION
** 0 16 Header string: "SQLite format 3\000"
** 16 2 Page size in bytes.
** 18 1 File format write version
** 19 1 File format read version
** 20 1 Bytes of unused space at the end of each page
** 21 1 Max embedded payload fraction
** 22 1 Min embedded payload fraction
** 23 1 Min leaf payload fraction
** 24 4 File change counter
** 28 4 Reserved for future use
** 32 4 First freelist page
** 36 4 Number of freelist pages in the file
** 40 60 15 4-byte meta values passed to higher layers
**
** All of the integer values are big-endian (most significant byte first).
**
** The file change counter is incremented every time the database is more
** than once within the same second. This counter, together with the
** modification time of the file, allows other processes to know
** when the file has changed and thus when they need to flush their
** cache.
**
** The max embedded payload fraction is the amount of the total usable
** space in a page that can be consumed by a single cell for standard
** B-tree (non-LEAFDATA) tables. A value of 255 means 100%. The default
** is to limit the maximum cell size so that at least 4 cells will fit
** on one pages. Thus the default max embedded payload fraction is 64.
**
** If the payload for a cell is larger than the max payload, then extra
** payload is spilled to overflow pages. Once an overflow page is allocated,
** as many bytes as possible are moved into the overflow pages without letting
** the cell size drop below the min embedded payload fraction.
**
** The min leaf payload fraction is like the min embedded payload fraction
** except that it applies to leaf nodes in a LEAFDATA tree. The maximum
** payload fraction for a LEAFDATA tree is always 100% (or 255) and it
** not specified in the header.
**
** Each btree page begins with a header described below. Note that the
** header for page one begins at byte 100. For all other btree pages, the
** header begins on byte zero.
**
** OFFSET SIZE DESCRIPTION
** 0 1 Flags. 1: intkey, 2: zerodata, 4: leafdata, 8: leaf
** 1 2 byte offset to the first freeblock
** 3 2 byte offset to the first cell
** 5 1 number of fragmented free bytes
** 6 4 Right child (the Ptr(N+1) value). Omitted if leaf
**
** The flags define the format of this btree page. The leaf flag means that
** this page has no children. The zerodata flag means that this page carries
** only keys and no data. The intkey flag means that the key is a single
** variable length integer at the beginning of the payload.
**
** A variable-length integer is 1 to 9 bytes where the lower 7 bits of each
** byte are used. The integer consists of all bytes that have bit 8 set and
** the first byte with bit 8 clear. The most significant byte of the integer
** appears first.
**
** 0x00 becomes 0x00000000
** 0x7f becomes 0x0000007f
** 0x81 0x00 becomes 0x00000080
** 0x82 0x00 becomes 0x00000100
** 0x80 0x7f becomes 0x0000007f
** 0x8a 0x91 0xd1 0xac 0x78 becomes 0x12345678
** 0x81 0x81 0x81 0x81 0x01 becomes 0x10204081
**
** Variable length integers are used for rowids and to hold the number of
** bytes of key and data in a btree cell.
**
** Unused space within a btree page is collected into a linked list of
** freeblocks. Each freeblock is at least 4 bytes in size. The byte offset
** to the first freeblock is given in the header. Freeblocks occur in
** increasing order. Because a freeblock is 4 bytes in size, the minimum
** size allocation on a btree page is 4 bytes. Because a freeblock must be
** at least 4 bytes in size, any group of 3 or fewer unused bytes cannot
** exist on the freeblock chain. The total number of such fragmented bytes
** is recorded in the page header at offset 5.
**
** SIZE DESCRIPTION
** 2 Byte offset of the next freeblock
** 2 Bytes in this freeblock
**
** Cells are of variable length. The first cell begins on the byte defined
** in the page header. Cells do not necessarily occur in order - they can
** skip around on the page.
**
** SIZE DESCRIPTION
** 2 Byte offset of the next cell. 0 if this is the last cell
** 4 Page number of the left child. Omitted if leaf flag is set.
** var Number of bytes of data. Omitted if the zerodata flag is set.
** var Number of bytes of key. Or the key itself if intkey flag is set.
** * Payload
** 4 First page of the overflow chain. Omitted if no overflow
**
** Overflow pages form a linked list. Each page except the last is completely
** filled with data (pagesize - 4 bytes). The last page can have as little
** as 1 byte of data.
**
** SIZE DESCRIPTION
** 4 Page number of next overflow page
** * Data
**
** Freelist pages come in two subtypes: trunk pages and leaf pages. The
** file header points to first in a linked list of trunk page. Each trunk
** page points to multiple leaf pages. The content of a leaf page is
** unspecified. A trunk page looks like this:
**
** SIZE DESCRIPTION
** 4 Page number of next trunk page
** 4 Number of leaf pointers on this page
** * zero or more pages numbers of leaves
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include <assert.h>
/* Maximum page size. The upper bound on this value is 65536 (a limit
** imposed by the 2-byte offset at the beginning of each cell.) The
** maximum page size determines the amount of stack space allocated
** by many of the routines in this module. On embedded architectures
** or any machine where memory and especially stack memory is limited,
** one may wish to chose a smaller value for the maximum page size.
*/
#ifndef MX_PAGE_SIZE
# define MX_PAGE_SIZE 1024
#endif
/* The following value is the maximum cell size assuming a maximum page
** size give above.
*/
#define MX_CELL_SIZE (MX_PAGE_SIZE-10)
/* The maximum number of cells on a single page of the database. This
** assumes a minimum cell size of 3 bytes. Such small cells will be
** exceedingly rare, but they are possible.
*/
#define MX_CELL ((MX_PAGE_SIZE-10)/3)
/* Forward declarations */
typedef struct MemPage MemPage;
/*
** This is a magic string that appears at the beginning of every
** SQLite database in order to identify the file as a real database.
** 123456789 123456 */
static const char zMagicHeader[] = "SQLite format 3";
/*
** Page type flags. An ORed combination of these flags appear as the
** first byte of every BTree page.
*/
#define PTF_INTKEY 0x01
#define PTF_ZERODATA 0x02
#define PTF_LEAFDATA 0x04
#define PTF_LEAF 0x08
/*
** As each page of the file is loaded into memory, an instance of the following
** structure is appended and initialized to zero. This structure stores
** information about the page that is decoded from the raw file page.
**
** The pParent field points back to the parent page. This allows us to
** walk up the BTree from any leaf to the root. Care must be taken to
** unref() the parent page pointer when this page is no longer referenced.
** The pageDestructor() routine handles that chore.
*/
struct MemPage {
u32 notUsed;
u8 isInit; /* True if previously initialized */
u8 idxShift; /* True if Cell indices have changed */
u8 isOverfull; /* Some aCell[] do not fit on page */
u8 intKey; /* True if intkey flag is set */
u8 leaf; /* True if leaf flag is set */
u8 zeroData; /* True if table stores keys only */
u8 leafData; /* True if tables stores data on leaves only */
u8 hasData; /* True if this page stores data */
u8 hdrOffset; /* 100 for page 1. 0 otherwise */
u8 needRelink; /* True if need to run relinkCellList() */
int idxParent; /* Index in pParent->aCell[] of this node */
int nFree; /* Number of free bytes on the page */
int nCell; /* Number of entries on this page */
int nCellAlloc; /* Number of slots allocated in aCell[] */
unsigned char **aCell; /* Pointer to start of each cell */
struct Btree *pBt; /* Pointer back to BTree structure */
unsigned char *aData; /* Pointer back to the start of the page */
Pgno pgno; /* Page number for this page */
MemPage *pParent; /* The parent of this page. NULL for root */
};
/*
** The in-memory image of a disk page has the auxiliary information appended
** to the end. EXTRA_SIZE is the number of bytes of space needed to hold
** that extra information.
*/
#define EXTRA_SIZE sizeof(MemPage)
/*
** Everything we need to know about an open database
*/
struct Btree {
Pager *pPager; /* The page cache */
BtCursor *pCursor; /* A list of all open cursors */
MemPage *pPage1; /* First page of the database */
u8 inTrans; /* True if a transaction is in progress */
u8 inStmt; /* True if there is a checkpoint on the transaction */
u8 readOnly; /* True if the underlying file is readonly */
int pageSize; /* Total number of bytes on a page */
int usableSize; /* Number of usable bytes on each page */
int maxLocal; /* Maximum local payload in non-LEAFDATA tables */
int minLocal; /* Minimum local payload in non-LEAFDATA tables */
int maxLeaf; /* Maximum local payload in a LEAFDATA table */
int minLeaf; /* Minimum local payload in a LEAFDATA table */
u8 maxEmbedFrac; /* Maximum payload as % of total page size */
u8 minEmbedFrac; /* Minimum payload as % of total page size */
u8 minLeafFrac; /* Minimum leaf payload as % of total page size */
};
typedef Btree Bt;
/*
** An instance of the following structure is used to hold information
** about a cell. The parseCell() function fills the structure in.
*/
typedef struct CellInfo CellInfo;
struct CellInfo {
i64 nKey; /* The key for INTKEY tables, or number of bytes in key */
u32 nData; /* Number of bytes of data */
u16 nHeader; /* Size of the header in bytes */
u16 nLocal; /* Amount of payload held locally */
u16 iOverflow; /* Offset to overflow page number. Zero if none */
u16 nSize; /* Size of the cell */
};
/*
** A cursor is a pointer to a particular entry in the BTree.
** The entry is identified by its MemPage and the index in
** MemPage.aCell[] of the entry.
*/
struct BtCursor {
Btree *pBt; /* The Btree to which this cursor belongs */
BtCursor *pNext, *pPrev; /* Forms a linked list of all cursors */
BtCursor *pShared; /* Loop of cursors with the same root page */
int (*xCompare)(void*,int,const void*,int,const void*); /* Key comp func */
void *pArg; /* First arg to xCompare() */
Pgno pgnoRoot; /* The root page of this tree */
MemPage *pPage; /* Page that contains the entry */
int idx; /* Index of the entry in pPage->aCell[] */
CellInfo info; /* A parse of the cell we are pointing at */
u8 infoValid; /* True if information in BtCursor.info is valid */
u8 wrFlag; /* True if writable */
u8 iMatch; /* compare result from last sqlite3BtreeMoveto() */
u8 isValid; /* TRUE if points to a valid entry */
u8 status; /* Set to SQLITE_ABORT if cursors is invalidated */
};
/*
** Read or write a two-, four-, and eight-byte big-endian integer values.
*/
static u32 get2byte(unsigned char *p){
return (p[0]<<8) | p[1];
}
static u32 get4byte(unsigned char *p){
return (p[0]<<24) | (p[1]<<16) | (p[2]<<8) | p[3];
}
static void put2byte(unsigned char *p, u32 v){
p[0] = v>>8;
p[1] = v;
}
static void put4byte(unsigned char *p, u32 v){
p[0] = v>>24;
p[1] = v>>16;
p[2] = v>>8;
p[3] = v;
}
/*
** Routines to read and write variable-length integers.
*/
#define getVarint sqlite3GetVarint
#define getVarint32 sqlite3GetVarint32
#define putVarint sqlite3PutVarint
/*
** Parse a cell header and fill in the CellInfo structure.
*/
static void parseCell(
MemPage *pPage, /* Page containing the cell */
unsigned char *pCell, /* The cell */
CellInfo *pInfo /* Fill in this structure */
){
int n;
int nPayload;
Btree *pBt;
int minLocal, maxLocal;
if( pPage->leaf ){
n = 2;
}else{
n = 6;
}
if( pPage->hasData ){
n += getVarint32(&pCell[n], &pInfo->nData);
}else{
pInfo->nData = 0;
}
n += getVarint(&pCell[n], &pInfo->nKey);
pInfo->nHeader = n;
nPayload = pInfo->nData;
if( !pPage->intKey ){
nPayload += pInfo->nKey;
}
pBt = pPage->pBt;
if( pPage->leafData ){
minLocal = pBt->minLeaf;
maxLocal = pBt->usableSize - 23;
}else{
minLocal = pBt->minLocal;
maxLocal = pBt->maxLocal;
}
if( nPayload<=maxLocal ){
pInfo->nLocal = nPayload;
pInfo->iOverflow = 0;
pInfo->nSize = nPayload + n;
}else{
int surplus = minLocal + (nPayload - minLocal)%(pBt->usableSize - 4);
if( surplus <= maxLocal ){
pInfo->nLocal = surplus;
}else{
pInfo->nLocal = minLocal;
}
pInfo->iOverflow = pInfo->nLocal + n;
pInfo->nSize = pInfo->iOverflow + 4;
}
}
/*
** Compute the total number of bytes that a Cell needs on the main
** database page. The number returned includes the Cell header,
** local payload storage, and the pointer to overflow pages (if
** applicable). Additional space allocated on overflow pages
** is NOT included in the value returned from this routine.
*/
static int cellSize(MemPage *pPage, unsigned char *pCell){
CellInfo info;
parseCell(pPage, pCell, &info);
return info.nSize;
}
/*
** Do sanity checking on a page. Throw an exception if anything is
** not right.
**
** This routine is used for internal error checking only. It is omitted
** from most builds.
*/
#if defined(BTREE_DEBUG) && !defined(NDEBUG) && 0
static void _pageIntegrity(MemPage *pPage){
int usableSize;
u8 *data;
int i, idx, c, pc, hdr, nFree;
u8 used[MX_PAGE_SIZE];
usableSize = pPage->pBt->usableSize;
assert( pPage->aData==&((unsigned char*)pPage)[-pPage->pBt->pageSize] );
hdr = pPage->hdrOffset;
assert( hdr==(pPage->pgno==1 ? 100 : 0) );
assert( pPage->pgno==sqlite3pager_pagenumber(pPage->aData) );
c = pPage->aData[hdr];
if( pPage->isInit ){
assert( pPage->leaf == ((c & PTF_LEAF)!=0) );
assert( pPage->zeroData == ((c & PTF_ZERODATA)!=0) );
assert( pPage->leafData == ((c & PTF_LEAFDATA)!=0) );
assert( pPage->intKey == ((c & (PTF_INTKEY|PTF_LEAFDATA))!=0) );
assert( pPage->hasData ==
!(pPage->zeroData || (!pPage->leaf && pPage->leafData)) );
}
data = pPage->aData;
memset(used, 0, usableSize);
for(i=0; i<hdr+10-pPage->leaf*4; i++) used[i] = 1;
nFree = 0;
pc = get2byte(&data[hdr+1]);
while( pc ){
int size;
assert( pc>0 && pc<usableSize-4 );
size = get2byte(&data[pc+2]);
assert( pc+size<=usableSize );
nFree += size;
for(i=pc; i<pc+size; i++){
assert( used[i]==0 );
used[i] = 1;
}
pc = get2byte(&data[pc]);
}
assert( pPage->isInit==0 || pPage->nFree==nFree+data[hdr+5] );
idx = 0;
pc = get2byte(&data[hdr+3]);
while( pc ){
int size;
assert( pPage->isInit==0 || idx<pPage->nCell );
assert( pc>0 && pc<usableSize-4 );
assert( pPage->isInit==0 || pPage->aCell[idx]==&data[pc] );
size = cellSize(pPage, &data[pc]);
assert( pc+size<=usableSize );
for(i=pc; i<pc+size; i++){
assert( used[i]==0 );
used[i] = 1;
}
pc = get2byte(&data[pc]);
idx++;
}
assert( idx==pPage->nCell );
nFree = 0;
for(i=0; i<usableSize; i++){
assert( used[i]<=1 );
if( used[i]==0 ) nFree++;
}
assert( nFree==data[hdr+5] );
}
#define pageIntegrity(X) _pageIntegrity(X)
#else
# define pageIntegrity(X)
#endif
/*
** Defragment the page given. All Cells are moved to the
** beginning of the page and all free space is collected
** into one big FreeBlk at the end of the page.
*/
static void defragmentPage(MemPage *pPage){
int pc, i, n, addr;
int start, hdr, size;
int leftover;
unsigned char *oldPage;
unsigned char newPage[MX_PAGE_SIZE];
assert( sqlite3pager_iswriteable(pPage->aData) );
assert( pPage->pBt!=0 );
assert( pPage->pBt->usableSize <= MX_PAGE_SIZE );
assert( !pPage->needRelink );
assert( !pPage->isOverfull );
oldPage = pPage->aData;
hdr = pPage->hdrOffset;
addr = 3+hdr;
n = 6+hdr;
if( !pPage->leaf ){
n += 4;
}
memcpy(&newPage[hdr], &oldPage[hdr], n-hdr);
start = n;
pc = get2byte(&oldPage[addr]);
i = 0;
while( pc>0 ){
assert( n<pPage->pBt->usableSize );
size = cellSize(pPage, &oldPage[pc]);
memcpy(&newPage[n], &oldPage[pc], size);
put2byte(&newPage[addr],n);
assert( pPage->aCell[i]==&oldPage[pc] );
pPage->aCell[i++] = &oldPage[n];
addr = n;
n += size;
pc = get2byte(&oldPage[pc]);
}
assert( i==pPage->nCell );
leftover = pPage->pBt->usableSize - n;
assert( leftover>=0 );
assert( pPage->nFree==leftover );
if( leftover<4 ){
oldPage[hdr+5] = leftover;
leftover = 0;
n = pPage->pBt->usableSize;
}
memcpy(&oldPage[hdr], &newPage[hdr], n-hdr);
if( leftover==0 ){
put2byte(&oldPage[hdr+1], 0);
}else if( leftover>=4 ){
put2byte(&oldPage[hdr+1], n);
put2byte(&oldPage[n], 0);
put2byte(&oldPage[n+2], leftover);
memset(&oldPage[n+4], 0, leftover-4);
}
oldPage[hdr+5] = 0;
}
/*
** Allocate nByte bytes of space on a page. If nByte is less than
** 4 it is rounded up to 4.
**
** Return the index into pPage->aData[] of the first byte of
** the new allocation. Or return 0 if there is not enough free
** space on the page to satisfy the allocation request.
**
** If the page contains nBytes of free space but does not contain
** nBytes of contiguous free space, then this routine automatically
** calls defragementPage() to consolidate all free space before
** allocating the new chunk.
**
** Algorithm: Carve a piece off of the first freeblock that is
** nByte in size or that larger.
*/
static int allocateSpace(MemPage *pPage, int nByte){
int addr, pc, hdr;
int size;
int nFrag;
unsigned char *data;
#ifndef NDEBUG
int cnt = 0;
#endif
data = pPage->aData;
assert( sqlite3pager_iswriteable(data) );
assert( pPage->pBt );
if( nByte<4 ) nByte = 4;
if( pPage->nFree<nByte || pPage->isOverfull ) return 0;
hdr = pPage->hdrOffset;
nFrag = data[hdr+5];
if( nFrag>=60 || nFrag>pPage->nFree-nByte ){
defragmentPage(pPage);
}
addr = hdr+1;
pc = get2byte(&data[addr]);
assert( addr<pc );
assert( pc<=pPage->pBt->usableSize-4 );
while( (size = get2byte(&data[pc+2]))<nByte ){
addr = pc;
pc = get2byte(&data[addr]);
assert( pc<=pPage->pBt->usableSize-4 );
assert( pc>=addr+size+4 || pc==0 );
if( pc==0 ){
assert( (cnt++)==0 );
defragmentPage(pPage);
assert( data[hdr+5]==0 );
addr = pPage->hdrOffset+1;
pc = get2byte(&data[addr]);
}
}
assert( pc>0 && size>=nByte );
assert( pc+size<=pPage->pBt->usableSize );
if( size>nByte+4 ){
int newStart = pc+nByte;
put2byte(&data[addr], newStart);
put2byte(&data[newStart], get2byte(&data[pc]));
put2byte(&data[newStart+2], size-nByte);
}else{
put2byte(&data[addr], get2byte(&data[pc]));
data[hdr+5] += size-nByte;
}
pPage->nFree -= nByte;
assert( pPage->nFree>=0 );
return pc;
}
/*
** Return a section of the pPage->aData to the freelist.
** The first byte of the new free block is pPage->aDisk[start]
** and the size of the block is "size" bytes.
**
** Most of the effort here is involved in coalesing adjacent
** free blocks into a single big free block.
*/
static void freeSpace(MemPage *pPage, int start, int size){
int end = start + size; /* End of the segment being freed */
int addr, pbegin;
#ifndef NDEBUG
int tsize = 0; /* Total size of all freeblocks */
#endif
unsigned char *data = pPage->aData;
assert( pPage->pBt!=0 );
assert( sqlite3pager_iswriteable(data) );
assert( start>=pPage->hdrOffset+6+(pPage->leaf?0:4) );
assert( end<=pPage->pBt->usableSize );
if( size<4 ) size = 4;
/* Add the space back into the linked list of freeblocks */
addr = pPage->hdrOffset + 1;
while( (pbegin = get2byte(&data[addr]))<start && pbegin>0 ){
assert( pbegin<=pPage->pBt->usableSize-4 );
assert( pbegin>addr );
addr = pbegin;
}
assert( pbegin<=pPage->pBt->usableSize-4 );
assert( pbegin>addr || pbegin==0 );
put2byte(&data[addr], start);
put2byte(&data[start], pbegin);
put2byte(&data[start+2], size);
pPage->nFree += size;
/* Coalesce adjacent free blocks */
addr = pPage->hdrOffset + 1;
while( (pbegin = get2byte(&data[addr]))>0 ){
int pnext, psize;
assert( pbegin>addr );
assert( pbegin<pPage->pBt->usableSize-4 );
pnext = get2byte(&data[pbegin]);
psize = get2byte(&data[pbegin+2]);
if( pbegin + psize + 3 >= pnext && pnext>0 ){
int frag = pnext - (pbegin+psize);
assert( frag<=data[pPage->hdrOffset+5] );
data[pPage->hdrOffset+5] -= frag;
put2byte(&data[pbegin], get2byte(&data[pnext]));
put2byte(&data[pbegin+2], pnext+get2byte(&data[pnext+2])-pbegin);
}else{
assert( (tsize += psize)>0 );
addr = pbegin;
}
}
assert( tsize+data[pPage->hdrOffset+5]==pPage->nFree );
}
/*
** Resize the aCell[] array of the given page so that it is able to
** hold at least nNewSz entries.
**
** Return SQLITE_OK or SQLITE_NOMEM.
*/
static int resizeCellArray(MemPage *pPage, int nNewSz){
if( pPage->nCellAlloc<nNewSz ){
int n = nNewSz*sizeof(pPage->aCell[0]);
if( pPage->aCell==0 ){
pPage->aCell = sqliteMallocRaw( n );
}else{
pPage->aCell = sqliteRealloc(pPage->aCell, n);
}
if( sqlite3_malloc_failed ) return SQLITE_NOMEM;
pPage->nCellAlloc = nNewSz;
}
return SQLITE_OK;
}
/*
** Initialize the auxiliary information for a disk block.
**
** The pParent parameter must be a pointer to the MemPage which
** is the parent of the page being initialized. The root of a
** BTree has no parent and so for that page, pParent==NULL.
**
** Return SQLITE_OK on success. If we see that the page does
** not contain a well-formed database page, then return
** SQLITE_CORRUPT. Note that a return of SQLITE_OK does not
** guarantee that the page is well-formed. It only shows that
** we failed to detect any corruption.
*/
static int initPage(
MemPage *pPage, /* The page to be initialized */
MemPage *pParent /* The parent. Might be NULL */
){
int c, pc, i, hdr;
unsigned char *data;
int usableSize;
int nCell, nFree;
u8 *aCell[MX_PAGE_SIZE/2];
assert( pPage->pBt!=0 );
assert( pParent==0 || pParent->pBt==pPage->pBt );
assert( pPage->pgno==sqlite3pager_pagenumber(pPage->aData) );
assert( pPage->aData == &((unsigned char*)pPage)[-pPage->pBt->pageSize] );
assert( pPage->pParent==0 || pPage->pParent==pParent );
assert( pPage->pParent==pParent || !pPage->isInit );
if( pPage->isInit ) return SQLITE_OK;
if( pPage->pParent==0 && pParent!=0 ){
pPage->pParent = pParent;
sqlite3pager_ref(pParent->aData);
}
pPage->nCell = pPage->nCellAlloc = 0;
assert( pPage->hdrOffset==(pPage->pgno==1 ? 100 : 0) );
hdr = pPage->hdrOffset;
data = pPage->aData;
c = data[hdr];
pPage->intKey = (c & (PTF_INTKEY|PTF_LEAFDATA))!=0;
pPage->zeroData = (c & PTF_ZERODATA)!=0;
pPage->leafData = (c & PTF_LEAFDATA)!=0;
pPage->leaf = (c & PTF_LEAF)!=0;
pPage->hasData = !(pPage->zeroData || (!pPage->leaf && pPage->leafData));
pPage->isOverfull = 0;
pPage->needRelink = 0;
pPage->idxShift = 0;
usableSize = pPage->pBt->usableSize;
/* Initialize the cell count and cell pointers */
i = 0;
pc = get2byte(&data[hdr+3]);
nCell = 0;
while( pc>0 ){
if( pc>=usableSize ) return SQLITE_CORRUPT;
if( nCell>sizeof(aCell)/sizeof(aCell[0]) ) return SQLITE_CORRUPT;
aCell[nCell++] = &data[pc];
pc = get2byte(&data[pc]);
}
if( resizeCellArray(pPage, nCell) ){
return SQLITE_NOMEM;
}
pPage->nCell = nCell;
memcpy(pPage->aCell, aCell, nCell*sizeof(aCell[0]));
/* Compute the total free space on the page */
pc = get2byte(&data[hdr+1]);
nFree = data[hdr+5];
i = 0;
while( pc>0 ){
int next, size;
if( pc>=usableSize ) return SQLITE_CORRUPT;
if( i++>MX_PAGE_SIZE ) return SQLITE_CORRUPT;
next = get2byte(&data[pc]);
size = get2byte(&data[pc+2]);
if( next>0 && next<=pc+size+3 ) return SQLITE_CORRUPT;
nFree += size;
pc = next;
}
pPage->nFree = nFree;
if( nFree>=usableSize ) return SQLITE_CORRUPT;
pPage->isInit = 1;
pageIntegrity(pPage);
return SQLITE_OK;
}
/*
** Set up a raw page so that it looks like a database page holding
** no entries.
*/
static void zeroPage(MemPage *pPage, int flags){
unsigned char *data = pPage->aData;
Btree *pBt = pPage->pBt;
int hdr = pPage->hdrOffset;
int first;
assert( sqlite3pager_pagenumber(data)==pPage->pgno );
assert( &data[pBt->pageSize] == (unsigned char*)pPage );
assert( sqlite3pager_iswriteable(data) );
memset(&data[hdr], 0, pBt->usableSize - hdr);
data[hdr] = flags;
first = hdr + 6 + 4*((flags&PTF_LEAF)==0);
put2byte(&data[hdr+1], first);
put2byte(&data[first+2], pBt->usableSize - first);
sqliteFree(pPage->aCell);
pPage->aCell = 0;
pPage->nCell = 0;
pPage->nCellAlloc = 0;
pPage->nFree = pBt->usableSize - first;
pPage->intKey = (flags & (PTF_INTKEY|PTF_LEAFDATA))!=0;
pPage->zeroData = (flags & PTF_ZERODATA)!=0;
pPage->leafData = (flags & PTF_LEAFDATA)!=0;
pPage->leaf = (flags & PTF_LEAF)!=0;
pPage->hasData = !(pPage->zeroData || (!pPage->leaf && pPage->leafData));
pPage->hdrOffset = hdr;
pPage->isOverfull = 0;
pPage->needRelink = 0;
pPage->idxShift = 0;
pPage->isInit = 1;
pageIntegrity(pPage);
}
/*
** Get a page from the pager. Initialize the MemPage.pBt and
** MemPage.aData elements if needed.
*/
static int getPage(Btree *pBt, Pgno pgno, MemPage **ppPage){
int rc;
unsigned char *aData;
MemPage *pPage;
rc = sqlite3pager_get(pBt->pPager, pgno, (void**)&aData);
if( rc ) return rc;
pPage = (MemPage*)&aData[pBt->pageSize];
pPage->aData = aData;
pPage->pBt = pBt;
pPage->pgno = pgno;
pPage->hdrOffset = pPage->pgno==1 ? 100 : 0;
*ppPage = pPage;
return SQLITE_OK;
}
/*
** Get a page from the pager and initialize it. This routine
** is just a convenience wrapper around separate calls to
** getPage() and initPage().
*/
static int getAndInitPage(
Btree *pBt, /* The database file */
Pgno pgno, /* Number of the page to get */
MemPage **ppPage, /* Write the page pointer here */
MemPage *pParent /* Parent of the page */
){
int rc;
rc = getPage(pBt, pgno, ppPage);
if( rc==SQLITE_OK && (*ppPage)->isInit==0 ){
rc = initPage(*ppPage, pParent);
}
return rc;
}
/*
** Release a MemPage. This should be called once for each prior
** call to getPage.
*/
static void releasePage(MemPage *pPage){
if( pPage ){
assert( pPage->aData );
assert( pPage->pBt );
assert( &pPage->aData[pPage->pBt->pageSize]==(unsigned char*)pPage );
sqlite3pager_unref(pPage->aData);
}
}
/*
** This routine is called when the reference count for a page
** reaches zero. We need to unref the pParent pointer when that
** happens.
*/
static void pageDestructor(void *pData, int pageSize){
MemPage *pPage = (MemPage*)&((char*)pData)[pageSize];
assert( pPage->isInit==0 || pPage->needRelink==0 );
if( pPage->pParent ){
MemPage *pParent = pPage->pParent;
pPage->pParent = 0;
releasePage(pParent);
}
sqliteFree(pPage->aCell);
pPage->aCell = 0;
pPage->isInit = 0;
}
/*
** Open a new database.
**
** Actually, this routine just sets up the internal data structures
** for accessing the database. We do not open the database file
** until the first page is loaded.
**
** zFilename is the name of the database file. If zFilename is NULL
** a new database with a random name is created. This randomly named
** database file will be deleted when sqlite3BtreeClose() is called.
*/
int sqlite3BtreeOpen(
const char *zFilename, /* Name of the file containing the BTree database */
Btree **ppBtree, /* Pointer to new Btree object written here */
int nCache, /* Number of cache pages */
int flags /* Options */
){
Btree *pBt;
int rc;
/*
** The following asserts make sure that structures used by the btree are
** the right size. This is to guard against size changes that result
** when compiling on a different architecture.
*/
assert( sizeof(i64)==8 );
assert( sizeof(u64)==8 );
assert( sizeof(u32)==4 );
assert( sizeof(u16)==2 );
assert( sizeof(Pgno)==4 );
assert( sizeof(ptr)==sizeof(char*) );
assert( sizeof(uptr)==sizeof(ptr) );
pBt = sqliteMalloc( sizeof(*pBt) );
if( pBt==0 ){
*ppBtree = 0;
return SQLITE_NOMEM;
}
if( nCache<10 ) nCache = 10;
rc = sqlite3pager_open(&pBt->pPager, zFilename, nCache, EXTRA_SIZE,
(flags & BTREE_OMIT_JOURNAL)==0);
if( rc!=SQLITE_OK ){
if( pBt->pPager ) sqlite3pager_close(pBt->pPager);
sqliteFree(pBt);
*ppBtree = 0;
return rc;
}
sqlite3pager_set_destructor(pBt->pPager, pageDestructor);
pBt->pCursor = 0;
pBt->pPage1 = 0;
pBt->readOnly = sqlite3pager_isreadonly(pBt->pPager);
pBt->pageSize = SQLITE_PAGE_SIZE; /* FIX ME - read from header */
pBt->usableSize = pBt->pageSize;
pBt->maxEmbedFrac = 64; /* FIX ME - read from header */
pBt->minEmbedFrac = 32; /* FIX ME - read from header */
pBt->minLeafFrac = 32; /* FIX ME - read from header */
*ppBtree = pBt;
return SQLITE_OK;
}
/*
** Close an open database and invalidate all cursors.
*/
int sqlite3BtreeClose(Btree *pBt){
while( pBt->pCursor ){
sqlite3BtreeCloseCursor(pBt->pCursor);
}
sqlite3pager_close(pBt->pPager);
sqliteFree(pBt);
return SQLITE_OK;
}
/*
** Change the limit on the number of pages allowed in the cache.
**
** The maximum number of cache pages is set to the absolute
** value of mxPage. If mxPage is negative, the pager will
** operate asynchronously - it will not stop to do fsync()s
** to insure data is written to the disk surface before
** continuing. Transactions still work if synchronous is off,
** and the database cannot be corrupted if this program
** crashes. But if the operating system crashes or there is
** an abrupt power failure when synchronous is off, the database
** could be left in an inconsistent and unrecoverable state.
** Synchronous is on by default so database corruption is not
** normally a worry.
*/
int sqlite3BtreeSetCacheSize(Btree *pBt, int mxPage){
sqlite3pager_set_cachesize(pBt->pPager, mxPage);
return SQLITE_OK;
}
/*
** Change the way data is synced to disk in order to increase or decrease
** how well the database resists damage due to OS crashes and power
** failures. Level 1 is the same as asynchronous (no syncs() occur and
** there is a high probability of damage) Level 2 is the default. There
** is a very low but non-zero probability of damage. Level 3 reduces the
** probability of damage to near zero but with a write performance reduction.
*/
int sqlite3BtreeSetSafetyLevel(Btree *pBt, int level){
sqlite3pager_set_safety_level(pBt->pPager, level);
return SQLITE_OK;
}
/*
** Get a reference to pPage1 of the database file. This will
** also acquire a readlock on that file.
**
** SQLITE_OK is returned on success. If the file is not a
** well-formed database file, then SQLITE_CORRUPT is returned.
** SQLITE_BUSY is returned if the database is locked. SQLITE_NOMEM
** is returned if we run out of memory. SQLITE_PROTOCOL is returned
** if there is a locking protocol violation.
*/
static int lockBtree(Btree *pBt){
int rc;
MemPage *pPage1;
if( pBt->pPage1 ) return SQLITE_OK;
rc = getPage(pBt, 1, &pPage1);
if( rc!=SQLITE_OK ) return rc;
/* Do some checking to help insure the file we opened really is
** a valid database file.
*/
rc = SQLITE_NOTADB;
if( sqlite3pager_pagecount(pBt->pPager)>0 ){
u8 *page1 = pPage1->aData;
if( memcmp(page1, zMagicHeader, 16)!=0 ){
goto page1_init_failed;
}
if( page1[18]>1 || page1[19]>1 ){
goto page1_init_failed;
}
pBt->pageSize = get2byte(&page1[16]);
pBt->usableSize = pBt->pageSize - page1[20];
if( pBt->usableSize<500 ){
goto page1_init_failed;
}
pBt->maxEmbedFrac = page1[21];
pBt->minEmbedFrac = page1[22];
pBt->minLeafFrac = page1[23];
}
/* maxLocal is the maximum amount of payload to store locally for
** a cell. Make sure it is small enough so that at least minFanout
** cells can will fit on one page. We assume a 10-byte page header.
** Besides the payload, the cell must store:
** 2-byte pointer to next cell
** 4-byte child pointer
** 9-byte nKey value
** 4-byte nData value
** 4-byte overflow page pointer
** So a cell consists of a header which is as much as 19 bytes long,
** 0 to N bytes of payload, and an optional 4 byte overflow page pointer.
*/
pBt->maxLocal = (pBt->usableSize-10)*pBt->maxEmbedFrac/255 - 23;
pBt->minLocal = (pBt->usableSize-10)*pBt->minEmbedFrac/255 - 23;
pBt->maxLeaf = pBt->usableSize - 33;
pBt->minLeaf = (pBt->usableSize-10)*pBt->minLeafFrac/255 - 23;
if( pBt->minLocal>pBt->maxLocal || pBt->maxLocal<0 ){
goto page1_init_failed;
}
assert( pBt->maxLeaf + 23 <= MX_CELL_SIZE );
pBt->pPage1 = pPage1;
return SQLITE_OK;
page1_init_failed:
releasePage(pPage1);
pBt->pPage1 = 0;
return rc;
}
/*
** If there are no outstanding cursors and we are not in the middle
** of a transaction but there is a read lock on the database, then
** this routine unrefs the first page of the database file which
** has the effect of releasing the read lock.
**
** If there are any outstanding cursors, this routine is a no-op.
**
** If there is a transaction in progress, this routine is a no-op.
*/
static void unlockBtreeIfUnused(Btree *pBt){
if( pBt->inTrans==0 && pBt->pCursor==0 && pBt->pPage1!=0 ){
releasePage(pBt->pPage1);
pBt->pPage1 = 0;
pBt->inTrans = 0;
pBt->inStmt = 0;
}
}
/*
** Create a new database by initializing the first page of the
** file.
*/
static int newDatabase(Btree *pBt){
MemPage *pP1;
unsigned char *data;
int rc;
if( sqlite3pager_pagecount(pBt->pPager)>0 ) return SQLITE_OK;
pP1 = pBt->pPage1;
assert( pP1!=0 );
data = pP1->aData;
rc = sqlite3pager_write(data);
if( rc ) return rc;
memcpy(data, zMagicHeader, sizeof(zMagicHeader));
assert( sizeof(zMagicHeader)==16 );
put2byte(&data[16], pBt->pageSize);
data[18] = 1;
data[19] = 1;
data[20] = pBt->pageSize - pBt->usableSize;
data[21] = pBt->maxEmbedFrac;
data[22] = pBt->minEmbedFrac;
data[23] = pBt->minLeafFrac;
memset(&data[24], 0, 100-24);
zeroPage(pP1, PTF_INTKEY|PTF_LEAF|PTF_LEAFDATA );
return SQLITE_OK;
}
/*
** Attempt to start a new transaction.
**
** A transaction must be started before attempting any changes
** to the database. None of the following routines will work
** unless a transaction is started first:
**
** sqlite3BtreeCreateTable()
** sqlite3BtreeCreateIndex()
** sqlite3BtreeClearTable()
** sqlite3BtreeDropTable()
** sqlite3BtreeInsert()
** sqlite3BtreeDelete()
** sqlite3BtreeUpdateMeta()
*/
int sqlite3BtreeBeginTrans(Btree *pBt){
int rc;
if( pBt->inTrans ) return SQLITE_ERROR;
if( pBt->readOnly ) return SQLITE_READONLY;
if( pBt->pPage1==0 ){
rc = lockBtree(pBt);
if( rc!=SQLITE_OK ){
return rc;
}
}
rc = sqlite3pager_begin(pBt->pPage1->aData);
if( rc==SQLITE_OK ){
rc = newDatabase(pBt);
}
if( rc==SQLITE_OK ){
pBt->inTrans = 1;
pBt->inStmt = 0;
}else{
unlockBtreeIfUnused(pBt);
}
return rc;
}
/*
** Commit the transaction currently in progress.
**
** This will release the write lock on the database file. If there
** are no active cursors, it also releases the read lock.
*/
int sqlite3BtreeCommit(Btree *pBt){
int rc;
rc = pBt->readOnly ? SQLITE_OK : sqlite3pager_commit(pBt->pPager);
pBt->inTrans = 0;
pBt->inStmt = 0;
unlockBtreeIfUnused(pBt);
return rc;
}
/*
** Invalidate all cursors
*/
static void invalidateCursors(Btree *pBt){
BtCursor *pCur;
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
MemPage *pPage = pCur->pPage;
if( pPage /* && !pPage->isInit */ ){
pageIntegrity(pPage);
releasePage(pPage);
pCur->pPage = 0;
pCur->isValid = 0;
pCur->status = SQLITE_ABORT;
}
}
}
#ifdef SQLITE_TEST
/*
** Print debugging information about all cursors to standard output.
*/
void sqlite3BtreeCursorList(Btree *pBt){
BtCursor *pCur;
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
MemPage *pPage = pCur->pPage;
char *zMode = pCur->wrFlag ? "rw" : "ro";
printf("CURSOR %08x rooted at %4d(%s) currently at %d.%d%s\n",
(int)pCur, pCur->pgnoRoot, zMode,
pPage ? pPage->pgno : 0, pCur->idx,
pCur->isValid ? "" : " eof"
);
}
}
#endif
/*
** Rollback the transaction in progress. All cursors will be
** invalided by this operation. Any attempt to use a cursor
** that was open at the beginning of this operation will result
** in an error.
**
** This will release the write lock on the database file. If there
** are no active cursors, it also releases the read lock.
*/
int sqlite3BtreeRollback(Btree *pBt){
int rc;
MemPage *pPage1;
if( pBt->inTrans==0 ) return SQLITE_OK;
pBt->inTrans = 0;
pBt->inStmt = 0;
if( pBt->readOnly ){
rc = SQLITE_OK;
}else{
rc = sqlite3pager_rollback(pBt->pPager);
/* The rollback may have destroyed the pPage1->aData value. So
** call getPage() on page 1 again to make sure pPage1->aData is
** set correctly. */
if( getPage(pBt, 1, &pPage1)==SQLITE_OK ){
releasePage(pPage1);
}
}
invalidateCursors(pBt);
unlockBtreeIfUnused(pBt);
return rc;
}
/*
** Set the checkpoint for the current transaction. The checkpoint serves
** as a sub-transaction that can be rolled back independently of the
** main transaction. You must start a transaction before starting a
** checkpoint. The checkpoint is ended automatically if the transaction
** commits or rolls back.
**
** Only one checkpoint may be active at a time. It is an error to try
** to start a new checkpoint if another checkpoint is already active.
*/
int sqlite3BtreeBeginStmt(Btree *pBt){
int rc;
if( !pBt->inTrans || pBt->inStmt ){
return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}
rc = pBt->readOnly ? SQLITE_OK : sqlite3pager_stmt_begin(pBt->pPager);
pBt->inStmt = 1;
return rc;
}
/*
** Commit a checkpoint to transaction currently in progress. If no
** checkpoint is active, this is a no-op.
*/
int sqlite3BtreeCommitStmt(Btree *pBt){
int rc;
if( pBt->inStmt && !pBt->readOnly ){
rc = sqlite3pager_stmt_commit(pBt->pPager);
}else{
rc = SQLITE_OK;
}
pBt->inStmt = 0;
return rc;
}
/*
** Rollback the checkpoint to the current transaction. If there
** is no active checkpoint or transaction, this routine is a no-op.
**
** All cursors will be invalided by this operation. Any attempt
** to use a cursor that was open at the beginning of this operation
** will result in an error.
*/
int sqlite3BtreeRollbackStmt(Btree *pBt){
int rc;
if( pBt->inStmt==0 || pBt->readOnly ) return SQLITE_OK;
rc = sqlite3pager_stmt_rollback(pBt->pPager);
invalidateCursors(pBt);
pBt->inStmt = 0;
return rc;
}
/*
** Default key comparison function to be used if no comparison function
** is specified on the sqlite3BtreeCursor() call.
*/
static int dfltCompare(
void *NotUsed, /* User data is not used */
int n1, const void *p1, /* First key to compare */
int n2, const void *p2 /* Second key to compare */
){
int c;
c = memcmp(p1, p2, n1<n2 ? n1 : n2);
if( c==0 ){
c = n1 - n2;
}
return c;
}
/*
** Create a new cursor for the BTree whose root is on the page
** iTable. The act of acquiring a cursor gets a read lock on
** the database file.
**
** If wrFlag==0, then the cursor can only be used for reading.
** If wrFlag==1, then the cursor can be used for reading or for
** writing if other conditions for writing are also met. These
** are the conditions that must be met in order for writing to
** be allowed:
**
** 1: The cursor must have been opened with wrFlag==1
**
** 2: No other cursors may be open with wrFlag==0 on the same table
**
** 3: The database must be writable (not on read-only media)
**
** 4: There must be an active transaction.
**
** Condition 2 warrants further discussion. If any cursor is opened
** on a table with wrFlag==0, that prevents all other cursors from
** writing to that table. This is a kind of "read-lock". When a cursor
** is opened with wrFlag==0 it is guaranteed that the table will not
** change as long as the cursor is open. This allows the cursor to
** do a sequential scan of the table without having to worry about
** entries being inserted or deleted during the scan. Cursors should
** be opened with wrFlag==0 only if this read-lock property is needed.
** That is to say, cursors should be opened with wrFlag==0 only if they
** intend to use the sqlite3BtreeNext() system call. All other cursors
** should be opened with wrFlag==1 even if they never really intend
** to write.
**
** No checking is done to make sure that page iTable really is the
** root page of a b-tree. If it is not, then the cursor acquired
** will not work correctly.
**
** The comparison function must be logically the same for every cursor
** on a particular table. Changing the comparison function will result
** in incorrect operations. If the comparison function is NULL, a
** default comparison function is used. The comparison function is
** always ignored for INTKEY tables.
*/
int sqlite3BtreeCursor(
Btree *pBt, /* The btree */
int iTable, /* Root page of table to open */
int wrFlag, /* 1 to write. 0 read-only */
int (*xCmp)(void*,int,const void*,int,const void*), /* Key Comparison func */
void *pArg, /* First arg to xCompare() */
BtCursor **ppCur /* Write new cursor here */
){
int rc;
BtCursor *pCur, *pRing;
if( pBt->readOnly && wrFlag ){
*ppCur = 0;
return SQLITE_READONLY;
}
if( pBt->pPage1==0 ){
rc = lockBtree(pBt);
if( rc!=SQLITE_OK ){
*ppCur = 0;
return rc;
}
}
pCur = sqliteMalloc( sizeof(*pCur) );
if( pCur==0 ){
rc = SQLITE_NOMEM;
goto create_cursor_exception;
}
pCur->pgnoRoot = (Pgno)iTable;
if( iTable==1 && sqlite3pager_pagecount(pBt->pPager)==0 ){
rc = SQLITE_EMPTY;
goto create_cursor_exception;
}
rc = getAndInitPage(pBt, pCur->pgnoRoot, &pCur->pPage, 0);
if( rc!=SQLITE_OK ){
goto create_cursor_exception;
}
pCur->xCompare = xCmp ? xCmp : dfltCompare;
pCur->pArg = pArg;
pCur->pBt = pBt;
pCur->wrFlag = wrFlag;
pCur->idx = 0;
pCur->infoValid = 0;
pCur->pNext = pBt->pCursor;
if( pCur->pNext ){
pCur->pNext->pPrev = pCur;
}
pCur->pPrev = 0;
pRing = pBt->pCursor;
while( pRing && pRing->pgnoRoot!=pCur->pgnoRoot ){ pRing = pRing->pNext; }
if( pRing ){
pCur->pShared = pRing->pShared;
pRing->pShared = pCur;
}else{
pCur->pShared = pCur;
}
pBt->pCursor = pCur;
pCur->isValid = 0;
pCur->status = SQLITE_OK;
*ppCur = pCur;
return SQLITE_OK;
create_cursor_exception:
*ppCur = 0;
if( pCur ){
releasePage(pCur->pPage);
sqliteFree(pCur);
}
unlockBtreeIfUnused(pBt);
return rc;
}
/*
** Change the value of the comparison function used by a cursor.
*/
void sqlite3BtreeSetCompare(
BtCursor *pCur, /* The cursor to whose comparison function is changed */
int(*xCmp)(void*,int,const void*,int,const void*), /* New comparison func */
void *pArg /* First argument to xCmp() */
){
pCur->xCompare = xCmp ? xCmp : dfltCompare;
pCur->pArg = pArg;
}
/*
** Close a cursor. The read lock on the database file is released
** when the last cursor is closed.
*/
int sqlite3BtreeCloseCursor(BtCursor *pCur){
Btree *pBt = pCur->pBt;
if( pCur->pPrev ){
pCur->pPrev->pNext = pCur->pNext;
}else{
pBt->pCursor = pCur->pNext;
}
if( pCur->pNext ){
pCur->pNext->pPrev = pCur->pPrev;
}
releasePage(pCur->pPage);
if( pCur->pShared!=pCur ){
BtCursor *pRing = pCur->pShared;
while( pRing->pShared!=pCur ){ pRing = pRing->pShared; }
pRing->pShared = pCur->pShared;
}
unlockBtreeIfUnused(pBt);
sqliteFree(pCur);
return SQLITE_OK;
}
/*
** Make a temporary cursor by filling in the fields of pTempCur.
** The temporary cursor is not on the cursor list for the Btree.
*/
static void getTempCursor(BtCursor *pCur, BtCursor *pTempCur){
memcpy(pTempCur, pCur, sizeof(*pCur));
pTempCur->pNext = 0;
pTempCur->pPrev = 0;
if( pTempCur->pPage ){
sqlite3pager_ref(pTempCur->pPage->aData);
}
}
/*
** Delete a temporary cursor such as was made by the CreateTemporaryCursor()
** function above.
*/
static void releaseTempCursor(BtCursor *pCur){
if( pCur->pPage ){
sqlite3pager_unref(pCur->pPage->aData);
}
}
/*
** Make sure the BtCursor.info field of the given cursor is valid.
*/
static void getCellInfo(BtCursor *pCur){
MemPage *pPage = pCur->pPage;
if( !pCur->infoValid ){
parseCell(pPage, pPage->aCell[pCur->idx], &pCur->info);
pCur->infoValid = 1;
}else{
#ifndef NDEBUG
CellInfo info;
parseCell(pPage, pPage->aCell[pCur->idx], &info);
assert( memcmp(&info, &pCur->info, sizeof(info))==0 );
#endif
}
}
/*
** Set *pSize to the size of the buffer needed to hold the value of
** the key for the current entry. If the cursor is not pointing
** to a valid entry, *pSize is set to 0.
**
** For a table with the INTKEY flag set, this routine returns the key
** itself, not the number of bytes in the key.
*/
int sqlite3BtreeKeySize(BtCursor *pCur, i64 *pSize){
if( !pCur->isValid ){
*pSize = 0;
}else{
getCellInfo(pCur);
*pSize = pCur->info.nKey;
}
return SQLITE_OK;
}
/*
** Set *pSize to the number of bytes of data in the entry the
** cursor currently points to. Always return SQLITE_OK.
** Failure is not possible. If the cursor is not currently
** pointing to an entry (which can happen, for example, if
** the database is empty) then *pSize is set to 0.
*/
int sqlite3BtreeDataSize(BtCursor *pCur, u32 *pSize){
if( !pCur->isValid ){
/* Not pointing at a valid entry - set *pSize to 0. */
*pSize = 0;
}else{
getCellInfo(pCur);
*pSize = pCur->info.nData;
}
return SQLITE_OK;
}
/*
** Read payload information from the entry that the pCur cursor is
** pointing to. Begin reading the payload at "offset" and read
** a total of "amt" bytes. Put the result in zBuf.
**
** This routine does not make a distinction between key and data.
** It just reads bytes from the payload area.
*/
static int getPayload(
BtCursor *pCur, /* Cursor pointing to entry to read from */
int offset, /* Begin reading this far into payload */
int amt, /* Read this many bytes */
unsigned char *pBuf, /* Write the bytes into this buffer */
int skipKey /* offset begins at data if this is true */
){
unsigned char *aPayload;
Pgno nextPage;
int rc;
MemPage *pPage;
Btree *pBt;
int ovflSize;
u32 nKey;
assert( pCur!=0 && pCur->pPage!=0 );
assert( pCur->isValid );
pBt = pCur->pBt;
pPage = pCur->pPage;
pageIntegrity(pPage);
assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
aPayload = pPage->aCell[pCur->idx];
getCellInfo(pCur);
aPayload += pCur->info.nHeader;
if( pPage->intKey ){
nKey = 0;
}else{
nKey = pCur->info.nKey;
}
assert( offset>=0 );
if( skipKey ){
offset += nKey;
}
if( offset+amt > nKey+pCur->info.nData ){
return SQLITE_ERROR;
}
if( offset<pCur->info.nLocal ){
int a = amt;
if( a+offset>pCur->info.nLocal ){
a = pCur->info.nLocal - offset;
}
memcpy(pBuf, &aPayload[offset], a);
if( a==amt ){
return SQLITE_OK;
}
offset = 0;
pBuf += a;
amt -= a;
}else{
offset -= pCur->info.nLocal;
}
if( amt>0 ){
nextPage = get4byte(&aPayload[pCur->info.nLocal]);
}
ovflSize = pBt->usableSize - 4;
while( amt>0 && nextPage ){
rc = sqlite3pager_get(pBt->pPager, nextPage, (void**)&aPayload);
if( rc!=0 ){
return rc;
}
nextPage = get4byte(aPayload);
if( offset<ovflSize ){
int a = amt;
if( a + offset > ovflSize ){
a = ovflSize - offset;
}
memcpy(pBuf, &aPayload[offset+4], a);
offset = 0;
amt -= a;
pBuf += a;
}else{
offset -= ovflSize;
}
sqlite3pager_unref(aPayload);
}
if( amt>0 ){
return SQLITE_CORRUPT;
}
return SQLITE_OK;
}
/*
** Read part of the key associated with cursor pCur. Exactly
** "amt" bytes will be transfered into pBuf[]. The transfer
** begins at "offset".
**
** Return SQLITE_OK on success or an error code if anything goes
** wrong. An error is returned if "offset+amt" is larger than
** the available payload.
*/
int sqlite3BtreeKey(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
assert( amt>=0 );
assert( offset>=0 );
if( pCur->isValid==0 ){
return pCur->status;
}
assert( pCur->pPage!=0 );
assert( pCur->pPage->intKey==0 );
assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
return getPayload(pCur, offset, amt, (unsigned char*)pBuf, 0);
}
/*
** Read part of the data associated with cursor pCur. Exactly
** "amt" bytes will be transfered into pBuf[]. The transfer
** begins at "offset".
**
** Return SQLITE_OK on success or an error code if anything goes
** wrong. An error is returned if "offset+amt" is larger than
** the available payload.
*/
int sqlite3BtreeData(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
if( !pCur->isValid ){
return pCur->status ? pCur->status : SQLITE_INTERNAL;
}
assert( amt>=0 );
assert( offset>=0 );
assert( pCur->pPage!=0 );
assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
return getPayload(pCur, offset, amt, pBuf, 1);
}
/*
** Return a pointer to payload information from the entry that the
** pCur cursor is pointing to. The pointer is to the beginning of
** the key if skipKey==0 and it points to the beginning of data if
** skipKey==1.
**
** At least amt bytes of information must be available on the local
** page or else this routine returns NULL. If amt<0 then the entire
** key/data must be available.
**
** This routine is an optimization. It is common for the entire key
** and data to fit on the local page and for there to be no overflow
** pages. When that is so, this routine can be used to access the
** key and data without making a copy. If the key and/or data spills
** onto overflow pages, then getPayload() must be used to reassembly
** the key/data and copy it into a preallocated buffer.
**
** The pointer returned by this routine looks directly into the cached
** page of the database. The data might change or move the next time
** any btree routine is called.
*/
static const unsigned char *fetchPayload(
BtCursor *pCur, /* Cursor pointing to entry to read from */
int amt, /* Amount requested */
int skipKey /* read beginning at data if this is true */
){
unsigned char *aPayload;
MemPage *pPage;
Btree *pBt;
u32 nKey;
int nLocal;
assert( pCur!=0 && pCur->pPage!=0 );
assert( pCur->isValid );
pBt = pCur->pBt;
pPage = pCur->pPage;
pageIntegrity(pPage);
assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
aPayload = pPage->aCell[pCur->idx];
getCellInfo(pCur);
aPayload += pCur->info.nHeader;
if( pPage->intKey ){
nKey = 0;
}else{
nKey = pCur->info.nKey;
}
if( skipKey ){
aPayload += nKey;
nLocal = pCur->info.nLocal - nKey;
if( amt<0 ) amt = pCur->info.nData;
assert( amt<=pCur->info.nData );
}else{
nLocal = pCur->info.nLocal;
if( amt<0 ) amt = nKey;
assert( amt<=nKey );
}
if( amt>nLocal ){
return 0; /* If any of the data is not local, return nothing */
}
return aPayload;
}
/*
** Return a pointer to the first amt bytes of the key or data
** for record that cursor pCur is point to if the entire request
** exists in contiguous memory on the main tree page. If any
** any part of the request is on an overflow page, return 0.
** If pCur is not pointing to a valid entry return 0.
**
** If amt<0 then return the entire key or data.
**
** The pointer returned is ephemeral. The key/data may move
** or be destroyed on the next call to any Btree routine.
**
** These routines is used to get quick access to key and data
** in the common case where no overflow pages are used.
**
** It is a fatal error to call these routines with amt values that
** are larger than the key/data size.
*/
const void *sqlite3BtreeKeyFetch(BtCursor *pCur, int amt){
return (const void*)fetchPayload(pCur, amt, 0);
}
const void *sqlite3BtreeDataFetch(BtCursor *pCur, int amt){
return (const void*)fetchPayload(pCur, amt, 1);
}
/*
** Move the cursor down to a new child page. The newPgno argument is the
** page number of the child page in the byte order of the disk image.
*/
static int moveToChild(BtCursor *pCur, u32 newPgno){
int rc;
MemPage *pNewPage;
MemPage *pOldPage;
Btree *pBt = pCur->pBt;
assert( pCur->isValid );
rc = getAndInitPage(pBt, newPgno, &pNewPage, pCur->pPage);
if( rc ) return rc;
pageIntegrity(pNewPage);
pNewPage->idxParent = pCur->idx;
pOldPage = pCur->pPage;
pOldPage->idxShift = 0;
releasePage(pOldPage);
pCur->pPage = pNewPage;
pCur->idx = 0;
pCur->infoValid = 0;
if( pNewPage->nCell<1 ){
return SQLITE_CORRUPT;
}
return SQLITE_OK;
}
/*
** Return true if the page is the virtual root of its table.
**
** The virtual root page is the root page for most tables. But
** for the table rooted on page 1, sometime the real root page
** is empty except for the right-pointer. In such cases the
** virtual root page is the page that the right-pointer of page
** 1 is pointing to.
*/
static int isRootPage(MemPage *pPage){
MemPage *pParent = pPage->pParent;
if( pParent==0 ) return 1;
if( pParent->pgno>1 ) return 0;
if( get2byte(&pParent->aData[pParent->hdrOffset+3])==0 ) return 1;
return 0;
}
/*
** Move the cursor up to the parent page.
**
** pCur->idx is set to the cell index that contains the pointer
** to the page we are coming from. If we are coming from the
** right-most child page then pCur->idx is set to one more than
** the largest cell index.
*/
static void moveToParent(BtCursor *pCur){
Pgno oldPgno;
MemPage *pParent;
MemPage *pPage;
int idxParent;
assert( pCur->isValid );
pPage = pCur->pPage;
assert( pPage!=0 );
assert( !isRootPage(pPage) );
pageIntegrity(pPage);
pParent = pPage->pParent;
assert( pParent!=0 );
pageIntegrity(pParent);
idxParent = pPage->idxParent;
sqlite3pager_ref(pParent->aData);
oldPgno = pPage->pgno;
releasePage(pPage);
pCur->pPage = pParent;
pCur->infoValid = 0;
assert( pParent->idxShift==0 );
if( pParent->idxShift==0 ){
pCur->idx = idxParent;
#ifndef NDEBUG
/* Verify that pCur->idx is the correct index to point back to the child
** page we just came from
*/
if( pCur->idx<pParent->nCell ){
assert( get4byte(&pParent->aCell[idxParent][2])==oldPgno );
}else{
assert( get4byte(&pParent->aData[pParent->hdrOffset+6])==oldPgno );
}
#endif
}else{
/* The MemPage.idxShift flag indicates that cell indices might have
** changed since idxParent was set and hence idxParent might be out
** of date. So recompute the parent cell index by scanning all cells
** and locating the one that points to the child we just came from.
*/
int i;
pCur->idx = pParent->nCell;
for(i=0; i<pParent->nCell; i++){
if( get4byte(&pParent->aCell[i][2])==oldPgno ){
pCur->idx = i;
break;
}
}
}
}
/*
** Move the cursor to the root page
*/
static int moveToRoot(BtCursor *pCur){
MemPage *pRoot;
int rc;
Btree *pBt = pCur->pBt;
rc = getAndInitPage(pBt, pCur->pgnoRoot, &pRoot, 0);
if( rc ){
pCur->isValid = 0;
return rc;
}
releasePage(pCur->pPage);
pageIntegrity(pRoot);
pCur->pPage = pRoot;
pCur->idx = 0;
pCur->infoValid = 0;
if( pRoot->nCell==0 && !pRoot->leaf ){
Pgno subpage;
assert( pRoot->pgno==1 );
subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+6]);
assert( subpage>0 );
pCur->isValid = 1;
rc = moveToChild(pCur, subpage);
}
pCur->isValid = pCur->pPage->nCell>0;
return rc;
}
/*
** Move the cursor down to the left-most leaf entry beneath the
** entry to which it is currently pointing.
*/
static int moveToLeftmost(BtCursor *pCur){
Pgno pgno;
int rc;
MemPage *pPage;
assert( pCur->isValid );
while( !(pPage = pCur->pPage)->leaf ){
assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
pgno = get4byte(&pPage->aCell[pCur->idx][2]);
rc = moveToChild(pCur, pgno);
if( rc ) return rc;
}
return SQLITE_OK;
}
/*
** Move the cursor down to the right-most leaf entry beneath the
** page to which it is currently pointing. Notice the difference
** between moveToLeftmost() and moveToRightmost(). moveToLeftmost()
** finds the left-most entry beneath the *entry* whereas moveToRightmost()
** finds the right-most entry beneath the *page*.
*/
static int moveToRightmost(BtCursor *pCur){
Pgno pgno;
int rc;
MemPage *pPage;
assert( pCur->isValid );
while( !(pPage = pCur->pPage)->leaf ){
pgno = get4byte(&pPage->aData[pPage->hdrOffset+6]);
pCur->idx = pPage->nCell;
rc = moveToChild(pCur, pgno);
if( rc ) return rc;
}
pCur->idx = pPage->nCell - 1;
pCur->infoValid = 0;
return SQLITE_OK;
}
/* Move the cursor to the first entry in the table. Return SQLITE_OK
** on success. Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite3BtreeFirst(BtCursor *pCur, int *pRes){
int rc;
if( pCur->status ){
return pCur->status;
}
rc = moveToRoot(pCur);
if( rc ) return rc;
if( pCur->isValid==0 ){
assert( pCur->pPage->nCell==0 );
*pRes = 1;
return SQLITE_OK;
}
assert( pCur->pPage->nCell>0 );
*pRes = 0;
rc = moveToLeftmost(pCur);
return rc;
}
/* Move the cursor to the last entry in the table. Return SQLITE_OK
** on success. Set *pRes to 0 if the cursor actually points to something
** or set *pRes to 1 if the table is empty.
*/
int sqlite3BtreeLast(BtCursor *pCur, int *pRes){
int rc;
if( pCur->status ){
return pCur->status;
}
rc = moveToRoot(pCur);
if( rc ) return rc;
if( pCur->isValid==0 ){
assert( pCur->pPage->nCell==0 );
*pRes = 1;
return SQLITE_OK;
}
assert( pCur->isValid );
*pRes = 0;
rc = moveToRightmost(pCur);
return rc;
}
/* Move the cursor so that it points to an entry near pKey/nKey.
** Return a success code.
**
** For INTKEY tables, only the nKey parameter is used. pKey is
** ignored. For other tables, nKey is the number of bytes of data
** in nKey. The comparison function specified when the cursor was
** created is used to compare keys.
**
** If an exact match is not found, then the cursor is always
** left pointing at a leaf page which would hold the entry if it
** were present. The cursor might point to an entry that comes
** before or after the key.
**
** The result of comparing the key with the entry to which the
** cursor is left pointing is stored in pCur->iMatch. The same
** value is also written to *pRes if pRes!=NULL. The meaning of
** this value is as follows:
**
** *pRes<0 The cursor is left pointing at an entry that
** is smaller than pKey or if the table is empty
** and the cursor is therefore left point to nothing.
**
** *pRes==0 The cursor is left pointing at an entry that
** exactly matches pKey.
**
** *pRes>0 The cursor is left pointing at an entry that
** is larger than pKey.
*/
int sqlite3BtreeMoveto(BtCursor *pCur, const void *pKey, i64 nKey, int *pRes){
int rc;
if( pCur->status ){
return pCur->status;
}
rc = moveToRoot(pCur);
if( rc ) return rc;
assert( pCur->pPage );
assert( pCur->pPage->isInit );
if( pCur->isValid==0 ){
*pRes = -1;
assert( pCur->pPage->nCell==0 );
return SQLITE_OK;
}
for(;;){
int lwr, upr;
Pgno chldPg;
MemPage *pPage = pCur->pPage;
int c = -1; /* pRes return if table is empty must be -1 */
lwr = 0;
upr = pPage->nCell-1;
pageIntegrity(pPage);
while( lwr<=upr ){
const void *pCellKey;
i64 nCellKey;
pCur->idx = (lwr+upr)/2;
pCur->infoValid = 0;
sqlite3BtreeKeySize(pCur, &nCellKey);
if( pPage->intKey ){
if( nCellKey<nKey ){
c = -1;
}else if( nCellKey>nKey ){
c = +1;
}else{
c = 0;
}
}else if( (pCellKey = sqlite3BtreeKeyFetch(pCur, nCellKey))!=0 ){
c = pCur->xCompare(pCur->pArg, nCellKey, pCellKey, nKey, pKey);
}else{
u8 *pCellKey = sqliteMalloc( nCellKey );
if( pCellKey==0 ) return SQLITE_NOMEM;
rc = sqlite3BtreeKey(pCur, 0, nCellKey, pCellKey);
c = pCur->xCompare(pCur->pArg, nCellKey, pCellKey, nKey, pKey);
sqliteFree(pCellKey);
if( rc ) return rc;
}
if( c==0 ){
if( pPage->leafData && !pPage->leaf ){
lwr = pCur->idx;
upr = lwr - 1;
break;
}else{
pCur->iMatch = c;
if( pRes ) *pRes = 0;
return SQLITE_OK;
}
}
if( c<0 ){
lwr = pCur->idx+1;
}else{
upr = pCur->idx-1;
}
}
assert( lwr==upr+1 );
assert( pPage->isInit );
if( pPage->leaf ){
chldPg = 0;
}else if( lwr>=pPage->nCell ){
chldPg = get4byte(&pPage->aData[pPage->hdrOffset+6]);
}else{
chldPg = get4byte(&pPage->aCell[lwr][2]);
}
if( chldPg==0 ){
pCur->iMatch = c;
assert( pCur->idx>=0 && pCur->idx<pCur->pPage->nCell );
if( pRes ) *pRes = c;
return SQLITE_OK;
}
pCur->idx = lwr;
pCur->infoValid = 0;
rc = moveToChild(pCur, chldPg);
if( rc ){
return rc;
}
}
/* NOT REACHED */
}
/*
** Return TRUE if the cursor is not pointing at an entry of the table.
**
** TRUE will be returned after a call to sqlite3BtreeNext() moves
** past the last entry in the table or sqlite3BtreePrev() moves past
** the first entry. TRUE is also returned if the table is empty.
*/
int sqlite3BtreeEof(BtCursor *pCur){
return pCur->isValid==0;
}
/*
** Advance the cursor to the next entry in the database. If
** successful then set *pRes=0. If the cursor
** was already pointing to the last entry in the database before
** this routine was called, then set *pRes=1.
*/
int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
int rc;
MemPage *pPage = pCur->pPage;
assert( pRes!=0 );
if( pCur->isValid==0 ){
*pRes = 1;
return SQLITE_OK;
}
assert( pPage->isInit );
assert( pCur->idx<pPage->nCell );
pCur->idx++;
pCur->infoValid = 0;
if( pCur->idx>=pPage->nCell ){
if( !pPage->leaf ){
rc = moveToChild(pCur, get4byte(&pPage->aData[pPage->hdrOffset+6]));
if( rc ) return rc;
rc = moveToLeftmost(pCur);
*pRes = 0;
return rc;
}
do{
if( isRootPage(pPage) ){
*pRes = 1;
pCur->isValid = 0;
return SQLITE_OK;
}
moveToParent(pCur);
pPage = pCur->pPage;
}while( pCur->idx>=pPage->nCell );
*pRes = 0;
if( pPage->leafData ){
rc = sqlite3BtreeNext(pCur, pRes);
}else{
rc = SQLITE_OK;
}
return rc;
}
*pRes = 0;
if( pPage->leaf ){
return SQLITE_OK;
}
rc = moveToLeftmost(pCur);
return rc;
}
/*
** Step the cursor to the back to the previous entry in the database. If
** successful then set *pRes=0. If the cursor
** was already pointing to the first entry in the database before
** this routine was called, then set *pRes=1.
*/
int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
int rc;
Pgno pgno;
MemPage *pPage;
if( pCur->isValid==0 ){
*pRes = 1;
return SQLITE_OK;
}
pPage = pCur->pPage;
assert( pPage->isInit );
assert( pCur->idx>=0 );
if( !pPage->leaf ){
pgno = get4byte(&pPage->aCell[pCur->idx][2]);
rc = moveToChild(pCur, pgno);
if( rc ) return rc;
rc = moveToRightmost(pCur);
}else{
while( pCur->idx==0 ){
if( isRootPage(pPage) ){
pCur->isValid = 0;
*pRes = 1;
return SQLITE_OK;
}
moveToParent(pCur);
pPage = pCur->pPage;
}
pCur->idx--;
pCur->infoValid = 0;
if( pPage->leafData ){
rc = sqlite3BtreePrevious(pCur, pRes);
}else{
rc = SQLITE_OK;
}
}
*pRes = 0;
return rc;
}
/*
** The TRACE macro will print high-level status information about the
** btree operation when the global variable sqlite3_btree_trace is
** enabled.
*/
#if SQLITE_TEST
# define TRACE(X) if( sqlite3_btree_trace ){ printf X; fflush(stdout); }
#else
# define TRACE(X)
#endif
int sqlite3_btree_trace=0; /* True to enable tracing */
/*
** Allocate a new page from the database file.
**
** The new page is marked as dirty. (In other words, sqlite3pager_write()
** has already been called on the new page.) The new page has also
** been referenced and the calling routine is responsible for calling
** sqlite3pager_unref() on the new page when it is done.
**
** SQLITE_OK is returned on success. Any other return value indicates
** an error. *ppPage and *pPgno are undefined in the event of an error.
** Do not invoke sqlite3pager_unref() on *ppPage if an error is returned.
**
** If the "nearby" parameter is not 0, then a (feeble) effort is made to
** locate a page close to the page number "nearby". This can be used in an
** attempt to keep related pages close to each other in the database file,
** which in turn can make database access faster.
*/
static int allocatePage(Btree *pBt, MemPage **ppPage, Pgno *pPgno, Pgno nearby){
MemPage *pPage1;
int rc;
int n; /* Number of pages on the freelist */
int k; /* Number of leaves on the trunk of the freelist */
pPage1 = pBt->pPage1;
n = get4byte(&pPage1->aData[36]);
if( n>0 ){
/* There are pages on the freelist. Reuse one of those pages. */
MemPage *pTrunk;
rc = sqlite3pager_write(pPage1->aData);
if( rc ) return rc;
put4byte(&pPage1->aData[36], n-1);
rc = getPage(pBt, get4byte(&pPage1->aData[32]), &pTrunk);
if( rc ) return rc;
rc = sqlite3pager_write(pTrunk->aData);
if( rc ){
releasePage(pTrunk);
return rc;
}
k = get4byte(&pTrunk->aData[4]);
if( k==0 ){
/* The trunk has no leaves. So extract the trunk page itself and
** use it as the newly allocated page */
*pPgno = get4byte(&pPage1->aData[32]);
memcpy(&pPage1->aData[32], &pTrunk->aData[0], 4);
*ppPage = pTrunk;
TRACE(("ALLOCATE: %d trunk - %d free pages left\n", *pPgno, n-1));
}else{
/* Extract a leaf from the trunk */
int closest;
unsigned char *aData = pTrunk->aData;
if( nearby>0 ){
int i, dist;
closest = 0;
dist = get4byte(&aData[8]) - nearby;
if( dist<0 ) dist = -dist;
for(i=1; i<k; i++){
int d2 = get4byte(&aData[8+i*4]) - nearby;
if( d2<0 ) d2 = -d2;
if( d2<dist ) closest = i;
}
}else{
closest = 0;
}
*pPgno = get4byte(&aData[8+closest*4]);
TRACE(("ALLOCATE: %d was leaf %d of %d on trunk %d: %d more free pages\n",
*pPgno, closest+1, k, pTrunk->pgno, n-1));
if( closest<k-1 ){
memcpy(&aData[8+closest*4], &aData[4+k*4], 4);
}
put4byte(&aData[4], k-1);
rc = getPage(pBt, *pPgno, ppPage);
releasePage(pTrunk);
if( rc==SQLITE_OK ){
sqlite3pager_dont_rollback((*ppPage)->aData);
rc = sqlite3pager_write((*ppPage)->aData);
}
}
}else{
/* There are no pages on the freelist, so create a new page at the
** end of the file */
*pPgno = sqlite3pager_pagecount(pBt->pPager) + 1;
rc = getPage(pBt, *pPgno, ppPage);
if( rc ) return rc;
rc = sqlite3pager_write((*ppPage)->aData);
TRACE(("ALLOCATE: %d from end of file\n", *pPgno));
}
return rc;
}
/*
** Add a page of the database file to the freelist.
**
** sqlite3pager_unref() is NOT called for pPage.
*/
static int freePage(MemPage *pPage){
Btree *pBt = pPage->pBt;
MemPage *pPage1 = pBt->pPage1;
int rc, n, k;
/* Prepare the page for freeing */
assert( pPage->pgno>1 );
pPage->isInit = 0;
releasePage(pPage->pParent);
pPage->pParent = 0;
/* Increment the free page count on pPage1 */
rc = sqlite3pager_write(pPage1->aData);
if( rc ) return rc;
n = get4byte(&pPage1->aData[36]);
put4byte(&pPage1->aData[36], n+1);
if( n==0 ){
/* This is the first free page */
rc = sqlite3pager_write(pPage->aData);
if( rc ) return rc;
memset(pPage->aData, 0, 8);
put4byte(&pPage1->aData[32], pPage->pgno);
TRACE(("FREE-PAGE: %d first\n", pPage->pgno));
}else{
/* Other free pages already exist. Retrive the first trunk page
** of the freelist and find out how many leaves it has. */
MemPage *pTrunk;
rc = getPage(pBt, get4byte(&pPage1->aData[32]), &pTrunk);
if( rc ) return rc;
k = get4byte(&pTrunk->aData[4]);
if( k==pBt->usableSize/4 - 8 ){
/* The trunk is full. Turn the page being freed into a new
** trunk page with no leaves. */
rc = sqlite3pager_write(pPage->aData);
if( rc ) return rc;
put4byte(pPage->aData, pTrunk->pgno);
put4byte(&pPage->aData[4], 0);
put4byte(&pPage1->aData[32], pPage->pgno);
TRACE(("FREE-PAGE: %d new trunk page replacing %d\n",
pPage->pgno, pTrunk->pgno));
}else{
/* Add the newly freed page as a leaf on the current trunk */
rc = sqlite3pager_write(pTrunk->aData);
if( rc ) return rc;
put4byte(&pTrunk->aData[4], k+1);
put4byte(&pTrunk->aData[8+k*4], pPage->pgno);
sqlite3pager_dont_write(pBt->pPager, pPage->pgno);
TRACE(("FREE-PAGE: %d leaf on trunk page %d\n",pPage->pgno,pTrunk->pgno));
}
releasePage(pTrunk);
}
return rc;
}
/*
** Free any overflow pages associated with the given Cell.
*/
static int clearCell(MemPage *pPage, unsigned char *pCell){
Btree *pBt = pPage->pBt;
CellInfo info;
Pgno ovflPgno;
int rc;
parseCell(pPage, pCell, &info);
if( info.iOverflow==0 ){
return SQLITE_OK; /* No overflow pages. Return without doing anything */
}
ovflPgno = get4byte(&pCell[info.iOverflow]);
while( ovflPgno!=0 ){
MemPage *pOvfl;
rc = getPage(pBt, ovflPgno, &pOvfl);
if( rc ) return rc;
ovflPgno = get4byte(pOvfl->aData);
rc = freePage(pOvfl);
if( rc ) return rc;
sqlite3pager_unref(pOvfl->aData);
}
return SQLITE_OK;
}
/*
** Create the byte sequence used to represent a cell on page pPage
** and write that byte sequence into pCell[]. Overflow pages are
** allocated and filled in as necessary. The calling procedure
** is responsible for making sure sufficient space has been allocated
** for pCell[].
**
** Note that pCell does not necessary need to point to the pPage->aData
** area. pCell might point to some temporary storage. The cell will
** be constructed in this temporary area then copied into pPage->aData
** later.
*/
static int fillInCell(
MemPage *pPage, /* The page that contains the cell */
unsigned char *pCell, /* Complete text of the cell */
const void *pKey, i64 nKey, /* The key */
const void *pData,int nData, /* The data */
int *pnSize /* Write cell size here */
){
int nPayload;
const void *pSrc;
int nSrc, n, rc;
int spaceLeft;
MemPage *pOvfl = 0;
MemPage *pToRelease = 0;
unsigned char *pPrior;
unsigned char *pPayload;
Btree *pBt = pPage->pBt;
Pgno pgnoOvfl = 0;
int nHeader;
CellInfo info;
/* Fill in the header. */
nHeader = 2;
if( !pPage->leaf ){
nHeader += 4;
}
if( pPage->hasData ){
nHeader += putVarint(&pCell[nHeader], nData);
}else{
nData = 0;
}
nHeader += putVarint(&pCell[nHeader], *(u64*)&nKey);
parseCell(pPage, pCell, &info);
assert( info.nHeader==nHeader );
assert( info.nKey==nKey );
assert( info.nData==nData );
/* Fill in the payload */
nPayload = nData;
if( pPage->intKey ){
pSrc = pData;
nSrc = nData;
nData = 0;
}else{
nPayload += nKey;
pSrc = pKey;
nSrc = nKey;
}
*pnSize = info.nSize;
spaceLeft = info.nLocal;
pPayload = &pCell[nHeader];
pPrior = &pCell[info.iOverflow];
while( nPayload>0 ){
if( spaceLeft==0 ){
rc = allocatePage(pBt, &pOvfl, &pgnoOvfl, pgnoOvfl);
if( rc ){
releasePage(pToRelease);
clearCell(pPage, pCell);
return rc;
}
put4byte(pPrior, pgnoOvfl);
releasePage(pToRelease);
pToRelease = pOvfl;
pPrior = pOvfl->aData;
put4byte(pPrior, 0);
pPayload = &pOvfl->aData[4];
spaceLeft = pBt->usableSize - 4;
}
n = nPayload;
if( n>spaceLeft ) n = spaceLeft;
if( n>nSrc ) n = nSrc;
memcpy(pPayload, pSrc, n);
nPayload -= n;
pPayload += n;
pSrc += n;
nSrc -= n;
spaceLeft -= n;
if( nSrc==0 ){
nSrc = nData;
pSrc = pData;
}
}
releasePage(pToRelease);
return SQLITE_OK;
}
/*
** Change the MemPage.pParent pointer on the page whose number is
** given in the second argument so that MemPage.pParent holds the
** pointer in the third argument.
*/
static void reparentPage(Btree *pBt, Pgno pgno, MemPage *pNewParent, int idx){
MemPage *pThis;
unsigned char *aData;
if( pgno==0 ) return;
assert( pBt->pPager!=0 );
aData = sqlite3pager_lookup(pBt->pPager, pgno);
if( aData ){
pThis = (MemPage*)&aData[pBt->usableSize];
if( pThis->isInit ){
if( pThis->pParent!=pNewParent ){
if( pThis->pParent ) sqlite3pager_unref(pThis->pParent->aData);
pThis->pParent = pNewParent;
if( pNewParent ) sqlite3pager_ref(pNewParent->aData);
}
pThis->idxParent = idx;
}
sqlite3pager_unref(aData);
}
}
/*
** Change the pParent pointer of all children of pPage to point back
** to pPage.
**
** In other words, for every child of pPage, invoke reparentPage()
** to make sure that each child knows that pPage is its parent.
**
** This routine gets called after you memcpy() one page into
** another.
*/
static void reparentChildPages(MemPage *pPage){
int i;
Btree *pBt;
if( pPage->leaf ) return;
pBt = pPage->pBt;
for(i=0; i<pPage->nCell; i++){
reparentPage(pBt, get4byte(&pPage->aCell[i][2]), pPage, i);
}
reparentPage(pBt, get4byte(&pPage->aData[pPage->hdrOffset+6]), pPage, i);
pPage->idxShift = 0;
}
/*
** Remove the i-th cell from pPage. This routine effects pPage only.
** The cell content is not freed or deallocated. It is assumed that
** the cell content has been copied someplace else. This routine just
** removes the reference to the cell from pPage.
**
** "sz" must be the number of bytes in the cell.
**
** Try to maintain the integrity of the linked list of cells. But if
** the cell being inserted does not fit on the page, this will not be
** possible. If the linked list is not maintained, then just update
** pPage->aCell[] and set the pPage->needRelink flag so that we will
** know to rebuild the linked list later.
*/
static void dropCell(MemPage *pPage, int idx, int sz){
int j, pc;
u8 *data;
assert( idx>=0 && idx<pPage->nCell );
assert( sz==cellSize(pPage, pPage->aCell[idx]) );
assert( sqlite3pager_iswriteable(pPage->aData) );
assert( pPage->aCell[idx]>=pPage->aData );
assert( pPage->aCell[idx]<=&pPage->aData[pPage->pBt->usableSize-sz] );
data = pPage->aData;
pc = Addr(pPage->aCell[idx]) - Addr(data);
assert( pc>pPage->hdrOffset && pc+sz<=pPage->pBt->usableSize );
freeSpace(pPage, pc, sz);
for(j=idx; j<pPage->nCell-1; j++){
pPage->aCell[j] = pPage->aCell[j+1];
}
pPage->nCell--;
if( !pPage->isOverfull && !pPage->needRelink ){
u8 *pPrev;
if( idx==0 ){
pPrev = &data[pPage->hdrOffset+3];
}else{
pPrev = pPage->aCell[idx-1];
}
if( idx<pPage->nCell ){
pc = Addr(pPage->aCell[idx]) - Addr(data);
}else{
pc = 0;
}
put2byte(pPrev, pc);
pageIntegrity(pPage);
}else{
pPage->needRelink = 1;
}
pPage->idxShift = 1;
}
/*
** Insert a new cell on pPage at cell index "i". pCell points to the
** content of the cell.
**
** If the cell content will fit on the page, then put it there. If it
** will not fit and pTemp is not NULL, then make a copy of the content
** into pTemp, set pPage->aCell[i] point to pTemp, and set pPage->isOverfull.
** If the content will not fit and pTemp is NULL, then make pPage->aCell[i]
** point to pCell and set pPage->isOverfull.
**
** Try to maintain the integrity of the linked list of cells. But if
** the cell being inserted does not fit on the page, this will not be
** possible. If the linked list is not maintained, then just update
** pPage->aCell[] and set the pPage->needRelink flag so that we will
** know to rebuild the linked list later.
*/
static void insertCell(
MemPage *pPage, /* Page into which we are copying */
int i, /* Which cell on pPage to insert after */
u8 *pCell, /* Text of the new cell to insert */
int sz, /* Bytes of data in pCell */
u8 *pTemp /* Temp storage space for pCell, if needed */
){
int idx, j;
assert( i>=0 && i<=pPage->nCell );
assert( sz==cellSize(pPage, pCell) );
assert( sqlite3pager_iswriteable(pPage->aData) );
idx = pPage->needRelink ? 0 : allocateSpace(pPage, sz);
resizeCellArray(pPage, pPage->nCell+1);
for(j=pPage->nCell; j>i; j--){
pPage->aCell[j] = pPage->aCell[j-1];
}
pPage->nCell++;
if( idx<=0 ){
pPage->isOverfull = 1;
if( pTemp ){
memcpy(pTemp, pCell, sz);
}else{
pTemp = pCell;
}
pPage->aCell[i] = pTemp;
}else{
u8 *data = pPage->aData;
memcpy(&data[idx], pCell, sz);
pPage->aCell[i] = &data[idx];
}
if( !pPage->isOverfull && !pPage->needRelink ){
u8 *pPrev;
int pc;
if( i==0 ){
pPrev = &pPage->aData[pPage->hdrOffset+3];
}else{
pPrev = pPage->aCell[i-1];
}
pc = get2byte(pPrev);
put2byte(pPrev, idx);
put2byte(pPage->aCell[i], pc);
pageIntegrity(pPage);
}else{
pPage->needRelink = 1;
}
pPage->idxShift = 1;
}
/*
** Add a list of cells to a page. The page should be initially empty.
** The cells are guaranteed to fit on the page.
*/
static void assemblePage(
MemPage *pPage, /* The page to be assemblied */
int nCell, /* The number of cells to add to this page */
u8 **apCell, /* Pointers to cell text */
int *aSize /* Sizes of the cells */
){
int i; /* Loop counter */
int totalSize; /* Total size of all cells */
int hdr; /* Index of page header */
int pc, prevpc; /* Addresses of cells being inserted */
u8 *data; /* Data for the page */
assert( pPage->needRelink==0 );
assert( pPage->isOverfull==0 );
totalSize = 0;
for(i=0; i<nCell; i++){
totalSize += aSize[i];
}
assert( totalSize<=pPage->nFree );
assert( pPage->nCell==0 );
resizeCellArray(pPage, nCell);
pc = allocateSpace(pPage, totalSize);
data = pPage->aData;
hdr = pPage->hdrOffset;
prevpc = hdr+3;
for(i=0; i<nCell; i++){
memcpy(data+pc, apCell[i], aSize[i]);
put2byte(data+prevpc, pc);
pPage->aCell[i] = data+pc;
prevpc = pc;
pc += aSize[i];
assert( pc<=pPage->pBt->usableSize );
}
pPage->nCell = nCell;
put2byte(data+prevpc, 0);
}
/*
** Rebuild the linked list of cells on a page so that the cells
** occur in the order specified by the pPage->aCell[] array.
** Invoke this routine once to repair damage after one or more
** invocations of either insertCell() or dropCell().
*/
static void relinkCellList(MemPage *pPage){
int i, idxFrom;
assert( sqlite3pager_iswriteable(pPage->aData) );
if( !pPage->needRelink ) return;
idxFrom = pPage->hdrOffset+3;
for(i=0; i<pPage->nCell; i++){
int idx = Addr(pPage->aCell[i]) - Addr(pPage->aData);
assert( idx>pPage->hdrOffset && idx<pPage->pBt->usableSize );
put2byte(&pPage->aData[idxFrom], idx);
idxFrom = idx;
}
put2byte(&pPage->aData[idxFrom], 0);
pPage->needRelink = 0;
}
/*
** GCC does not define the offsetof() macro so we'll have to do it
** ourselves.
*/
#ifndef offsetof
#define offsetof(STRUCTURE,FIELD) ((int)((char*)&((STRUCTURE*)0)->FIELD))
#endif
/*
** Move the content of the page at pFrom over to pTo. The pFrom->aCell[]
** pointers that point into pFrom->aData[] must be adjusted to point
** into pTo->aData[] instead. But some pFrom->aCell[] entries might
** not point to pFrom->aData[]. Those are unchanged.
**
** Over this operation completes, the meta data for pFrom is zeroed.
*/
static void movePage(MemPage *pTo, MemPage *pFrom){
uptr from, to;
int i;
int usableSize;
int ofst;
assert( pTo->hdrOffset==0 );
assert( pFrom->isInit );
ofst = pFrom->hdrOffset;
usableSize = pFrom->pBt->usableSize;
sqliteFree(pTo->aCell);
memcpy(pTo->aData, &pFrom->aData[ofst], usableSize - ofst);
memcpy(pTo, pFrom, offsetof(MemPage, aData));
pFrom->isInit = 0;
pFrom->aCell = 0;
assert( pTo->aData[5]<155 );
pTo->aData[5] += ofst;
pTo->isOverfull = pFrom->isOverfull;
to = Addr(pTo->aData);
from = Addr(&pFrom->aData[ofst]);
for(i=0; i<pTo->nCell; i++){
uptr x = Addr(pTo->aCell[i]);
if( x>from && x<from+usableSize-ofst ){
*((uptr*)&pTo->aCell[i]) = x + to - from;
}
}
}
/*
** The following parameters determine how many adjacent pages get involved
** in a balancing operation. NN is the number of neighbors on either side
** of the page that participate in the balancing operation. NB is the
** total number of pages that participate, including the target page and
** NN neighbors on either side.
**
** The minimum value of NN is 1 (of course). Increasing NN above 1
** (to 2 or 3) gives a modest improvement in SELECT and DELETE performance
** in exchange for a larger degradation in INSERT and UPDATE performance.
** The value of NN appears to give the best results overall.
*/
#define NN 1 /* Number of neighbors on either side of pPage */
#define NB (NN*2+1) /* Total pages involved in the balance */
/*
** This routine redistributes Cells on pPage and up to two siblings
** of pPage so that all pages have about the same amount of free space.
** Usually one sibling on either side of pPage is used in the balancing,
** though both siblings might come from one side if pPage is the first
** or last child of its parent. If pPage has fewer than two siblings
** (something which can only happen if pPage is the root page or a
** child of root) then all available siblings participate in the balancing.
**
** The number of siblings of pPage might be increased or decreased by
** one in an effort to keep pages between 66% and 100% full. The root page
** is special and is allowed to be less than 66% full. If pPage is
** the root page, then the depth of the tree might be increased
** or decreased by one, as necessary, to keep the root page from being
** overfull or empty.
**
** This routine alwyas calls relinkCellList() on its input page regardless of
** whether or not it does any real balancing. Client routines will typically
** invoke insertCell() or dropCell() before calling this routine, so we
** need to call relinkCellList() to clean up the mess that those other
** routines left behind.
**
** Note that when this routine is called, some of the Cells on pPage
** might not actually be stored in pPage->aData[]. This can happen
** if the page is overfull. Part of the job of this routine is to
** make sure all Cells for pPage once again fit in pPage->aData[].
**
** In the course of balancing the siblings of pPage, the parent of pPage
** might become overfull or underfull. If that happens, then this routine
** is called recursively on the parent.
**
** If this routine fails for any reason, it might leave the database
** in a corrupted state. So if this routine fails, the database should
** be rolled back.
*/
static int balance(MemPage *pPage){
MemPage *pParent; /* The parent of pPage */
Btree *pBt; /* The whole database */
int nCell; /* Number of cells in aCell[] */
int nOld; /* Number of pages in apOld[] */
int nNew; /* Number of pages in apNew[] */
int nDiv; /* Number of cells in apDiv[] */
int i, j, k; /* Loop counters */
int idx; /* Index of pPage in pParent->aCell[] */
int nxDiv; /* Next divider slot in pParent->aCell[] */
int rc; /* The return code */
int leafCorrection; /* 4 if pPage is a leaf. 0 if not */
int leafData; /* True if pPage is a leaf of a LEAFDATA tree */
int usableSpace; /* Bytes in pPage beyond the header */
int pageFlags; /* Value of pPage->aData[0] */
int subtotal; /* Subtotal of bytes in cells on one page */
int iSpace = 0; /* First unused byte of aSpace[] */
MemPage *extraUnref = 0; /* Unref this page if not zero */
MemPage *apOld[NB]; /* pPage and up to two siblings */
Pgno pgnoOld[NB]; /* Page numbers for each page in apOld[] */
MemPage *apCopy[NB]; /* Private copies of apOld[] pages */
MemPage *apNew[NB+1]; /* pPage and up to NB siblings after balancing */
Pgno pgnoNew[NB+1]; /* Page numbers for each page in apNew[] */
int idxDiv[NB]; /* Indices of divider cells in pParent */
u8 *apDiv[NB]; /* Divider cells in pParent */
int cntNew[NB+1]; /* Index in aCell[] of cell after i-th page */
int szNew[NB+1]; /* Combined size of cells place on i-th page */
u8 *apCell[(MX_CELL+2)*NB]; /* All cells from pages being balanced */
int szCell[(MX_CELL+2)*NB]; /* Local size of all cells */
u8 aCopy[NB][MX_PAGE_SIZE+sizeof(MemPage)]; /* Space for apCopy[] */
u8 aSpace[MX_PAGE_SIZE*4]; /* Space to copies of divider cells */
/*
** Return without doing any work if pPage is neither overfull nor
** underfull.
*/
assert( pPage->isInit );
assert( sqlite3pager_iswriteable(pPage->aData) );
pBt = pPage->pBt;
if( !pPage->isOverfull && pPage->nFree<pBt->usableSize*2/3
&& pPage->nCell>=2){
relinkCellList(pPage);
return SQLITE_OK;
}
/*
** Find the parent of the page to be balanced. If there is no parent,
** it means this page is the root page and special rules apply.
*/
pParent = pPage->pParent;
if( pParent==0 ){
Pgno pgnoChild;
MemPage *pChild;
assert( pPage->isInit );
if( pPage->nCell==0 ){
if( pPage->leaf ){
/* The table is completely empty */
relinkCellList(pPage);
TRACE(("BALANCE: empty table %d\n", pPage->pgno));
}else{
/* The root page is empty but has one child. Transfer the
** information from that one child into the root page if it
** will fit. This reduces the depth of the tree by one.
**
** If the root page is page 1, it has less space available than
** its child (due to the 100 byte header that occurs at the beginning
** of the database fle), so it might not be able to hold all of the
** information currently contained in the child. If this is the
** case, then do not do the transfer. Leave page 1 empty except
** for the right-pointer to the child page. The child page becomes
** the virtual root of the tree.
*/
pgnoChild = get4byte(&pPage->aData[pPage->hdrOffset+6]);
assert( pgnoChild>0 && pgnoChild<=sqlite3pager_pagecount(pBt->pPager) );
rc = getPage(pBt, pgnoChild, &pChild);
if( rc ) return rc;
if( pPage->pgno==1 ){
rc = initPage(pChild, pPage);
if( rc ) return rc;
if( pChild->nFree>=100 ){
/* The child information will fit on the root page, so do the
** copy */
zeroPage(pPage, pChild->aData[0]);
for(i=0; i<pChild->nCell; i++){
szCell[i] = cellSize(pChild, pChild->aCell[i]);
}
assemblePage(pPage, pChild->nCell, pChild->aCell, szCell);
freePage(pChild);
TRACE(("BALANCE: child %d transfer to page 1\n", pChild->pgno));
}else{
/* The child has more information that will fit on the root.
** The tree is already balanced. Do nothing. */
TRACE(("BALANCE: child %d will not fit on page 1\n", pChild->pgno));
}
}else{
memcpy(pPage->aData, pChild->aData, pBt->usableSize);
pPage->isInit = 0;
pPage->pParent = 0;
rc = initPage(pPage, 0);
assert( rc==SQLITE_OK );
freePage(pChild);
TRACE(("BALANCE: transfer child %d into root %d\n",
pChild->pgno, pPage->pgno));
}
reparentChildPages(pPage);
releasePage(pChild);
}
return SQLITE_OK;
}
if( !pPage->isOverfull ){
/* It is OK for the root page to be less than half full.
*/
relinkCellList(pPage);
TRACE(("BALANCE: root page %d is low - no changes\n", pPage->pgno));
return SQLITE_OK;
}
/*
** If we get to here, it means the root page is overfull.
** When this happens, Create a new child page and copy the
** contents of the root into the child. Then make the root
** page an empty page with rightChild pointing to the new
** child. Then fall thru to the code below which will cause
** the overfull child page to be split.
*/
rc = allocatePage(pBt, &pChild, &pgnoChild, pPage->pgno);
if( rc ) return rc;
assert( sqlite3pager_iswriteable(pChild->aData) );
movePage(pChild, pPage);
assert( pChild->aData[0]==pPage->aData[pPage->hdrOffset] );
pChild->pParent = pPage;
sqlite3pager_ref(pPage->aData);
pChild->idxParent = 0;
pChild->isOverfull = 1;
zeroPage(pPage, pChild->aData[0] & ~PTF_LEAF);
put4byte(&pPage->aData[pPage->hdrOffset+6], pChild->pgno);
pParent = pPage;
pPage = pChild;
extraUnref = pChild;
TRACE(("BALANCE: copy root %d into %d and balance %d\n",
pParent->pgno, pPage->pgno, pPage->pgno));
}else{
TRACE(("BALANCE: begin page %d child of %d\n",
pPage->pgno, pParent->pgno));
}
rc = sqlite3pager_write(pParent->aData);
if( rc ) return rc;
assert( pParent->isInit );
/*
** Find the cell in the parent page whose left child points back
** to pPage. The "idx" variable is the index of that cell. If pPage
** is the rightmost child of pParent then set idx to pParent->nCell
*/
if( pParent->idxShift ){
Pgno pgno;
pgno = pPage->pgno;
assert( pgno==sqlite3pager_pagenumber(pPage->aData) );
for(idx=0; idx<pParent->nCell; idx++){
if( get4byte(&pParent->aCell[idx][2])==pgno ){
break;
}
}
assert( idx<pParent->nCell
|| get4byte(&pParent->aData[pParent->hdrOffset+6])==pgno );
}else{
idx = pPage->idxParent;
}
/*
** Initialize variables so that it will be safe to jump
** directly to balance_cleanup at any moment.
*/
nOld = nNew = 0;
sqlite3pager_ref(pParent->aData);
/*
** Find sibling pages to pPage and the cells in pParent that divide
** the siblings. An attempt is made to find NN siblings on either
** side of pPage. More siblings are taken from one side, however, if
** pPage there are fewer than NN siblings on the other side. If pParent
** has NB or fewer children then all children of pParent are taken.
*/
nxDiv = idx - NN;
if( nxDiv + NB > pParent->nCell ){
nxDiv = pParent->nCell - NB + 1;
}
if( nxDiv<0 ){
nxDiv = 0;
}
nDiv = 0;
for(i=0, k=nxDiv; i<NB; i++, k++){
if( k<pParent->nCell ){
idxDiv[i] = k;
apDiv[i] = pParent->aCell[k];
nDiv++;
assert( !pParent->leaf );
pgnoOld[i] = get4byte(&apDiv[i][2]);
}else if( k==pParent->nCell ){
pgnoOld[i] = get4byte(&pParent->aData[pParent->hdrOffset+6]);
}else{
break;
}
rc = getAndInitPage(pBt, pgnoOld[i], &apOld[i], pParent);
if( rc ) goto balance_cleanup;
apOld[i]->idxParent = k;
apCopy[i] = 0;
assert( i==nOld );
nOld++;
}
/*
** Make copies of the content of pPage and its siblings into aOld[].
** The rest of this function will use data from the copies rather
** that the original pages since the original pages will be in the
** process of being overwritten.
*/
for(i=0; i<nOld; i++){
MemPage *p = apCopy[i] = (MemPage*)&aCopy[i+1][-sizeof(MemPage)];
p->aData = &((u8*)p)[-pBt->usableSize];
p->aCell = 0;
p->hdrOffset = 0;
movePage(p, apOld[i]);
}
/*
** Load pointers to all cells on sibling pages and the divider cells
** into the local apCell[] array. Make copies of the divider cells
** into space obtained form aSpace[] and remove the the divider Cells
** from pParent.
**
** If the siblings are on leaf pages, then the child pointers of the
** divider cells are stripped from the cells before they are copied
** into aSpace[]. In this way, all cells in apCell[] are without
** child pointers. If siblings are not leaves, then all cell in
** apCell[] include child pointers. Either way, all cells in apCell[]
** are alike.
**
** leafCorrection: 4 if pPage is a leaf. 0 if pPage is not a leaf.
** leafData: 1 if pPage holds key+data and pParent holds only keys.
*/
nCell = 0;
leafCorrection = pPage->leaf*4;
leafData = pPage->leafData && pPage->leaf;
for(i=0; i<nOld; i++){
MemPage *pOld = apCopy[i];
for(j=0; j<pOld->nCell; j++){
apCell[nCell] = pOld->aCell[j];
szCell[nCell] = cellSize(pOld, apCell[nCell]);
nCell++;
}
if( i<nOld-1 ){
int sz = cellSize(pParent, apDiv[i]);
if( leafData ){
/* With the LEAFDATA flag, pParent cells hold only INTKEYs that
** are duplicates of keys on the child pages. We need to remove
** the divider cells from pParent, but the dividers cells are not
** added to apCell[] because they are duplicates of child cells.
*/
dropCell(pParent, nxDiv, sz);
}else{
u8 *pTemp;
szCell[nCell] = sz;
pTemp = &aSpace[iSpace];
iSpace += sz;
assert( iSpace<=sizeof(aSpace) );
memcpy(pTemp, apDiv[i], sz);
apCell[nCell] = pTemp+leafCorrection;
dropCell(pParent, nxDiv, sz);
szCell[nCell] -= leafCorrection;
assert( get4byte(pTemp+2)==pgnoOld[i] );
if( !pOld->leaf ){
assert( leafCorrection==0 );
/* The right pointer of the child page pOld becomes the left
** pointer of the divider cell */
memcpy(&apCell[nCell][2], &pOld->aData[pOld->hdrOffset+6], 4);
}else{
assert( leafCorrection==4 );
}
nCell++;
}
}
}
/*
** Figure out the number of pages needed to hold all nCell cells.
** Store this number in "k". Also compute szNew[] which is the total
** size of all cells on the i-th page and cntNew[] which is the index
** in apCell[] of the cell that divides page i from page i+1.
** cntNew[k] should equal nCell.
**
** Values computed by this block:
**
** k: The total number of sibling pages
** szNew[i]: Spaced used on the i-th sibling page.
** cntNew[i]: Index in apCell[] and szCell[] for the first cell to
** the right of the i-th sibling page.
** usableSpace: Number of bytes of space available on each sibling.
**
*/
usableSpace = pBt->usableSize - 10 + leafCorrection;
for(subtotal=k=i=0; i<nCell; i++){
subtotal += szCell[i];
if( subtotal > usableSpace ){
szNew[k] = subtotal - szCell[i];
cntNew[k] = i;
if( leafData ){ i--; }
subtotal = 0;
k++;
}
}
szNew[k] = subtotal;
cntNew[k] = nCell;
k++;
/*
** The packing computed by the previous block is biased toward the siblings
** on the left side. The left siblings are always nearly full, while the
** right-most sibling might be nearly empty. This block of code attempts
** to adjust the packing of siblings to get a better balance.
**
** This adjustment is more than an optimization. The packing above might
** be so out of balance as to be illegal. For example, the right-most
** sibling might be completely empty. This adjustment is not optional.
*/
for(i=k-1; i>0; i--){
int szRight = szNew[i]; /* Size of sibling on the right */
int szLeft = szNew[i-1]; /* Size of sibling on the left */
int r; /* Index of right-most cell in left sibling */
int d; /* Index of first cell to the left of right sibling */
r = cntNew[i-1] - 1;
d = r + 1 - leafData;
while( szRight==0 || szRight+szCell[d]<=szLeft-szCell[r] ){
szRight += szCell[d];
szLeft -= szCell[r];
cntNew[i-1]--;
r = cntNew[i-1] - 1;
d = r + 1 - leafData;
}
szNew[i] = szRight;
szNew[i-1] = szLeft;
}
assert( cntNew[0]>0 );
/*
** Allocate k new pages. Reuse old pages where possible.
*/
assert( pPage->pgno>1 );
pageFlags = pPage->aData[0];
for(i=0; i<k; i++){
MemPage *pNew;
if( i<nOld ){
pNew = apNew[i] = apOld[i];
pgnoNew[i] = pgnoOld[i];
apOld[i] = 0;
sqlite3pager_write(pNew->aData);
}else{
rc = allocatePage(pBt, &pNew, &pgnoNew[i], pgnoNew[i-1]);
if( rc ) goto balance_cleanup;
apNew[i] = pNew;
}
nNew++;
zeroPage(pNew, pageFlags);
}
/* Free any old pages that were not reused as new pages.
*/
while( i<nOld ){
rc = freePage(apOld[i]);
if( rc ) goto balance_cleanup;
releasePage(apOld[i]);
apOld[i] = 0;
i++;
}
/*
** Put the new pages in accending order. This helps to
** keep entries in the disk file in order so that a scan
** of the table is a linear scan through the file. That
** in turn helps the operating system to deliver pages
** from the disk more rapidly.
**
** An O(n^2) insertion sort algorithm is used, but since
** n is never more than NB (a small constant), that should
** not be a problem.
**
** When NB==3, this one optimization makes the database
** about 25% faster for large insertions and deletions.
*/
for(i=0; i<k-1; i++){
int minV = pgnoNew[i];
int minI = i;
for(j=i+1; j<k; j++){
if( pgnoNew[j]<(unsigned)minV ){
minI = j;
minV = pgnoNew[j];
}
}
if( minI>i ){
int t;
MemPage *pT;
t = pgnoNew[i];
pT = apNew[i];
pgnoNew[i] = pgnoNew[minI];
apNew[i] = apNew[minI];
pgnoNew[minI] = t;
apNew[minI] = pT;
}
}
TRACE(("BALANCE: old: %d %d %d new: %d(%d) %d(%d) %d(%d) %d(%d)\n",
pgnoOld[0],
nOld>=2 ? pgnoOld[1] : 0,
nOld>=3 ? pgnoOld[2] : 0,
pgnoNew[0], szNew[0],
nNew>=2 ? pgnoNew[1] : 0, nNew>=2 ? szNew[1] : 0,
nNew>=3 ? pgnoNew[2] : 0, nNew>=3 ? szNew[2] : 0,
nNew>=4 ? pgnoNew[3] : 0, nNew>=4 ? szNew[3] : 0));
/*
** Evenly distribute the data in apCell[] across the new pages.
** Insert divider cells into pParent as necessary.
*/
j = 0;
for(i=0; i<nNew; i++){
MemPage *pNew = apNew[i];
assert( pNew->pgno==pgnoNew[i] );
resizeCellArray(pNew, cntNew[i] - j);
assemblePage(pNew, cntNew[i]-j, &apCell[j], &szCell[j]);
j = cntNew[i];
assert( pNew->nCell>0 );
assert( !pNew->isOverfull );
relinkCellList(pNew);
if( i<nNew-1 && j<nCell ){
u8 *pCell;
u8 *pTemp;
int sz;
pCell = apCell[j];
sz = szCell[j] + leafCorrection;
if( !pNew->leaf ){
memcpy(&pNew->aData[6], pCell+2, 4);
pTemp = 0;
}else if( leafData ){
CellInfo info;
j--;
parseCell(pNew, apCell[j], &info);
pCell = &aSpace[iSpace];
fillInCell(pParent, pCell, 0, info.nKey, 0, 0, &sz);
iSpace += sz;
assert( iSpace<=sizeof(aSpace) );
pTemp = 0;
}else{
pCell -= 4;
pTemp = &aSpace[iSpace];
iSpace += sz;
assert( iSpace<=sizeof(aSpace) );
}
insertCell(pParent, nxDiv, pCell, sz, pTemp);
put4byte(&pParent->aCell[nxDiv][2], pNew->pgno);
j++;
nxDiv++;
}
}
assert( j==nCell );
if( (pageFlags & PTF_LEAF)==0 ){
memcpy(&apNew[nNew-1]->aData[6], &apCopy[nOld-1]->aData[6], 4);
}
if( nxDiv==pParent->nCell ){
/* Right-most sibling is the right-most child of pParent */
put4byte(&pParent->aData[pParent->hdrOffset+6], pgnoNew[nNew-1]);
}else{
/* Right-most sibling is the left child of the first entry in pParent
** past the right-most divider entry */
put4byte(&pParent->aCell[nxDiv][2], pgnoNew[nNew-1]);
}
/*
** Reparent children of all cells.
*/
for(i=0; i<nNew; i++){
reparentChildPages(apNew[i]);
}
reparentChildPages(pParent);
/*
** Balance the parent page. Note that the current page (pPage) might
** have been added to the freelist is it might no longer be initialized.
** But the parent page will always be initialized.
*/
assert( pParent->isInit );
/* assert( pPage->isInit ); // No! pPage might have been added to freelist */
/* pageIntegrity(pPage); // No! pPage might have been added to freelist */
rc = balance(pParent);
/*
** Cleanup before returning.
*/
balance_cleanup:
for(i=0; i<nOld; i++){
releasePage(apOld[i]);
if( apCopy[i] ){
sqliteFree(apCopy[i]->aCell);
}
}
for(i=0; i<nNew; i++){
releasePage(apNew[i]);
}
releasePage(pParent);
releasePage(extraUnref);
TRACE(("BALANCE: finished with %d: old=%d new=%d cells=%d\n",
pPage->pgno, nOld, nNew, nCell));
return rc;
}
/*
** This routine checks all cursors that point to the same table
** as pCur points to. If any of those cursors were opened with
** wrFlag==0 then this routine returns SQLITE_LOCKED. If all
** cursors point to the same table were opened with wrFlag==1
** then this routine returns SQLITE_OK.
**
** In addition to checking for read-locks (where a read-lock
** means a cursor opened with wrFlag==0) this routine also moves
** all cursors other than pCur so that they are pointing to the
** first Cell on root page. This is necessary because an insert
** or delete might change the number of cells on a page or delete
** a page entirely and we do not want to leave any cursors
** pointing to non-existant pages or cells.
*/
static int checkReadLocks(BtCursor *pCur){
BtCursor *p;
assert( pCur->wrFlag );
for(p=pCur->pShared; p!=pCur; p=p->pShared){
assert( p );
assert( p->pgnoRoot==pCur->pgnoRoot );
assert( p->pPage->pgno==sqlite3pager_pagenumber(p->pPage->aData) );
if( p->wrFlag==0 ) return SQLITE_LOCKED;
if( p->pPage->pgno!=p->pgnoRoot ){
moveToRoot(p);
}
}
return SQLITE_OK;
}
/*
** Insert a new record into the BTree. The key is given by (pKey,nKey)
** and the data is given by (pData,nData). The cursor is used only to
** define what table the record should be inserted into. The cursor
** is left pointing at a random location.
**
** For an INTKEY table, only the nKey value of the key is used. pKey is
** ignored. For a ZERODATA table, the pData and nData are both ignored.
*/
int sqlite3BtreeInsert(
BtCursor *pCur, /* Insert data into the table of this cursor */
const void *pKey, i64 nKey, /* The key of the new record */
const void *pData, int nData /* The data of the new record */
){
int rc;
int loc;
int szNew;
MemPage *pPage;
Btree *pBt = pCur->pBt;
unsigned char *oldCell;
unsigned char newCell[MX_CELL_SIZE];
if( pCur->status ){
return pCur->status; /* A rollback destroyed this cursor */
}
if( !pBt->inTrans ){
/* Must start a transaction before doing an insert */
return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}
assert( !pBt->readOnly );
if( !pCur->wrFlag ){
return SQLITE_PERM; /* Cursor not open for writing */
}
if( checkReadLocks(pCur) ){
return SQLITE_LOCKED; /* The table pCur points to has a read lock */
}
rc = sqlite3BtreeMoveto(pCur, pKey, nKey, &loc);
if( rc ) return rc;
pPage = pCur->pPage;
assert( pPage->intKey || nKey>=0 );
assert( pPage->leaf || !pPage->leafData );
TRACE(("INSERT: table=%d nkey=%lld ndata=%d page=%d %s\n",
pCur->pgnoRoot, nKey, nData, pPage->pgno,
loc==0 ? "overwrite" : "new entry"));
assert( pPage->isInit );
rc = sqlite3pager_write(pPage->aData);
if( rc ) return rc;
rc = fillInCell(pPage, newCell, pKey, nKey, pData, nData, &szNew);
if( rc ) return rc;
assert( szNew==cellSize(pPage, newCell) );
assert( szNew<=sizeof(newCell) );
if( loc==0 && pCur->isValid ){
int szOld;
assert( pCur->idx>=0 && pCur->idx<pPage->nCell );
oldCell = pPage->aCell[pCur->idx];
if( !pPage->leaf ){
memcpy(&newCell[2], &oldCell[2], 4);
}
szOld = cellSize(pPage, oldCell);
rc = clearCell(pPage, oldCell);
if( rc ) return rc;
dropCell(pPage, pCur->idx, szOld);
}else if( loc<0 && pPage->nCell>0 ){
assert( pPage->leaf );
pCur->idx++;
pCur->infoValid = 0;
}else{
assert( pPage->leaf );
}
insertCell(pPage, pCur->idx, newCell, szNew, 0);
rc = balance(pPage);
/* sqlite3BtreePageDump(pCur->pBt, pCur->pgnoRoot, 1); */
/* fflush(stdout); */
moveToRoot(pCur);
return rc;
}
/*
** Delete the entry that the cursor is pointing to. The cursor
** is left pointing at a random location.
*/
int sqlite3BtreeDelete(BtCursor *pCur){
MemPage *pPage = pCur->pPage;
unsigned char *pCell;
int rc;
Pgno pgnoChild;
Btree *pBt = pCur->pBt;
assert( pPage->isInit );
if( pCur->status ){
return pCur->status; /* A rollback destroyed this cursor */
}
if( !pBt->inTrans ){
/* Must start a transaction before doing a delete */
return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}
assert( !pBt->readOnly );
if( pCur->idx >= pPage->nCell ){
return SQLITE_ERROR; /* The cursor is not pointing to anything */
}
if( !pCur->wrFlag ){
return SQLITE_PERM; /* Did not open this cursor for writing */
}
if( checkReadLocks(pCur) ){
return SQLITE_LOCKED; /* The table pCur points to has a read lock */
}
rc = sqlite3pager_write(pPage->aData);
if( rc ) return rc;
pCell = pPage->aCell[pCur->idx];
if( !pPage->leaf ){
pgnoChild = get4byte(&pCell[2]);
}
clearCell(pPage, pCell);
if( !pPage->leaf ){
/*
** The entry we are about to delete is not a leaf so if we do not
** do something we will leave a hole on an internal page.
** We have to fill the hole by moving in a cell from a leaf. The
** next Cell after the one to be deleted is guaranteed to exist and
** to be a leaf so we can use it.
*/
BtCursor leafCur;
unsigned char *pNext;
int szNext;
int notUsed;
unsigned char tempCell[MX_CELL_SIZE];
assert( !pPage->leafData );
getTempCursor(pCur, &leafCur);
rc = sqlite3BtreeNext(&leafCur, &notUsed);
if( rc!=SQLITE_OK ){
if( rc!=SQLITE_NOMEM ) rc = SQLITE_CORRUPT;
return rc;
}
rc = sqlite3pager_write(leafCur.pPage->aData);
if( rc ) return rc;
TRACE(("DELETE: table=%d delete internal from %d replace from leaf %d\n",
pCur->pgnoRoot, pPage->pgno, leafCur.pPage->pgno));
dropCell(pPage, pCur->idx, cellSize(pPage, pCell));
pNext = leafCur.pPage->aCell[leafCur.idx];
szNext = cellSize(leafCur.pPage, pNext);
assert( sizeof(tempCell)>=szNext+4 );
insertCell(pPage, pCur->idx, pNext-4, szNext+4, tempCell);
put4byte(pPage->aCell[pCur->idx]+2, pgnoChild);
rc = balance(pPage);
if( rc ) return rc;
dropCell(leafCur.pPage, leafCur.idx, szNext);
rc = balance(leafCur.pPage);
releaseTempCursor(&leafCur);
}else{
TRACE(("DELETE: table=%d delete from leaf %d\n",
pCur->pgnoRoot, pPage->pgno));
dropCell(pPage, pCur->idx, cellSize(pPage, pCell));
rc = balance(pPage);
}
moveToRoot(pCur);
return rc;
}
/*
** Create a new BTree table. Write into *piTable the page
** number for the root page of the new table.
**
** In the current implementation, BTree tables and BTree indices are the
** the same. In the future, we may change this so that BTree tables
** are restricted to having a 4-byte integer key and arbitrary data and
** BTree indices are restricted to having an arbitrary key and no data.
** But for now, this routine also serves to create indices.
*/
int sqlite3BtreeCreateTable(Btree *pBt, int *piTable, int flags){
MemPage *pRoot;
Pgno pgnoRoot;
int rc;
if( !pBt->inTrans ){
/* Must start a transaction first */
return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}
if( pBt->readOnly ){
return SQLITE_READONLY;
}
rc = allocatePage(pBt, &pRoot, &pgnoRoot, 1);
if( rc ) return rc;
assert( sqlite3pager_iswriteable(pRoot->aData) );
zeroPage(pRoot, flags | PTF_LEAF);
sqlite3pager_unref(pRoot->aData);
*piTable = (int)pgnoRoot;
return SQLITE_OK;
}
/*
** Erase the given database page and all its children. Return
** the page to the freelist.
*/
static int clearDatabasePage(
Btree *pBt, /* The BTree that contains the table */
Pgno pgno, /* Page number to clear */
MemPage *pParent, /* Parent page. NULL for the root */
int freePageFlag /* Deallocate page if true */
){
MemPage *pPage;
int rc;
unsigned char *pCell;
int i;
rc = getAndInitPage(pBt, pgno, &pPage, pParent);
if( rc ) return rc;
rc = sqlite3pager_write(pPage->aData);
if( rc ) return rc;
for(i=0; i<pPage->nCell; i++){
pCell = pPage->aCell[i];
if( !pPage->leaf ){
rc = clearDatabasePage(pBt, get4byte(&pCell[2]), pPage->pParent, 1);
if( rc ) return rc;
}
rc = clearCell(pPage, pCell);
if( rc ) return rc;
}
if( !pPage->leaf ){
rc = clearDatabasePage(pBt, get4byte(&pPage->aData[6]), pPage->pParent, 1);
if( rc ) return rc;
}
if( freePageFlag ){
rc = freePage(pPage);
}else{
zeroPage(pPage, pPage->aData[0] | PTF_LEAF);
}
releasePage(pPage);
return rc;
}
/*
** Delete all information from a single table in the database.
*/
int sqlite3BtreeClearTable(Btree *pBt, int iTable){
int rc;
BtCursor *pCur;
if( !pBt->inTrans ){
return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
if( pCur->pgnoRoot==(Pgno)iTable ){
if( pCur->wrFlag==0 ) return SQLITE_LOCKED;
moveToRoot(pCur);
}
}
rc = clearDatabasePage(pBt, (Pgno)iTable, 0, 0);
if( rc ){
sqlite3BtreeRollback(pBt);
}
return rc;
}
/*
** Erase all information in a table and add the root of the table to
** the freelist. Except, the root of the principle table (the one on
** page 2) is never added to the freelist.
*/
int sqlite3BtreeDropTable(Btree *pBt, int iTable){
int rc;
MemPage *pPage;
BtCursor *pCur;
if( !pBt->inTrans ){
return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
if( pCur->pgnoRoot==(Pgno)iTable ){
return SQLITE_LOCKED; /* Cannot drop a table that has a cursor */
}
}
rc = getPage(pBt, (Pgno)iTable, &pPage);
if( rc ) return rc;
rc = sqlite3BtreeClearTable(pBt, iTable);
if( rc ) return rc;
if( iTable>1 ){
rc = freePage(pPage);
}else{
zeroPage(pPage, PTF_INTKEY|PTF_LEAF );
}
releasePage(pPage);
return rc;
}
/*
** Read the meta-information out of a database file. Meta[0]
** is the number of free pages currently in the database. Meta[1]
** through meta[15] are available for use by higher layers. Meta[0]
** is read-only, the others are read/write.
**
** The schema layer numbers meta values differently. At the schema
** layer (and the SetCookie and ReadCookie opcodes) the number of
** free pages is not visible. So Cookie[0] is the same as Meta[1].
*/
int sqlite3BtreeGetMeta(Btree *pBt, int idx, u32 *pMeta){
int rc;
unsigned char *pP1;
assert( idx>=0 && idx<=15 );
rc = sqlite3pager_get(pBt->pPager, 1, (void**)&pP1);
if( rc ) return rc;
*pMeta = get4byte(&pP1[36 + idx*4]);
sqlite3pager_unref(pP1);
return SQLITE_OK;
}
/*
** Write meta-information back into the database. Meta[0] is
** read-only and may not be written.
*/
int sqlite3BtreeUpdateMeta(Btree *pBt, int idx, u32 iMeta){
unsigned char *pP1;
int rc;
assert( idx>=1 && idx<=15 );
if( !pBt->inTrans ){
return pBt->readOnly ? SQLITE_READONLY : SQLITE_ERROR;
}
assert( pBt->pPage1!=0 );
pP1 = pBt->pPage1->aData;
rc = sqlite3pager_write(pP1);
if( rc ) return rc;
put4byte(&pP1[36 + idx*4], iMeta);
return SQLITE_OK;
}
/*
** Return the flag byte at the beginning of the page that the cursor
** is currently pointing to.
*/
int sqlite3BtreeFlags(BtCursor *pCur){
MemPage *pPage = pCur->pPage;
return pPage ? pPage->aData[pPage->hdrOffset] : 0;
}
/******************************************************************************
** The complete implementation of the BTree subsystem is above this line.
** All the code the follows is for testing and troubleshooting the BTree
** subsystem. None of the code that follows is used during normal operation.
******************************************************************************/
/*
** Print a disassembly of the given page on standard output. This routine
** is used for debugging and testing only.
*/
#ifdef SQLITE_TEST
int sqlite3BtreePageDump(Btree *pBt, int pgno, int recursive){
int rc;
MemPage *pPage;
int i, j, c;
int nFree;
u16 idx;
int hdr;
unsigned char *data;
char range[20];
unsigned char payload[20];
rc = getPage(pBt, (Pgno)pgno, &pPage);
if( rc ){
return rc;
}
hdr = pPage->hdrOffset;
data = pPage->aData;
c = data[hdr];
pPage->intKey = (c & (PTF_INTKEY|PTF_LEAFDATA))!=0;
pPage->zeroData = (c & PTF_ZERODATA)!=0;
pPage->leafData = (c & PTF_LEAFDATA)!=0;
pPage->leaf = (c & PTF_LEAF)!=0;
pPage->hasData = !(pPage->zeroData || (!pPage->leaf && pPage->leafData));
printf("PAGE %d: flags=0x%02x frag=%d parent=%d\n", pgno,
data[hdr], data[hdr+5],
(pPage->isInit && pPage->pParent) ? pPage->pParent->pgno : 0);
i = 0;
assert( hdr == (pgno==1 ? 100 : 0) );
idx = get2byte(&data[hdr+3]);
while( idx>0 && idx<=pBt->usableSize ){
CellInfo info;
Pgno child;
unsigned char *pCell = &data[idx];
int sz;
pCell = &data[idx];
parseCell(pPage, pCell, &info);
sz = info.nSize;
sprintf(range,"%d..%d", idx, idx+sz-1);
if( pPage->leaf ){
child = 0;
}else{
child = get4byte(&pCell[2]);
}
sz = info.nData;
if( !pPage->intKey ) sz += info.nKey;
if( sz>sizeof(payload)-1 ) sz = sizeof(payload)-1;
memcpy(payload, &pCell[info.nHeader], sz);
for(j=0; j<sz; j++){
if( payload[j]<0x20 || payload[j]>0x7f ) payload[j] = '.';
}
payload[sz] = 0;
printf(
"cell %2d: i=%-10s chld=%-4d nk=%-4lld nd=%-4d payload=%s\n",
i, range, child, info.nKey, info.nData, payload
);
if( pPage->isInit && pPage->aCell[i]!=pCell ){
printf("**** aCell[%d] does not match on prior entry ****\n", i);
}
i++;
idx = get2byte(pCell);
}
if( idx!=0 ){
printf("ERROR: next cell index out of range: %d\n", idx);
}
if( !pPage->leaf ){
printf("right_child: %d\n", get4byte(&data[hdr+6]));
}
nFree = 0;
i = 0;
idx = get2byte(&data[hdr+1]);
while( idx>0 && idx<pPage->pBt->usableSize ){
int sz = get2byte(&data[idx+2]);
sprintf(range,"%d..%d", idx, idx+sz-1);
nFree += sz;
printf("freeblock %2d: i=%-10s size=%-4d total=%d\n",
i, range, sz, nFree);
idx = get2byte(&data[idx]);
i++;
}
if( idx!=0 ){
printf("ERROR: next freeblock index out of range: %d\n", idx);
}
if( recursive && !pPage->leaf ){
idx = get2byte(&data[hdr+3]);
while( idx>0 && idx<pBt->usableSize ){
unsigned char *pCell = &data[idx];
sqlite3BtreePageDump(pBt, get4byte(&pCell[2]), 1);
idx = get2byte(pCell);
}
sqlite3BtreePageDump(pBt, get4byte(&data[hdr+6]), 1);
}
sqlite3pager_unref(data);
fflush(stdout);
return SQLITE_OK;
}
#endif
#ifdef SQLITE_TEST
/*
** Fill aResult[] with information about the entry and page that the
** cursor is pointing to.
**
** aResult[0] = The page number
** aResult[1] = The entry number
** aResult[2] = Total number of entries on this page
** aResult[3] = Size of this entry
** aResult[4] = Number of free bytes on this page
** aResult[5] = Number of free blocks on the page
** aResult[6] = Page number of the left child of this entry
** aResult[7] = Page number of the right child for the whole page
**
** This routine is used for testing and debugging only.
*/
int sqlite3BtreeCursorInfo(BtCursor *pCur, int *aResult){
int cnt, idx;
MemPage *pPage = pCur->pPage;
pageIntegrity(pPage);
assert( pPage->isInit );
aResult[0] = sqlite3pager_pagenumber(pPage->aData);
assert( aResult[0]==pPage->pgno );
aResult[1] = pCur->idx;
aResult[2] = pPage->nCell;
if( pCur->idx>=0 && pCur->idx<pPage->nCell ){
aResult[3] = cellSize(pPage, pPage->aCell[pCur->idx]);
aResult[6] = pPage->leaf ? 0 : get4byte(&pPage->aCell[pCur->idx][2]);
}else{
aResult[3] = 0;
aResult[6] = 0;
}
aResult[4] = pPage->nFree;
cnt = 0;
idx = get2byte(&pPage->aData[pPage->hdrOffset+1]);
while( idx>0 && idx<pPage->pBt->usableSize ){
cnt++;
idx = get2byte(&pPage->aData[idx]);
}
aResult[5] = cnt;
aResult[7] = pPage->leaf ? 0 : get4byte(&pPage->aData[pPage->hdrOffset+6]);
return SQLITE_OK;
}
#endif
/*
** Return the pager associated with a BTree. This routine is used for
** testing and debugging only.
*/
Pager *sqlite3BtreePager(Btree *pBt){
return pBt->pPager;
}
/*
** This structure is passed around through all the sanity checking routines
** in order to keep track of some global state information.
*/
typedef struct IntegrityCk IntegrityCk;
struct IntegrityCk {
Btree *pBt; /* The tree being checked out */
Pager *pPager; /* The associated pager. Also accessible by pBt->pPager */
int nPage; /* Number of pages in the database */
int *anRef; /* Number of times each page is referenced */
char *zErrMsg; /* An error message. NULL of no errors seen. */
};
/*
** Append a message to the error message string.
*/
static void checkAppendMsg(IntegrityCk *pCheck, char *zMsg1, char *zMsg2){
if( pCheck->zErrMsg ){
char *zOld = pCheck->zErrMsg;
pCheck->zErrMsg = 0;
sqlite3SetString(&pCheck->zErrMsg, zOld, "\n", zMsg1, zMsg2, (char*)0);
sqliteFree(zOld);
}else{
sqlite3SetString(&pCheck->zErrMsg, zMsg1, zMsg2, (char*)0);
}
}
/*
** Add 1 to the reference count for page iPage. If this is the second
** reference to the page, add an error message to pCheck->zErrMsg.
** Return 1 if there are 2 ore more references to the page and 0 if
** if this is the first reference to the page.
**
** Also check that the page number is in bounds.
*/
static int checkRef(IntegrityCk *pCheck, int iPage, char *zContext){
if( iPage==0 ) return 1;
if( iPage>pCheck->nPage || iPage<0 ){
char zBuf[100];
sprintf(zBuf, "invalid page number %d", iPage);
checkAppendMsg(pCheck, zContext, zBuf);
return 1;
}
if( pCheck->anRef[iPage]==1 ){
char zBuf[100];
sprintf(zBuf, "2nd reference to page %d", iPage);
checkAppendMsg(pCheck, zContext, zBuf);
return 1;
}
return (pCheck->anRef[iPage]++)>1;
}
/*
** Check the integrity of the freelist or of an overflow page list.
** Verify that the number of pages on the list is N.
*/
static void checkList(
IntegrityCk *pCheck, /* Integrity checking context */
int isFreeList, /* True for a freelist. False for overflow page list */
int iPage, /* Page number for first page in the list */
int N, /* Expected number of pages in the list */
char *zContext /* Context for error messages */
){
int i;
int expected = N;
int iFirst = iPage;
char zMsg[100];
while( N-- > 0 ){
unsigned char *pOvfl;
if( iPage<1 ){
sprintf(zMsg, "%d of %d pages missing from overflow list starting at %d",
N+1, expected, iFirst);
checkAppendMsg(pCheck, zContext, zMsg);
break;
}
if( checkRef(pCheck, iPage, zContext) ) break;
if( sqlite3pager_get(pCheck->pPager, (Pgno)iPage, (void**)&pOvfl) ){
sprintf(zMsg, "failed to get page %d", iPage);
checkAppendMsg(pCheck, zContext, zMsg);
break;
}
if( isFreeList ){
int n = get4byte(&pOvfl[4]);
for(i=0; i<n; i++){
checkRef(pCheck, get4byte(&pOvfl[8+i*4]), zContext);
}
N -= n;
}
iPage = get4byte(pOvfl);
sqlite3pager_unref(pOvfl);
}
}
/*
** Do various sanity checks on a single page of a tree. Return
** the tree depth. Root pages return 0. Parents of root pages
** return 1, and so forth.
**
** These checks are done:
**
** 1. Make sure that cells and freeblocks do not overlap
** but combine to completely cover the page.
** NO 2. Make sure cell keys are in order.
** NO 3. Make sure no key is less than or equal to zLowerBound.
** NO 4. Make sure no key is greater than or equal to zUpperBound.
** 5. Check the integrity of overflow pages.
** 6. Recursively call checkTreePage on all children.
** 7. Verify that the depth of all children is the same.
** 8. Make sure this page is at least 33% full or else it is
** the root of the tree.
*/
static int checkTreePage(
IntegrityCk *pCheck, /* Context for the sanity check */
int iPage, /* Page number of the page to check */
MemPage *pParent, /* Parent page */
char *zParentContext, /* Parent context */
char *zLowerBound, /* All keys should be greater than this, if not NULL */
int nLower, /* Number of characters in zLowerBound */
char *zUpperBound, /* All keys should be less than this, if not NULL */
int nUpper /* Number of characters in zUpperBound */
){
MemPage *pPage;
int i, rc, depth, d2, pgno, cnt;
int hdr;
u8 *data;
BtCursor cur;
Btree *pBt;
int maxLocal, usableSize;
char zMsg[100];
char zContext[100];
char hit[MX_PAGE_SIZE];
/* Check that the page exists
*/
cur.pBt = pBt = pCheck->pBt;
usableSize = pBt->usableSize;
if( iPage==0 ) return 0;
if( checkRef(pCheck, iPage, zParentContext) ) return 0;
if( (rc = getPage(pBt, (Pgno)iPage, &pPage))!=0 ){
sprintf(zMsg, "unable to get the page. error code=%d", rc);
checkAppendMsg(pCheck, zContext, zMsg);
return 0;
}
maxLocal = pPage->leafData ? pBt->maxLeaf : pBt->maxLocal;
if( (rc = initPage(pPage, pParent))!=0 ){
sprintf(zMsg, "initPage() returns error code %d", rc);
checkAppendMsg(pCheck, zContext, zMsg);
releasePage(pPage);
return 0;
}
/* Check out all the cells.
*/
depth = 0;
cur.pPage = pPage;
for(i=0; i<pPage->nCell; i++){
u8 *pCell;
int sz;
CellInfo info;
/* Check payload overflow pages
*/
sprintf(zContext, "On tree page %d cell %d: ", iPage, i);
pCell = pPage->aCell[i];
parseCell(pPage, pCell, &info);
sz = info.nData;
if( !pPage->intKey ) sz += info.nKey;
if( sz>info.nLocal ){
int nPage = (sz - info.nLocal + usableSize - 5)/(usableSize - 4);
checkList(pCheck, 0, get4byte(&pCell[info.iOverflow]),nPage,zContext);
}
/* Check sanity of left child page.
*/
if( !pPage->leaf ){
pgno = get4byte(&pCell[2]);
d2 = checkTreePage(pCheck,pgno,pPage,zContext,0,0,0,0);
if( i>0 && d2!=depth ){
checkAppendMsg(pCheck, zContext, "Child page depth differs");
}
depth = d2;
}
}
if( !pPage->leaf ){
pgno = get4byte(&pPage->aData[pPage->hdrOffset+6]);
sprintf(zContext, "On page %d at right child: ", iPage);
checkTreePage(pCheck, pgno, pPage, zContext,0,0,0,0);
}
/* Check for complete coverage of the page
*/
memset(hit, 0, usableSize);
memset(hit, 1, pPage->hdrOffset+10-4*(pPage->leaf));
data = pPage->aData;
hdr = pPage->hdrOffset;
for(cnt=0, i=get2byte(&data[hdr+3]); i>0 && i<usableSize && cnt<10000; cnt++){
int size = cellSize(pPage, &data[i]);
int j;
for(j=i+size-1; j>=i; j--) hit[j]++;
i = get2byte(&data[i]);
}
for(cnt=0, i=get2byte(&data[hdr+1]); i>0 && i<usableSize && cnt<10000; cnt++){
int size = get2byte(&data[i+2]);
int j;
for(j=i+size-1; j>=i; j--) hit[j]++;
i = get2byte(&data[i]);
}
for(i=cnt=0; i<usableSize; i++){
if( hit[i]==0 ){
cnt++;
}else if( hit[i]>1 ){
sprintf(zMsg, "Multiple uses for byte %d of page %d", i, iPage);
checkAppendMsg(pCheck, zMsg, 0);
break;
}
}
if( cnt!=data[hdr+5] ){
sprintf(zMsg, "Fragmented space is %d byte reported as %d on page %d",
cnt, data[hdr+5], iPage);
checkAppendMsg(pCheck, zMsg, 0);
}
releasePage(pPage);
return depth+1;
}
/*
** This routine does a complete check of the given BTree file. aRoot[] is
** an array of pages numbers were each page number is the root page of
** a table. nRoot is the number of entries in aRoot.
**
** If everything checks out, this routine returns NULL. If something is
** amiss, an error message is written into memory obtained from malloc()
** and a pointer to that error message is returned. The calling function
** is responsible for freeing the error message when it is done.
*/
char *sqlite3BtreeIntegrityCheck(Btree *pBt, int *aRoot, int nRoot){
int i;
int nRef;
IntegrityCk sCheck;
nRef = *sqlite3pager_stats(pBt->pPager);
if( lockBtree(pBt)!=SQLITE_OK ){
return sqliteStrDup("Unable to acquire a read lock on the database");
}
sCheck.pBt = pBt;
sCheck.pPager = pBt->pPager;
sCheck.nPage = sqlite3pager_pagecount(sCheck.pPager);
if( sCheck.nPage==0 ){
unlockBtreeIfUnused(pBt);
return 0;
}
sCheck.anRef = sqliteMallocRaw( (sCheck.nPage+1)*sizeof(sCheck.anRef[0]) );
for(i=0; i<=sCheck.nPage; i++){ sCheck.anRef[i] = 0; }
sCheck.zErrMsg = 0;
/* Check the integrity of the freelist
*/
checkList(&sCheck, 1, get4byte(&pBt->pPage1->aData[32]),
get4byte(&pBt->pPage1->aData[36]), "Main freelist: ");
/* Check all the tables.
*/
for(i=0; i<nRoot; i++){
if( aRoot[i]==0 ) continue;
checkTreePage(&sCheck, aRoot[i], 0, "List of tree roots: ", 0,0,0,0);
}
/* Make sure every page in the file is referenced
*/
for(i=1; i<=sCheck.nPage; i++){
if( sCheck.anRef[i]==0 ){
char zBuf[100];
sprintf(zBuf, "Page %d is never used", i);
checkAppendMsg(&sCheck, zBuf, 0);
}
}
/* Make sure this analysis did not leave any unref() pages
*/
unlockBtreeIfUnused(pBt);
if( nRef != *sqlite3pager_stats(pBt->pPager) ){
char zBuf[100];
sprintf(zBuf,
"Outstanding page count goes from %d to %d during this analysis",
nRef, *sqlite3pager_stats(pBt->pPager)
);
checkAppendMsg(&sCheck, zBuf, 0);
}
/* Clean up and report errors.
*/
sqliteFree(sCheck.anRef);
return sCheck.zErrMsg;
}
/*
** Return the full pathname of the underlying database file.
*/
const char *sqlite3BtreeGetFilename(Btree *pBt){
assert( pBt->pPager!=0 );
return sqlite3pager_filename(pBt->pPager);
}
/*
** Copy the complete content of pBtFrom into pBtTo. A transaction
** must be active for both files.
**
** The size of file pBtFrom may be reduced by this operation.
** If anything goes wrong, the transaction on pBtFrom is rolled back.
*/
int sqlite3BtreeCopyFile(Btree *pBtTo, Btree *pBtFrom){
int rc = SQLITE_OK;
Pgno i, nPage, nToPage;
if( !pBtTo->inTrans || !pBtFrom->inTrans ) return SQLITE_ERROR;
if( pBtTo->pCursor ) return SQLITE_BUSY;
memcpy(pBtTo->pPage1->aData, pBtFrom->pPage1->aData, pBtFrom->usableSize);
rc = sqlite3pager_overwrite(pBtTo->pPager, 1, pBtFrom->pPage1->aData);
nToPage = sqlite3pager_pagecount(pBtTo->pPager);
nPage = sqlite3pager_pagecount(pBtFrom->pPager);
for(i=2; rc==SQLITE_OK && i<=nPage; i++){
void *pPage;
rc = sqlite3pager_get(pBtFrom->pPager, i, &pPage);
if( rc ) break;
rc = sqlite3pager_overwrite(pBtTo->pPager, i, pPage);
if( rc ) break;
sqlite3pager_unref(pPage);
}
for(i=nPage+1; rc==SQLITE_OK && i<=nToPage; i++){
void *pPage;
rc = sqlite3pager_get(pBtTo->pPager, i, &pPage);
if( rc ) break;
rc = sqlite3pager_write(pPage);
sqlite3pager_unref(pPage);
sqlite3pager_dont_write(pBtTo->pPager, i);
}
if( !rc && nPage<nToPage ){
rc = sqlite3pager_truncate(pBtTo->pPager, nPage);
}
if( rc ){
sqlite3BtreeRollback(pBtTo);
}
return rc;
}
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