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Merge the recent performance enhancements implemented on trunk into the

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threads branch.

FossilOrigin-Name: dfdc900f5d1a31ee5c5f35a630c4a8253e69093b
This commit is contained in:
drh
2014-08-25 13:27:02 +00:00
parent 8d09dfe8f3 c137807a87
commit 4d015c6902
55 changed files with 1252 additions and 874 deletions
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267
src/btree.c
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@@ -629,16 +629,42 @@ static int saveCursorPosition(BtCursor *pCur){
return rc;
}
/* Forward reference */
static int SQLITE_NOINLINE saveCursorsOnList(BtCursor*,Pgno,BtCursor*);
/*
** Save the positions of all cursors (except pExcept) that are open on
** the table with root-page iRoot. Usually, this is called just before cursor
** pExcept is used to modify the table (BtreeDelete() or BtreeInsert()).
** the table with root-page iRoot. "Saving the cursor position" means that
** the location in the btree is remembered in such a way that it can be
** moved back to the same spot after the btree has been modified. This
** routine is called just before cursor pExcept is used to modify the
** table, for example in BtreeDelete() or BtreeInsert().
**
** Implementation note: This routine merely checks to see if any cursors
** need to be saved. It calls out to saveCursorsOnList() in the (unusual)
** event that cursors are in need to being saved.
*/
static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){
BtCursor *p;
assert( sqlite3_mutex_held(pBt->mutex) );
assert( pExcept==0 || pExcept->pBt==pBt );
for(p=pBt->pCursor; p; p=p->pNext){
if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) ) break;
}
return p ? saveCursorsOnList(p, iRoot, pExcept) : SQLITE_OK;
}
/* This helper routine to saveAllCursors does the actual work of saving
** the cursors if and when a cursor is found that actually requires saving.
** The common case is that no cursors need to be saved, so this routine is
** broken out from its caller to avoid unnecessary stack pointer movement.
*/
static int SQLITE_NOINLINE saveCursorsOnList(
BtCursor *p, /* The first cursor that needs saving */
Pgno iRoot, /* Only save cursor with this iRoot. Save all if zero */
BtCursor *pExcept /* Do not save this cursor */
){
do{
if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) ){
if( p->eState==CURSOR_VALID ){
int rc = saveCursorPosition(p);
@@ -650,7 +676,8 @@ static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){
btreeReleaseAllCursorPages(p);
}
}
}
p = p->pNext;
}while( p );
return SQLITE_OK;
}
@@ -735,37 +762,48 @@ static int btreeRestoreCursorPosition(BtCursor *pCur){
SQLITE_OK)
/*
** Determine whether or not a cursor has moved from the position it
** was last placed at. Cursors can move when the row they are pointing
** at is deleted out from under them.
** Determine whether or not a cursor has moved from the position where
** it was last placed, or has been invalidated for any other reason.
** Cursors can move when the row they are pointing at is deleted out
** from under them, for example. Cursor might also move if a btree
** is rebalanced.
**
** This routine returns an error code if something goes wrong. The
** integer *pHasMoved is set as follows:
** Calling this routine with a NULL cursor pointer returns false.
**
** 0: The cursor is unchanged
** 1: The cursor is still pointing at the same row, but the pointers
** returned by sqlite3BtreeKeyFetch() or sqlite3BtreeDataFetch()
** might now be invalid because of a balance() or other change to the
** b-tree.
** 2: The cursor is no longer pointing to the row. The row might have
** been deleted out from under the cursor.
** Use the separate sqlite3BtreeCursorRestore() routine to restore a cursor
** back to where it ought to be if this routine returns true.
*/
int sqlite3BtreeCursorHasMoved(BtCursor *pCur, int *pHasMoved){
int sqlite3BtreeCursorHasMoved(BtCursor *pCur){
return pCur && pCur->eState!=CURSOR_VALID;
}
/*
** This routine restores a cursor back to its original position after it
** has been moved by some outside activity (such as a btree rebalance or
** a row having been deleted out from under the cursor).
**
** On success, the *pDifferentRow parameter is false if the cursor is left
** pointing at exactly the same row. *pDifferntRow is the row the cursor
** was pointing to has been deleted, forcing the cursor to point to some
** nearby row.
**
** This routine should only be called for a cursor that just returned
** TRUE from sqlite3BtreeCursorHasMoved().
*/
int sqlite3BtreeCursorRestore(BtCursor *pCur, int *pDifferentRow){
int rc;
if( pCur->eState==CURSOR_VALID ){
*pHasMoved = 0;
return SQLITE_OK;
}
assert( pCur!=0 );
assert( pCur->eState!=CURSOR_VALID );
rc = restoreCursorPosition(pCur);
if( rc ){
*pHasMoved = 2;
*pDifferentRow = 1;
return rc;
}
if( pCur->eState!=CURSOR_VALID || NEVER(pCur->skipNext!=0) ){
*pHasMoved = 2;
*pDifferentRow = 1;
}else{
*pHasMoved = 1;
*pDifferentRow = 0;
}
return SQLITE_OK;
}
@@ -1197,7 +1235,6 @@ static int defragmentPage(MemPage *pPage){
static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
const int hdr = pPage->hdrOffset; /* Local cache of pPage->hdrOffset */
u8 * const data = pPage->aData; /* Local cache of pPage->aData */
int nFrag; /* Number of fragmented bytes on pPage */
int top; /* First byte of cell content area */
int gap; /* First byte of gap between cell pointers and cell content */
int rc; /* Integer return code */
@@ -1212,25 +1249,26 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
usableSize = pPage->pBt->usableSize;
assert( nByte < usableSize-8 );
nFrag = data[hdr+7];
assert( pPage->cellOffset == hdr + 12 - 4*pPage->leaf );
gap = pPage->cellOffset + 2*pPage->nCell;
top = get2byteNotZero(&data[hdr+5]);
if( gap>top ) return SQLITE_CORRUPT_BKPT;
assert( gap<=65536 );
top = get2byte(&data[hdr+5]);
if( gap>top ){
if( top==0 ){
top = 65536;
}else{
return SQLITE_CORRUPT_BKPT;
}
}
/* If there is enough space between gap and top for one more cell pointer
** array entry offset, and if the freelist is not empty, then search the
** freelist looking for a free slot big enough to satisfy the request.
*/
testcase( gap+2==top );
testcase( gap+1==top );
testcase( gap==top );
if( nFrag>=60 ){
/* Always defragment highly fragmented pages */
rc = defragmentPage(pPage);
if( rc ) return rc;
top = get2byteNotZero(&data[hdr+5]);
}else if( gap+2<=top ){
/* Search the freelist looking for a free slot big enough to satisfy
** the request. The allocation is made from the first free slot in
** the list that is large enough to accommodate it.
*/
if( gap+2<=top && (data[hdr+1] || data[hdr+2]) ){
int pc, addr;
for(addr=hdr+1; (pc = get2byte(&data[addr]))>0; addr=pc){
int size; /* Size of the free slot */
@@ -1243,10 +1281,11 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
testcase( x==4 );
testcase( x==3 );
if( x<4 ){
if( data[hdr+7]>=60 ) goto defragment_page;
/* Remove the slot from the free-list. Update the number of
** fragmented bytes within the page. */
memcpy(&data[addr], &data[pc], 2);
data[hdr+7] = (u8)(nFrag + x);
data[hdr+7] += (u8)x;
}else if( size+pc > usableSize ){
return SQLITE_CORRUPT_BKPT;
}else{
@@ -1260,11 +1299,13 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
}
}
/* Check to make sure there is enough space in the gap to satisfy
** the allocation. If not, defragment.
/* The request could not be fulfilled using a freelist slot. Check
** to see if defragmentation is necessary.
*/
testcase( gap+2+nByte==top );
if( gap+2+nByte>top ){
defragment_page:
testcase( pPage->nCell==0 );
rc = defragmentPage(pPage);
if( rc ) return rc;
top = get2byteNotZero(&data[hdr+5]);
@@ -1287,90 +1328,100 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
/*
** 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.
** The first byte of the new free block is pPage->aData[iStart]
** and the size of the block is iSize bytes.
**
** Most of the effort here is involved in coalesing adjacent
** free blocks into a single big free block.
** Adjacent freeblocks are coalesced.
**
** Note that even though the freeblock list was checked by btreeInitPage(),
** that routine will not detect overlap between cells or freeblocks. Nor
** does it detect cells or freeblocks that encrouch into the reserved bytes
** at the end of the page. So do additional corruption checks inside this
** routine and return SQLITE_CORRUPT if any problems are found.
*/
static int freeSpace(MemPage *pPage, int start, int size){
int addr, pbegin, hdr;
int iLast; /* Largest possible freeblock offset */
unsigned char *data = pPage->aData;
static int freeSpace(MemPage *pPage, u16 iStart, u16 iSize){
u16 iPtr; /* Address of pointer to next freeblock */
u16 iFreeBlk; /* Address of the next freeblock */
u8 hdr; /* Page header size. 0 or 100 */
u8 nFrag = 0; /* Reduction in fragmentation */
u16 iOrigSize = iSize; /* Original value of iSize */
u32 iLast = pPage->pBt->usableSize-4; /* Largest possible freeblock offset */
u32 iEnd = iStart + iSize; /* First byte past the iStart buffer */
unsigned char *data = pPage->aData; /* Page content */
assert( pPage->pBt!=0 );
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
assert( start>=pPage->hdrOffset+6+pPage->childPtrSize );
assert( (start + size) <= (int)pPage->pBt->usableSize );
assert( iStart>=pPage->hdrOffset+6+pPage->childPtrSize );
assert( iEnd <= pPage->pBt->usableSize );
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
assert( size>=0 ); /* Minimum cell size is 4 */
assert( iSize>=4 ); /* Minimum cell size is 4 */
assert( iStart<=iLast );
/* Overwrite deleted information with zeros when the secure_delete
** option is enabled */
if( pPage->pBt->btsFlags & BTS_SECURE_DELETE ){
/* Overwrite deleted information with zeros when the secure_delete
** option is enabled */
memset(&data[start], 0, size);
memset(&data[iStart], 0, iSize);
}
/* Add the space back into the linked list of freeblocks. Note that
** even though the freeblock list was checked by btreeInitPage(),
** btreeInitPage() did not detect overlapping cells or
** freeblocks that overlapped cells. Nor does it detect when the
** cell content area exceeds the value in the page header. If these
** situations arise, then subsequent insert operations might corrupt
** the freelist. So we do need to check for corruption while scanning
** the freelist.
/* The list of freeblocks must be in ascending order. Find the
** spot on the list where iStart should be inserted.
*/
hdr = pPage->hdrOffset;
addr = hdr + 1;
iLast = pPage->pBt->usableSize - 4;
assert( start<=iLast );
while( (pbegin = get2byte(&data[addr]))<start && pbegin>0 ){
if( pbegin<addr+4 ){
return SQLITE_CORRUPT_BKPT;
iPtr = hdr + 1;
if( data[iPtr+1]==0 && data[iPtr]==0 ){
iFreeBlk = 0; /* Shortcut for the case when the freelist is empty */
}else{
while( (iFreeBlk = get2byte(&data[iPtr]))>0 && iFreeBlk<iStart ){
if( iFreeBlk<iPtr+4 ) return SQLITE_CORRUPT_BKPT;
iPtr = iFreeBlk;
}
addr = pbegin;
}
if( pbegin>iLast ){
return SQLITE_CORRUPT_BKPT;
}
assert( pbegin>addr || pbegin==0 );
put2byte(&data[addr], start);
put2byte(&data[start], pbegin);
put2byte(&data[start+2], size);
pPage->nFree = pPage->nFree + (u16)size;
/* Coalesce adjacent free blocks */
addr = hdr + 1;
while( (pbegin = get2byte(&data[addr]))>0 ){
int pnext, psize, x;
assert( pbegin>addr );
assert( pbegin <= (int)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);
if( (frag<0) || (frag>(int)data[hdr+7]) ){
return SQLITE_CORRUPT_BKPT;
if( iFreeBlk>iLast ) return SQLITE_CORRUPT_BKPT;
assert( iFreeBlk>iPtr || iFreeBlk==0 );
/* At this point:
** iFreeBlk: First freeblock after iStart, or zero if none
** iPtr: The address of a pointer iFreeBlk
**
** Check to see if iFreeBlk should be coalesced onto the end of iStart.
*/
if( iFreeBlk && iEnd+3>=iFreeBlk ){
nFrag = iFreeBlk - iEnd;
if( iEnd>iFreeBlk ) return SQLITE_CORRUPT_BKPT;
iEnd = iFreeBlk + get2byte(&data[iFreeBlk+2]);
iSize = iEnd - iStart;
iFreeBlk = get2byte(&data[iFreeBlk]);
}
/* If iPtr is another freeblock (that is, if iPtr is not the freelist pointer
** in the page header) then check to see if iStart should be coalesced
** onto the end of iPtr.
*/
if( iPtr>hdr+1 ){
int iPtrEnd = iPtr + get2byte(&data[iPtr+2]);
if( iPtrEnd+3>=iStart ){
if( iPtrEnd>iStart ) return SQLITE_CORRUPT_BKPT;
nFrag += iStart - iPtrEnd;
iSize = iEnd - iPtr;
iStart = iPtr;
}
data[hdr+7] -= (u8)frag;
x = get2byte(&data[pnext]);
put2byte(&data[pbegin], x);
x = pnext + get2byte(&data[pnext+2]) - pbegin;
put2byte(&data[pbegin+2], x);
}else{
addr = pbegin;
}
if( nFrag>data[hdr+7] ) return SQLITE_CORRUPT_BKPT;
data[hdr+7] -= nFrag;
}
/* If the cell content area begins with a freeblock, remove it. */
if( data[hdr+1]==data[hdr+5] && data[hdr+2]==data[hdr+6] ){
int top;
pbegin = get2byte(&data[hdr+1]);
memcpy(&data[hdr+1], &data[pbegin], 2);
top = get2byte(&data[hdr+5]) + get2byte(&data[pbegin+2]);
put2byte(&data[hdr+5], top);
if( iStart==get2byte(&data[hdr+5]) ){
/* The new freeblock is at the beginning of the cell content area,
** so just extend the cell content area rather than create another
** freelist entry */
if( iPtr!=hdr+1 ) return SQLITE_CORRUPT_BKPT;
put2byte(&data[hdr+1], iFreeBlk);
put2byte(&data[hdr+5], iEnd);
}else{
/* Insert the new freeblock into the freelist */
put2byte(&data[iPtr], iStart);
put2byte(&data[iStart], iFreeBlk);
put2byte(&data[iStart+2], iSize);
}
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
pPage->nFree += iOrigSize;
return SQLITE_OK;
}