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Back out changes allowing writes to tables that have open cursors. (CVS 2133)

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FossilOrigin-Name: 91acd87e52509a8f78894d0f4b625b54376cac21
This commit is contained in:
danielk1977
2004-11-22 10:02:10 +00:00
parent 0fa8ddbdec
commit 299b187d76
8 changed files with 148 additions and 375 deletions
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370
src/btree.c
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@@ -9,7 +9,7 @@
** May you share freely, never taking more than you give.
**
*************************************************************************
** $Id: btree.c,v 1.222 2004/11/22 05:26:27 danielk1977 Exp $
** $Id: btree.c,v 1.223 2004/11/22 10:02:10 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
@@ -344,16 +344,6 @@ struct CellInfo {
** 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.
**
** Normally, the BtCursor.delShift variable is 0. If non-zero, this
** indicates that the entry to which the cursor logically points
** was deleted (by a BtreeDelete() call). If this is the case, the
** BtreeKeySize() and BtreeDataSize() calls both return 0.
** If BtCursor.delShift is +1, then do not move the cursor for a
** BtreeNext() operation (it was already advanced when the entry the
** cursor logically points to was deleted). If BtCursor.delShift is
** -1, then ignore the next BtreePrevious() call.
*/
struct BtCursor {
Btree *pBt; /* The Btree to which this cursor belongs */
@@ -367,7 +357,6 @@ struct BtCursor {
u8 wrFlag; /* True if writable */
u8 isValid; /* TRUE if points to a valid entry */
u8 status; /* Set to SQLITE_ABORT if cursors is invalidated */
int delShift; /* See above. */
};
/*
@@ -2125,7 +2114,6 @@ int sqlite3BtreeCursor(
pBt->pCursor = pCur;
pCur->isValid = 0;
pCur->status = SQLITE_OK;
pCur->delShift = 0;
*ppCur = pCur;
return SQLITE_OK;
@@ -2224,7 +2212,7 @@ static void getCellInfo(BtCursor *pCur){
** itself, not the number of bytes in the key.
*/
int sqlite3BtreeKeySize(BtCursor *pCur, i64 *pSize){
if( !pCur->isValid || pCur->delShift ){
if( !pCur->isValid ){
*pSize = 0;
}else{
getCellInfo(pCur);
@@ -2241,7 +2229,7 @@ int sqlite3BtreeKeySize(BtCursor *pCur, i64 *pSize){
** the database is empty) then *pSize is set to 0.
*/
int sqlite3BtreeDataSize(BtCursor *pCur, u32 *pSize){
if( !pCur->isValid || pCur->delShift ){
if( !pCur->isValid ){
/* Not pointing at a valid entry - set *pSize to 0. */
*pSize = 0;
}else{
@@ -2352,7 +2340,7 @@ static int getPayload(
** the available payload.
*/
int sqlite3BtreeKey(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
if( !pCur->isValid || pCur->delShift ){
if( !pCur->isValid ){
return pCur->status;
}
assert( pCur->pPage!=0 );
@@ -2371,7 +2359,7 @@ int sqlite3BtreeKey(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
** the available payload.
*/
int sqlite3BtreeData(BtCursor *pCur, u32 offset, u32 amt, void *pBuf){
if( !pCur->isValid || pCur->delShift ){
if( !pCur->isValid ){
return pCur->status ? pCur->status : SQLITE_INTERNAL;
}
assert( pCur->pPage!=0 );
@@ -2559,7 +2547,6 @@ static int moveToRoot(BtCursor *pCur){
rc = moveToChild(pCur, subpage);
}
pCur->isValid = pCur->pPage->nCell>0;
pCur->delShift = 0;
return rc;
}
@@ -2797,15 +2784,6 @@ int sqlite3BtreeNext(BtCursor *pCur, int *pRes){
assert( pPage->isInit );
assert( pCur->idx<pPage->nCell );
/* If BtCursor.delShift is 1, the cursor has already been advanced. */
if( pCur->delShift==1 ){
*pRes = 0;
pCur->delShift = 0;
return SQLITE_OK;
}else{
pCur->delShift = 0;
}
pCur->idx++;
pCur->info.nSize = 0;
if( pCur->idx>=pPage->nCell ){
@@ -2856,15 +2834,6 @@ int sqlite3BtreePrevious(BtCursor *pCur, int *pRes){
return SQLITE_OK;
}
/* If BtCursor.delShift is -1, the cursor has already been advanced. */
if( pCur->delShift==-1 ){
*pRes = 0;
pCur->delShift = 0;
return SQLITE_OK;
}else{
pCur->delShift = 0;
}
pPage = pCur->pPage;
assert( pPage->isInit );
assert( pCur->idx>=0 );
@@ -3656,7 +3625,6 @@ static int balance_nonroot(MemPage *pPage){
int *szCell; /* Local size of all cells in apCell[] */
u8 *aCopy[NB]; /* Space for holding data of apCopy[] */
u8 *aSpace; /* Space to hold copies of dividers cells */
BtCursor *pCur;
/*
** Find the parent page.
@@ -3905,6 +3873,16 @@ static int balance_nonroot(MemPage *pPage){
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
@@ -3949,95 +3927,6 @@ static int balance_nonroot(MemPage *pPage){
nNew>=4 ? pgnoNew[3] : 0, nNew>=4 ? szNew[3] : 0,
nNew>=5 ? pgnoNew[4] : 0, nNew>=5 ? szNew[4] : 0));
/* If there are other cursors that refer to one of the pages involved
** in the balancing, then adjust these cursors so that they still
** point to the same cells.
*/
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
int nCellCnt = 0;
int iCell = -1;
Pgno pgno = pCur->pPage->pgno;
/* If the cursor is not valid, do not do anything with it. */
if( !pCur->isValid ) continue;
/* If the cursor pointed to one of the cells moved around during the
** balancing, then set variable iCell to the index of the cell in apCell.
** This is used by the block below to figure out where the cell was
** moved to, and adjust the cursor appropriately.
**
** If the cursor points to the parent page, but the cell was not involved
** in the balance, then declare the cache of the cell-parse invalid, as a
** defragmentation may of occured during the balance. Also, if the index
** of the cell is greater than that of the divider cells, then it may
** need to be adjusted (in case there are now more or less divider cells
** than there were before the balancing).
*/
for(i=0; iCell<0 && i<nOld; i++){
if( pgno==apCopy[i]->pgno ){
iCell = nCellCnt + pCur->idx;
break;
}
nCellCnt += (apCopy[i]->nCell + apCopy[i]->nOverflow) + (leafData?0:1);
}
if( pgno==pParent->pgno ){
assert( !leafData );
assert( iCell==-1 );
if( pCur->idx>=nxDiv && pCur->idx<(nxDiv+nOld-1) ){
for(i=0; i<=(pCur->idx-nxDiv); i++){
iCell += (apCopy[i]->nCell + apCopy[i]->nOverflow + 1);
}
}
if( pCur->idx>=(nxDiv+nOld-1) ){
TRACE(("BALANCE: Cursor %p migrates from %d,%d to %d,%d\n",
pCur, pgno, pCur->idx, pgno, pCur->idx+(nNew-nOld)));
pCur->idx += (nNew-nOld);
}
pCur->info.nSize = 0;
}
/* If iCell is greater than or equal to zero, then pCur points at a
** cell that was moved around during the balance. Figure out where
** the cell was moved to and adjust pCur to match.
*/
if( iCell>=0 ){
int idxNew;
Pgno pgnoNew;
int x = 0;
assert( iCell<nCell );
while( cntNew[x]<=iCell ) x++;
if( x>0 && !leafData && cntNew[x-1]==iCell ){
/* The cell that pCur points to is a divider cell in pParent. */
pgnoNew = pParent->pgno;
idxNew = nxDiv + x-1;
}else{
/* The cell that pCur points to is on page apNew[x]. */
idxNew = iCell-(x>0?cntNew[x-1]:0)-((leafData||x==0)?0:1);
pgnoNew = apNew[x]->pgno;
}
TRACE(("BALANCE: Cursor %p migrates from %d,%d to %d,%d\n",
pCur, pgno, pCur->idx, pgnoNew, idxNew));
pCur->idx = idxNew;
releasePage(pCur->pPage);
rc = getPage(pBt, pgnoNew, &pCur->pPage);
assert( rc==SQLITE_OK );
assert( pCur->pPage->isInit );
pCur->info.nSize = 0;
}
}
/* Free any old pages that were not reused as new pages.
*/
for(i=nNew; i<nOld; i++){
rc = freePage(apOld[i]);
if( rc ) goto balance_cleanup;
releasePage(apOld[i]);
apOld[i] = 0;
}
/*
** Evenly distribute the data in apCell[] across the new pages.
** Insert divider cells into pParent as necessary.
@@ -4181,7 +4070,6 @@ static int balance_shallower(MemPage *pPage){
/* The child information will fit on the root page, so do the
** copy */
int i;
BtCursor *pCur;
zeroPage(pPage, pChild->aData[0]);
for(i=0; i<pChild->nCell; i++){
apCell[i] = findCell(pChild,i);
@@ -4190,26 +4078,12 @@ static int balance_shallower(MemPage *pPage){
assemblePage(pPage, pChild->nCell, apCell, szCell);
freePage(pChild);
TRACE(("BALANCE: child %d transfer to page 1\n", pChild->pgno));
/* If there were cursors pointing at this page, point them at the
** new page instead. Decrement the reference count for the old
** page and increment it for the new one.
*/
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
if( pCur->pPage==pChild ){
TRACE(("BALANCE: Cursor %p migrates from %d,%d to %d,%d\n",
pCur, pPage->pgno, pCur->idx, pPage->pgno, pCur->idx));
releasePage(pCur->pPage);
rc = getPage(pBt, 1, &pCur->pPage);
assert( rc==SQLITE_OK );
}
}
}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{
BtCursor *pCur;
memcpy(pPage->aData, pChild->aData, pPage->pBt->usableSize);
pPage->isInit = 0;
pPage->pParent = 0;
@@ -4218,15 +4092,6 @@ static int balance_shallower(MemPage *pPage){
freePage(pChild);
TRACE(("BALANCE: transfer child %d into root %d\n",
pChild->pgno, pPage->pgno));
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
if( pCur->pPage==pChild ){
TRACE(("BALANCE: Cursor %p migrates from %d,%d to %d,%d\n",
pCur, pChild->pgno, pCur->idx, pPage->pgno, pCur->idx));
releasePage(pCur->pPage);
rc = getPage(pBt, pPage->pgno, &pCur->pPage);
assert( rc==SQLITE_OK );
}
}
}
rc = reparentChildPages(pPage);
if( rc!=SQLITE_OK ) goto end_shallow_balance;
@@ -4257,7 +4122,6 @@ static int balance_deeper(MemPage *pPage){
u8 *cdata; /* Content of the child page */
int hdr; /* Offset to page header in parent */
int brk; /* Offset to content of first cell in parent */
BtCursor *pCur;
assert( pPage->pParent==0 );
assert( pPage->nOverflow>0 );
@@ -4284,21 +4148,6 @@ static int balance_deeper(MemPage *pPage){
zeroPage(pPage, pChild->aData[0] & ~PTF_LEAF);
put4byte(&pPage->aData[pPage->hdrOffset+8], pgnoChild);
TRACE(("BALANCE: copy root %d into %d\n", pPage->pgno, pChild->pgno));
/* If there were cursors pointing at this page, point them at the new
** page instead. Decrement the reference count for the old page and
** increment it for the new one.
*/
for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
if( pCur->pPage==pPage ){
TRACE(("BALANCE: Cursor %p migrates from %d,%d to %d,%d\n",
pCur, pPage->pgno, pCur->idx, pChild->pgno, pCur->idx));
releasePage(pCur->pPage);
rc = getPage(pBt, pChild->pgno, &pCur->pPage);
assert( rc==SQLITE_OK );
}
}
rc = balance_nonroot(pChild);
releasePage(pChild);
return rc;
@@ -4331,8 +4180,24 @@ static int balance(MemPage *pPage){
** wrFlag==0 then this routine returns SQLITE_LOCKED. If all
** cursors that point to pgnoRoot 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 pExclude 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(Btree *pBt, Pgno pgnoRoot, BtCursor *pExclude){
BtCursor *p;
for(p=pBt->pCursor; p; p=p->pNext){
if( p->pgnoRoot!=pgnoRoot || p==pExclude ) continue;
if( p->wrFlag==0 ) return SQLITE_LOCKED;
if( p->pPage->pgno!=p->pgnoRoot ){
moveToRoot(p);
}
}
return SQLITE_OK;
}
@@ -4357,7 +4222,6 @@ int sqlite3BtreeInsert(
Btree *pBt = pCur->pBt;
unsigned char *oldCell;
unsigned char *newCell = 0;
BtCursor *pCur2;
if( pCur->status ){
return pCur->status; /* A rollback destroyed this cursor */
@@ -4409,30 +4273,13 @@ int sqlite3BtreeInsert(
assert( pPage->leaf );
}
rc = insertCell(pPage, pCur->idx, newCell, szNew, 0);
pCur->isValid = 1;
/* If there are other cursors pointing at this page with a BtCursor.idx
** field greater than or equal to 'i', then the cell they refer to
** has been modified or moved within the page. Fix the cursor.
*/
for(pCur2=pPage->pBt->pCursor; pCur2; pCur2 = pCur2->pNext){
if( pCur2->pPage==pPage ){
if( pCur2->idx>=pCur->idx && pCur!=pCur2 && loc!=0 ){
/* The cell pointed to by pCur2 was shifted one to the right on it's
** page by this Insert().
*/
TRACE(("INSERT: Cursor %p migrates from %d,%d to %d,%d\n",
pCur2, pPage->pgno, pCur2->idx, pPage->pgno, pCur2->idx+1));
pCur2->idx++;
}
pCur2->info.nSize = 0;
}
}
if( rc!=SQLITE_OK ) goto end_insert;
rc = balance(pPage);
/* sqlite3BtreePageDump(pCur->pBt, pCur->pgnoRoot, 1); */
/* fflush(stdout); */
if( rc==SQLITE_OK ){
moveToRoot(pCur);
}
end_insert:
sqliteFree(newCell);
return rc;
@@ -4448,8 +4295,6 @@ int sqlite3BtreeDelete(BtCursor *pCur){
int rc;
Pgno pgnoChild = 0;
Btree *pBt = pCur->pBt;
int idx; /* Index of the cell to delete */
BtCursor *pCur2; /* Iterator variable for the pBt.pCursor link-list */
assert( pPage->isInit );
if( pCur->status ){
@@ -4472,50 +4317,11 @@ int sqlite3BtreeDelete(BtCursor *pCur){
rc = sqlite3pager_write(pPage->aData);
if( rc ) return rc;
/* Set index to the index in pPage that contains the cell to delete. Also
** increment the reference count for pPage. This allows us to move the
** cursor pCur before the delete takes place.
*/
idx = pCur->idx;
rc = getPage(pBt, pPage->pgno, &pPage);
if( rc ) return rc;
assert( pPage==pCur->pPage );
/* If there are any cursors that point to the cell being deleted,
** move them to the next or previous entry in the table. It is preferable
** to move the cursor to the 'next' location, rather than the 'previous'
** one, as most table scans are done in the forward direction (also, code
** below depends on this). If neither entry exists, declare the cursor
** invalid.
*/
for(pCur2=pBt->pCursor; pCur2; pCur2 = pCur2->pNext){
if( pCur2->pPage==pPage && pCur2->idx==idx && pCur2->isValid ){
int res;
pCur2->delShift = 0;
rc = sqlite3BtreeNext(pCur2, &res);
if( rc ) goto delete_out;
if( res ){
/* If the next tree entry cannot be found, then the cursor must
** already point to the last table entry. So point it to the
** second last by calling BtreeLast(), BtreePrevious().
*/
rc = sqlite3BtreeLast(pCur2, &res);
if( rc ) goto delete_out;
assert( res==0 );
rc = sqlite3BtreePrevious(pCur2, &res);
if( rc ) goto delete_out;
pCur2->delShift = -1;
}else{
pCur2->delShift = 1;
}
}
}
/* Locate the cell within it's page and leave pCell pointing to the
** data. The clearCell() call frees any overflow pages associated with the
** cell. The cell itself is still intact.
*/
pCell = findCell(pPage, idx);
pCell = findCell(pPage, pCur->idx);
if( !pPage->leaf ){
pgnoChild = get4byte(pCell);
}
@@ -4527,120 +4333,48 @@ int sqlite3BtreeDelete(BtCursor *pCur){
** 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. Conveniantly, pCur now points
** at this cell (because it was advanced above).
** to be a leaf so we can use it.
*/
BtCursor leafCur;
unsigned char *pNext;
int szNext;
int notUsed;
unsigned char *tempCell;
assert( !pPage->leafData );
/* Make a copy of *pCur in leafCur. leafCur now points to the cell
** that will be moved into the space left by the cell being deleted.
*/
assert( pCur->delShift==1 );
assert( pCur->isValid );
getTempCursor(pCur, &leafCur);
rc = sqlite3BtreeNext(&leafCur, &notUsed);
if( rc!=SQLITE_OK ){
if( rc!=SQLITE_NOMEM ){
rc = SQLITE_CORRUPT; /* bkpt-CORRUPT */
}
goto delete_out;
return rc;
}
rc = sqlite3pager_write(leafCur.pPage->aData);
if( rc ) goto delete_out;
TRACE(("DELETE: table=%d delete internal from %d,%d replace "
"from leaf %d,%d\n", pCur->pgnoRoot, pPage->pgno, idx,
leafCur.pPage->pgno, leafCur.idx));
/* Drop the cell from the internal page. Make a copy of the cell from
** the leaf page into memory obtained from malloc(). Insert it into
** the internal page, at the position vacated by the delete. There
** are now two copies of the leaf-cell in the tree.
*/
dropCell(pPage, idx, cellSizePtr(pPage, pCell));
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, cellSizePtr(pPage, pCell));
pNext = findCell(leafCur.pPage, leafCur.idx);
szNext = cellSizePtr(leafCur.pPage, pNext);
assert( MX_CELL_SIZE(pBt)>=szNext+4 );
tempCell = sqliteMallocRaw( MX_CELL_SIZE(pBt) );
if( tempCell==0 ){
rc = SQLITE_NOMEM;
goto delete_out;
}
rc = insertCell(pPage, idx, pNext-4, szNext+4, tempCell);
if( rc!=SQLITE_OK ) goto delete_out;
put4byte(findOverflowCell(pPage, idx), pgnoChild);
pPage->idxShift = 0;
/* If there are any cursors that point to the leaf-cell, move them
** so that they point at internal cell. This is easiest done by
** calling BtreePrevious().
**
** Also, any cursors that point to the internal page have their
** cached parses invalidated, as the insertCell() above may have
** caused a defragmation.
*/
for(pCur2=pBt->pCursor; pCur2; pCur2 = pCur2->pNext){
if( pCur2->pPage==leafCur.pPage && pCur2->idx==leafCur.idx ){
int res;
int delShiftSave = pCur2->delShift;
assert( leafCur.idx==0 );
pCur2->delShift = 0;
rc = sqlite3BtreePrevious(pCur2, &res);
if( rc ) goto delete_out;
assert( res==0 );
assert( pCur2->pPage==pPage );
assert( pCur2->idx==idx );
pCur2->delShift = delShiftSave;
}
if( pCur2->pPage==pPage ){
pCur2->info.nSize = 0;
}
}
/* Balance the internal page. Free the memory allocated for the
** copy of the leaf cell. Then delete the cell from the leaf page.
*/
if( tempCell==0 ) return SQLITE_NOMEM;
rc = insertCell(pPage, pCur->idx, pNext-4, szNext+4, tempCell);
if( rc!=SQLITE_OK ) return rc;
put4byte(findOverflowCell(pPage, pCur->idx), pgnoChild);
rc = balance(pPage);
sqliteFree(tempCell);
if( rc ) goto delete_out;
if( rc ) return rc;
dropCell(leafCur.pPage, leafCur.idx, szNext);
for(pCur2=pBt->pCursor; pCur2; pCur2 = pCur2->pNext){
if( pCur2->pPage==leafCur.pPage && pCur2->idx>leafCur.idx ){
TRACE(("DELETE: Cursor %p migrates from %d,%d to %d,%d\n", pCur2,
leafCur.pPage->pgno,pCur2->idx,leafCur.pPage->pgno, pCur2->idx-1));
pCur2->idx--;
pCur2->info.nSize = 0;
}
}
rc = balance(leafCur.pPage);
releaseTempCursor(&leafCur);
}else{
TRACE(("DELETE: table=%d delete %d from leaf %d\n",
pCur->pgnoRoot, idx, pPage->pgno));
dropCell(pPage, idx, cellSizePtr(pPage, pCell));
/* If there were cursors pointing to cells on pPage with index values
** greater than idx, decrement the index values now.
*/
for(pCur2=pBt->pCursor; pCur2; pCur2 = pCur2->pNext){
assert( !pCur2->isValid || pCur2->pPage!=pPage || pCur2->idx!=idx );
if( pCur2->pPage==pPage && pCur2->idx>idx ){
TRACE(("DELETE: Cursor %p migrates from %d,%d to %d,%d\n",
pCur2, pPage->pgno, pCur2->idx, pPage->pgno, pCur2->idx-1));
pCur2->idx--;
pCur2->info.nSize = 0;
}
}
TRACE(("DELETE: table=%d delete from leaf %d\n",
pCur->pgnoRoot, pPage->pgno));
dropCell(pPage, pCur->idx, cellSizePtr(pPage, pCell));
rc = balance(pPage);
}
delete_out:
releasePage(pPage);
moveToRoot(pCur);
return rc;
}