** May you share freely, never taking more than you give.
**
*************************************************************************
-** $Id: btree.c,v 1.619 2009/06/05 18:44:15 drh Exp $
+** $Id: btree.c,v 1.620 2009/06/08 14:49:46 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** See the header comment on "btreeInt.h" for additional information.
** macro.
*/
#if 0
-int sqlite3BtreeTrace=0; /* True to enable tracing */
+int sqlite3BtreeTrace=1; /* True to enable tracing */
# define TRACE(X) if(sqlite3BtreeTrace){printf X;fflush(stdout);}
#else
# define TRACE(X)
return rc;
}
-#endif /* ifndef SQLITE_OMIT_AUTOVACUUM */
+#else /* ifndef SQLITE_OMIT_AUTOVACUUM */
+# define setChildPtrmaps(x) SQLITE_OK
+#endif
/*
** This routine does the first phase of a two-phase commit. This routine
return SQLITE_CORRUPT_BKPT;
}
(*ppPage)->isInit = 0;
+ }else{
+ *ppPage = 0;
}
return rc;
}
#define NN 1 /* Number of neighbors on either side of pPage */
#define NB (NN*2+1) /* Total pages involved in the balance */
-/* Forward reference */
-static int balance(BtCursor*, int);
#ifndef SQLITE_OMIT_QUICKBALANCE
/*
** pPage is the leaf page which is the right-most page in the tree.
** pParent is its parent. pPage must have a single overflow entry
** which is also the right-most entry on the page.
+**
+** The pSpace buffer is used to store a temporary copy of the divider
+** cell that will be inserted into pParent. Such a cell consists of a 4
+** byte page number followed by a variable length integer. In other
+** words, at most 13 bytes. Hence the pSpace buffer must be at
+** least 13 bytes in size.
*/
-static int balance_quick(BtCursor *pCur){
- MemPage *const pPage = pCur->apPage[pCur->iPage];
- BtShared *const pBt = pCur->pBt;
+static int balance_quick(MemPage *pParent, MemPage *pPage, u8 *pSpace){
+ BtShared *const pBt = pPage->pBt; /* B-Tree Database */
MemPage *pNew = 0; /* Newly allocated page */
int rc; /* Return Code */
Pgno pgnoNew; /* Page number of pNew */
assert( sqlite3_mutex_held(pPage->pBt->mutex) );
+ assert( sqlite3PagerIswriteable(pParent->pDbPage) );
if( pPage->nCell<=0 ) return SQLITE_CORRUPT_BKPT;
- /* Allocate a new page. This page will become the right-sibling of pPage */
+ /* Allocate a new page. This page will become the right-sibling of
+ ** pPage. Make the parent page writable, so that the new divider cell
+ ** may be inserted. If both these operations are successful, proceed.
+ */
rc = allocateBtreePage(pBt, &pNew, &pgnoNew, 0, 0);
-
if( rc==SQLITE_OK ){
- /* The parentCell buffer is used to store a temporary copy of the divider
- ** cell that will be inserted into pParent. Such a cell consists of a 4
- ** byte page number followed by a variable length integer. In other
- ** words, at most 13 bytes. Hence the parentCell buffer must be at
- ** least 13 bytes in size.
- */
- MemPage * const pParent = pCur->apPage[pCur->iPage-1];
- u8 parentCell[13];
- u8 *pOut = &parentCell[4];
+
+ u8 *pOut = &pSpace[4];
u8 *pCell = pPage->aOvfl[0].pCell;
u16 szCell = cellSizePtr(pPage, pCell);
u8 *pStop;
assert( sqlite3PagerIswriteable(pNew->pDbPage) );
+
zeroPage(pNew, pPage->aData[0]);
assemblePage(pNew, 1, &pCell, &szCell);
pPage->nOverflow = 0;
** and the key value (a variable length integer, may have any value).
** The first of the while(...) loops below skips over the record-length
** field. The second while(...) loop copies the key value from the
- ** cell on pPage into the parentCell buffer.
+ ** cell on pPage into the pSpace buffer.
*/
- put4byte(parentCell, pPage->pgno);
+ put4byte(pSpace, pPage->pgno);
pCell = findCell(pPage, pPage->nCell-1);
pStop = &pCell[9];
while( (*(pCell++)&0x80) && pCell<pStop );
while( ((*(pOut++) = *(pCell++))&0x80) && pCell<pStop );
/* Insert the new divider cell into pParent */
- insertCell(pParent, pParent->nCell, parentCell, pOut-parentCell, 0, 0);
+ insertCell(pParent, pParent->nCell, pSpace, pOut-pSpace, 0, 0);
/* Set the right-child pointer of pParent to point to the new page. */
put4byte(&pParent->aData[pParent->hdrOffset+8], pgnoNew);
/* Release the reference to the new page. */
releasePage(pNew);
- }
- /* At this point the pPage->nFree variable is not set correctly with
- ** respect to the content of the page (because it was set to 0 by
- ** insertCell). So call sqlite3BtreeInitPage() to make sure it is
- ** correct.
- **
- ** This has to be done even if an error will be returned. Normally, if
- ** an error occurs during tree balancing, the contents of MemPage are
- ** not important, as they will be recalculated when the page is rolled
- ** back. But here, in balance_quick(), it is possible that pPage has
- ** not yet been marked dirty or written into the journal file. Therefore
- ** it will not be rolled back and so it is important to make sure that
- ** the page data and contents of MemPage are consistent.
- */
- pPage->isInit = 0;
- sqlite3BtreeInitPage(pPage);
- assert( pPage->nOverflow==0 );
-
- /* If everything else succeeded, balance the parent page, in
- ** case the divider cell inserted caused it to become overfull.
- */
- if( rc==SQLITE_OK ){
- releasePage(pPage);
- pCur->iPage--;
- rc = balance(pCur, 0);
+ /* At this point the pPage->nFree variable is not set correctly with
+ ** respect to the content of the page (because it was set to 0 by
+ ** insertCell). So call sqlite3BtreeInitPage() to make sure it is
+ ** correct.
+ **
+ ** This has to be done even if an error will be returned. Normally, if
+ ** an error occurs during tree balancing, the contents of MemPage are
+ ** not important, as they will be recalculated when the page is rolled
+ ** back. But here, in balance_quick(), it is possible that pPage has
+ ** not yet been marked dirty or written into the journal file. Therefore
+ ** it will not be rolled back and so it is important to make sure that
+ ** the page data and contents of MemPage are consistent.
+ */
+ pPage->isInit = 0;
+ sqlite3BtreeInitPage(pPage);
+ assert( pPage->nOverflow==0 );
}
+
return rc;
}
#endif /* SQLITE_OMIT_QUICKBALANCE */
** in a corrupted state. So if this routine fails, the database should
** be rolled back.
*/
-static int balance_nonroot(BtCursor *pCur){
- MemPage *pPage; /* The over or underfull page to balance */
- MemPage *pParent; /* The parent of pPage */
+static int balance_nonroot(MemPage *pParent, int iParentIdx, u8 *aSpace2){
BtShared *pBt; /* The whole database */
int nCell = 0; /* Number of cells in apCell[] */
int nMaxCells = 0; /* Allocated size of apCell, szCell, aFrom. */
int nOld = 0; /* Number of pages in apOld[] */
int nNew = 0; /* 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 */
u16 *szCell; /* Local size of all cells in apCell[] */
u8 *aCopy[NB]; /* Space for holding data of apCopy[] */
u8 *aSpace1; /* Space for copies of dividers cells before balance */
- u8 *aSpace2 = 0; /* Space for overflow dividers cells after balance */
u8 *aFrom = 0;
- pPage = pCur->apPage[pCur->iPage];
- assert( sqlite3_mutex_held(pPage->pBt->mutex) );
- VVA_ONLY( pCur->pagesShuffled = 1 );
-
- /*
- ** Find the parent page.
- */
- assert( pCur->iPage>0 );
- assert( pPage->isInit );
- assert( sqlite3PagerIswriteable(pPage->pDbPage) || pPage->nOverflow==1 );
- pBt = pPage->pBt;
- pParent = pCur->apPage[pCur->iPage-1];
- assert( pParent );
- if( SQLITE_OK!=(rc = sqlite3PagerWrite(pParent->pDbPage)) ){
- goto balance_cleanup;
- }
+ pBt = pParent->pBt;
+ assert( sqlite3_mutex_held(pBt->mutex) );
+ assert( sqlite3PagerIswriteable(pParent->pDbPage) );
TRACE(("BALANCE: begin page %d child of %d\n", pPage->pgno, pParent->pgno));
-#ifndef SQLITE_OMIT_QUICKBALANCE
- /*
- ** A special case: If a new entry has just been inserted into a
- ** table (that is, a btree with integer keys and all data at the leaves)
- ** and the new entry is the right-most entry in the tree (it has the
- ** largest key) then use the special balance_quick() routine for
- ** balancing. balance_quick() is much faster and results in a tighter
- ** packing of data in the common case.
- */
- if( pPage->leaf &&
- pPage->intKey &&
- pPage->nOverflow==1 &&
- pPage->aOvfl[0].idx==pPage->nCell &&
- pParent->pgno!=1 &&
- get4byte(&pParent->aData[pParent->hdrOffset+8])==pPage->pgno
- ){
- assert( pPage->intKey );
- /*
- ** TODO: Check the siblings to the left of pPage. It may be that
- ** they are not full and no new page is required.
- */
- return balance_quick(pCur);
- }
-#endif
-
- if( SQLITE_OK!=(rc = sqlite3PagerWrite(pPage->pDbPage)) ){
- goto balance_cleanup;
- }
-
- /*
- ** 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
- */
- idx = pCur->aiIdx[pCur->iPage-1];
- assertParentIndex(pParent, idx, pPage->pgno);
-
- /*
- ** 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
+ /* Find the sibling pages to balance. Also locate 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 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;
+ nxDiv = iParentIdx - 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 ){
apDiv[i] = findCell(pParent, k);
- nDiv++;
assert( !pParent->leaf );
pgnoOld[i] = get4byte(apDiv[i]);
}else if( k==pParent->nCell ){
}
rc = getAndInitPage(pBt, pgnoOld[i], &apOld[i]);
if( rc ) goto balance_cleanup;
- /* apOld[i]->idxParent = k; */
apCopy[i] = 0;
assert( i==nOld );
nOld++;
if( ISAUTOVACUUM ){
aFrom = &aSpace1[pBt->pageSize];
}
- aSpace2 = sqlite3PageMalloc(pBt->pageSize);
+ /* aSpace2 = sqlite3PageMalloc(pBt->pageSize); */
if( aSpace2==0 ){
rc = SQLITE_NOMEM;
goto balance_cleanup;
** leafData: 1 if pPage holds key+data and pParent holds only keys.
*/
nCell = 0;
- leafCorrection = pPage->leaf*4;
- leafData = pPage->hasData;
+ leafCorrection = apOld[0]->leaf*4;
+ leafData = apOld[0]->hasData;
for(i=0; i<nOld; i++){
MemPage *pOld = apCopy[i];
int limit = pOld->nCell+pOld->nOverflow;
/*
** Allocate k new pages. Reuse old pages where possible.
*/
- assert( pPage->pgno>1 );
- pageFlags = pPage->aData[0];
+ assert( apOld[0]->pgno>1 );
+ pageFlags = apOld[0]->aData[0];
for(i=0; i<k; i++){
MemPage *pNew;
if( i<nOld ){
apCell = 0;
TRACE(("BALANCE: finished with %d: old=%d new=%d cells=%d\n",
pPage->pgno, nOld, nNew, nCell));
- pPage->nOverflow = 0;
- releasePage(pPage);
- pCur->iPage--;
- rc = balance(pCur, 0);
/*
** Cleanup before returning.
*/
balance_cleanup:
- sqlite3PageFree(aSpace2);
sqlite3ScratchFree(apCell);
for(i=0; i<nOld; i++){
releasePage(apOld[i]);
for(i=0; i<nNew; i++){
releasePage(apNew[i]);
}
- pCur->apPage[pCur->iPage]->nOverflow = 0;
return rc;
}
/*
-** This routine is called for the root page of a btree when the root
-** page contains no cells. This is an opportunity to make the tree
-** shallower by one level.
+** This function is used to copy the contents of the b-tree node stored
+** on page pFrom to page pTo. If page pFrom was not a leaf page, then
+** the pointer-map entries for each child page are updated so that the
+** parent page stored in the pointer map is page pTo. If pFrom contained
+** any cells with overflow page pointers, then the corresponding pointer
+** map entries are also updated so that the parent page is page pTo.
+**
+** If pFrom is currently carrying any overflow cells (entries in the
+** MemPage.aOvfl[] array), they are not copied to pTo.
+**
+** Before returning, page pTo is reinitialized using sqlite3BtreeInitPage().
+**
+** The performance of this function is not critical. It is only used by
+** the balance_shallower() and balance_deeper() procedures, neither of
+** which are called often under normal circumstances.
*/
-static int balance_shallower(BtCursor *pCur){
- MemPage *pPage; /* Root page of B-Tree */
- MemPage *pChild; /* The only child page of pPage */
- Pgno pgnoChild; /* Page number for pChild */
- int rc = SQLITE_OK; /* Return code from subprocedures */
- BtShared *pBt; /* The main BTree structure */
- int mxCellPerPage; /* Maximum number of cells per page */
- u8 **apCell; /* All cells from pages being balanced */
- u16 *szCell; /* Local size of all cells */
+static int copyNodeContent(MemPage *pFrom, MemPage *pTo){
+ BtShared * const pBt = pFrom->pBt;
+ u8 * const aFrom = pFrom->aData;
+ u8 * const aTo = pTo->aData;
+ int const iFromHdr = pFrom->hdrOffset;
+ int const iToHdr = ((pTo->pgno==1) ? 100 : 0);
+ int rc = SQLITE_OK;
+ int iData;
+
+ assert( pFrom->isInit );
+ assert( pFrom->nFree>=iToHdr );
+ assert( get2byte(&aFrom[iFromHdr+5])<=pBt->usableSize );
+
+ /* Copy the b-tree node content from page pFrom to page pTo. */
+ iData = get2byte(&aFrom[iFromHdr+5]);
+ memcpy(&aTo[iData], &aFrom[iData], pBt->usableSize-iData);
+ memcpy(&aTo[iToHdr], &aFrom[iFromHdr], pFrom->cellOffset + 2*pFrom->nCell);
+
+ /* Reinitialize page pTo so that the contents of the MemPage structure
+ ** match the new data. The initialization of pTo "cannot" fail, as the
+ ** data copied from pFrom is known to be valid. */
+ pTo->isInit = 0;
+ TESTONLY(rc = ) sqlite3BtreeInitPage(pTo);
+ assert( rc==SQLITE_OK );
+
+ /* If this is an auto-vacuum database, update the pointer-map entries
+ ** for any b-tree or overflow pages that pTo now contains the pointers to. */
+ if( ISAUTOVACUUM ){
+ rc = setChildPtrmaps(pTo);
+ }
+ return rc;
+}
- assert( pCur->iPage==0 );
- pPage = pCur->apPage[0];
+/*
+** This routine is called on the root page of a btree when the root
+** page contains no cells. This is an opportunity to make the tree
+** shallower by one level.
+*/
+static int balance_shallower(MemPage *pRoot){
- assert( pPage->nCell==0 );
- assert( sqlite3_mutex_held(pPage->pBt->mutex) );
- pBt = pPage->pBt;
- mxCellPerPage = MX_CELL(pBt);
- apCell = sqlite3Malloc( mxCellPerPage*(sizeof(u8*)+sizeof(u16)) );
- if( apCell==0 ) return SQLITE_NOMEM;
- szCell = (u16*)&apCell[mxCellPerPage];
- if( pPage->leaf ){
- /* The table is completely empty */
- 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.
- */
- VVA_ONLY( pCur->pagesShuffled = 1 );
- pgnoChild = get4byte(&pPage->aData[pPage->hdrOffset+8]);
- assert( pgnoChild>0 );
- assert( pgnoChild<=pagerPagecount(pPage->pBt) );
- rc = sqlite3BtreeGetPage(pPage->pBt, pgnoChild, &pChild, 0);
- if( rc ) goto end_shallow_balance;
- if( pPage->pgno==1 ){
- rc = sqlite3BtreeInitPage(pChild);
- if( rc ) goto end_shallow_balance;
- assert( pChild->nOverflow==0 );
- if( pChild->nFree>=100 ){
- /* The child information will fit on the root page, so do the
- ** copy */
- int i;
- zeroPage(pPage, pChild->aData[0]);
- for(i=0; i<pChild->nCell; i++){
- apCell[i] = findCell(pChild,i);
- szCell[i] = cellSizePtr(pChild, apCell[i]);
- }
- assemblePage(pPage, pChild->nCell, apCell, szCell);
- /* Copy the right-pointer of the child to the parent. */
- assert( sqlite3PagerIswriteable(pPage->pDbPage) );
- put4byte(&pPage->aData[pPage->hdrOffset+8],
- get4byte(&pChild->aData[pChild->hdrOffset+8]));
+ /* 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.
+ */
+ int rc = SQLITE_OK; /* Return code */
+ int const hdr = pRoot->hdrOffset; /* Offset of root page header */
+ MemPage *pChild; /* Only child of pRoot */
+ Pgno const pgnoChild = get4byte(&pRoot->aData[pRoot->hdrOffset+8]);
+
+ assert( pRoot->nCell==0 );
+ assert( sqlite3_mutex_held(pRoot->pBt->mutex) );
+ assert( !pRoot->leaf );
+ assert( pgnoChild>0 );
+ assert( pgnoChild<=pagerPagecount(pRoot->pBt) );
+ assert( hdr==0 || pRoot->pgno==1 );
+
+ rc = sqlite3BtreeGetPage(pRoot->pBt, pgnoChild, &pChild, 0);
+ if( rc==SQLITE_OK ){
+ if( pChild->nFree>=hdr ){
+ if( hdr ){
+ rc = defragmentPage(pChild);
+ }
+ if( rc==SQLITE_OK ){
+ rc = copyNodeContent(pChild, pRoot);
+ }
+ if( rc==SQLITE_OK ){
rc = 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, pPage->pBt->usableSize);
- pPage->isInit = 0;
- rc = sqlite3BtreeInitPage(pPage);
- assert( rc==SQLITE_OK );
- freePage(pChild);
- TRACE(("BALANCE: transfer child %d into root %d\n",
- pChild->pgno, pPage->pgno));
- }
- assert( pPage->nOverflow==0 );
-#ifndef SQLITE_OMIT_AUTOVACUUM
- if( ISAUTOVACUUM && rc==SQLITE_OK ){
- rc = setChildPtrmaps(pPage);
+ /* 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));
}
-#endif
releasePage(pChild);
}
-end_shallow_balance:
- sqlite3_free(apCell);
+
return rc;
}
/*
-** The root page is overfull
+** This function is called when the root page of a b-tree structure is
+** overfull (has one or more overflow pages).
**
-** 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. Finally, call balance_internal() on the new child
-** to cause it to split.
+** A new child page is allocated and the contents of the current root
+** page, including overflow cells, are copied into the child. The root
+** page is then overwritten to make it an empty page with the right-child
+** pointer pointing to the new page.
+**
+** Before returning, all pointer-map entries corresponding to pages
+** that the new child-page now contains pointers to are updated. The
+** entry corresponding to the new right-child pointer of the root
+** page is also updated.
+**
+** If successful, *ppChild is set to contain a reference to the child
+** page and SQLITE_OK is returned. In this case the caller is required
+** to call releasePage() on *ppChild exactly once. If an error occurs,
+** an error code is returned and *ppChild is set to 0.
*/
-static int balance_deeper(BtCursor *pCur){
- int rc; /* Return value from subprocedures */
- MemPage *pPage; /* Pointer to the root page */
- MemPage *pChild; /* Pointer to a new child page */
- Pgno pgnoChild; /* Page number of the new child page */
- BtShared *pBt; /* The BTree */
- int usableSize; /* Total usable size of a page */
- u8 *data; /* Content of the parent page */
- u8 *cdata; /* Content of the child page */
- int hdr; /* Offset to page header in parent */
- int cbrk; /* Offset to content of first cell in parent */
-
- assert( pCur->iPage==0 );
- assert( pCur->apPage[0]->nOverflow>0 );
+static int balance_deeper(MemPage *pRoot, MemPage **ppChild){
+ int rc; /* Return value from subprocedures */
+ MemPage *pChild = 0; /* Pointer to a new child page */
+ Pgno pgnoChild; /* Page number of the new child page */
+ BtShared *pBt = pRoot->pBt; /* The BTree */
- VVA_ONLY( pCur->pagesShuffled = 1 );
- pPage = pCur->apPage[0];
- pBt = pPage->pBt;
+ assert( pRoot->nOverflow>0 );
assert( sqlite3_mutex_held(pBt->mutex) );
- assert( sqlite3PagerIswriteable(pPage->pDbPage) );
- rc = allocateBtreePage(pBt, &pChild, &pgnoChild, pPage->pgno, 0);
- if( rc ) return rc;
- assert( sqlite3PagerIswriteable(pChild->pDbPage) );
- usableSize = pBt->usableSize;
- data = pPage->aData;
- hdr = pPage->hdrOffset;
- cbrk = get2byte(&data[hdr+5]);
- cdata = pChild->aData;
- memcpy(cdata, &data[hdr], pPage->cellOffset+2*pPage->nCell-hdr);
- memcpy(&cdata[cbrk], &data[cbrk], usableSize-cbrk);
-
- assert( pChild->isInit==0 );
- rc = sqlite3BtreeInitPage(pChild);
- if( rc==SQLITE_OK ){
- int nCopy = pPage->nOverflow*sizeof(pPage->aOvfl[0]);
- memcpy(pChild->aOvfl, pPage->aOvfl, nCopy);
- pChild->nOverflow = pPage->nOverflow;
- if( pChild->nOverflow ){
- pChild->nFree = 0;
- }
- assert( pChild->nCell==pPage->nCell );
- assert( sqlite3PagerIswriteable(pPage->pDbPage) );
- 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( ISAUTOVACUUM ){
- rc = ptrmapPut(pBt, pChild->pgno, PTRMAP_BTREE, pPage->pgno);
-#ifndef SQLITE_OMIT_AUTOVACUUM
- if( rc==SQLITE_OK ){
- rc = setChildPtrmaps(pChild);
- }
- if( rc ){
- pChild->nOverflow = 0;
- }
-#endif
- }
- }
- if( rc==SQLITE_OK ){
- pCur->iPage++;
- pCur->apPage[1] = pChild;
- pCur->aiIdx[0] = 0;
- rc = balance_nonroot(pCur);
- }else{
+ /* Make pRoot, the root page of the b-tree, writable. Allocate a new
+ ** page that will become the new right-child of pPage. Copy the contents
+ ** of the node stored on pRoot into the new child page.
+ */
+ if( SQLITE_OK!=(rc = sqlite3PagerWrite(pRoot->pDbPage))
+ || SQLITE_OK!=(rc = allocateBtreePage(pBt,&pChild,&pgnoChild,pRoot->pgno,0))
+ || SQLITE_OK!=(rc = copyNodeContent(pRoot, pChild))
+ || (ISAUTOVACUUM &&
+ SQLITE_OK!=(rc = ptrmapPut(pBt, pgnoChild, PTRMAP_BTREE, pRoot->pgno)))
+ ){
+ *ppChild = 0;
releasePage(pChild);
+ return rc;
}
+ assert( sqlite3PagerIswriteable(pChild->pDbPage) );
+ assert( sqlite3PagerIswriteable(pRoot->pDbPage) );
+ assert( pChild->nCell==pRoot->nCell );
- return rc;
+ TRACE(("BALANCE: copy root %d into %d\n", pRoot->pgno, pChild->pgno));
+
+ /* Copy the overflow cells from pRoot to pChild */
+ memcpy(pChild->aOvfl, pRoot->aOvfl, pRoot->nOverflow*sizeof(pRoot->aOvfl[0]));
+ pChild->nOverflow = pRoot->nOverflow;
+ pChild->nFree = 0;
+
+ /* Zero the contents of pRoot. Then install pChild as the right-child. */
+ zeroPage(pRoot, pChild->aData[0] & ~PTF_LEAF);
+ put4byte(&pRoot->aData[pRoot->hdrOffset+8], pgnoChild);
+
+ *ppChild = pChild;
+ return SQLITE_OK;
}
/*
** The page that pCur currently points to has just been modified in
** some way. This function figures out if this modification means the
** tree needs to be balanced, and if so calls the appropriate balancing
-** routine.
-**
-** Parameter isInsert is true if a new cell was just inserted into the
-** page, or false otherwise.
+** routine. Balancing routines are:
+**
+** balance_quick()
+** balance_shallower()
+** balance_deeper()
+** balance_nonroot()
+**
+** If built with SQLITE_DEBUG, pCur->pagesShuffled is set to true if
+** balance_shallower(), balance_deeper() or balance_nonroot() is called.
+** If none of these functions are invoked, pCur->pagesShuffled is left
+** unmodified.
*/
-static int balance(BtCursor *pCur, int isInsert){
+static int balance(BtCursor *pCur){
int rc = SQLITE_OK;
- MemPage *pPage = pCur->apPage[pCur->iPage];
+ const int nMin = pCur->pBt->usableSize * 2 / 3;
+ u8 aBalanceQuickSpace[13];
+ u8 *pFree = 0;
- assert( sqlite3_mutex_held(pPage->pBt->mutex) );
- if( pCur->iPage==0 ){
- rc = sqlite3PagerWrite(pPage->pDbPage);
- if( rc==SQLITE_OK && pPage->nOverflow>0 ){
- rc = balance_deeper(pCur);
- assert( pCur->apPage[0]==pPage );
- assert( pPage->nOverflow==0 || rc!=SQLITE_OK );
- }
- if( rc==SQLITE_OK && pPage->nCell==0 ){
- rc = balance_shallower(pCur);
- assert( pCur->apPage[0]==pPage );
- assert( pPage->nOverflow==0 || rc!=SQLITE_OK );
- }
- }else{
- if( pPage->nOverflow>0 ||
- (!isInsert && pPage->nFree>pPage->pBt->usableSize*2/3) ){
- rc = balance_nonroot(pCur);
+ TESTONLY( int balance_quick_called = 0; );
+ TESTONLY( int balance_deeper_called = 0; );
+
+ do {
+ int iPage = pCur->iPage;
+ MemPage *pPage = pCur->apPage[iPage];
+
+ if( iPage==0 ){
+ if( pPage->nOverflow ){
+ /* The root page of the b-tree is overfull. In this case call the
+ ** balance_deeper() function to create a new child for the root-page
+ ** and copy the current contents of the root-page to it. The
+ ** next iteration of the do-loop will balance the child page.
+ */
+ assert( (balance_deeper_called++)==0 );
+ rc = balance_deeper(pPage, &pCur->apPage[1]);
+ if( rc==SQLITE_OK ){
+ pCur->iPage = 1;
+ pCur->aiIdx[0] = 0;
+ pCur->aiIdx[1] = 0;
+ assert( pCur->apPage[1]->nOverflow );
+ }
+ VVA_ONLY( pCur->pagesShuffled = 1 );
+ }else{
+ /* The root page of the b-tree is now empty. If the root-page is not
+ ** also a leaf page, it will have a single child page. Call
+ ** balance_shallower to attempt to copy the contents of the single
+ ** child-page into the root page (this may not be possible if the
+ ** root page is page 1).
+ **
+ ** Whether or not this is possible , the tree is now balanced.
+ ** Therefore is no next iteration of the do-loop.
+ */
+ if( pPage->nCell==0 && !pPage->leaf ){
+ rc = balance_shallower(pPage);
+ VVA_ONLY( pCur->pagesShuffled = 1 );
+ }
+ break;
+ }
+ }else if( pPage->nOverflow==0 && pPage->nFree<=nMin ){
+ break;
+ }else{
+ MemPage * const pParent = pCur->apPage[iPage-1];
+ int const iIdx = pCur->aiIdx[iPage-1];
+
+ rc = sqlite3PagerWrite(pParent->pDbPage);
+ if( rc==SQLITE_OK ){
+#ifndef SQLITE_OMIT_QUICKBALANCE
+ if( pPage->hasData
+ && pPage->nOverflow==1
+ && pPage->aOvfl[0].idx==pPage->nCell
+ && pParent->pgno!=1
+ && pParent->nCell==iIdx
+ ){
+ /* Call balance_quick() to create a new sibling of pPage on which
+ ** to store the overflow cell. balance_quick() inserts a new cell
+ ** into pParent, which may cause pParent overflow. If this
+ ** happens, the next interation of the do-loop will balance pParent
+ ** use either balance_nonroot() or balance_deeper(). Until this
+ ** happens, the overflow cell is stored in the aBalanceQuickSpace[]
+ ** buffer.
+ **
+ ** The purpose of the following assert() is to check that only a
+ ** single call to balance_quick() is made for each call to this
+ ** function. If this were not verified, a subtle bug involving reuse
+ ** of the aBalanceQuickSpace[] might sneak in.
+ */
+ assert( (balance_quick_called++)==0 );
+ rc = balance_quick(pParent, pPage, aBalanceQuickSpace);
+ }else
+#endif
+ {
+ /* In this case, call balance_nonroot() to redistribute cells
+ ** between pPage and up to 2 of its sibling pages. This involves
+ ** modifying the contents of pParent, which may cause pParent to
+ ** become overfull or underfull. The next iteration of the do-loop
+ ** will balance the parent page to correct this.
+ **
+ ** If the parent page becomes overfull, the overflow cell or cells
+ ** are stored in the pSpace buffer allocated immediately below.
+ ** A subsequent iteration of the do-loop will deal with this by
+ ** calling balance_nonroot() (balance_deeper() may be called first,
+ ** but it doesn't deal with overflow cells - just moves them to a
+ ** different page). Once this subsequent call to balance_nonroot()
+ ** has completed, it is safe to release the pSpace buffer used by
+ ** the previous call, as the overflow cell data will have been
+ ** copied either into the body of a database page or into the new
+ ** pSpace buffer passed to the latter call to balance_nonroot().
+ */
+ u8 *pSpace = sqlite3PageMalloc(pCur->pBt->pageSize);
+ rc = balance_nonroot(pParent, iIdx, pSpace);
+ if( pFree ){
+ /* If pFree is not NULL, it points to the pSpace buffer used
+ ** by a previous call to balance_nonroot(). Its contents are
+ ** now stored either on real database pages or within the
+ ** new pSpace buffer, so it may be safely freed here. */
+ sqlite3PageFree(pFree);
+ }
+
+ /* The pSpace buffer will be freed after the next call to
+ ** balance_nonroot(), or just before this function returns, whichever
+ ** comes first. */
+ pFree = pSpace;
+ VVA_ONLY( pCur->pagesShuffled = 1 );
+ }
+ }
+
+ pPage->nOverflow = 0;
+
+ /* The next iteration of the do-loop balances the parent page. */
+ releasePage(pPage);
+ pCur->iPage--;
}
+ }while( rc==SQLITE_OK );
+
+ if( pFree ){
+ sqlite3PageFree(pFree);
}
return rc;
}
pPage = pCur->apPage[pCur->iPage];
assert( pPage->intKey || nKey>=0 );
+ assert( pPage->intKey || nKey>=0 );
assert( pPage->leaf || !pPage->intKey );
TRACE(("INSERT: table=%d nkey=%lld ndata=%d page=%d %s\n",
pCur->pgnoRoot, nKey, nData, pPage->pgno,
}else if( loc<0 && pPage->nCell>0 ){
assert( pPage->leaf );
idx = ++pCur->aiIdx[pCur->iPage];
- pCur->info.nSize = 0;
- pCur->validNKey = 0;
}else{
assert( pPage->leaf );
}
rc = insertCell(pPage, idx, newCell, szNew, 0, 0);
assert( rc!=SQLITE_OK || pPage->nCell>0 || pPage->nOverflow>0 );
- /* If no error has occured, call balance() to deal with any overflow and
- ** move the cursor to point at the root of the table (since balance may
- ** have rearranged the table in such a way as to invalidate BtCursor.apPage[]
- ** or BtCursor.aiIdx[]).
- **
- ** Except, if all of the following are true, do nothing:
- **
- ** * Inserting the new cell did not cause overflow,
+ /* If no error has occured and pPage has an overflow cell, call balance()
+ ** to redistribute the cells within the tree. Since balance() may move
+ ** the cursor, zero the BtCursor.info.nSize and BtCursor.validNKey
+ ** variables.
**
- ** * Before inserting the new cell the cursor was pointing at the
- ** largest key in an intkey B-Tree, and
+ ** Previous versions of SQLite called moveToRoot() to move the cursor
+ ** back to the root page as balance() used to invalidate the contents
+ ** of BtCursor.apPage[] and BtCursor.aiIdx[]. This is no longer necessary,
+ ** as balance() always leaves the cursor pointing to a valid entry.
**
- ** * The key value associated with the new cell is now the largest
- ** in the B-Tree.
- **
- ** In this case the cursor can be safely left pointing at the (new)
- ** largest key value in the B-Tree. Doing so speeds up inserting a set
- ** of entries with increasing integer key values via a single cursor
- ** (comes up with "INSERT INTO ... SELECT ..." statements), as
- ** the next insert operation is not required to seek the cursor.
+ ** There is a subtle but important optimization here too. When inserting
+ ** multiple records into an intkey b-tree using a single cursor (as can
+ ** happen while processing an "INSERT INTO ... SELECT" statement), it
+ ** is advantageous to leave the cursor pointing to the last entry in
+ ** the b-tree if possible. If the cursor is left pointing to the last
+ ** entry in the table, and the next row inserted has an integer key
+ ** larger than the largest existing key, it is possible to insert the
+ ** row without seeking the cursor. This can be a big performance boost.
*/
- if( rc==SQLITE_OK
- && (pPage->nOverflow || !pCur->atLast || loc>=0 || !pCur->apPage[0]->intKey)
- ){
- rc = balance(pCur, 1);
- if( rc==SQLITE_OK ){
- moveToRoot(pCur);
- }
+ pCur->info.nSize = 0;
+ pCur->validNKey = 0;
+ if( rc==SQLITE_OK && pPage->nOverflow ){
+ pCur->atLast = 0;
+ rc = balance(pCur);
+
+ /* Must make sure nOverflow is reset to zero even if the balance()
+ ** fails. Internal data structure corruption will result otherwise. */
+ pCur->apPage[pCur->iPage]->nOverflow = 0;
}
-
- /* Must make sure nOverflow is reset to zero even if the balance()
- ** fails. Internal data structure corruption will result otherwise. */
- pCur->apPage[pCur->iPage]->nOverflow = 0;
+ assert( pCur->apPage[pCur->iPage]->nOverflow==0 );
end_insert:
return rc;
assert( sqlite3PagerIswriteable(pPage->pDbPage) );
put4byte(findOverflowCell(pPage, idx), pgnoChild);
VVA_ONLY( pCur->pagesShuffled = 0 );
- rc = balance(pCur, 0);
+ rc = balance(pCur);
}
if( rc==SQLITE_OK && leafCursorInvalid ){
){
dropCell(pLeafPage, 0, szNext);
VVA_ONLY( leafCur.pagesShuffled = 0 );
- rc = balance(&leafCur, 0);
+ rc = balance(&leafCur);
assert( leafCursorInvalid || !leafCur.pagesShuffled
|| !pCur->pagesShuffled );
}
pCur->pgnoRoot, pPage->pgno));
rc = dropCell(pPage, idx, cellSizePtr(pPage, pCell));
if( rc==SQLITE_OK ){
- rc = balance(pCur, 0);
+ rc = balance(pCur);
}
}
if( rc==SQLITE_OK ){
projects / thirdparty / sqlite.git / commitdiff
