Optimize defragmentPage() in the case where the page contains either one or
two free-blocks and a small number of fragmented bytes. FossilOrigin-Name: 202b1c0276aec6b8da64d3277de1ad91c9d62d80
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dan
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manifest
15
manifest
@ -1,5 +1,5 @@
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C Save\sa\sfew\sbytes\sand\sa\sfew\scycles\sby\ssetting\sVdbe.expmask\sto\szero\sfor\nstatements\sprepared\susing\slegacy\sinterface\ssqlite3_prepare().
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D 2017-02-23T16:30:16.521
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C Optimize\sdefragmentPage()\sin\sthe\scase\swhere\sthe\spage\scontains\seither\sone\sor\ntwo\sfree-blocks\sand\sa\ssmall\snumber\sof\sfragmented\sbytes.
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D 2017-02-24T19:58:22.394
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F Makefile.in edb6bcdd37748d2b1c3422ff727c748df7ffe918
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F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
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F Makefile.msc a89ea37ab5928026001569f056973b9059492fe2
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@ -338,7 +338,7 @@ F src/auth.c 930b376a9c56998557367e6f7f8aaeac82a2a792
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F src/backup.c faf17e60b43233c214aae6a8179d24503a61e83b
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F src/bitvec.c 17ea48eff8ba979f1f5b04cc484c7bb2be632f33
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F src/btmutex.c 0e9ce2d56159b89b9bc8e197e023ee11e39ff8ca
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F src/btree.c 3ae66974881e74df9909093818b4c3428f8d7982
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F src/btree.c 1763e0ec3a6cbda48d3a5cb5a7451e46fbc8784d
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F src/btree.h e6d352808956ec163a17f832193a3e198b3fb0ac
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F src/btreeInt.h cd55d39d9916270837a88c12e701047cba0729b0
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F src/build.c 51b473eec465f471d607b54e8dbc00751c3f8a1f
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@ -1557,7 +1557,10 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
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F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
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F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
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F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
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P d6afd98de3ee8b714dfd6477ead955096f623972
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R d82d78a185c578681c4bad1233af7bd3
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P a8fd705258643863493476f8b42ee981608a339f
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R c55510e117c3384aa955b9dc66959921
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T *branch * defragmentpage-opt
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T *sym-defragmentpage-opt *
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T -sym-trunk *
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U dan
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Z 013ae364526d4d7cd1569b7a9709f5c0
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Z a194b2944e8972170f1e898920de81d2
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@ -1 +1 @@
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a8fd705258643863493476f8b42ee981608a339f
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202b1c0276aec6b8da64d3277de1ad91c9d62d80
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62
src/btree.c
62
src/btree.c
@ -1317,17 +1317,18 @@ static void ptrmapPutOvflPtr(MemPage *pPage, u8 *pCell, int *pRC){
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/*
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** Defragment the page given. All Cells are moved to the
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** end of the page and all free space is collected into one
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** big FreeBlk that occurs in between the header and cell
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** pointer array and the cell content area.
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** Defragment the page given. This routine reorganizes cells within the
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** page so that there are no free-blocks on the free-block list.
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**
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** Parameter nMaxFrag is the maximum amount of fragmented space that may be
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** present in the page after this routine returns.
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**
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** EVIDENCE-OF: R-44582-60138 SQLite may from time to time reorganize a
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** b-tree page so that there are no freeblocks or fragment bytes, all
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** unused bytes are contained in the unallocated space region, and all
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** cells are packed tightly at the end of the page.
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*/
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static int defragmentPage(MemPage *pPage){
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static int defragmentPage(MemPage *pPage, int nMaxFrag){
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int i; /* Loop counter */
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int pc; /* Address of the i-th cell */
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int hdr; /* Offset to the page header */
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@ -1342,7 +1343,6 @@ static int defragmentPage(MemPage *pPage){
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int iCellFirst; /* First allowable cell index */
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int iCellLast; /* Last possible cell index */
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assert( sqlite3PagerIswriteable(pPage->pDbPage) );
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assert( pPage->pBt!=0 );
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assert( pPage->pBt->usableSize <= SQLITE_MAX_PAGE_SIZE );
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@ -1354,10 +1354,44 @@ static int defragmentPage(MemPage *pPage){
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cellOffset = pPage->cellOffset;
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nCell = pPage->nCell;
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assert( nCell==get2byte(&data[hdr+3]) );
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iCellFirst = cellOffset + 2*nCell;
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/* This block handles pages with two or fewer free blocks and nMaxFrag
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** or fewer fragmented bytes. In this case it is faster to move the
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** two (or one) blocks of cells using memmove() and add the required
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** offsets to each pointer in the cell-pointer array than it is to
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** reconstruct the entire page. */
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if( (int)data[hdr+7]<=nMaxFrag ){
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int iFree = get2byte(&data[hdr+1]);
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if( iFree ){
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int iFree2 = get2byte(&data[iFree]);
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if( 0==iFree2 || (data[iFree2]==0 && data[iFree2+1]==0) ){
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u8 *pEnd = &data[cellOffset + nCell*2];
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u8 *pAddr;
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int sz2 = 0;
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int sz = get2byte(&data[iFree+2]);
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int top = get2byte(&data[hdr+5]);
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if( iFree2 ){
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sz2 = get2byte(&data[iFree2+2]);
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memmove(&data[iFree+sz+sz2], &data[iFree+sz], iFree2-(iFree+sz));
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sz += sz2;
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}
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cbrk = top+sz;
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memmove(&data[cbrk], &data[top], iFree-top);
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for(pAddr=&data[cellOffset]; pAddr<pEnd; pAddr+=2){
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pc = get2byte(pAddr);
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if( pc<iFree ){ put2byte(pAddr, pc+sz); }
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else if( pc<iFree2 ){ put2byte(pAddr, pc+sz2); }
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}
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goto defragment_out;
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}
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}
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}
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usableSize = pPage->pBt->usableSize;
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cbrk = usableSize;
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iCellFirst = cellOffset + 2*nCell;
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iCellLast = usableSize - 4;
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for(i=0; i<nCell; i++){
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u8 *pAddr; /* The i-th cell pointer */
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pAddr = &data[cellOffset + i*2];
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@ -1390,16 +1424,18 @@ static int defragmentPage(MemPage *pPage){
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}
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memcpy(&data[cbrk], &src[pc], size);
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}
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data[hdr+7] = 0;
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if( cbrk-iCellFirst!=pPage->nFree ){
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return SQLITE_CORRUPT_BKPT;
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}
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defragment_out:
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assert( cbrk>=iCellFirst );
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put2byte(&data[hdr+5], cbrk);
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data[hdr+1] = 0;
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data[hdr+2] = 0;
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data[hdr+7] = 0;
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memset(&data[iCellFirst], 0, cbrk-iCellFirst);
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assert( sqlite3PagerIswriteable(pPage->pDbPage) );
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if( cbrk-iCellFirst!=pPage->nFree ){
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return SQLITE_CORRUPT_BKPT;
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}
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return SQLITE_OK;
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}
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@ -1537,7 +1573,7 @@ static int allocateSpace(MemPage *pPage, int nByte, int *pIdx){
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testcase( gap+2+nByte==top );
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if( gap+2+nByte>top ){
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assert( pPage->nCell>0 || CORRUPT_DB );
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rc = defragmentPage(pPage);
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rc = defragmentPage(pPage, MIN(4, pPage->nFree - (2+nByte)));
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if( rc ) return rc;
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top = get2byteNotZero(&data[hdr+5]);
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assert( gap+nByte<=top );
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@ -7689,7 +7725,7 @@ static int balance_nonroot(
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** free space needs to be up front.
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*/
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assert( nNew==1 || CORRUPT_DB );
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rc = defragmentPage(apNew[0]);
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rc = defragmentPage(apNew[0], 0);
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testcase( rc!=SQLITE_OK );
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assert( apNew[0]->nFree ==
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(get2byte(&apNew[0]->aData[5])-apNew[0]->cellOffset-apNew[0]->nCell*2)
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