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Overview
Comment: | Omit the check for cell-pointer consistency in sqlite3BtreeInitPage() for a 2.5% performance gain. (CVS 5433) |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA1: |
b88087e69dffb743c5b552703e14a030 |
User & Date: | drh 2008-07-18 02:44:18.000 |
Context
2008-07-18
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03:32 | The zeroPage() routine in btree.c need not actually zero the whole page, just the header. (CVS 5434) (check-in: c69633ec69 user: drh tags: trunk) | |
02:44 | Omit the check for cell-pointer consistency in sqlite3BtreeInitPage() for a 2.5% performance gain. (CVS 5433) (check-in: b88087e69d user: drh tags: trunk) | |
00:57 | Optimization to sqltie3BtreeParseCellPtr. 0.3% performance increase. (CVS 5432) (check-in: 77e099ad7d user: drh tags: trunk) | |
Changes
Changes to src/btree.c.
1 2 3 4 5 6 7 8 9 10 11 | /* ** 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. ** ************************************************************************* | | | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | /* ** 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 1.486 2008/07/18 02:44:18 drh Exp $ ** ** This file implements a external (disk-based) database using BTrees. ** See the header comment on "btreeInt.h" for additional information. ** Including a description of file format and an overview of operation. */ #include "btreeInt.h" |
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512 513 514 515 516 517 518 | /* ** Given a btree page and a cell index (0 means the first cell on ** the page, 1 means the second cell, and so forth) return a pointer ** to the cell content. ** ** This routine works only for pages that do not contain overflow cells. */ | | | | 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 | /* ** Given a btree page and a cell index (0 means the first cell on ** the page, 1 means the second cell, and so forth) return a pointer ** to the cell content. ** ** This routine works only for pages that do not contain overflow cells. */ #define findCell(P,I) \ ((P)->aData + ((P)->maskPage & get2byte(&(P)->aData[(P)->cellOffset+2*(I)]))) /* ** This a more complex version of findCell() that works for ** pages that do contain overflow cells. See insert */ static u8 *findOverflowCell(MemPage *pPage, int iCell){ int i; |
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925 926 927 928 929 930 931 | int hdr; /* Offset to beginning of page header */ u8 *data; /* Equal to pPage->aData */ BtShared *pBt; /* The main btree structure */ int usableSize; /* Amount of usable space on each page */ int cellOffset; /* Offset from start of page to first cell pointer */ int nFree; /* Number of unused bytes on the page */ int top; /* First byte of the cell content area */ | < < < > > | 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 | int hdr; /* Offset to beginning of page header */ u8 *data; /* Equal to pPage->aData */ BtShared *pBt; /* The main btree structure */ int usableSize; /* Amount of usable space on each page */ int cellOffset; /* Offset from start of page to first cell pointer */ int nFree; /* Number of unused bytes on the page */ int top; /* First byte of the cell content area */ pBt = pPage->pBt; assert( pBt!=0 ); assert( pParent==0 || pParent->pBt==pBt ); assert( sqlite3_mutex_held(pBt->mutex) ); assert( pPage->pgno==sqlite3PagerPagenumber(pPage->pDbPage) ); assert( pPage == sqlite3PagerGetExtra(pPage->pDbPage) ); assert( pPage->aData == sqlite3PagerGetData(pPage->pDbPage) ); if( pPage->pParent!=pParent && (pPage->pParent!=0 || pPage->isInit) ){ /* The parent page should never change unless the file is corrupt */ return SQLITE_CORRUPT_BKPT; } if( pPage->isInit ) return SQLITE_OK; if( pPage->pParent==0 && pParent!=0 ){ pPage->pParent = pParent; sqlite3PagerRef(pParent->pDbPage); } hdr = pPage->hdrOffset; data = pPage->aData; if( decodeFlags(pPage, data[hdr]) ) return SQLITE_CORRUPT_BKPT; assert( pBt->pageSize>=512 && pBt->pageSize<=32768 ); pPage->maskPage = pBt->pageSize - 1; pPage->nOverflow = 0; pPage->idxShift = 0; usableSize = pBt->usableSize; pPage->cellOffset = cellOffset = hdr + 12 - 4*pPage->leaf; top = get2byte(&data[hdr+5]); pPage->nCell = get2byte(&data[hdr+3]); if( pPage->nCell>MX_CELL(pBt) ){ |
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987 988 989 990 991 992 993 | } pPage->nFree = nFree; if( nFree>=usableSize ){ /* Free space cannot exceed total page size */ return SQLITE_CORRUPT_BKPT; } | > | > > > > > > > > > | | | | | | > > | 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 | } pPage->nFree = nFree; if( nFree>=usableSize ){ /* Free space cannot exceed total page size */ return SQLITE_CORRUPT_BKPT; } #if 0 /* Check that all the offsets in the cell offset array are within range. ** ** Omitting this consistency check and using the pPage->maskPage mask ** to prevent overrunning the page buffer in findCell() results in a ** 2.5% performance gain. */ { u8 *pOff; /* Iterator used to check all cell offsets are in range */ u8 *pEnd; /* Pointer to end of cell offset array */ u8 mask; /* Mask of bits that must be zero in MSB of cell offsets */ mask = ~(((u8)(pBt->pageSize>>8))-1); pEnd = &data[cellOffset + pPage->nCell*2]; for(pOff=&data[cellOffset]; pOff!=pEnd && !((*pOff)&mask); pOff+=2); if( pOff!=pEnd ){ return SQLITE_CORRUPT_BKPT; } } #endif pPage->isInit = 1; return SQLITE_OK; } /* ** Set up a raw page so that it looks like a database page holding |
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1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 | data[hdr+7] = 0; put2byte(&data[hdr+5], pBt->usableSize); pPage->nFree = pBt->usableSize - first; decodeFlags(pPage, flags); pPage->hdrOffset = hdr; pPage->cellOffset = first; pPage->nOverflow = 0; pPage->idxShift = 0; pPage->nCell = 0; pPage->isInit = 1; } /* ** Get a page from the pager. Initialize the MemPage.pBt and | > > | 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 | data[hdr+7] = 0; put2byte(&data[hdr+5], pBt->usableSize); pPage->nFree = pBt->usableSize - first; decodeFlags(pPage, flags); pPage->hdrOffset = hdr; pPage->cellOffset = first; pPage->nOverflow = 0; assert( pBt->pageSize>=512 && pBt->pageSize<=32768 ); pPage->maskPage = pBt->pageSize - 1; pPage->idxShift = 0; pPage->nCell = 0; pPage->isInit = 1; } /* ** Get a page from the pager. Initialize the MemPage.pBt and |
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Changes to src/btreeInt.h.
1 2 3 4 5 6 7 8 9 10 11 | /* ** 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. ** ************************************************************************* | | | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | /* ** 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: btreeInt.h,v 1.28 2008/07/18 02:44:18 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. |
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280 281 282 283 284 285 286 287 288 289 290 291 292 293 | u8 childPtrSize; /* 0 if leaf==1. 4 if leaf==0 */ u16 maxLocal; /* Copy of BtShared.maxLocal or BtShared.maxLeaf */ u16 minLocal; /* Copy of BtShared.minLocal or BtShared.minLeaf */ u16 cellOffset; /* Index in aData of first cell pointer */ u16 idxParent; /* Index in parent of this node */ u16 nFree; /* Number of free bytes on the page */ u16 nCell; /* Number of cells on this page, local and ovfl */ struct _OvflCell { /* Cells that will not fit on aData[] */ u8 *pCell; /* Pointers to the body of the overflow cell */ u16 idx; /* Insert this cell before idx-th non-overflow cell */ } aOvfl[5]; BtShared *pBt; /* Pointer to BtShared that this page is part of */ u8 *aData; /* Pointer to disk image of the page data */ DbPage *pDbPage; /* Pager page handle */ | > | 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 | u8 childPtrSize; /* 0 if leaf==1. 4 if leaf==0 */ u16 maxLocal; /* Copy of BtShared.maxLocal or BtShared.maxLeaf */ u16 minLocal; /* Copy of BtShared.minLocal or BtShared.minLeaf */ u16 cellOffset; /* Index in aData of first cell pointer */ u16 idxParent; /* Index in parent of this node */ u16 nFree; /* Number of free bytes on the page */ u16 nCell; /* Number of cells on this page, local and ovfl */ u16 maskPage; /* Mask for page offset */ struct _OvflCell { /* Cells that will not fit on aData[] */ u8 *pCell; /* Pointers to the body of the overflow cell */ u16 idx; /* Insert this cell before idx-th non-overflow cell */ } aOvfl[5]; BtShared *pBt; /* Pointer to BtShared that this page is part of */ u8 *aData; /* Pointer to disk image of the page data */ DbPage *pDbPage; /* Pager page handle */ |
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