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Overview
Comment: | Change the internal btree routine moveToRoot() to return SQLITE_EMPTY if the table is empty or if it has pgnoRoot==0. This simplifies the callers, making them smaller and faster. The SQLITE_EMPTY result code is intercepted and changed into SQLITE_OK before surfacing in an API. |
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240d57143d943eaddd5f7c2d473f47a1 |
User & Date: | drh 2017-08-14 18:13:52.027 |
Context
2017-08-14
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23:53 | Minor size and performance optimization to sqlite3BtreeCloseCursor(). (check-in: 1696933884 user: drh tags: trunk) | |
18:13 | Change the internal btree routine moveToRoot() to return SQLITE_EMPTY if the table is empty or if it has pgnoRoot==0. This simplifies the callers, making them smaller and faster. The SQLITE_EMPTY result code is intercepted and changed into SQLITE_OK before surfacing in an API. (check-in: 240d57143d user: drh tags: trunk) | |
17:03 | Fix harmless indentation error. (check-in: 25e92baaae user: drh tags: trunk) | |
Changes
Changes to src/btree.c.
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4910 4911 4912 4913 4914 4915 4916 | ** ** If the table has a virtual root page, then the cursor is moved to point ** to the virtual root page instead of the actual root page. A table has a ** virtual root page when the actual root page contains no cells and a ** single child page. This can only happen with the table rooted at page 1. ** ** If the b-tree structure is empty, the cursor state is set to | > | | < > | | 4910 4911 4912 4913 4914 4915 4916 4917 4918 4919 4920 4921 4922 4923 4924 4925 4926 4927 4928 4929 4930 4931 4932 4933 4934 4935 4936 4937 4938 4939 4940 4941 4942 4943 4944 4945 4946 4947 4948 4949 4950 4951 4952 4953 4954 4955 4956 4957 | ** ** If the table has a virtual root page, then the cursor is moved to point ** to the virtual root page instead of the actual root page. A table has a ** virtual root page when the actual root page contains no cells and a ** single child page. This can only happen with the table rooted at page 1. ** ** If the b-tree structure is empty, the cursor state is set to ** CURSOR_INVALID and this routine returns SQLITE_EMPTY. Otherwise, ** the cursor is set to point to the first cell located on the root ** (or virtual root) page and the cursor state is set to CURSOR_VALID. ** ** If this function returns successfully, it may be assumed that the ** page-header flags indicate that the [virtual] root-page is the expected ** kind of b-tree page (i.e. if when opening the cursor the caller did not ** specify a KeyInfo structure the flags byte is set to 0x05 or 0x0D, ** indicating a table b-tree, or if the caller did specify a KeyInfo ** structure the flags byte is set to 0x02 or 0x0A, indicating an index ** b-tree). */ static int moveToRoot(BtCursor *pCur){ MemPage *pRoot; int rc = SQLITE_OK; assert( cursorOwnsBtShared(pCur) ); assert( CURSOR_INVALID < CURSOR_REQUIRESEEK ); assert( CURSOR_VALID < CURSOR_REQUIRESEEK ); assert( CURSOR_FAULT > CURSOR_REQUIRESEEK ); assert( pCur->eState < CURSOR_REQUIRESEEK || pCur->iPage<0 ); assert( pCur->pgnoRoot>0 || pCur->iPage<0 ); if( pCur->iPage>=0 ){ if( pCur->iPage ){ do{ assert( pCur->apPage[pCur->iPage]!=0 ); releasePageNotNull(pCur->apPage[pCur->iPage--]); }while( pCur->iPage); goto skip_init; } }else if( pCur->pgnoRoot==0 ){ pCur->eState = CURSOR_INVALID; return SQLITE_EMPTY; }else{ assert( pCur->iPage==(-1) ); if( pCur->eState>=CURSOR_REQUIRESEEK ){ if( pCur->eState==CURSOR_FAULT ){ assert( pCur->skipNext!=SQLITE_OK ); return pCur->skipNext; } |
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4995 4996 4997 4998 4999 5000 5001 5002 5003 5004 5005 5006 5007 5008 | Pgno subpage; if( pRoot->pgno!=1 ) return SQLITE_CORRUPT_BKPT; subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+8]); pCur->eState = CURSOR_VALID; rc = moveToChild(pCur, subpage); }else{ pCur->eState = CURSOR_INVALID; } return rc; } /* ** Move the cursor down to the left-most leaf entry beneath the ** entry to which it is currently pointing. | > | 4996 4997 4998 4999 5000 5001 5002 5003 5004 5005 5006 5007 5008 5009 5010 | Pgno subpage; if( pRoot->pgno!=1 ) return SQLITE_CORRUPT_BKPT; subpage = get4byte(&pRoot->aData[pRoot->hdrOffset+8]); pCur->eState = CURSOR_VALID; rc = moveToChild(pCur, subpage); }else{ pCur->eState = CURSOR_INVALID; rc = SQLITE_EMPTY; } return rc; } /* ** Move the cursor down to the left-most leaf entry beneath the ** entry to which it is currently pointing. |
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5061 5062 5063 5064 5065 5066 5067 | int sqlite3BtreeFirst(BtCursor *pCur, int *pRes){ int rc; assert( cursorOwnsBtShared(pCur) ); assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) ); rc = moveToRoot(pCur); if( rc==SQLITE_OK ){ | < | | > | | | | < | 5063 5064 5065 5066 5067 5068 5069 5070 5071 5072 5073 5074 5075 5076 5077 5078 5079 5080 5081 5082 5083 | int sqlite3BtreeFirst(BtCursor *pCur, int *pRes){ int rc; assert( cursorOwnsBtShared(pCur) ); assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) ); rc = moveToRoot(pCur); if( rc==SQLITE_OK ){ assert( pCur->apPage[pCur->iPage]->nCell>0 ); *pRes = 0; rc = moveToLeftmost(pCur); }else if( rc==SQLITE_EMPTY ){ assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 ); *pRes = 1; rc = SQLITE_OK; } return rc; } /* Move the cursor to the last entry in the table. Return SQLITE_OK ** on success. Set *pRes to 0 if the cursor actually points to something ** or set *pRes to 1 if the table is empty. |
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5100 5101 5102 5103 5104 5105 5106 | assert( pCur->apPage[pCur->iPage]->leaf ); #endif return SQLITE_OK; } rc = moveToRoot(pCur); if( rc==SQLITE_OK ){ | < < < < | | | | | | | | | < > > > | 5101 5102 5103 5104 5105 5106 5107 5108 5109 5110 5111 5112 5113 5114 5115 5116 5117 5118 5119 5120 5121 5122 5123 5124 5125 5126 | assert( pCur->apPage[pCur->iPage]->leaf ); #endif return SQLITE_OK; } rc = moveToRoot(pCur); if( rc==SQLITE_OK ){ assert( pCur->eState==CURSOR_VALID ); *pRes = 0; rc = moveToRightmost(pCur); if( rc==SQLITE_OK ){ pCur->curFlags |= BTCF_AtLast; }else{ pCur->curFlags &= ~BTCF_AtLast; } }else if( rc==SQLITE_EMPTY ){ assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 ); *pRes = 1; rc = SQLITE_OK; } return rc; } /* Move the cursor so that it points to an entry near the key ** specified by pIdxKey or intKey. Return a success code. ** |
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5212 5213 5214 5215 5216 5217 5218 5219 5220 | ); }else{ xRecordCompare = 0; /* All keys are integers */ } rc = moveToRoot(pCur); if( rc ){ return rc; } | > > > > > | | | < < | < < | 5211 5212 5213 5214 5215 5216 5217 5218 5219 5220 5221 5222 5223 5224 5225 5226 5227 5228 5229 5230 5231 5232 5233 5234 5235 | ); }else{ xRecordCompare = 0; /* All keys are integers */ } rc = moveToRoot(pCur); if( rc ){ if( rc==SQLITE_EMPTY ){ assert( pCur->pgnoRoot==0 || pCur->apPage[pCur->iPage]->nCell==0 ); *pRes = -1; return SQLITE_OK; } return rc; } assert( pCur->apPage[pCur->iPage] ); assert( pCur->apPage[pCur->iPage]->isInit ); assert( pCur->eState==CURSOR_VALID ); assert( pCur->apPage[pCur->iPage]->nCell > 0 ); assert( pCur->apPage[0]->intKey==pCur->curIntKey ); assert( pCur->curIntKey || pIdxKey ); for(;;){ int lwr, upr, idx, c; Pgno chldPg; MemPage *pPage = pCur->apPage[pCur->iPage]; u8 *pCell; /* Pointer to current cell in pPage */ |
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8435 8436 8437 8438 8439 8440 8441 8442 8443 8444 8445 8446 8447 8448 | } }else{ rc = moveToRoot(pCur); if( bPreserve ){ btreeReleaseAllCursorPages(pCur); pCur->eState = CURSOR_REQUIRESEEK; } } } return rc; } /* ** Create a new BTree table. Write into *piTable the page | > | 8435 8436 8437 8438 8439 8440 8441 8442 8443 8444 8445 8446 8447 8448 8449 | } }else{ rc = moveToRoot(pCur); if( bPreserve ){ btreeReleaseAllCursorPages(pCur); pCur->eState = CURSOR_REQUIRESEEK; } if( rc==SQLITE_EMPTY ) rc = SQLITE_OK; } } return rc; } /* ** Create a new BTree table. Write into *piTable the page |
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8899 8900 8901 8902 8903 8904 8905 | ** Otherwise, if an error is encountered (i.e. an IO error or database ** corruption) an SQLite error code is returned. */ int sqlite3BtreeCount(BtCursor *pCur, i64 *pnEntry){ i64 nEntry = 0; /* Value to return in *pnEntry */ int rc; /* Return code */ | | > < | 8900 8901 8902 8903 8904 8905 8906 8907 8908 8909 8910 8911 8912 8913 8914 8915 8916 8917 8918 | ** Otherwise, if an error is encountered (i.e. an IO error or database ** corruption) an SQLite error code is returned. */ int sqlite3BtreeCount(BtCursor *pCur, i64 *pnEntry){ i64 nEntry = 0; /* Value to return in *pnEntry */ int rc; /* Return code */ rc = moveToRoot(pCur); if( rc==SQLITE_EMPTY ){ *pnEntry = 0; return SQLITE_OK; } /* Unless an error occurs, the following loop runs one iteration for each ** page in the B-Tree structure (not including overflow pages). */ while( rc==SQLITE_OK ){ int iIdx; /* Index of child node in parent */ MemPage *pPage; /* Current page of the b-tree */ |
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Changes to src/sqlite.h.in.
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428 429 430 431 432 433 434 | #define SQLITE_INTERRUPT 9 /* Operation terminated by sqlite3_interrupt()*/ #define SQLITE_IOERR 10 /* Some kind of disk I/O error occurred */ #define SQLITE_CORRUPT 11 /* The database disk image is malformed */ #define SQLITE_NOTFOUND 12 /* Unknown opcode in sqlite3_file_control() */ #define SQLITE_FULL 13 /* Insertion failed because database is full */ #define SQLITE_CANTOPEN 14 /* Unable to open the database file */ #define SQLITE_PROTOCOL 15 /* Database lock protocol error */ | | | 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 | #define SQLITE_INTERRUPT 9 /* Operation terminated by sqlite3_interrupt()*/ #define SQLITE_IOERR 10 /* Some kind of disk I/O error occurred */ #define SQLITE_CORRUPT 11 /* The database disk image is malformed */ #define SQLITE_NOTFOUND 12 /* Unknown opcode in sqlite3_file_control() */ #define SQLITE_FULL 13 /* Insertion failed because database is full */ #define SQLITE_CANTOPEN 14 /* Unable to open the database file */ #define SQLITE_PROTOCOL 15 /* Database lock protocol error */ #define SQLITE_EMPTY 16 /* Internal use only */ #define SQLITE_SCHEMA 17 /* The database schema changed */ #define SQLITE_TOOBIG 18 /* String or BLOB exceeds size limit */ #define SQLITE_CONSTRAINT 19 /* Abort due to constraint violation */ #define SQLITE_MISMATCH 20 /* Data type mismatch */ #define SQLITE_MISUSE 21 /* Library used incorrectly */ #define SQLITE_NOLFS 22 /* Uses OS features not supported on host */ #define SQLITE_AUTH 23 /* Authorization denied */ |
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