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Overview
Comment: | Put BtCursor objects on a singly-linked list instead of a doubly-linked list. Add the BTCF_Multiple flag. Only invoke saveAllCursors() when using a cursor that has BTCF_Multiple set. |
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SHA1: |
429ccef2b36fc46e92914eb54afd5f80 |
User & Date: | drh 2015-06-30 02:47:36.537 |
Context
2015-06-30
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03:13 | Change sqlite3ApiExit() so that its first argument is never NULL. (check-in: 791b706ec6 user: drh tags: trunk) | |
02:47 | Put BtCursor objects on a singly-linked list instead of a doubly-linked list. Add the BTCF_Multiple flag. Only invoke saveAllCursors() when using a cursor that has BTCF_Multiple set. (check-in: 429ccef2b3 user: drh tags: trunk) | |
01:25 | Convert several 5-year-old and older NEVER() macros into assert(). (check-in: ed54c14ea8 user: drh tags: trunk) | |
Changes
Changes to src/btree.c.
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650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 | /* ** Save the positions of all cursors (except pExcept) that are open on ** the table with root-page iRoot. "Saving the cursor position" means that ** the location in the btree is remembered in such a way that it can be ** moved back to the same spot after the btree has been modified. This ** routine is called just before cursor pExcept is used to modify the ** table, for example in BtreeDelete() or BtreeInsert(). ** ** Implementation note: This routine merely checks to see if any cursors ** need to be saved. It calls out to saveCursorsOnList() in the (unusual) ** event that cursors are in need to being saved. */ static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){ BtCursor *p; assert( sqlite3_mutex_held(pBt->mutex) ); assert( pExcept==0 || pExcept->pBt==pBt ); for(p=pBt->pCursor; p; p=p->pNext){ if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) ) break; } | > > > > > > > > > | > > | 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 | /* ** Save the positions of all cursors (except pExcept) that are open on ** the table with root-page iRoot. "Saving the cursor position" means that ** the location in the btree is remembered in such a way that it can be ** moved back to the same spot after the btree has been modified. This ** routine is called just before cursor pExcept is used to modify the ** table, for example in BtreeDelete() or BtreeInsert(). ** ** If there are two or more cursors on the same btree, then all such ** cursors should have their BTCF_Multiple flag set. The btreeCursor() ** routine enforces that rule. This routine only needs to be called in ** the uncommon case when pExpect has the BTCF_Multiple flag set. ** ** If pExpect!=NULL and if no other cursors are found on the same root-page, ** then the BTCF_Multiple flag on pExpect is cleared, to avoid another ** pointless call to this routine. ** ** Implementation note: This routine merely checks to see if any cursors ** need to be saved. It calls out to saveCursorsOnList() in the (unusual) ** event that cursors are in need to being saved. */ static int saveAllCursors(BtShared *pBt, Pgno iRoot, BtCursor *pExcept){ BtCursor *p; assert( sqlite3_mutex_held(pBt->mutex) ); assert( pExcept==0 || pExcept->pBt==pBt ); for(p=pBt->pCursor; p; p=p->pNext){ if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) ) break; } if( p ) return saveCursorsOnList(p, iRoot, pExcept); if( pExcept ) pExcept->curFlags &= ~BTCF_Multiple; return SQLITE_OK; } /* This helper routine to saveAllCursors does the actual work of saving ** the cursors if and when a cursor is found that actually requires saving. ** The common case is that no cursors need to be saved, so this routine is ** broken out from its caller to avoid unnecessary stack pointer movement. */ |
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4011 4012 4013 4014 4015 4016 4017 4018 4019 4020 4021 4022 4023 4024 | Btree *p, /* The btree */ int iTable, /* Root page of table to open */ int wrFlag, /* 1 to write. 0 read-only */ struct KeyInfo *pKeyInfo, /* First arg to comparison function */ BtCursor *pCur /* Space for new cursor */ ){ BtShared *pBt = p->pBt; /* Shared b-tree handle */ assert( sqlite3BtreeHoldsMutex(p) ); assert( wrFlag==0 || wrFlag==1 ); /* The following assert statements verify that if this is a sharable ** b-tree database, the connection is holding the required table locks, ** and that no other connection has any open cursor that conflicts with | > | 4022 4023 4024 4025 4026 4027 4028 4029 4030 4031 4032 4033 4034 4035 4036 | Btree *p, /* The btree */ int iTable, /* Root page of table to open */ int wrFlag, /* 1 to write. 0 read-only */ struct KeyInfo *pKeyInfo, /* First arg to comparison function */ BtCursor *pCur /* Space for new cursor */ ){ BtShared *pBt = p->pBt; /* Shared b-tree handle */ BtCursor *pX; /* Looping over other all cursors */ assert( sqlite3BtreeHoldsMutex(p) ); assert( wrFlag==0 || wrFlag==1 ); /* The following assert statements verify that if this is a sharable ** b-tree database, the connection is holding the required table locks, ** and that no other connection has any open cursor that conflicts with |
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4047 4048 4049 4050 4051 4052 4053 | pCur->iPage = -1; pCur->pKeyInfo = pKeyInfo; pCur->pBtree = p; pCur->pBt = pBt; assert( wrFlag==0 || wrFlag==BTCF_WriteFlag ); pCur->curFlags = wrFlag; pCur->curPagerFlags = wrFlag ? 0 : PAGER_GET_READONLY; | > > | | > | | > > | 4059 4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080 4081 | pCur->iPage = -1; pCur->pKeyInfo = pKeyInfo; pCur->pBtree = p; pCur->pBt = pBt; assert( wrFlag==0 || wrFlag==BTCF_WriteFlag ); pCur->curFlags = wrFlag; pCur->curPagerFlags = wrFlag ? 0 : PAGER_GET_READONLY; /* If there are two or more cursors on the same btree, then all such ** cursors *must* have the BTCF_Multiple flag set. */ for(pX=pBt->pCursor; pX; pX=pX->pNext){ if( pX->pgnoRoot==(Pgno)iTable ){ pX->curFlags |= BTCF_Multiple; pCur->curFlags |= BTCF_Multiple; } } pCur->pNext = pBt->pCursor; pBt->pCursor = pCur; pCur->eState = CURSOR_INVALID; return SQLITE_OK; } int sqlite3BtreeCursor( Btree *p, /* The btree */ int iTable, /* Root page of table to open */ |
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4108 4109 4110 4111 4112 4113 4114 | int sqlite3BtreeCloseCursor(BtCursor *pCur){ Btree *pBtree = pCur->pBtree; if( pBtree ){ int i; BtShared *pBt = pCur->pBt; sqlite3BtreeEnter(pBtree); sqlite3BtreeClearCursor(pCur); | > | | > > > | > | | | | 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 | int sqlite3BtreeCloseCursor(BtCursor *pCur){ Btree *pBtree = pCur->pBtree; if( pBtree ){ int i; BtShared *pBt = pCur->pBt; sqlite3BtreeEnter(pBtree); sqlite3BtreeClearCursor(pCur); assert( pBt->pCursor!=0 ); if( pBt->pCursor==pCur ){ pBt->pCursor = pCur->pNext; }else{ BtCursor *pPrev = pBt->pCursor; do{ if( pPrev->pNext==pCur ){ pPrev->pNext = pCur->pNext; break; } pPrev = pPrev->pNext; }while( ALWAYS(pPrev) ); } for(i=0; i<=pCur->iPage; i++){ releasePage(pCur->apPage[i]); } unlockBtreeIfUnused(pBt); sqlite3_free(pCur->aOverflow); /* sqlite3_free(pCur); */ |
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7891 7892 7893 7894 7895 7896 7897 | ** keys, the VDBE layer invokes sqlite3BtreeLast() to figure out the ** integer key to use. It then calls this function to actually insert the ** data into the intkey B-Tree. In this case btreeMoveto() recognizes ** that the cursor is already where it needs to be and returns without ** doing any work. To avoid thwarting these optimizations, it is important ** not to clear the cursor here. */ | > | | > | 7913 7914 7915 7916 7917 7918 7919 7920 7921 7922 7923 7924 7925 7926 7927 7928 7929 7930 | ** keys, the VDBE layer invokes sqlite3BtreeLast() to figure out the ** integer key to use. It then calls this function to actually insert the ** data into the intkey B-Tree. In this case btreeMoveto() recognizes ** that the cursor is already where it needs to be and returns without ** doing any work. To avoid thwarting these optimizations, it is important ** not to clear the cursor here. */ if( pCur->curFlags & BTCF_Multiple ){ rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur); if( rc ) return rc; } if( pCur->pKeyInfo==0 ){ assert( pKey==0 ); /* If this is an insert into a table b-tree, invalidate any incrblob ** cursors open on the row being replaced */ invalidateIncrblobCursors(p, nKey, 0); |
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8038 8039 8040 8041 8042 8043 8044 | } /* Save the positions of any other cursors open on this table before ** making any modifications. Make the page containing the entry to be ** deleted writable. Then free any overflow pages associated with the ** entry and finally remove the cell itself from within the page. */ | > | | > | 8062 8063 8064 8065 8066 8067 8068 8069 8070 8071 8072 8073 8074 8075 8076 8077 8078 8079 | } /* Save the positions of any other cursors open on this table before ** making any modifications. Make the page containing the entry to be ** deleted writable. Then free any overflow pages associated with the ** entry and finally remove the cell itself from within the page. */ if( pCur->curFlags & BTCF_Multiple ){ rc = saveAllCursors(pBt, pCur->pgnoRoot, pCur); if( rc ) return rc; } /* If this is a delete operation to remove a row from a table b-tree, ** invalidate any incrblob cursors open on the row being deleted. */ if( pCur->pKeyInfo==0 ){ invalidateIncrblobCursors(p, pCur->info.nKey, 0); } |
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Changes to src/btreeInt.h.
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503 504 505 506 507 508 509 | ** eState==SKIPNEXT && skipNext>0: Next sqlite3BtreeNext() is no-op. ** eState==SKIPNEXT && skipNext<0: Next sqlite3BtreePrevious() is no-op. ** eState==FAULT: Cursor fault with skipNext as error code. */ struct BtCursor { Btree *pBtree; /* The Btree to which this cursor belongs */ BtShared *pBt; /* The BtShared this cursor points to */ | | > > | 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 | ** eState==SKIPNEXT && skipNext>0: Next sqlite3BtreeNext() is no-op. ** eState==SKIPNEXT && skipNext<0: Next sqlite3BtreePrevious() is no-op. ** eState==FAULT: Cursor fault with skipNext as error code. */ struct BtCursor { Btree *pBtree; /* The Btree to which this cursor belongs */ BtShared *pBt; /* The BtShared this cursor points to */ BtCursor *pNext; /* Forms a linked list of all cursors */ Pgno *aOverflow; /* Cache of overflow page locations */ CellInfo info; /* A parse of the cell we are pointing at */ i64 nKey; /* Size of pKey, or last integer key */ void *pKey; /* Saved key that was cursor last known position */ Pgno pgnoRoot; /* The root page of this tree */ int nOvflAlloc; /* Allocated size of aOverflow[] array */ int skipNext; /* Prev() is noop if negative. Next() is noop if positive. ** Error code if eState==CURSOR_FAULT */ u8 curFlags; /* zero or more BTCF_* flags defined below */ u8 curPagerFlags; /* Flags to send to sqlite3PagerAcquire() */ u8 eState; /* One of the CURSOR_XXX constants (see below) */ u8 hints; /* As configured by CursorSetHints() */ /* All fields above are zeroed when the cursor is allocated. See ** sqlite3BtreeCursorZero(). Fields that follow must be manually ** initialized. */ i8 iPage; /* Index of current page in apPage */ u8 curIntKey; /* Value of apPage[0]->intKey */ struct KeyInfo *pKeyInfo; /* Argument passed to comparison function */ void *padding1; /* Make object size a multiple of 16 */ u16 aiIdx[BTCURSOR_MAX_DEPTH]; /* Current index in apPage[i] */ MemPage *apPage[BTCURSOR_MAX_DEPTH]; /* Pages from root to current page */ }; /* ** Legal values for BtCursor.curFlags */ #define BTCF_WriteFlag 0x01 /* True if a write cursor */ #define BTCF_ValidNKey 0x02 /* True if info.nKey is valid */ #define BTCF_ValidOvfl 0x04 /* True if aOverflow is valid */ #define BTCF_AtLast 0x08 /* Cursor is pointing ot the last entry */ #define BTCF_Incrblob 0x10 /* True if an incremental I/O handle */ #define BTCF_Multiple 0x20 /* Maybe another cursor on the same btree */ /* ** Potential values for BtCursor.eState. ** ** CURSOR_INVALID: ** Cursor does not point to a valid entry. This can happen (for example) ** because the table is empty or because BtreeCursorFirst() has not been |
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