diff options
Diffstat (limited to 'src/btree.c')
| -rw-r--r-- | src/btree.c | 60 |
1 files changed, 27 insertions, 33 deletions
diff --git a/src/btree.c b/src/btree.c index 916919928..577de2bee 100644 --- a/src/btree.c +++ b/src/btree.c @@ -7893,8 +7893,6 @@ static int balance_nonroot( Pgno pgno; /* Temp var to store a page number in */ u8 abDone[NB+2]; /* True after i'th new page is populated */ Pgno aPgno[NB+2]; /* Page numbers of new pages before shuffling */ - Pgno aPgOrder[NB+2]; /* Copy of aPgno[] used for sorting pages */ - u16 aPgFlags[NB+2]; /* flags field of new pages before shuffling */ CellArray b; /* Parsed information on cells being balanced */ memset(abDone, 0, sizeof(abDone)); @@ -8318,43 +8316,39 @@ static int balance_nonroot( ** of the table is closer to a linear scan through the file. That in turn ** helps the operating system to deliver pages from the disk more rapidly. ** - ** An O(n^2) insertion sort algorithm is used, but since n is never more - ** than (NB+2) (a small constant), that should not be a problem. + ** An O(N*N) sort algorithm is used, but since N is never more than NB+2 + ** (5), that is not a performance concern. ** ** When NB==3, this one optimization makes the database about 25% faster ** for large insertions and deletions. */ for(i=0; i<nNew; i++){ - aPgOrder[i] = aPgno[i] = apNew[i]->pgno; - aPgFlags[i] = apNew[i]->pDbPage->flags; - for(j=0; j<i; j++){ - if( NEVER(aPgno[j]==aPgno[i]) ){ - /* This branch is taken if the set of sibling pages somehow contains - ** duplicate entries. This can happen if the database is corrupt. - ** It would be simpler to detect this as part of the loop below, but - ** we do the detection here in order to avoid populating the pager - ** cache with two separate objects associated with the same - ** page number. */ - assert( CORRUPT_DB ); - rc = SQLITE_CORRUPT_BKPT; - goto balance_cleanup; - } - } + aPgno[i] = apNew[i]->pgno; + assert( apNew[i]->pDbPage->flags & PGHDR_WRITEABLE ); + assert( apNew[i]->pDbPage->flags & PGHDR_DIRTY ); } - for(i=0; i<nNew; i++){ - int iBest = 0; /* aPgno[] index of page number to use */ - for(j=1; j<nNew; j++){ - if( aPgOrder[j]<aPgOrder[iBest] ) iBest = j; - } - pgno = aPgOrder[iBest]; - aPgOrder[iBest] = 0xffffffff; - if( iBest!=i ){ - if( iBest>i ){ - sqlite3PagerRekey(apNew[iBest]->pDbPage, pBt->nPage+iBest+1, - aPgFlags[iBest]); - } - sqlite3PagerRekey(apNew[i]->pDbPage, pgno, aPgFlags[iBest]); - apNew[i]->pgno = pgno; + for(i=0; i<nNew-1; i++){ + int iB = i; + for(j=i+1; j<nNew; j++){ + if( apNew[j]->pgno < apNew[iB]->pgno ) iB = j; + } + + /* If apNew[i] has a page number that is bigger than any of the + ** subsequence apNew[i] entries, then swap apNew[i] with the subsequent + ** entry that has the smallest page number (which we know to be + ** entry apNew[iB]). + */ + if( iB!=i ){ + Pgno pgnoA = apNew[i]->pgno; + Pgno pgnoB = apNew[iB]->pgno; + Pgno pgnoTemp = (PENDING_BYTE/pBt->pageSize)+1; + u16 fgA = apNew[i]->pDbPage->flags; + u16 fgB = apNew[iB]->pDbPage->flags; + sqlite3PagerRekey(apNew[i]->pDbPage, pgnoTemp, fgB); + sqlite3PagerRekey(apNew[iB]->pDbPage, pgnoA, fgA); + sqlite3PagerRekey(apNew[i]->pDbPage, pgnoB, fgB); + apNew[i]->pgno = pgnoB; + apNew[iB]->pgno = pgnoA; } } |