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Overview
| Comment: | When constructing automatic indices do not include the same column more than once. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | experimental |
| Files: | files | file ages | folders |
| SHA1: | d067d9f7a9138e026c1018361127e343 |
| User & Date: | drh 2010-04-08 00:40:15 |
| Original Comment: | When constructing automatic indices do not include the same column more than once. |
Context
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2010-04-08
| ||
| 01:16 | Merge automatic index changes into the trunk. check-in: bf7b8d86 user: drh tags: trunk | |
| 00:40 | When constructing automatic indices do not include the same column more than once. Closed-Leaf check-in: d067d9f7 user: drh tags: experimental | |
|
2010-04-07
| ||
| 20:32 | Pull over the latest changes from the trunk. check-in: e388fe8b user: drh tags: experimental | |
Changes
Changes to src/where.c.
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nColumn = 0;
pTable = pSrc->pTab;
pWCEnd = &pWC->a[pWC->nTerm];
idxCols = 0;
for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
if( termCanDriveIndex(pTerm, pSrc, notReady) ){
int iCol = pTerm->u.leftColumn;
if( iCol<BMS && iCol>=0 ) idxCols |= 1<<iCol;
nColumn++;
}
}
assert( nColumn>0 );
pLevel->plan.nEq = nColumn;
/* Count the number of additional columns needed to create a
** covering index. A "covering index" is an index that contains all
** columns that are needed by the query. With a covering index, the
** original table never needs to be accessed. Automatic indices must
** be a covering index because the index will not be updated if the
** original table changes and the index and table cannot both be used
** if they go out of sync.
*/
extraCols = pSrc->colUsed & ~idxCols;
mxBitCol = (pTable->nCol >= BMS-1) ? BMS-1 : pTable->nCol;
for(i=0; i<mxBitCol; i++){
if( extraCols & (1<<i) ) nColumn++;
}
if( pSrc->colUsed & (((Bitmask)1)<<(BMS-1)) ){
nColumn += pTable->nCol - BMS + 1;
}
................................................................................
pIdx->azColl = (char**)&pIdx[1];
pIdx->aiColumn = (int*)&pIdx->azColl[nColumn];
pIdx->aSortOrder = (u8*)&pIdx->aiColumn[nColumn];
pIdx->zName = "auto-index";
pIdx->nColumn = nColumn;
pIdx->pTable = pTable;
n = 0;
for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
if( termCanDriveIndex(pTerm, pSrc, notReady) ){
Expr *pX = pTerm->pExpr;
pIdx->aiColumn[n] = pTerm->u.leftColumn;
pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
pIdx->azColl[n] = pColl->zName;
n++;
}
}
assert( n==pLevel->plan.nEq );
/* Add additional columns needed to make the automatic index into
** a covering index */
for(i=0; i<mxBitCol; i++){
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nColumn = 0;
pTable = pSrc->pTab;
pWCEnd = &pWC->a[pWC->nTerm];
idxCols = 0;
for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
if( termCanDriveIndex(pTerm, pSrc, notReady) ){
int iCol = pTerm->u.leftColumn;
Bitmask cMask = iCol>=BMS ? ((Bitmask)1)<<(BMS-1) : ((Bitmask)1)<<iCol;
if( (idxCols & cMask)==0 ){
nColumn++;
idxCols |= cMask;
}
}
}
assert( nColumn>0 );
pLevel->plan.nEq = nColumn;
/* Count the number of additional columns needed to create a
** covering index. A "covering index" is an index that contains all
** columns that are needed by the query. With a covering index, the
** original table never needs to be accessed. Automatic indices must
** be a covering index because the index will not be updated if the
** original table changes and the index and table cannot both be used
** if they go out of sync.
*/
extraCols = pSrc->colUsed & (~idxCols | (((Bitmask)1)<<(BMS-1)));
mxBitCol = (pTable->nCol >= BMS-1) ? BMS-1 : pTable->nCol;
for(i=0; i<mxBitCol; i++){
if( extraCols & (1<<i) ) nColumn++;
}
if( pSrc->colUsed & (((Bitmask)1)<<(BMS-1)) ){
nColumn += pTable->nCol - BMS + 1;
}
................................................................................
pIdx->azColl = (char**)&pIdx[1];
pIdx->aiColumn = (int*)&pIdx->azColl[nColumn];
pIdx->aSortOrder = (u8*)&pIdx->aiColumn[nColumn];
pIdx->zName = "auto-index";
pIdx->nColumn = nColumn;
pIdx->pTable = pTable;
n = 0;
idxCols = 0;
for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
if( termCanDriveIndex(pTerm, pSrc, notReady) ){
int iCol = pTerm->u.leftColumn;
Bitmask cMask = iCol>=BMS ? ((Bitmask)1)<<(BMS-1) : ((Bitmask)1)<<iCol;
if( (idxCols & cMask)==0 ){
Expr *pX = pTerm->pExpr;
idxCols |= cMask;
pIdx->aiColumn[n] = pTerm->u.leftColumn;
pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
pIdx->azColl[n] = pColl->zName;
n++;
}
}
}
assert( n==pLevel->plan.nEq );
/* Add additional columns needed to make the automatic index into
** a covering index */
for(i=0; i<mxBitCol; i++){
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