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Make sure that all automatic indices are covering indices. Otherwise, the

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table and index might be used together in a query but the table could get
out of sync with the automatic index through out-of-band changes.

FossilOrigin-Name: 2364313142668b3d0ad144447b4862709be929cd
This commit is contained in:
drh
2010-04-07 14:59:45 +00:00
parent 2a6a7eeba5
commit 4139c99eba
3 changed files with 85 additions and 39 deletions
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104
src/where.c
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@@ -1637,9 +1637,28 @@ static void bestOrClauseIndex(
#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
}
/*
** Return TRUE if the WHERE clause term pTerm is of a form where it
** could be used with an index to access pSrc, assuming an appropriate
** index existed.
*/
static int termCanDriveIndex(
WhereTerm *pTerm, /* WHERE clause term to check */
struct SrcList_item *pSrc, /* Table we are trying to access */
Bitmask notReady /* Tables in outer loops of the join */
){
char aff;
if( pTerm->leftCursor!=pSrc->iCursor ) return 0;
if( pTerm->eOperator!=WO_EQ ) return 0;
if( (pTerm->prereqRight & notReady)!=0 ) return 0;
aff = pSrc->pTab->aCol[pTerm->u.leftColumn].affinity;
if( !sqlite3IndexAffinityOk(pTerm->pExpr, aff) ) return 0;
return 1;
}
/*
** If the query plan for pSrc specified in pCost is a full table scan
** an indexing is allows (if there is no NOT INDEXED clause) and it
** and indexing is allows (if there is no NOT INDEXED clause) and it
** possible to construct a transient index that would perform better
** than a full table scan even when the cost of constructing the index
** is taken into account, then alter the query plan to use the
@@ -1682,12 +1701,7 @@ static void bestTransientIndex(
pTable = pSrc->pTab;
pWCEnd = &pWC->a[pWC->nTerm];
for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
if( pTerm->leftCursor==pSrc->iCursor
&& (pTerm->prereqRight & notReady)==0
&& (pTerm->eOperator & WO_EQ)!=0
&& sqlite3IndexAffinityOk(pTerm->pExpr,
pTable->aCol[pTerm->u.leftColumn].affinity)
){
if( termCanDriveIndex(pTerm, pSrc, notReady) ){
WHERETRACE(("auto-index reduces cost from %.2f to %.2f\n",
pCost->rCost, costTempIdx));
pCost->rCost = costTempIdx;
@@ -1723,7 +1737,11 @@ static void constructTransientIndex(
int addrTop; /* Top of the index fill loop */
int regRecord; /* Register holding an index record */
int n; /* Column counter */
int i; /* Loop counter */
int mxBitCol; /* Maximum column in pSrc->colUsed */
CollSeq *pColl; /* Collating sequence to on a column */
Bitmask idxCols; /* Bitmap of columns used for indexing */
Bitmask extraCols; /* Bitmap of additional columns */
/* Generate code to skip over the creation and initialization of the
** transient index on 2nd and subsequent iterations of the loop. */
@@ -1733,23 +1751,39 @@ static void constructTransientIndex(
addrInit = sqlite3VdbeAddOp1(v, OP_If, regIsInit);
sqlite3VdbeAddOp2(v, OP_Integer, 1, regIsInit);
/* Count the number of columns that will be added to the index */
/* Count the number of columns that will be added to the index
** and used to match WHERE clause constraints */
nColumn = 0;
pTable = pSrc->pTab;
pWCEnd = &pWC->a[pWC->nTerm];
idxCols = 0;
for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
if( pTerm->leftCursor==pSrc->iCursor
&& (pTerm->prereqRight & notReady)==0
&& (pTerm->eOperator & WO_EQ)!=0
&& sqlite3IndexAffinityOk(pTerm->pExpr,
pTable->aCol[pTerm->u.leftColumn].affinity)
){
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;
pLevel->plan.wsFlags |= WHERE_COLUMN_EQ | WO_EQ;
/* 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;
}
pLevel->plan.wsFlags |= WHERE_COLUMN_EQ | WHERE_IDX_ONLY | WO_EQ;
/* Construct the Index object to describe this index */
nByte = sizeof(Index);
@@ -1767,22 +1801,32 @@ static void constructTransientIndex(
pIdx->pTable = pTable;
n = 0;
for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
if( pTerm->leftCursor==pSrc->iCursor
&& (pTerm->prereqRight & notReady)==0
&& (pTerm->eOperator & WO_EQ)!=0
&& sqlite3IndexAffinityOk(pTerm->pExpr,
pTable->aCol[pTerm->u.leftColumn].affinity)
){
int iCol = pTerm->u.leftColumn;
Expr *pX;
pIdx->aiColumn[n] = iCol;
pX = pTerm->pExpr;
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==pIdx->nColumn );
assert( n==pLevel->plan.nEq );
/* Add additional columns needed to make the index into a covering index */
for(i=0; i<mxBitCol; i++){
if( extraCols & (1<<i) ){
pIdx->aiColumn[n] = i;
pIdx->azColl[n] = "BINARY";
n++;
}
}
if( pSrc->colUsed & (((Bitmask)1)<<(BMS-1)) ){
for(i=BMS-1; i<pTable->nCol; i++){
pIdx->aiColumn[n] = i;
pIdx->azColl[n] = "BINARY";
n++;
}
}
assert( n==nColumn );
/* Create the transient index */
pKeyinfo = sqlite3IndexKeyinfo(pParse, pIdx);
@@ -2594,7 +2638,7 @@ static void bestBtreeIndex(
/* If currently calculating the cost of using an index (not the IPK
** index), determine if all required column data may be obtained without
** seeking to entries in the main table (i.e. if the index is a covering
** using the main table (i.e. if the index is a covering
** index for this query). If it is, set the WHERE_IDX_ONLY flag in
** wsFlags. Otherwise, set the bLookup variable to true. */
if( pIdx && wsFlags ){
@@ -4264,8 +4308,10 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
Table *pTab = pTabItem->pTab;
assert( pTab!=0 );
if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ) continue;
if( (pWInfo->wctrlFlags & WHERE_OMIT_CLOSE)==0 ){
if( (pTab->tabFlags & TF_Ephemeral)==0
&& pTab->pSelect==0
&& (pWInfo->wctrlFlags & WHERE_OMIT_CLOSE)==0
){
int ws = pLevel->plan.wsFlags;
if( !pWInfo->okOnePass && (ws & WHERE_IDX_ONLY)==0 ){
sqlite3VdbeAddOp1(v, OP_Close, pTabItem->iCursor);