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Enhancements to skip-scan such that it is operable when a middle column of

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an index is skipped while the left-most column is constrained in the WHERE
clause.

FossilOrigin-Name: bc985caa7816f1f873ad8e4467c5278399f315ce
This commit is contained in:
drh
2014-08-20 23:38:07 +00:00
parent 7bc4c454da
commit f3f69ac942
4 changed files with 97 additions and 12 deletions
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21
src/where.c
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@@ -3781,8 +3781,8 @@ static void whereLoopPrint(WhereLoop *p, WhereClause *pWC){
sqlite3DebugPrintf(" %12s",
pItem->zAlias ? pItem->zAlias : pTab->zName);
if( (p->wsFlags & WHERE_VIRTUALTABLE)==0 ){
const char *zName;
if( p->u.btree.pIndex && (zName = p->u.btree.pIndex->zName)!=0 ){
const char *zName;
if( p->u.btree.pIndex && (zName = p->u.btree.pIndex->zName)!=0 ){
if( strncmp(zName, "sqlite_autoindex_", 17)==0 ){
int i = sqlite3Strlen30(zName) - 1;
while( zName[i]!='_' ) i--;
@@ -3803,7 +3803,11 @@ static void whereLoopPrint(WhereLoop *p, WhereClause *pWC){
sqlite3DebugPrintf(" %-19s", z);
sqlite3_free(z);
}
sqlite3DebugPrintf(" f %05x N %d", p->wsFlags, p->nLTerm);
if( p->wsFlags & WHERE_SKIPSCAN ){
sqlite3DebugPrintf(" f %05x %d-%d", p->wsFlags, p->nLTerm,p->u.btree.nSkip);
}else{
sqlite3DebugPrintf(" f %05x N %d", p->wsFlags, p->nLTerm);
}
sqlite3DebugPrintf(" cost %d,%d,%d\n", p->rSetup, p->rRun, p->nOut);
#ifdef SQLITE_ENABLE_TREE_EXPLAIN
/* If the 0x100 bit of wheretracing is set, then show all of the constraint
@@ -4316,8 +4320,7 @@ static int whereLoopAddBtreeIndex(
** On the other hand, the extra seeks could end up being significantly
** more expensive. */
assert( 42==sqlite3LogEst(18) );
if( pTerm==0
&& saved_nEq==saved_nSkip
if( saved_nEq==saved_nSkip
&& saved_nEq+1<pProbe->nKeyCol
&& pProbe->aiRowLogEst[saved_nEq+1]>=42 /* TUNING: Minimum for skip-scan */
&& (rc = whereLoopResize(db, pNew, pNew->nLTerm+1))==SQLITE_OK
@@ -4328,9 +4331,17 @@ static int whereLoopAddBtreeIndex(
pNew->aLTerm[pNew->nLTerm++] = 0;
pNew->wsFlags |= WHERE_SKIPSCAN;
nIter = pProbe->aiRowLogEst[saved_nEq] - pProbe->aiRowLogEst[saved_nEq+1];
if( pTerm ){
/* TUNING: When estimating skip-scan for a term that is also indexable,
** increase the cost of the skip-scan by 2x, to make it a little less
** desirable than the regular index lookup. */
nIter += 10; assert( 10==sqlite3LogEst(2) );
}
pNew->nOut -= nIter;
whereLoopAddBtreeIndex(pBuilder, pSrc, pProbe, nIter + nInMul);
pNew->nOut = saved_nOut;
pNew->u.btree.nEq = saved_nEq;
pNew->u.btree.nSkip = saved_nSkip;
}
for(; rc==SQLITE_OK && pTerm!=0; pTerm = whereScanNext(&scan)){
u16 eOp = pTerm->eOperator; /* Shorthand for pTerm->eOperator */