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Update the explain virtual table to make use of SQLITE_CONSTRAINT.

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FossilOrigin-Name: b2d41ff7027b44ccb5dffc303c47d42f1f6fd66ce22e90450d3a666c73fe8b8e
This commit is contained in:
drh
2018-11-16 19:19:58 +00:00
parent 43579191e8
commit d16f26a708
3 changed files with 30 additions and 18 deletions
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34
ext/misc/explain.c
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@ -18,6 +18,10 @@
** .load ./explain
** SELECT p2 FROM explain('SELECT * FROM sqlite_master')
** WHERE opcode='OpenRead';
**
** This module was originally written to help simplify SQLite testing,
** by providing an easier means of verifying certain patterns in the
** generated bytecode.
*/
#if !defined(SQLITEINT_H)
#include "sqlite3ext.h"
@ -232,23 +236,31 @@ static int explainBestIndex(
sqlite3_vtab *tab,
sqlite3_index_info *pIdxInfo
){
int i;
int i; /* Loop counter */
int idx = -1; /* Index of a usable == constraint against SQL */
int unusable = 0; /* True if there are unusable constraints on SQL */
pIdxInfo->estimatedCost = (double)1000000;
pIdxInfo->estimatedRows = 500;
for(i=0; i<pIdxInfo->nConstraint; i++){
struct sqlite3_index_constraint *p = &pIdxInfo->aConstraint[i];
if( p->usable
&& p->iColumn==EXPLN_COLUMN_SQL
&& p->op==SQLITE_INDEX_CONSTRAINT_EQ
){
pIdxInfo->estimatedCost = 10.0;
pIdxInfo->idxNum = 1;
pIdxInfo->aConstraintUsage[i].argvIndex = 1;
pIdxInfo->aConstraintUsage[i].omit = 1;
break;
if( p->iColumn!=EXPLN_COLUMN_SQL ) continue;
if( !p->usable ){
unusable = 1;
}else if( p->op==SQLITE_INDEX_CONSTRAINT_EQ ){
idx = i;
}
}
if( idx>=0 ){
/* There exists a usable == constraint against the SQL column */
pIdxInfo->estimatedCost = 10.0;
pIdxInfo->idxNum = 1;
pIdxInfo->aConstraintUsage[idx].argvIndex = 1;
pIdxInfo->aConstraintUsage[idx].omit = 1;
}else if( unusable ){
/* There are unusable constraints against the SQL column. Do not allow
** this plan to continue forward. */
return SQLITE_CONSTRAINT;
}
return SQLITE_OK;
}