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Updated comments. No code changes.

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FossilOrigin-Name: e842ad391e62df273a5b1ed569d42ea46d03a99b
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drh
2017-02-18 22:52:40 +00:00
parent 4a54bb5794
commit 99d5b4cde6
3 changed files with 39 additions and 16 deletions
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41
src/pragma.c
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@@ -1830,16 +1830,33 @@ void sqlite3Pragma(
/*
** PRAGMA analyze_as_needed
** PRAGMA schema.analyze_as_needed
**
** This pragma runs ANALYZE on any tables which would have benefitted
** from having recent statistics at some point since the start of the
** current connection. Only tables in "schema" are analyzed in the
** second form. In the first form, all tables except TEMP tables are
** checked.
**
** A table is analyzed only if both of the following are true:
**
** (1) The query planner used sqlite_stat1-style statistics for one or
** more indexes of the table at some point during the lifetime of
** the current connection.
**
** (2) One or more indexes of the table are currently unanalyzed OR
** the number of rows in the table has increased by 25 times or more
** since the last time ANALYZE was run.
*/
case PragTyp_ANALYZE_AS_NEEDED: {
int iDbLast;
int iTabCur;
HashElem *k;
Schema *pSchema;
Table *pTab;
Index *pIdx;
LogEst szThreshold;
char *zSubSql;
int iDbLast; /* Loop termination point for the schema loop */
int iTabCur; /* Cursor for a table whose size needs checking */
HashElem *k; /* Loop over tables of a schema */
Schema *pSchema; /* The current schema */
Table *pTab; /* A table in the schema */
Index *pIdx; /* An index of the table */
LogEst szThreshold; /* Size threshold above which reanalysis is needd */
char *zSubSql; /* SQL statement for the OP_SqlExec opcode */
iTabCur = pParse->nTab++;
for(iDbLast = zDb?iDb:db->nDb-1; iDb<=iDbLast; iDb++){
@@ -1848,11 +1865,17 @@ void sqlite3Pragma(
pSchema = db->aDb[iDb].pSchema;
for(k=sqliteHashFirst(&pSchema->tblHash); k; k=sqliteHashNext(k)){
pTab = (Table*)sqliteHashData(k);
/* If table pTab has not been used in a way that would benefit from
** having analysis statistics during the current session, then skip it.
** This also has the effect of skipping virtual tables and views */
if( (pTab->tabFlags & TF_StatsUsed)==0 ) continue;
/* Reanalyze if the table is 25 times larger than the last analysis */
szThreshold = pTab->nRowLogEst + 46; assert( sqlite3LogEst(25)==46 );
for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
if( !pIdx->hasStat1 ){
szThreshold = 0;
szThreshold = 0; /* Always analyze if any index lacks statistics */
break;
}
}