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Add "PRAGMA analysis_limit=N;" to limit the number of rows visited by

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ANALYZE when N is positive.  Positive N also disables collecting stat4.

FossilOrigin-Name: a279b151c1623807774daf4975175c62ea252eefb71f9820ced6773769b392c5
This commit is contained in:
drh
2020-03-31 20:57:06 +00:00
parent dcdd707a9c
commit 49a76a8fe5
7 changed files with 109 additions and 79 deletions
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49
src/analyze.c
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@@ -282,6 +282,7 @@ struct StatAccum {
sqlite3 *db; /* Database connection, for malloc() */
tRowcnt nEst; /* Estimated number of rows */
tRowcnt nRow; /* Number of rows visited so far */
int nLimit; /* Analysis row-scan limit */
int nCol; /* Number of columns in index + pk/rowid */
int nKeyCol; /* Number of index columns w/o the pk/rowid */
u8 nSkipAhead; /* Number of times of skip-ahead */
@@ -375,11 +376,12 @@ static void statAccumDestructor(void *pOld){
}
/*
** Implementation of the stat_init(N,K,C) SQL function. The three parameters
** Implementation of the stat_init(N,K,C,L) SQL function. The four parameters
** are:
** N: The number of columns in the index including the rowid/pk (note 1)
** K: The number of columns in the index excluding the rowid/pk.
** C: Estimated number of rows in the index
** L: A limit on the number of rows to scan, or 0 for no-limit
**
** Note 1: In the special case of the covering index that implements a
** WITHOUT ROWID table, N is the number of PRIMARY KEY columns, not the
@@ -441,6 +443,11 @@ static void statInit(
p->db = db;
p->nEst = sqlite3_value_int64(argv[2]);
p->nRow = 0;
p->nLimit = sqlite3_value_int64(argv[3]);
#ifdef SQLITE_ENABLE_STAT4
/* Disable STAT4 statistics gathering if there is a analysis_limit set */
if( p->nLimit>0 ) p->mxSample = 0;
#endif
p->nCol = nCol;
p->nKeyCol = nKeyCol;
p->nSkipAhead = 0;
@@ -677,15 +684,6 @@ static void samplePushPrevious(StatAccum *p, int iChng){
}
#endif /* SQLITE_ENABLE_STAT4 */
/*
** A limit on the number of rows of an index that will be examined
** by ANALYZE before it starts going with approximations. Zero means
** "no limit".
*/
#ifndef SQLITE_ANALYZE_LIMIT
# define SQLITE_ANALYZE_LIMIT 0
#endif
/*
** Implementation of the stat_push SQL function: stat_push(P,C,R)
** Arguments:
@@ -774,14 +772,10 @@ static void statPush(
}
}else
#endif
#if SQLITE_ANALYZE_LIMIT
if( p->nRow>SQLITE_ANALYZE_LIMIT*(p->nSkipAhead+1) ){
if( p->nLimit && p->nRow>p->nLimit*(p->nSkipAhead+1) ){
p->nSkipAhead++;
sqlite3_result_int(context, p->current.anDLt[0]>0);
}
#else
{}
#endif
}
static const FuncDef statPushFuncdef = {
@@ -987,6 +981,7 @@ static void analyzeOneTable(
int regChng = iMem++; /* Index of changed index field */
int regRowid = iMem++; /* Rowid argument passed to stat_push() */
int regTemp = iMem++; /* Temporary use register */
int regTemp2 = iMem++; /* Second temporary use register */
int regTabname = iMem++; /* Register containing table name */
int regIdxname = iMem++; /* Register containing index name */
int regStat1 = iMem++; /* Value for the stat column of sqlite_stat1 */
@@ -1131,7 +1126,9 @@ static void analyzeOneTable(
VdbeCoverage(v);
sqlite3VdbeAddOp3(v, OP_Count, iIdxCur, regTemp, 1);
}
sqlite3VdbeAddFunctionCall(pParse, 0, regStat+1, regStat, 3,
assert( regTemp2==regStat+4 );
sqlite3VdbeAddOp2(v, OP_Integer, db->nAnalysisLimit, regTemp2);
sqlite3VdbeAddFunctionCall(pParse, 0, regStat+1, regStat, 4,
&statInitFuncdef, 0);
/* Implementation of the following:
@@ -1230,16 +1227,20 @@ static void analyzeOneTable(
#endif
assert( regChng==(regStat+1) );
{
int j1, j2, j3;
sqlite3VdbeAddFunctionCall(pParse, 1, regStat, regTemp, 2+IsStat4,
&statPushFuncdef, 0);
j1 = sqlite3VdbeAddOp1(v, OP_IsNull, regTemp);
j2 = sqlite3VdbeAddOp1(v, OP_If, regTemp);
j3 = sqlite3VdbeAddOp4Int(v, OP_SeekGT, iIdxCur, 0, regPrev, 1);
sqlite3VdbeJumpHere(v, j1);
sqlite3VdbeAddOp2(v, OP_Next, iIdxCur, addrNextRow); VdbeCoverage(v);
sqlite3VdbeJumpHere(v, j2);
sqlite3VdbeJumpHere(v, j3);
if( db->nAnalysisLimit ){
int j1, j2, j3;
j1 = sqlite3VdbeAddOp1(v, OP_IsNull, regTemp); VdbeCoverage(v);
j2 = sqlite3VdbeAddOp1(v, OP_If, regTemp); VdbeCoverage(v);
j3 = sqlite3VdbeAddOp4Int(v, OP_SeekGT, iIdxCur, 0, regPrev, 1);
sqlite3VdbeJumpHere(v, j1);
sqlite3VdbeAddOp2(v, OP_Next, iIdxCur, addrNextRow); VdbeCoverage(v);
sqlite3VdbeJumpHere(v, j2);
sqlite3VdbeJumpHere(v, j3);
}else{
sqlite3VdbeAddOp2(v, OP_Next, iIdxCur, addrNextRow); VdbeCoverage(v);
}
}
/* Add the entry to the stat1 table. */