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Add the SQLITE_ANALYZE_LIMIT compile-time option (expected to be temporary)

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that sets a threshold at which ANALYZE starts to use approximations during
the analysis process.

FossilOrigin-Name: a773fd4698d474fda5e57bc77ed66a79cf74efee2706f43f6def6f450bfd1fc0
This commit is contained in:
drh
2020-03-18 14:43:05 +00:00
parent 9f27463684
commit 59a8cb7931
3 changed files with 50 additions and 18 deletions
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54
src/analyze.c
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@@ -284,6 +284,7 @@ struct StatAccum {
tRowcnt nRow; /* Number of rows visited so far */
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 */
StatSample current; /* Current row as a StatSample */
#ifdef SQLITE_ENABLE_STAT4
tRowcnt nPSample; /* How often to do a periodic sample */
@@ -404,10 +405,10 @@ static void statInit(
int nKeyCol; /* Number of key columns */
int nColUp; /* nCol rounded up for alignment */
int n; /* Bytes of space to allocate */
sqlite3 *db; /* Database connection */
sqlite3 *db = sqlite3_context_db_handle(context); /* Database connection */
#ifdef SQLITE_ENABLE_STAT4
/* Maximum number of samples. 0 if STAT4 data is not collected */
int mxSample = sqlite3_value_int64(argv[2]) ? SQLITE_STAT4_SAMPLES : 0;
int mxSample = OptimizationEnabled(db,SQLITE_Stat4) ?SQLITE_STAT4_SAMPLES :0;
#endif
/* Decode the three function arguments */
@@ -442,16 +443,17 @@ static void statInit(
p->nRow = 0;
p->nCol = nCol;
p->nKeyCol = nKeyCol;
p->nSkipAhead = 0;
p->current.anDLt = (tRowcnt*)&p[1];
p->current.anEq = &p->current.anDLt[nColUp];
#ifdef SQLITE_ENABLE_STAT4
p->mxSample = mxSample;
if( mxSample ){
u8 *pSpace; /* Allocated space not yet assigned */
int i; /* Used to iterate through p->aSample[] */
p->iGet = -1;
p->mxSample = mxSample;
p->nPSample = (tRowcnt)(p->nEst/(mxSample/3+1) + 1);
p->current.anLt = &p->current.anEq[nColUp];
p->iPrn = 0x689e962d*(u32)nCol ^ 0xd0944565*(u32)sqlite3_value_int(argv[2]);
@@ -675,6 +677,15 @@ 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:
@@ -684,10 +695,13 @@ static void samplePushPrevious(StatAccum *p, int iChng){
** R Rowid for the current row. Might be a key record for
** WITHOUT ROWID tables.
**
** This SQL function always returns NULL. It's purpose it to accumulate
** statistical data and/or samples in the StatAccum object about the
** index being analyzed. The stat_get() SQL function will later be used to
** extract relevant information for constructing the sqlite_statN tables.
** The purpose of this routine is to collect statistical data and/or
** samples from the index being analyzed into the StatAccum object.
** The stat_get() SQL function will be used afterwards to
** retrieve the information gathered.
**
** This SQL function usually returns NULL, but might return an integer
** if it wants the byte-code to do special processing.
**
** The R parameter is only used for STAT4
*/
@@ -729,6 +743,7 @@ static void statPush(
p->current.anEq[i] = 1;
}
}
p->nRow++;
#ifdef SQLITE_ENABLE_STAT4
if( p->mxSample ){
@@ -757,9 +772,16 @@ static void statPush(
sampleCopy(p, &p->aBest[i], &p->current);
}
}
}else
#endif
#if SQLITE_ANALYZE_LIMIT
if( p->nRow>SQLITE_ANALYZE_LIMIT*(p->nSkipAhead+1) ){
p->nSkipAhead++;
sqlite3_result_int(context, p->current.anDLt[0]>0);
}
#endif
}
static const FuncDef statPushFuncdef = {
2+IsStat4, /* nArg */
SQLITE_UTF8, /* funcFlags */
@@ -847,7 +869,8 @@ static void statGet(
return;
}
sqlite3_snprintf(24, zRet, "%llu", (u64)p->nRow);
sqlite3_snprintf(24, zRet, "%llu",
p->nSkipAhead ? (u64)p->nEst : (u64)p->nRow);
z = zRet + sqlite3Strlen30(zRet);
for(i=0; i<p->nKeyCol; i++){
u64 nDistinct = p->current.anDLt[i] + 1;
@@ -1204,9 +1227,18 @@ static void analyzeOneTable(
}
#endif
assert( regChng==(regStat+1) );
sqlite3VdbeAddFunctionCall(pParse, 1, regStat, regTemp, 2+IsStat4,
&statPushFuncdef, 0);
sqlite3VdbeAddOp2(v, OP_Next, iIdxCur, addrNextRow); VdbeCoverage(v);
{
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);
}
/* Add the entry to the stat1 table. */
callStatGet(pParse, regStat, STAT_GET_STAT1, regStat1);