/ Check-in [f86b75b6]
Login
SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Adjustments to #ifdefs in analyze.c to all a clean compile with no extra code with both ENABLE_STAT3 and ENABLE_STAT4 and with neither.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | sqlite_stat4
Files: files | file ages | folders
SHA1: f86b75b6c7290ee6ddb3636090b00e99fc68c45e
User & Date: drh 2013-08-17 18:57:15
Context
2013-08-26
23:18
Merge the STAT4 capability into trunk. check-in: a32af0ab user: drh tags: trunk
2013-08-17
18:57
Adjustments to #ifdefs in analyze.c to all a clean compile with no extra code with both ENABLE_STAT3 and ENABLE_STAT4 and with neither. Closed-Leaf check-in: f86b75b6 user: drh tags: sqlite_stat4
2013-08-16
17:46
Add a test for the problem fixed by [91733bc485]. check-in: 5c591104 user: dan tags: sqlite_stat4
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/analyze.c.

137
138
139
140
141
142
143
144
145

146
147
148

149
150
151

152
153
154
155
156
157
158
...
362
363
364
365
366
367
368

369
370
371
372
373
374
375
...
483
484
485
486
487
488
489

490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518

519
520

521
522
523
524
525
526
527
528
...
530
531
532
533
534
535
536

537
538
539
540
541
542
543
...
579
580
581
582
583
584
585
586

587
588
589
590
591
592
593
...
598
599
600
601
602
603
604

605
606
607
608
609
610
611
...
620
621
622
623
624
625
626
627
628
629
630
631

632
633
634
635
636
637
638
639
640
641
642


643

644
645
646
647
648
649




650
651
652
653
654
655
656
...
685
686
687
688
689
690
691


692
693
694
695
696
697
698
699
...
726
727
728
729
730
731
732

733
734
735
736
737
738
739
...
743
744
745
746
747
748
749

750



751
752
753
754
755
756
757
758
759
760
....
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
....
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
....
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
....
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
....
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
** all contain just a single integer which is the same as the first
** integer in the equivalent columns in sqlite_stat4.
*/
#ifndef SQLITE_OMIT_ANALYZE
#include "sqliteInt.h"

#if defined(SQLITE_ENABLE_STAT4)
# define IsStat4 1
# define IsStat3 0

#elif defined(SQLITE_ENABLE_STAT3)
# define IsStat4 0
# define IsStat3 1

#else
# define IsStat4 0
# define IsStat3 0

#endif

/*
** This routine generates code that opens the sqlite_stat1 table for
** writing with cursor iStatCur. If the library was built with the
** SQLITE_ENABLE_STAT4 macro defined, then the sqlite_stat4 table is
** opened for writing using cursor (iStatCur+1)
................................................................................
  0,               /* xStep */
  0,               /* xFinalize */
  "stat_init",     /* zName */
  0,               /* pHash */
  0                /* pDestructor */
};


/*
** Return true if pNew is to be preferred over pOld.
*/
static int sampleIsBetter(Stat4Sample *pNew, Stat4Sample *pOld){
  tRowcnt nEqNew = pNew->anEq[pNew->iCol];
  tRowcnt nEqOld = pOld->anEq[pOld->iCol];

................................................................................
        iMin = i;
      }
    }
    assert( iMin>=0 );
    p->iMin = iMin;
  }
}


/*
** Field iChng of the index being scanned has changed. So at this point
** p->current contains a sample that reflects the previous row of the
** index. The value of anEq[iChng] and subsequent anEq[] elements are
** correct at this point.
*/
static void samplePushPrevious(Stat4Accum *p, int iChng){
  if( IsStat4 ){
    int i;

    /* Check if any samples from the aBest[] array should be pushed
    ** into IndexSample.a[] at this point.  */
    for(i=(p->nCol-2); i>=iChng; i--){
      Stat4Sample *pBest = &p->aBest[i];
      if( p->nSample<p->mxSample
       || sampleIsBetter(pBest, &p->a[p->iMin])
      ){
        sampleInsert(p, pBest, i);
      }
    }

    /* Update the anEq[] fields of any samples already collected. */
    for(i=p->nSample-1; i>=0; i--){
      int j;
      for(j=iChng; j<p->nCol; j++){
        if( p->a[i].anEq[j]==0 ) p->a[i].anEq[j] = p->current.anEq[j];
      }
    }

  }


  if( IsStat3 && iChng==0 ){
    tRowcnt nLt = p->current.anLt[0];
    tRowcnt nEq = p->current.anEq[0];

    /* Check if this is to be a periodic sample. If so, add it. */
    if( (nLt/p->nPSample)!=(nLt+nEq)/p->nPSample ){
      p->current.isPSample = 1;
      sampleInsert(p, &p->current, 0);
................................................................................
    }else 

    /* Or if it is a non-periodic sample. Add it in this case too. */
    if( p->nSample<p->mxSample || sampleIsBetter(&p->current, &p->a[p->iMin]) ){
      sampleInsert(p, &p->current, 0);
    }
  }

}

/*
** Implementation of the stat_push SQL function. 
**
**    stat_push(P,R,C)
**
................................................................................
  }

  if( IsStat4 || IsStat3 ){
    p->current.iRowid = rowid;
    p->current.iHash = p->iPrn = p->iPrn*1103515245 + 12345;
  }

  if( IsStat4 ){

    tRowcnt nLt = p->current.anLt[p->nCol-1];

    /* Check if this is to be a periodic sample. If so, add it. */
    if( (nLt/p->nPSample)!=(nLt+1)/p->nPSample ){
      p->current.isPSample = 1;
      p->current.iCol = 0;
      sampleInsert(p, &p->current, p->nCol-1);
................................................................................
    for(i=0; i<(p->nCol-1); i++){
      p->current.iCol = i;
      if( i>=iChng || sampleIsBetter(&p->current, &p->aBest[i]) ){
        sampleCopy(p, &p->aBest[i], &p->current);
      }
    }
  }

}
static const FuncDef statPushFuncdef = {
  3,               /* nArg */
  SQLITE_UTF8,     /* iPrefEnc */
  0,               /* flags */
  0,               /* pUserData */
  0,               /* pNext */
................................................................................
#define STAT_GET_STAT1 0          /* "stat" column of stat1 table */
#define STAT_GET_ROWID 1          /* "rowid" column of stat[34] entry */
#define STAT_GET_NEQ   2          /* "neq" column of stat[34] entry */
#define STAT_GET_NLT   3          /* "nlt" column of stat[34] entry */
#define STAT_GET_NDLT  4          /* "ndlt" column of stat[34] entry */

/*
** Implementation of the stat3_get(P,N,...) SQL function.  This routine is
** used to query the results.  Content is returned for the Nth sqlite_stat3
** row where N is between 0 and S-1 and S is the number of samples.  The
** value returned depends on the number of arguments.
**

**   argc==2    result:  rowid
**   argc==3    result:  nEq
**   argc==4    result:  nLt
**   argc==5    result:  nDLt
*/
static void statGet(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  Stat4Accum *p = (Stat4Accum*)sqlite3_value_blob(argv[0]);


  int eCall = sqlite3_value_int(argv[1]);

  assert( eCall==STAT_GET_STAT1 || eCall==STAT_GET_NEQ 
       || eCall==STAT_GET_ROWID || eCall==STAT_GET_NLT
       || eCall==STAT_GET_NDLT 
  );

  if( eCall==STAT_GET_STAT1 ){




    /* Return the value to store in the "stat" column of the sqlite_stat1
    ** table for this index.
    **
    ** The value is a string composed of a list of integers describing 
    ** the index. The first integer in the list is the total number of 
    ** entries in the index. There is one additional integer in the list 
    ** for each indexed column. This additional integer is an estimate of
................................................................................
      sqlite3_snprintf(24, z, " %lld", iVal);
      z += sqlite3Strlen30(z);
      assert( p->current.anEq[i] );
    }
    assert( z[0]=='\0' && z>zRet );

    sqlite3_result_text(context, zRet, -1, sqlite3_free);


  }else if( eCall==STAT_GET_ROWID ){
    if( p->iGet<0 ){
      samplePushPrevious(p, 0);
      p->iGet = 0;
    }
    if( p->iGet<p->nSample ){
      sqlite3_result_int64(context, p->a[p->iGet].iRowid);
    }
................................................................................
        }
        assert( z[0]=='\0' && z>zRet );
        z[-1] = '\0';
        sqlite3_result_text(context, zRet, -1, sqlite3_free);
      }
    }
  }

}
static const FuncDef statGetFuncdef = {
  2,               /* nArg */
  SQLITE_UTF8,     /* iPrefEnc */
  0,               /* flags */
  0,               /* pUserData */
  0,               /* pNext */
................................................................................
  "stat_get",      /* zName */
  0,               /* pHash */
  0                /* pDestructor */
};

static void callStatGet(Vdbe *v, int regStat4, int iParam, int regOut){
  assert( regOut!=regStat4 && regOut!=regStat4+1 );

  sqlite3VdbeAddOp2(v, OP_Integer, iParam, regStat4+1);



  sqlite3VdbeAddOp3(v, OP_Function, 0, regStat4, regOut);
  sqlite3VdbeChangeP4(v, -1, (char*)&statGetFuncdef, P4_FUNCDEF);
  sqlite3VdbeChangeP5(v, 2);
}

/*
** Generate code to do an analysis of all indices associated with
** a single table.
*/
static void analyzeOneTable(
................................................................................
}

/*
** If the Index.aSample variable is not NULL, delete the aSample[] array
** and its contents.
*/
void sqlite3DeleteIndexSamples(sqlite3 *db, Index *pIdx){
#if defined(SQLITE_ENABLE_STAT4) || defined(SQLITE_ENABLE_STAT3)
  if( pIdx->aSample ){
    int j;
    for(j=0; j<pIdx->nSample; j++){
      IndexSample *p = &pIdx->aSample[j];
      sqlite3DbFree(db, p->p);
    }
    sqlite3DbFree(db, pIdx->aSample);
................................................................................
  if( db && db->pnBytesFreed==0 ){
    pIdx->nSample = 0;
    pIdx->aSample = 0;
  }
#else
  UNUSED_PARAMETER(db);
  UNUSED_PARAMETER(pIdx);
#endif
}

#if defined(SQLITE_ENABLE_STAT4) || defined(SQLITE_ENABLE_STAT3)

/*
** Populate the pIdx->aAvgEq[] array based on the samples currently
** stored in pIdx->aSample[]. 
*/
static void initAvgEq(Index *pIdx){
  if( pIdx ){
    IndexSample *aSample = pIdx->aSample;
................................................................................
      "SELECT idx,neq,nlt,ndlt,sqlite_record(sample) FROM %Q.sqlite_stat3",
      zDb
    );
  }

  return rc;
}
#endif /* SQLITE_ENABLE_STAT4 */

/*
** Load the content of the sqlite_stat1 and sqlite_stat4 tables. The
** contents of sqlite_stat1 are used to populate the Index.aiRowEst[]
** arrays. The contents of sqlite_stat4 are used to populate the
** Index.aSample[] arrays.
**
** If the sqlite_stat1 table is not present in the database, SQLITE_ERROR
** is returned. In this case, even if SQLITE_ENABLE_STAT4 was defined 
** during compilation and the sqlite_stat4 table is present, no data is 
** read from it.
**
** If SQLITE_ENABLE_STAT4 was defined during compilation and the 
** sqlite_stat4 table is not present in the database, SQLITE_ERROR is
** returned. However, in this case, data is read from the sqlite_stat1
** table (if it is present) before returning.
**
** If an OOM error occurs, this function always sets db->mallocFailed.
** This means if the caller does not care about other errors, the return
** code may be ignored.
................................................................................
  assert( db->aDb[iDb].pBt!=0 );

  /* Clear any prior statistics */
  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
  for(i=sqliteHashFirst(&db->aDb[iDb].pSchema->idxHash);i;i=sqliteHashNext(i)){
    Index *pIdx = sqliteHashData(i);
    sqlite3DefaultRowEst(pIdx);
#if defined(SQLITE_ENABLE_STAT4) || defined(SQLITE_ENABLE_STAT3)
    sqlite3DeleteIndexSamples(db, pIdx);
    pIdx->aSample = 0;
#endif
  }

  /* Check to make sure the sqlite_stat1 table exists */
  sInfo.db = db;
................................................................................
  }else{
    rc = sqlite3_exec(db, zSql, analysisLoader, &sInfo, 0);
    sqlite3DbFree(db, zSql);
  }


  /* Load the statistics from the sqlite_stat4 table. */
#if defined(SQLITE_ENABLE_STAT4) || defined(SQLITE_ENABLE_STAT3)
  if( rc==SQLITE_OK ){
    int lookasideEnabled = db->lookaside.bEnabled;
    db->lookaside.bEnabled = 0;
    rc = loadStat4(db, sInfo.zDatabase);
    db->lookaside.bEnabled = lookasideEnabled;
  }
#endif







|
|
>

|
|
>

|
|
>







 







>







 







>








|
|

|
|
|
|
|
|
|
|
|
|

|
|
|
|
|
|
|
>
|
<
>
|







 







>







 







|
>







 







>







 







|
|
|
<

>
|
|
|
<







>
>

>




<
|
>
>
>
>







 







>
>
|







 







>







 







>

>
>
>


|







 







|







 







|


|
<







 







|


|

|



|
|


|







 







|







 







|







137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
...
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
...
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525

526
527
528
529
530
531
532
533
534
...
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
...
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
...
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
...
629
630
631
632
633
634
635
636
637
638

639
640
641
642
643

644
645
646
647
648
649
650
651
652
653
654
655
656
657
658

659
660
661
662
663
664
665
666
667
668
669
670
...
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
...
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
...
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
....
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
....
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291

1292
1293
1294
1295
1296
1297
1298
....
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
....
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
....
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
** all contain just a single integer which is the same as the first
** integer in the equivalent columns in sqlite_stat4.
*/
#ifndef SQLITE_OMIT_ANALYZE
#include "sqliteInt.h"

#if defined(SQLITE_ENABLE_STAT4)
# define IsStat4     1
# define IsStat3     0
# define SQLITE_ENABLE_STAT34 1
#elif defined(SQLITE_ENABLE_STAT3)
# define IsStat4     0
# define IsStat3     1
# define SQLITE_ENABLE_STAT34 1
#else
# define IsStat4     0
# define IsStat3     0
# undef SQLITE_ENABLE_STAT34
#endif

/*
** This routine generates code that opens the sqlite_stat1 table for
** writing with cursor iStatCur. If the library was built with the
** SQLITE_ENABLE_STAT4 macro defined, then the sqlite_stat4 table is
** opened for writing using cursor (iStatCur+1)
................................................................................
  0,               /* xStep */
  0,               /* xFinalize */
  "stat_init",     /* zName */
  0,               /* pHash */
  0                /* pDestructor */
};

#ifdef SQLITE_ENABLE_STAT34
/*
** Return true if pNew is to be preferred over pOld.
*/
static int sampleIsBetter(Stat4Sample *pNew, Stat4Sample *pOld){
  tRowcnt nEqNew = pNew->anEq[pNew->iCol];
  tRowcnt nEqOld = pOld->anEq[pOld->iCol];

................................................................................
        iMin = i;
      }
    }
    assert( iMin>=0 );
    p->iMin = iMin;
  }
}
#endif /* SQLITE_ENABLE_STAT34 */

/*
** Field iChng of the index being scanned has changed. So at this point
** p->current contains a sample that reflects the previous row of the
** index. The value of anEq[iChng] and subsequent anEq[] elements are
** correct at this point.
*/
static void samplePushPrevious(Stat4Accum *p, int iChng){
#ifdef SQLITE_ENABLE_STAT4
  int i;

  /* Check if any samples from the aBest[] array should be pushed
  ** into IndexSample.a[] at this point.  */
  for(i=(p->nCol-2); i>=iChng; i--){
    Stat4Sample *pBest = &p->aBest[i];
    if( p->nSample<p->mxSample
     || sampleIsBetter(pBest, &p->a[p->iMin])
    ){
      sampleInsert(p, pBest, i);
    }
  }

  /* Update the anEq[] fields of any samples already collected. */
  for(i=p->nSample-1; i>=0; i--){
    int j;
    for(j=iChng; j<p->nCol; j++){
      if( p->a[i].anEq[j]==0 ) p->a[i].anEq[j] = p->current.anEq[j];
    }
  }
#endif


#if defined(SQLITE_ENABLE_STAT3) && !defined(SQLITE_ENABLE_STAT4)
  if( iChng==0 ){
    tRowcnt nLt = p->current.anLt[0];
    tRowcnt nEq = p->current.anEq[0];

    /* Check if this is to be a periodic sample. If so, add it. */
    if( (nLt/p->nPSample)!=(nLt+nEq)/p->nPSample ){
      p->current.isPSample = 1;
      sampleInsert(p, &p->current, 0);
................................................................................
    }else 

    /* Or if it is a non-periodic sample. Add it in this case too. */
    if( p->nSample<p->mxSample || sampleIsBetter(&p->current, &p->a[p->iMin]) ){
      sampleInsert(p, &p->current, 0);
    }
  }
#endif
}

/*
** Implementation of the stat_push SQL function. 
**
**    stat_push(P,R,C)
**
................................................................................
  }

  if( IsStat4 || IsStat3 ){
    p->current.iRowid = rowid;
    p->current.iHash = p->iPrn = p->iPrn*1103515245 + 12345;
  }

#ifdef SQLITE_ENABLE_STAT4
  {
    tRowcnt nLt = p->current.anLt[p->nCol-1];

    /* Check if this is to be a periodic sample. If so, add it. */
    if( (nLt/p->nPSample)!=(nLt+1)/p->nPSample ){
      p->current.isPSample = 1;
      p->current.iCol = 0;
      sampleInsert(p, &p->current, p->nCol-1);
................................................................................
    for(i=0; i<(p->nCol-1); i++){
      p->current.iCol = i;
      if( i>=iChng || sampleIsBetter(&p->current, &p->aBest[i]) ){
        sampleCopy(p, &p->aBest[i], &p->current);
      }
    }
  }
#endif
}
static const FuncDef statPushFuncdef = {
  3,               /* nArg */
  SQLITE_UTF8,     /* iPrefEnc */
  0,               /* flags */
  0,               /* pUserData */
  0,               /* pNext */
................................................................................
#define STAT_GET_STAT1 0          /* "stat" column of stat1 table */
#define STAT_GET_ROWID 1          /* "rowid" column of stat[34] entry */
#define STAT_GET_NEQ   2          /* "neq" column of stat[34] entry */
#define STAT_GET_NLT   3          /* "nlt" column of stat[34] entry */
#define STAT_GET_NDLT  4          /* "ndlt" column of stat[34] entry */

/*
** Implementation of the stat_get(P,J) SQL function.  This routine is
** used to query the results.  Content is returned for parameter J
** which is one of the STAT_GET_xxxx values defined above.

**
** If neither STAT3 nor STAT4 are enabled, then J is always
** STAT_GET_STAT1 and is hence omitted and this routine becomes
** a one-parameter function, stat_get(P), that always returns the
** stat1 table entry information.

*/
static void statGet(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  Stat4Accum *p = (Stat4Accum*)sqlite3_value_blob(argv[0]);
#ifdef SQLITE_ENABLE_STAT34
  /* STAT3 and STAT4 have a parameter on this routine. */
  int eCall = sqlite3_value_int(argv[1]);
  assert( argc==2 );
  assert( eCall==STAT_GET_STAT1 || eCall==STAT_GET_NEQ 
       || eCall==STAT_GET_ROWID || eCall==STAT_GET_NLT
       || eCall==STAT_GET_NDLT 
  );

  if( eCall==STAT_GET_STAT1 )
#else
  assert( argc==1 );
#endif
  {
    /* Return the value to store in the "stat" column of the sqlite_stat1
    ** table for this index.
    **
    ** The value is a string composed of a list of integers describing 
    ** the index. The first integer in the list is the total number of 
    ** entries in the index. There is one additional integer in the list 
    ** for each indexed column. This additional integer is an estimate of
................................................................................
      sqlite3_snprintf(24, z, " %lld", iVal);
      z += sqlite3Strlen30(z);
      assert( p->current.anEq[i] );
    }
    assert( z[0]=='\0' && z>zRet );

    sqlite3_result_text(context, zRet, -1, sqlite3_free);
  }
#ifdef SQLITE_ENABLE_STAT34
  else if( eCall==STAT_GET_ROWID ){
    if( p->iGet<0 ){
      samplePushPrevious(p, 0);
      p->iGet = 0;
    }
    if( p->iGet<p->nSample ){
      sqlite3_result_int64(context, p->a[p->iGet].iRowid);
    }
................................................................................
        }
        assert( z[0]=='\0' && z>zRet );
        z[-1] = '\0';
        sqlite3_result_text(context, zRet, -1, sqlite3_free);
      }
    }
  }
#endif /* SQLITE_ENABLE_STAT34 */
}
static const FuncDef statGetFuncdef = {
  2,               /* nArg */
  SQLITE_UTF8,     /* iPrefEnc */
  0,               /* flags */
  0,               /* pUserData */
  0,               /* pNext */
................................................................................
  "stat_get",      /* zName */
  0,               /* pHash */
  0                /* pDestructor */
};

static void callStatGet(Vdbe *v, int regStat4, int iParam, int regOut){
  assert( regOut!=regStat4 && regOut!=regStat4+1 );
#ifdef SQLITE_ENABLE_STAT34
  sqlite3VdbeAddOp2(v, OP_Integer, iParam, regStat4+1);
#else
  assert( iParam==STAT_GET_STAT1 );
#endif
  sqlite3VdbeAddOp3(v, OP_Function, 0, regStat4, regOut);
  sqlite3VdbeChangeP4(v, -1, (char*)&statGetFuncdef, P4_FUNCDEF);
  sqlite3VdbeChangeP5(v, 1 + IsStat3 + IsStat4);
}

/*
** Generate code to do an analysis of all indices associated with
** a single table.
*/
static void analyzeOneTable(
................................................................................
}

/*
** If the Index.aSample variable is not NULL, delete the aSample[] array
** and its contents.
*/
void sqlite3DeleteIndexSamples(sqlite3 *db, Index *pIdx){
#ifdef SQLITE_ENABLE_STAT34
  if( pIdx->aSample ){
    int j;
    for(j=0; j<pIdx->nSample; j++){
      IndexSample *p = &pIdx->aSample[j];
      sqlite3DbFree(db, p->p);
    }
    sqlite3DbFree(db, pIdx->aSample);
................................................................................
  if( db && db->pnBytesFreed==0 ){
    pIdx->nSample = 0;
    pIdx->aSample = 0;
  }
#else
  UNUSED_PARAMETER(db);
  UNUSED_PARAMETER(pIdx);
#endif /* SQLITE_ENABLE_STAT34 */
}

#ifdef SQLITE_ENABLE_STAT34

/*
** Populate the pIdx->aAvgEq[] array based on the samples currently
** stored in pIdx->aSample[]. 
*/
static void initAvgEq(Index *pIdx){
  if( pIdx ){
    IndexSample *aSample = pIdx->aSample;
................................................................................
      "SELECT idx,neq,nlt,ndlt,sqlite_record(sample) FROM %Q.sqlite_stat3",
      zDb
    );
  }

  return rc;
}
#endif /* SQLITE_ENABLE_STAT34 */

/*
** Load the content of the sqlite_stat1 and sqlite_stat3/4 tables. The
** contents of sqlite_stat1 are used to populate the Index.aiRowEst[]
** arrays. The contents of sqlite_stat3/4 are used to populate the
** Index.aSample[] arrays.
**
** If the sqlite_stat1 table is not present in the database, SQLITE_ERROR
** is returned. In this case, even if SQLITE_ENABLE_STAT3/4 was defined 
** during compilation and the sqlite_stat3/4 table is present, no data is 
** read from it.
**
** If SQLITE_ENABLE_STAT3/4 was defined during compilation and the 
** sqlite_stat4 table is not present in the database, SQLITE_ERROR is
** returned. However, in this case, data is read from the sqlite_stat1
** table (if it is present) before returning.
**
** If an OOM error occurs, this function always sets db->mallocFailed.
** This means if the caller does not care about other errors, the return
** code may be ignored.
................................................................................
  assert( db->aDb[iDb].pBt!=0 );

  /* Clear any prior statistics */
  assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
  for(i=sqliteHashFirst(&db->aDb[iDb].pSchema->idxHash);i;i=sqliteHashNext(i)){
    Index *pIdx = sqliteHashData(i);
    sqlite3DefaultRowEst(pIdx);
#ifdef SQLITE_ENABLE_STAT34
    sqlite3DeleteIndexSamples(db, pIdx);
    pIdx->aSample = 0;
#endif
  }

  /* Check to make sure the sqlite_stat1 table exists */
  sInfo.db = db;
................................................................................
  }else{
    rc = sqlite3_exec(db, zSql, analysisLoader, &sInfo, 0);
    sqlite3DbFree(db, zSql);
  }


  /* Load the statistics from the sqlite_stat4 table. */
#ifdef SQLITE_ENABLE_STAT34
  if( rc==SQLITE_OK ){
    int lookasideEnabled = db->lookaside.bEnabled;
    db->lookaside.bEnabled = 0;
    rc = loadStat4(db, sInfo.zDatabase);
    db->lookaside.bEnabled = lookasideEnabled;
  }
#endif