SQLite

Check-in [c62e358243]
Login

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

Overview
Comment:Avoid creating a temp table in the user database in the sqlite3_expert code. Trouble is, this makes sampling for stat1 data much slower.
Downloads: Tarball | ZIP archive
Timelines: family | ancestors | descendants | both | schemalint-failure
Files: files | file ages | folders
SHA3-256: c62e358243d96cb38a7ce2aa679fc640b62bf46080eab4bd5fc2acf5997d6cd5
User & Date: dan 2017-04-20 16:08:33.333
Context
2017-04-20
16:43
Speed this branch up a bit by filtering before the virtual table layer when sampling user data. (Closed-Leaf check-in: 8e57c31340 user: dan tags: schemalint-failure)
16:08
Avoid creating a temp table in the user database in the sqlite3_expert code. Trouble is, this makes sampling for stat1 data much slower. (check-in: c62e358243 user: dan tags: schemalint-failure)
09:54
Add an option to generate stat1 data based on a subset of the user database table contents to sqlite3_expert. (check-in: c69c3e21db user: dan tags: schemalint)
Changes
Unified Diff Ignore Whitespace Patch
Changes to ext/expert/sqlite3expert.c.
277
278
279
280
281
282
283





















































284
285
286
287
288
289
290
291
292
293











294
295
296
297
298
299
300
  if( pNew ){
    pNew->zColl = (char*)&pNew[1];
    memcpy(pNew->zColl, zColl, nColl+1);
  }
  return pNew;
}























































/*************************************************************************
** Beginning of virtual table implementation.
*/
typedef struct ExpertVtab ExpertVtab;
struct ExpertVtab {
  sqlite3_vtab base;
  IdxTable *pTab;
  sqlite3expert *pExpert;
};












static char *expertDequote(const char *zIn){
  int n = strlen(zIn);
  char *zRet = sqlite3_malloc(n);

  assert( zIn[0]=='\'' );
  assert( zIn[n-1]=='\'' );







>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>










>
>
>
>
>
>
>
>
>
>
>







277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
  if( pNew ){
    pNew->zColl = (char*)&pNew[1];
    memcpy(pNew->zColl, zColl, nColl+1);
  }
  return pNew;
}

/*
** An error associated with database handle db has just occurred. Pass
** the error message to callback function xOut.
*/
static void idxDatabaseError(
  sqlite3 *db,                    /* Database handle */
  char **pzErrmsg                 /* Write error here */
){
  *pzErrmsg = sqlite3_mprintf("%s", sqlite3_errmsg(db));
}

/*
** Prepare an SQL statement.
*/
static int idxPrepareStmt(
  sqlite3 *db,                    /* Database handle to compile against */
  sqlite3_stmt **ppStmt,          /* OUT: Compiled SQL statement */
  char **pzErrmsg,                /* OUT: sqlite3_malloc()ed error message */
  const char *zSql                /* SQL statement to compile */
){
  int rc = sqlite3_prepare_v2(db, zSql, -1, ppStmt, 0);
  if( rc!=SQLITE_OK ){
    *ppStmt = 0;
    idxDatabaseError(db, pzErrmsg);
  }
  return rc;
}

/*
** Prepare an SQL statement using the results of a printf() formatting.
*/
static int idxPrintfPrepareStmt(
  sqlite3 *db,                    /* Database handle to compile against */
  sqlite3_stmt **ppStmt,          /* OUT: Compiled SQL statement */
  char **pzErrmsg,                /* OUT: sqlite3_malloc()ed error message */
  const char *zFmt,               /* printf() format of SQL statement */
  ...                             /* Trailing printf() arguments */
){
  va_list ap;
  int rc;
  char *zSql;
  va_start(ap, zFmt);
  zSql = sqlite3_vmprintf(zFmt, ap);
  if( zSql==0 ){
    rc = SQLITE_NOMEM;
  }else{
    rc = idxPrepareStmt(db, ppStmt, pzErrmsg, zSql);
    sqlite3_free(zSql);
  }
  va_end(ap);
  return rc;
}


/*************************************************************************
** Beginning of virtual table implementation.
*/
typedef struct ExpertVtab ExpertVtab;
struct ExpertVtab {
  sqlite3_vtab base;
  IdxTable *pTab;
  sqlite3expert *pExpert;
};

typedef struct ExpertCsr ExpertCsr;
struct ExpertCsr {
  sqlite3_vtab_cursor base;
  sqlite3_stmt *pData;

  int iTarget;                    /* Target as a percentage */
  double target;                  /* Target nRet/nRow value */
  double nRow;                    /* Rows seen */
  double nRet;                    /* Rows returned */
};

static char *expertDequote(const char *zIn){
  int n = strlen(zIn);
  char *zRet = sqlite3_malloc(n);

  assert( zIn[0]=='\'' );
  assert( zIn[n-1]=='\'' );
385
386
387
388
389
390
391
392




393
394
395
396
397
398
399
    pScan->pTab = p->pTab;
    pScan->pNextScan = p->pExpert->pScan;
    p->pExpert->pScan = pScan;

    /* Add the constraints to the IdxScan object */
    for(i=0; i<pIdxInfo->nConstraint; i++){
      struct sqlite3_index_constraint *pCons = &pIdxInfo->aConstraint[i];
      if( pCons->usable && pCons->iColumn>=0 && (pCons->op & opmask) ){




        IdxConstraint *pNew;
        const char *zColl = sqlite3_vtab_collation(dbv, i);
        pNew = idxNewConstraint(&rc, zColl);
        if( pNew ){
          pNew->iCol = pCons->iColumn;
          if( pCons->op==SQLITE_INDEX_CONSTRAINT_EQ ){
            pNew->pNext = pScan->pEq;







|
>
>
>
>







449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
    pScan->pTab = p->pTab;
    pScan->pNextScan = p->pExpert->pScan;
    p->pExpert->pScan = pScan;

    /* Add the constraints to the IdxScan object */
    for(i=0; i<pIdxInfo->nConstraint; i++){
      struct sqlite3_index_constraint *pCons = &pIdxInfo->aConstraint[i];
      if( pCons->usable 
       && pCons->iColumn>=0 
       && p->pTab->aCol[pCons->iColumn].iPk==0
       && (pCons->op & opmask) 
      ){
        IdxConstraint *pNew;
        const char *zColl = sqlite3_vtab_collation(dbv, i);
        pNew = idxNewConstraint(&rc, zColl);
        if( pNew ){
          pNew->iCol = pCons->iColumn;
          if( pCons->op==SQLITE_INDEX_CONSTRAINT_EQ ){
            pNew->pNext = pScan->pEq;
434
435
436
437
438
439
440




















































































































441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
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
529
530
531
532
533
534
  sqlite3_vtab *pVtab, 
  int nData, 
  sqlite3_value **azData, 
  sqlite_int64 *pRowid
){
  return SQLITE_OK;
}





















































































































static int idxRegisterVtab(sqlite3expert *p){
  static sqlite3_module expertModule = {
    2,                            /* iVersion */
    expertConnect,                /* xCreate - create a table */
    expertConnect,                /* xConnect - connect to an existing table */
    expertBestIndex,              /* xBestIndex - Determine search strategy */
    expertDisconnect,             /* xDisconnect - Disconnect from a table */
    expertDisconnect,             /* xDestroy - Drop a table */
    0,                            /* xOpen - open a cursor */
    0,                            /* xClose - close a cursor */
    0,                            /* xFilter - configure scan constraints */
    0,                            /* xNext - advance a cursor */
    0,                            /* xEof */
    0,                            /* xColumn - read data */
    0,                            /* xRowid - read data */
    expertUpdate,                 /* xUpdate - write data */
    0,                            /* xBegin - begin transaction */
    0,                            /* xSync - sync transaction */
    0,                            /* xCommit - commit transaction */
    0,                            /* xRollback - rollback transaction */
    0,                            /* xFindFunction - function overloading */
    0,                            /* xRename - rename the table */
    0,                            /* xSavepoint */
    0,                            /* xRelease */
    0,                            /* xRollbackTo */
  };

  return sqlite3_create_module(p->dbv, "expert", &expertModule, (void*)p);
}
/*
** End of virtual table implementation.
*************************************************************************/

/*
** An error associated with database handle db has just occurred. Pass
** the error message to callback function xOut.
*/
static void idxDatabaseError(
  sqlite3 *db,                    /* Database handle */
  char **pzErrmsg                 /* Write error here */
){
  *pzErrmsg = sqlite3_mprintf("%s", sqlite3_errmsg(db));
}

/*
** Prepare an SQL statement.
*/
static int idxPrepareStmt(
  sqlite3 *db,                    /* Database handle to compile against */
  sqlite3_stmt **ppStmt,          /* OUT: Compiled SQL statement */
  char **pzErrmsg,                /* OUT: sqlite3_malloc()ed error message */
  const char *zSql                /* SQL statement to compile */
){
  int rc = sqlite3_prepare_v2(db, zSql, -1, ppStmt, 0);
  if( rc!=SQLITE_OK ){
    *ppStmt = 0;
    idxDatabaseError(db, pzErrmsg);
  }
  return rc;
}

/*
** Prepare an SQL statement using the results of a printf() formatting.
*/
static int idxPrintfPrepareStmt(
  sqlite3 *db,                    /* Database handle to compile against */
  sqlite3_stmt **ppStmt,          /* OUT: Compiled SQL statement */
  char **pzErrmsg,                /* OUT: sqlite3_malloc()ed error message */
  const char *zFmt,               /* printf() format of SQL statement */
  ...                             /* Trailing printf() arguments */
){
  va_list ap;
  int rc;
  char *zSql;
  va_start(ap, zFmt);
  zSql = sqlite3_vmprintf(zFmt, ap);
  if( zSql==0 ){
    rc = SQLITE_NOMEM;
  }else{
    rc = idxPrepareStmt(db, ppStmt, pzErrmsg, zSql);
    sqlite3_free(zSql);
  }
  va_end(ap);
  return rc;
}

/*
** Finalize SQL statement pStmt. If (*pRc) is SQLITE_OK when this function
** is called, set it to the return value of sqlite3_finalize() before
** returning. Otherwise, discard the sqlite3_finalize() return value.
*/
static void idxFinalize(int *pRc, sqlite3_stmt *pStmt){
  int rc = sqlite3_finalize(pStmt);







>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>









|
|
|
|
|
|
|

















<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<
<







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
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
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
657






















































658
659
660
661
662
663
664
  sqlite3_vtab *pVtab, 
  int nData, 
  sqlite3_value **azData, 
  sqlite_int64 *pRowid
){
  return SQLITE_OK;
}

/* 
** Virtual table module xOpen method.
*/
static int expertOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
  int rc = SQLITE_OK;
  ExpertCsr *pCsr;
  pCsr = idxMalloc(&rc, sizeof(ExpertCsr));
  *ppCursor = (sqlite3_vtab_cursor*)pCsr;
  return rc;
}

/* 
** Virtual table module xClose method.
*/
static int expertClose(sqlite3_vtab_cursor *cur){
  ExpertCsr *pCsr = (ExpertCsr*)cur;
  sqlite3_finalize(pCsr->pData);
  sqlite3_free(pCsr);
  return SQLITE_OK;
}

/*
** Virtual table module xEof method.
**
** Return non-zero if the cursor does not currently point to a valid 
** record (i.e if the scan has finished), or zero otherwise.
*/
static int expertEof(sqlite3_vtab_cursor *cur){
  ExpertCsr *pCsr = (ExpertCsr*)cur;
  return pCsr->pData==0;
}

/* 
** Virtual table module xNext method.
*/
static int expertNext(sqlite3_vtab_cursor *cur){
  ExpertCsr *pCsr = (ExpertCsr*)cur;
  int rc = SQLITE_OK;
  int bRet;
  assert( pCsr->pData );

  do {
    rc = sqlite3_step(pCsr->pData);
    if( rc!=SQLITE_ROW ){
      rc = sqlite3_finalize(pCsr->pData);
      pCsr->pData = 0;
      bRet = 1;
    }else{
      rc = SQLITE_OK;
      bRet = (pCsr->nRow==0.0 || pCsr->nRow/pCsr->nRet < pCsr->target);
      if( bRet==0 ){
        unsigned short rnd;
        sqlite3_randomness(2, (void*)&rnd);
        bRet = ((int)rnd % 100) <= pCsr->iTarget;
      }
    }
    pCsr->nRow += 1.0;
  }while( bRet==0 );

  pCsr->nRet += 1.0;
  return rc;
}

/* 
** Virtual table module xRowid method.
*/
static int expertRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
  *pRowid = 0;
  return SQLITE_OK;
}

/* 
** Virtual table module xColumn method.
*/
static int expertColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
  ExpertCsr *pCsr = (ExpertCsr*)cur;
  sqlite3_value *pVal;
  pVal = sqlite3_column_value(pCsr->pData, i);
  if( pVal ){
    sqlite3_result_value(ctx, pVal);
  }
  return SQLITE_OK;
}

/* 
** Virtual table module xFilter method.
*/
static int expertFilter(
  sqlite3_vtab_cursor *cur, 
  int idxNum, const char *idxStr,
  int argc, sqlite3_value **argv
){
  ExpertCsr *pCsr = (ExpertCsr*)cur;
  ExpertVtab *pVtab = (ExpertVtab*)(cur->pVtab);
  sqlite3expert *pExpert = pVtab->pExpert;
  int rc;

  rc = sqlite3_finalize(pCsr->pData);
  pCsr->pData = 0;
  pCsr->nRow = 0.0;
  pCsr->nRet = 0.0;
  pCsr->iTarget = pExpert->iSample;
  pCsr->target = (double)pExpert->iSample / 100.0;

  if( rc==SQLITE_OK ){
    rc = idxPrintfPrepareStmt(pExpert->db, &pCsr->pData, &pVtab->base.zErrMsg,
        "SELECT * FROM main.%Q", pVtab->pTab->zName
    );
  }

  if( rc==SQLITE_OK ){
    rc = expertNext(cur);
  }
  return rc;
}

static int idxRegisterVtab(sqlite3expert *p){
  static sqlite3_module expertModule = {
    2,                            /* iVersion */
    expertConnect,                /* xCreate - create a table */
    expertConnect,                /* xConnect - connect to an existing table */
    expertBestIndex,              /* xBestIndex - Determine search strategy */
    expertDisconnect,             /* xDisconnect - Disconnect from a table */
    expertDisconnect,             /* xDestroy - Drop a table */
    expertOpen,                   /* xOpen - open a cursor */
    expertClose,                  /* xClose - close a cursor */
    expertFilter,                 /* xFilter - configure scan constraints */
    expertNext,                   /* xNext - advance a cursor */
    expertEof,                    /* xEof */
    expertColumn,                 /* xColumn - read data */
    expertRowid,                  /* xRowid - read data */
    expertUpdate,                 /* xUpdate - write data */
    0,                            /* xBegin - begin transaction */
    0,                            /* xSync - sync transaction */
    0,                            /* xCommit - commit transaction */
    0,                            /* xRollback - rollback transaction */
    0,                            /* xFindFunction - function overloading */
    0,                            /* xRename - rename the table */
    0,                            /* xSavepoint */
    0,                            /* xRelease */
    0,                            /* xRollbackTo */
  };

  return sqlite3_create_module(p->dbv, "expert", &expertModule, (void*)p);
}
/*
** End of virtual table implementation.
*************************************************************************/






















































/*
** Finalize SQL statement pStmt. If (*pRc) is SQLITE_OK when this function
** is called, set it to the return value of sqlite3_finalize() before
** returning. Otherwise, discard the sqlite3_finalize() return value.
*/
static void idxFinalize(int *pRc, sqlite3_stmt *pStmt){
  int rc = sqlite3_finalize(pStmt);
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
){
  sqlite3_stmt *p1 = 0;
  int nCol = 0;
  int nTab = strlen(zTab);
  int nByte = sizeof(IdxTable) + nTab + 1;
  IdxTable *pNew = 0;
  int rc, rc2;
  char *pCsr;

  rc = idxPrintfPrepareStmt(db, &p1, pzErrmsg, "PRAGMA table_info=%Q", zTab);
  while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(p1) ){
    const char *zCol = (const char*)sqlite3_column_text(p1, 1);
    nByte += 1 + strlen(zCol);
    rc = sqlite3_table_column_metadata(
        db, "main", zTab, zCol, 0, &zCol, 0, 0, 0







|







683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
){
  sqlite3_stmt *p1 = 0;
  int nCol = 0;
  int nTab = strlen(zTab);
  int nByte = sizeof(IdxTable) + nTab + 1;
  IdxTable *pNew = 0;
  int rc, rc2;
  char *pCsr = 0;

  rc = idxPrintfPrepareStmt(db, &p1, pzErrmsg, "PRAGMA table_info=%Q", zTab);
  while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(p1) ){
    const char *zCol = (const char*)sqlite3_column_text(p1, 1);
    nByte += 1 + strlen(zCol);
    rc = sqlite3_table_column_metadata(
        db, "main", zTab, zCol, 0, &zCol, 0, 0, 0
1421
1422
1423
1424
1425
1426
1427

1428
1429
1430
1431
1432
1433
1434
1435
    }
  }
  sqlite3_free(zCols);
  sqlite3_free(zOrder);

  /* Formulate the query text */
  if( rc==SQLITE_OK ){

    rc = idxPrepareStmt(p->db, &pQuery, pzErr, zQuery);
  }
  sqlite3_free(zQuery);

  if( rc==SQLITE_OK ){
    aStat = (int*)idxMalloc(&rc, sizeof(int)*(nCol+1));
  }
  if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pQuery) ){







>
|







1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
    }
  }
  sqlite3_free(zCols);
  sqlite3_free(zOrder);

  /* Formulate the query text */
  if( rc==SQLITE_OK ){
    sqlite3 *dbrem = (p->iSample==100 ? p->db : p->dbv);
    rc = idxPrepareStmt(dbrem, &pQuery, pzErr, zQuery);
  }
  sqlite3_free(zQuery);

  if( rc==SQLITE_OK ){
    aStat = (int*)idxMalloc(&rc, sizeof(int)*(nCol+1));
  }
  if( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pQuery) ){
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
  return rc;
}

static int idxBuildSampleTable(sqlite3expert *p, const char *zTab){
  int rc;
  char *zSql;

  rc = sqlite3_exec(p->db, "DROP TABLE IF EXISTS temp."UNIQUE_TABLE_NAME,0,0,0);
  if( rc!=SQLITE_OK ) return rc;

  zSql = sqlite3_mprintf(
      "CREATE TABLE temp." UNIQUE_TABLE_NAME 
      "  AS SELECT * FROM %Q WHERE sample()"
      , zTab
  );
  if( zSql==0 ) return SQLITE_NOMEM;
  rc = sqlite3_exec(p->db, zSql, 0, 0, 0);
  sqlite3_free(zSql);

  return rc;
}

/*
** This function is called as part of sqlite3_expert_analyze(). Candidate







|



|
<
<


|







1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619


1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
  return rc;
}

static int idxBuildSampleTable(sqlite3expert *p, const char *zTab){
  int rc;
  char *zSql;

  rc = sqlite3_exec(p->dbv,"DROP TABLE IF EXISTS temp."UNIQUE_TABLE_NAME,0,0,0);
  if( rc!=SQLITE_OK ) return rc;

  zSql = sqlite3_mprintf(
      "CREATE TABLE temp." UNIQUE_TABLE_NAME " AS SELECT * FROM %Q", zTab


  );
  if( zSql==0 ) return SQLITE_NOMEM;
  rc = sqlite3_exec(p->dbv, zSql, 0, 0, 0);
  sqlite3_free(zSql);

  return rc;
}

/*
** This function is called as part of sqlite3_expert_analyze(). Candidate
1533
1534
1535
1536
1537
1538
1539

1540
1541
1542
1543
1544
1545
1546
1547
1548

  if( rc==SQLITE_OK ){
    int nByte = sizeof(struct IdxRemCtx) + (sizeof(struct IdxRemSlot) * nMax);
    pCtx = (struct IdxRemCtx*)idxMalloc(&rc, nByte);
  }

  if( rc==SQLITE_OK ){

    rc = sqlite3_create_function(
        p->db, "rem", 2, SQLITE_UTF8, (void*)pCtx, idxRemFunc, 0, 0
    );
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3_create_function(
        p->db, "sample", 0, SQLITE_UTF8, (void*)&samplectx, idxSampleFunc, 0, 0
    );
  }







>

|







1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678

  if( rc==SQLITE_OK ){
    int nByte = sizeof(struct IdxRemCtx) + (sizeof(struct IdxRemSlot) * nMax);
    pCtx = (struct IdxRemCtx*)idxMalloc(&rc, nByte);
  }

  if( rc==SQLITE_OK ){
    sqlite3 *dbrem = (p->iSample==100 ? p->db : p->dbv);
    rc = sqlite3_create_function(
        dbrem, "rem", 2, SQLITE_UTF8, (void*)pCtx, idxRemFunc, 0, 0
    );
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3_create_function(
        p->db, "sample", 0, SQLITE_UTF8, (void*)&samplectx, idxSampleFunc, 0, 0
    );
  }