SQLite

  pDb = &db->aDb[iDb];

  /* Drop all statistics tables that this version of SQLite does not
  ** understand.
  */
  for(i=0; i<ArraySize(azToDrop); i++){
    Table *pTab = sqlite3FindTable(db, azToDrop[i], pDb->zName);
    if( pTab ){
      sqlite3CodeDropTable(pParse, pTab, iDb, 0);
      break;
    }
  }

  /* Create new statistic tables if they do not exist, or clear them
  ** if they do already exist.
  */
  for(i=0; i<ArraySize(aTable); i++){
    const char *zTab = aTable[i].zName;

  }else{
    if( nEq>p->a[iMin].nEq || (nEq==p->a[iMin].nEq && h>p->a[iMin].iHash) ){
      doInsert = 1;
    }
  }
  if( !doInsert ) return;
  if( p->nSample==p->mxSample ){
    assert( p->nSample - iMin - 1 >= 0 );
    memmove(&p->a[iMin], &p->a[iMin+1], sizeof(p->a[0])*(p->nSample-iMin-1));

    pSample = &p->a[p->nSample-1];
  }else{
    pSample = &p->a[p->nSample++];
  }
  pSample->iRowid = rowid;
  pSample->nEq = nEq;
  pSample->nLt = nLt;

){
  int n = sqlite3_value_int(argv[1]);
  Stat3Accum *p = (Stat3Accum*)sqlite3_value_blob(argv[0]);

  assert( p!=0 );
  if( p->nSample<=n ) return;
  switch( argc ){
    case 2:  sqlite3_result_int64(context, p->a[n].iRowid); break;
    case 3:  sqlite3_result_int64(context, p->a[n].nEq);    break;
    case 4:  sqlite3_result_int64(context, p->a[n].nLt);    break;
    default: sqlite3_result_int64(context, p->a[n].nDLt);   break;
  }
}
static const FuncDef stat3GetFuncdef = {
  -1,               /* nArg */
  SQLITE_UTF8,      /* iPrefEnc */
  0,                /* flags */
  0,                /* pUserData */

    zIndex = (char *)sqlite3_column_text(pStmt, 0);
    if( zIndex==0 ) continue;
    nSample = sqlite3_column_int(pStmt, 1);
    if( nSample>255 ) continue;
    pIdx = sqlite3FindIndex(db, zIndex, zDb);
    if( pIdx==0 ) continue;
    assert( pIdx->nSample==0 );
    testcase( nSample==255 );
    pIdx->nSample = (u8)nSample;
    pIdx->aSample = sqlite3MallocZero( nSample*sizeof(IndexSample) );
    pIdx->avgEq = pIdx->aiRowEst[1];
    if( pIdx->aSample==0 ){
      db->mallocFailed = 1;
      sqlite3_finalize(pStmt);
      return SQLITE_NOMEM;

      default: assert( eType==SQLITE_TEXT || eType==SQLITE_BLOB ); {
        const char *z = (const char *)(
              (eType==SQLITE_BLOB) ?
              sqlite3_column_blob(pStmt, 4):
              sqlite3_column_text(pStmt, 4)
           );
        int n = z ? sqlite3_column_bytes(pStmt, 4) : 0;

        pSample->nByte = n;
        if( n < 1){
          pSample->u.z = 0;
        }else{
          pSample->u.z = sqlite3Malloc(n);
          if( pSample->u.z==0 ){
            db->mallocFailed = 1;
            sqlite3_finalize(pStmt);

struct IndexSample {
  union {
    char *z;        /* Value if eType is SQLITE_TEXT or SQLITE_BLOB */
    double r;       /* Value if eType is SQLITE_FLOAT */
    i64 i;          /* Value if eType is SQLITE_INTEGER */
  } u;
  u8 eType;         /* SQLITE_NULL, SQLITE_INTEGER ... etc. */
  int nByte;        /* Size in byte of text or blob. */
  tRowcnt nEq;      /* Est. number of rows where the key equals this sample */
  tRowcnt nLt;      /* Est. number of rows where key is less than this sample */
  tRowcnt nDLt;     /* Est. number of distinct keys less than this sample */
};

/*
** Each token coming out of the lexer is an instance of

  IndexSample *aSample;
  int i, eType;
  int isEq = 0;
  i64 v;
  double r, rS;

  assert( roundUp==0 || roundUp==1 );
  assert( pIdx->nSample>0 );
  if( pVal==0 ) return SQLITE_ERROR;
  n = pIdx->aiRowEst[0];
  aSample = pIdx->aSample;
  i = 0;
  eType = sqlite3_value_type(pVal);

  if( eType==SQLITE_INTEGER ){

      if( rS>=r ){
        isEq = rS==r;
        break;
      }
    }
  }else if( eType==SQLITE_NULL ){
    i = 0;
    if( aSample[0].eType==SQLITE_NULL ) isEq = 1;
  }else{
    assert( eType==SQLITE_TEXT || eType==SQLITE_BLOB );
    for(i=0; i<pIdx->nSample; i++){
      if( aSample[i].eType==SQLITE_TEXT || aSample[i].eType==SQLITE_BLOB ){
        break;
      }
    }

){
  sqlite3_value *pRhs = 0;  /* VALUE on right-hand side of pTerm */
  u8 aff;                   /* Column affinity */
  int rc;                   /* Subfunction return code */
  tRowcnt a[2];             /* Statistics */

  assert( p->aSample!=0 );
  assert( p->nSample>0 );
  aff = p->pTable->aCol[p->aiColumn[0]].affinity;
  if( pExpr ){
    rc = valueFromExpr(pParse, pExpr, aff, &pRhs);
    if( rc ) goto whereEqualScanEst_cancel;
  }else{
    pRhs = sqlite3ValueNew(pParse->db);
  }