SQLite

  UnpackedRecord *pRec = pBuilder->pRec;
  u8 aff;                   /* Column affinity */
  int rc;                   /* Subfunction return code */
  tRowcnt a[2];             /* Statistics */
  int bOk;

  assert( nEq>=1 );
  assert( nEq<=p->nColumn );
  assert( p->aSample!=0 );
  assert( p->nSample>0 );
  assert( pBuilder->nRecValid<nEq );

  /* If values are not available for all fields of the index to the left
  ** of this one, no estimate can be made. Return SQLITE_NOTFOUND. */
  if( pBuilder->nRecValid<(nEq-1) ){
    return SQLITE_NOTFOUND;
  }

  /* This is an optimization only. The call to sqlite3Stat4ProbeSetValue()
  ** below would return the same value.  */
  if( nEq>=p->nColumn ){
    *pnRow = 1;
    return SQLITE_OK;
  }

  aff = p->pTable->aCol[p->aiColumn[nEq-1]].affinity;
  rc = sqlite3Stat4ProbeSetValue(pParse, p, &pRec, pExpr, aff, nEq-1, &bOk);
  pBuilder->pRec = pRec;

for {set i 0} {$i<16} {incr i} {
    set val "$i $i $i $i"
    do_execsql_test 20.3.$i {
      SELECT count(*) FROM sqlite_stat4 
      WHERE lrange(test_decode(sample), 0, 3)=$val
    } {1}
}

#-------------------------------------------------------------------------
#
reset_db

do_execsql_test 21.0 {
  CREATE TABLE t2(a, b);
  CREATE INDEX i2 ON t2(a);
}

do_test 21.1 {
  for {set i 1} {$i < 100} {incr i} {
    execsql { 
      INSERT INTO t2 VALUES(CASE WHEN $i < 80 THEN 'one' ELSE 'two' END, $i) 
    }
  }
  execsql ANALYZE
} {}

# Condition (a='one') matches 80% of the table. (rowid<10) reduces this to
# 10%, but (rowid<50) only reduces it to 50%. So in the first case below
# the index is used. In the second, it is not. 
#
do_eqp_test 21.2 {
  SELECT * FROM t2 WHERE a='one' AND rowid < 10
} {/*USING INDEX i2 (a=? AND rowid<?)*/}
do_eqp_test 21.3 {
  SELECT * FROM t2 WHERE a='one' AND rowid < 50
} {/*USING INTEGER PRIMARY KEY*/}

#-------------------------------------------------------------------------
#
reset_db
do_execsql_test 22.0 {
  CREATE TABLE t3(a, b, c, d, PRIMARY KEY(a, b)) WITHOUT ROWID;
}
do_execsql_test 22.1 {
  WITH r(x) AS (
    SELECT 1
    UNION ALL
    SELECT x+1 FROM r WHERE x<=100
  )

  INSERT INTO t3 SELECT
    CASE WHEN (x>45 AND x<96) THEN 'B' ELSE 'A' END,  /* Column "a" */
    x,                                                /* Column "b" */
    CASE WHEN (x<51) THEN 'one' ELSE 'two' END,       /* Column "c" */
    x                                                 /* Column "d" */
  FROM r;

  CREATE INDEX i3 ON t3(c);
  CREATE INDEX i4 ON t3(d);
  ANALYZE;
}

# Expression (c='one' AND a='B') matches 5 table rows. But (c='one' AND a=A')
# matches 45. Expression (d<?) matches 20. Neither index is a covering index.
#
# Therefore, with stat4 data, SQLite prefers (c='one' AND a='B') over (d<20),
# and (d<20) over (c='one' AND a='A').
foreach {tn where res} {
  1 "c='one' AND a='B' AND d < 20"   {/*INDEX i3 (c=? AND a=?)*/}
  2 "c='one' AND a='A' AND d < 20"   {/*INDEX i4 (d<?)*/}
} {
  do_eqp_test 22.2.$tn "SELECT * FROM t3 WHERE $where" $res
}

finish_test