SQLite

**           to suppress it. **)
**
**   (2) The inner query is the recursive part of a common table expression.
**
**   (3) The inner query has a LIMIT clause (since the changes to the WHERE
**       close would change the meaning of the LIMIT).
**

**   (4) The inner query is the right operand of a LEFT JOIN and the
**       expression to be pushed down does not come from the ON clause
**       on that LEFT JOIN.
**
**   (5) The WHERE clause expression originates in the ON or USING clause
**       of a LEFT JOIN where iCursor is not the right-hand table of that
**       left join.  An example:
**
**           SELECT *
**           FROM (SELECT 1 AS a1 UNION ALL SELECT 2) AS aa

** Return 0 if no changes are made and non-zero if one or more WHERE clause
** terms are duplicated into the subquery.
*/
static int pushDownWhereTerms(
  Parse *pParse,        /* Parse context (for malloc() and error reporting) */
  Select *pSubq,        /* The subquery whose WHERE clause is to be augmented */
  Expr *pWhere,         /* The WHERE clause of the outer query */
  int iCursor,          /* Cursor number of the subquery */
  int isLeftJoin        /* True if pSubq is the right term of a LEFT JOIN */
){
  Expr *pNew;
  int nChng = 0;
  if( pWhere==0 ) return 0;
  if( pSubq->selFlags & SF_Recursive ) return 0;  /* restriction (2) */

#ifdef SQLITE_DEBUG

  }
#endif

  if( pSubq->pLimit!=0 ){
    return 0; /* restriction (3) */
  }
  while( pWhere->op==TK_AND ){
    nChng += pushDownWhereTerms(pParse, pSubq, pWhere->pRight,
                                iCursor, isLeftJoin);
    pWhere = pWhere->pLeft;
  }
  if( isLeftJoin
   && (ExprHasProperty(pWhere,EP_FromJoin)==0
         || pWhere->iRightJoinTable!=iCursor)
  ){
    return 0; /* restriction (4) */
  }
  if( ExprHasProperty(pWhere,EP_FromJoin) && pWhere->iRightJoinTable!=iCursor ){
    return 0; /* restriction (5) */
  }
  if( sqlite3ExprIsTableConstant(pWhere, iCursor) ){
    nChng++;
    while( pSubq ){
      SubstContext x;

    */
    pParse->nHeight += sqlite3SelectExprHeight(p);

    /* Make copies of constant WHERE-clause terms in the outer query down
    ** inside the subquery.  This can help the subquery to run more efficiently.
    */
    if( OptimizationEnabled(db, SQLITE_PushDown)
     && pushDownWhereTerms(pParse, pSub, p->pWhere, pItem->iCursor,
                           (pItem->fg.jointype & JT_OUTER)!=0)
    ){
#if SELECTTRACE_ENABLED
      if( sqlite3SelectTrace & 0x100 ){
        SELECTTRACE(0x100,pParse,p,("After WHERE-clause push-down:\n"));
        sqlite3TreeViewSelect(0, p, 0);
      }
#endif

  CREATE INDEX u1ab ON u1(b, c);
}
do_eqp_test 6.1 {
  SELECT u2.* FROM u2 LEFT JOIN u1 ON( u1.a=u2.a AND u1.b=u2.b AND u1.c=u2.c );
} {
  0 0 0 {SCAN TABLE u2}
}

db close
sqlite3 db :memory:
do_execsql_test 7.0 {
  CREATE TABLE t1(a,b);  INSERT INTO t1 VALUES(1,2),(3,4),(5,6);
  CREATE TABLE t2(c,d);  INSERT INTO t2 VALUES(2,4),(3,6);
  CREATE TABLE t3(x);    INSERT INTO t3 VALUES(9);
  CREATE VIEW test AS
    SELECT *, 'x'
      FROM t1 LEFT JOIN (SELECT * FROM t2, t3) ON (c=b AND x=9)
      WHERE c IS NULL;
  SELECT * FROM test;
} {3 4 {} {} {} x 5 6 {} {} {} x}


finish_test