SQLite

** Flattening is only attempted if all of the following are true:
**
**   (1)  The subquery and the outer query do not both use aggregates.
**
**   (2)  The subquery is not an aggregate or the outer query is not a join.
**
**   (3)  The subquery is not the right operand of a left outer join
**        (Originally ticket #306.  Strengthened by ticket #3300)
**
**   (4)  The subquery is not DISTINCT.
**
**  (**)  At one point restrictions (4) and (5) defined a subset of DISTINCT
**        sub-queries that were excluded from this optimization. Restriction 
**        (4) has since been expanded to exclude all DISTINCT subqueries.
**
**   (6)  The subquery does not use aggregates or the outer query is not
**        DISTINCT.
**
**   (7)  The subquery has a FROM clause.
**
**   (8)  The subquery does not use LIMIT or the outer query is not a join.
**
**   (9)  The subquery does not use LIMIT or the outer query does not use
**        aggregates.
**
**  (10)  The subquery does not use aggregates or the outer query does not
**        use LIMIT.
**
**  (11)  The subquery and the outer query do not both have ORDER BY clauses.
**
**  (**)  Not implemented.  Subsumed into restriction (3).  Was previously
**        a separate restriction deriving from ticket #350.
**
**  (13)  The subquery and outer query do not both use LIMIT.
**
**  (14)  The subquery does not use OFFSET.
**
**  (15)  The outer query is not part of a compound select or the
**        subquery does not have a LIMIT clause.
**        (See ticket #2339 and ticket [02a8e81d44]).
**
**  (16)  The outer query is not an aggregate or the subquery does
**        not contain ORDER BY.  (Ticket #2942)  This used to not matter

  ** and (14). */
  if( pSub->pLimit && p->pLimit ) return 0;              /* Restriction (13) */
  if( pSub->pOffset ) return 0;                          /* Restriction (14) */
  if( p->pRightmost && pSub->pLimit ){
    return 0;                                            /* Restriction (15) */
  }
  if( pSubSrc->nSrc==0 ) return 0;                       /* Restriction (7)  */
  if( pSub->selFlags & SF_Distinct ) return 0;           /* Restriction (5)  */
  if( pSub->pLimit && (pSrc->nSrc>1 || isAgg) ){
     return 0;         /* Restrictions (8)(9) */
  }
  if( (p->selFlags & SF_Distinct)!=0 && subqueryIsAgg ){
     return 0;         /* Restriction (6)  */
  }
  if( p->pOrderBy && pSub->pOrderBy ){
     return 0;                                           /* Restriction (11) */
  }

} {abc xxxabc def yyydef}
do_test selectC-3.3 {
  execsql {
    SELECT b, max(a || b) FROM t2 WHERE (b||b||b)!='value' GROUP BY a;
  }
} {xxx abcxxx yyy defyyy}


proc udf {} { incr ::udf }
set ::udf 0
db function udf udf

do_execsql_test selectC-4.1 {
  create table t_distinct_bug (a, b, c);
  insert into t_distinct_bug values ('1', '1', 'a');
  insert into t_distinct_bug values ('1', '2', 'b');
  insert into t_distinct_bug values ('1', '3', 'c');
  insert into t_distinct_bug values ('1', '1', 'd');
  insert into t_distinct_bug values ('1', '2', 'e');
  insert into t_distinct_bug values ('1', '3', 'f');
} {}

do_execsql_test selectC-4.2 {
  select a from (select distinct a, b from t_distinct_bug)
} {1 1 1}

do_execsql_test selectC-4.3 {
  select a, udf() from (select distinct a, b from t_distinct_bug)
} {1 1 1 2 1 3}

finish_test