Commit 375749b8 authored by unknown's avatar unknown
Browse files

Fixed bug #14927. 

A query with a group by and having clauses could return a wrong
result set if the having condition contained a constant conjunct 
evaluated to FALSE.
It happened because the pushdown condition for table with
grouping columns lost its constant conjuncts.
Pushdown conditions are always built by the function make_cond_for_table
that ignores constant conjuncts. This is apparently not correct when
constant false conjuncts are present.



mysql-test/r/having.result:
  Added a test case for bug #14927.
mysql-test/t/having.test:
  Added a test case for bug #14927.
sql/sql_lex.cc:
  Fixed bug #14927.
  Initialized fields for having conditions in  st_select_lex::init_query().
sql/sql_lex.h:
  Fixed bug #14927.
  Added a field to restore having condititions for execution in SP and PS.
sql/sql_prepare.cc:
  Fixed bug #14927.
  Added code to restore havinf conditions for execution in SP and PS.
sql/sql_select.cc:
  Fixed bug #14927.
  Performed evaluation of constant expressions in having clauses.
  If the having condition contains a constant conjunct that is always false
  an empty result set is returned after the optimization phase.
  In this case the corresponding EXPLAIN command now returns 
  "Impossible HAVING" in the last column.
parent 427bcfb4

mysql-test/r/having.result

+17 −0
Original line number Diff line number Diff line
@@ -141,3 +141,20 @@ SUM(a) 
6

4

DROP TABLE t1;

CREATE TABLE t1 (a int);

INSERT INTO t1 VALUES (1), (2), (1), (3), (2), (1);

SELECT a FROM t1 GROUP BY a HAVING a > 1;

a

2

3

SELECT a FROM t1 GROUP BY a HAVING 1 != 1 AND a > 1;

a

SELECT 0 AS x, a FROM t1 GROUP BY x,a HAVING x=1 AND a > 1;

x	a

EXPLAIN SELECT a FROM t1 GROUP BY a HAVING 1 != 1 AND a > 1;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible HAVING

EXPLAIN SELECT 0 AS x, a FROM t1 GROUP BY x,a HAVING x=1 AND a > 1;

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible HAVING

DROP table t1;

mysql-test/t/having.test

+16 −0
Original line number Diff line number Diff line
@@ -135,4 +135,20 @@ SELECT SUM(a) FROM t1 GROUP BY a HAVING SUM(a); 


DROP TABLE t1;



#

# Bug #14927: HAVING clause containing constant false conjunct

#



CREATE TABLE t1 (a int);

INSERT INTO t1 VALUES (1), (2), (1), (3), (2), (1);



SELECT a FROM t1 GROUP BY a HAVING a > 1;

SELECT a FROM t1 GROUP BY a HAVING 1 != 1 AND a > 1;

SELECT 0 AS x, a FROM t1 GROUP BY x,a HAVING x=1 AND a > 1;



EXPLAIN SELECT a FROM t1 GROUP BY a HAVING 1 != 1 AND a > 1;

EXPLAIN SELECT 0 AS x, a FROM t1 GROUP BY x,a HAVING x=1 AND a > 1;



DROP table t1;  



# End of 4.1 tests

sql/sql_lex.cc

+2 −0
Original line number Diff line number Diff line
@@ -1074,6 +1074,7 @@ void st_select_lex::init_query() 
  item_list.empty();

  join= 0;

  where= 0;

  having= 0;

  olap= UNSPECIFIED_OLAP_TYPE;

  having_fix_field= 0;

  resolve_mode= NOMATTER_MODE;
@@ -1081,6 +1082,7 @@ void st_select_lex::init_query() 
  ref_pointer_array= 0;

  select_n_having_items= 0;

  prep_where= 0;

  prep_having= 0;

  subquery_in_having= explicit_limit= 0;

  parsing_place= NO_MATTER;

  is_item_list_lookup= 0;

sql/sql_lex.h

+1 −0
Original line number Diff line number Diff line
@@ -422,6 +422,7 @@ class st_select_lex: public st_select_lex_node 
  char *db, *db1, *table1, *db2, *table2;      	/* For outer join using .. */

  Item *where, *having;                         /* WHERE & HAVING clauses */

  Item *prep_where; /* saved WHERE clause for prepared statement processing */

  Item *prep_having;/* saved HAVING clause for prepared statement processing */

  enum olap_type olap;

  SQL_LIST	      table_list, group_list;   /* FROM & GROUP BY clauses */

  List<Item>          item_list; /* list of fields & expressions */

sql/sql_prepare.cc

+8 −2
Original line number Diff line number Diff line
@@ -1667,10 +1667,11 @@ int mysql_stmt_prepare(THD *thd, char *packet, uint packet_length, 
    for (; sl; sl= sl->next_select_in_list())

    {

      /*

        Save WHERE clause pointers, because they may be changed

        Save WHERE, HAVING clause pointers, because they may be changed

        during query optimisation.

      */

      sl->prep_where= sl->where;

      sl->prep_having= sl->having;

      /*

        Switch off a temporary flag that prevents evaluation of

        subqueries in statement prepare.
@@ -1696,13 +1697,18 @@ static void reset_stmt_for_execute(Prepared_statement *stmt) 
    /* remove option which was put by mysql_explain_union() */

    sl->options&= ~SELECT_DESCRIBE;

    /*

      Copy WHERE clause pointers to avoid damaging they by optimisation

      Copy WHERE, HAVING clause pointers to avoid damaging they by optimisation

    */

    if (sl->prep_where)

    {

      sl->where= sl->prep_where->copy_andor_structure(thd);

      sl->where->cleanup();

    }

    if (sl->prep_having)

    {

      sl->having= sl->prep_having->copy_andor_structure(thd);

      sl->having->cleanup();

    }

    DBUG_ASSERT(sl->join == 0);

    ORDER *order;

    /* Fix GROUP list */