#At file:///localhome/jl208045/mysql/mysql-next-mr-bugfixing/ based on revid:guilhem@stripped
3275 Jorgen Loland 2010-06-30
Bug#54511: Assertion failed: cache != 0L in file
sql_select.cc::sub_select_cache on HAVING
Code cleanup followup patch: make JOIN::having_value and
cond_value point to select_lex versions of the variables
with same name to avoid duplication of information. Also
add documentation to having_value and cond_value in
st_select_lex and JOIN and to optimize_cond().
@ sql/sql_lex.h
Add documentation to st_select_lex::having_value and cond_value
@ sql/sql_select.cc
Make JOIN::having_value and cond_value point to select_lex
variables with same name and document optimize_cond()
@ sql/sql_select.h
Make JOIN::having_value and cond_value point to select_lex
variables with same name and document how they work.
modified:
sql/sql_lex.h
sql/sql_select.cc
sql/sql_select.h
=== modified file 'sql/sql_lex.h'
--- a/sql/sql_lex.h 2010-06-26 07:43:14 +0000
+++ b/sql/sql_lex.h 2010-06-30 08:33:05 +0000
@@ -639,7 +639,17 @@ public:
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 */
- /* Saved values of the WHERE and HAVING clauses*/
+ /**
+ Saved values of the WHERE and HAVING clauses. Allowed values are:
+ - COND_UNDEF if the condition was not specified in the query or if it
+ has not been optimized yet
+ - COND_TRUE if the condition is always true
+ - COND_FALSE if the condition is impossible
+ - COND_OK otherwise
+ NOTE: In contrast to JOIN::{having|conds}, conds and having are
+ not set to NULL here even if the associated *_value is set to
+ COND_TRUE or COND_FALSE.
+ */
Item::cond_result cond_value, having_value;
/* point on lex in which it was created, used in view subquery detection */
LEX *parent_lex;
=== modified file 'sql/sql_select.cc'
--- a/sql/sql_select.cc 2010-06-26 07:43:14 +0000
+++ b/sql/sql_select.cc 2010-06-30 08:33:05 +0000
@@ -508,6 +508,8 @@ JOIN::prepare(Item ***rref_pointer_array
tables_list= tables_init;
select_lex= select_lex_arg;
select_lex->join= this;
+ having_value= &select_lex->having_value;
+ cond_value= &select_lex->cond_value;
join_list= &select_lex->top_join_list;
union_part= unit_arg->is_union();
@@ -898,7 +900,7 @@ JOIN::optimize()
thd->restore_active_arena(arena, &backup);
}
- conds= optimize_cond(this, conds, join_list, &cond_value);
+ conds= optimize_cond(this, conds, join_list, cond_value);
if (thd->is_error())
{
error= 1;
@@ -907,24 +909,19 @@ JOIN::optimize()
}
{
- having= optimize_cond(this, having, join_list, &having_value);
+ having= optimize_cond(this, having, join_list, having_value);
if (thd->is_error())
{
error= 1;
DBUG_PRINT("error",("Error from optimize_cond"));
DBUG_RETURN(1);
}
- if (select_lex->where)
- select_lex->cond_value= cond_value;
- if (select_lex->having)
- select_lex->having_value= having_value;
-
- if (cond_value == Item::COND_FALSE || having_value == Item::COND_FALSE ||
+ if (*cond_value == Item::COND_FALSE || *having_value == Item::COND_FALSE ||
(!unit->select_limit_cnt && !(select_options & OPTION_FOUND_ROWS)))
{ /* Impossible cond */
- DBUG_PRINT("info", (having_value == Item::COND_FALSE ?
+ DBUG_PRINT("info", (*having_value == Item::COND_FALSE ?
"Impossible HAVING" : "Impossible WHERE"));
- zero_result_cause= having_value == Item::COND_FALSE ?
+ zero_result_cause= *having_value == Item::COND_FALSE ?
"Impossible HAVING" : "Impossible WHERE";
tables= 0;
error= 0;
@@ -1149,10 +1146,9 @@ JOIN::optimize()
if (having && const_table_map)
{
having->update_used_tables();
- having= remove_eq_conds(thd, having, &having_value);
- if (having_value == Item::COND_FALSE)
+ having= remove_eq_conds(thd, having, having_value);
+ if (*having_value == Item::COND_FALSE)
{
- having= new Item_int((longlong) 0,1);
zero_result_cause= "Impossible HAVING noticed after reading const tables";
error= 0;
DBUG_RETURN(0);
@@ -1823,8 +1819,8 @@ JOIN::exec()
In this case JOIN::exec must check for JOIN::having_value, in the
same way it checks for JOIN::cond_value.
*/
- if (cond_value != Item::COND_FALSE &&
- having_value != Item::COND_FALSE &&
+ if (*cond_value != Item::COND_FALSE &&
+ *having_value != Item::COND_FALSE &&
(!conds || conds->val_int()) &&
(!having || having->val_int()))
{
@@ -9278,6 +9274,28 @@ static void restore_prev_nj_state(JOIN_T
}
+/**
+ Optimize conditions by
+
+ a) applying transitivity to build multiple equality predicates
+ (MEP): if x=y and y=z the MEP x=y=z is built.
+ b) apply constants where possible. If the value of x is known to be
+ 42, x is replaced with a constant of value 42. By transitivity, this
+ also applies to MEPs, so the MEP in a) will become 42=x=y=z.
+ c) remove conditions that are impossible or always true
+
+ @param join pointer to the structure providing all context info
+ for the query
+ @param conds conditions to optimize
+ @param join_list list of join tables to which the condition
+ refers to
+ @param[out] cond_value Not changed if conds was empty
+ COND_TRUE if conds is always true
+ COND_FALSE if conds is impossible
+ COND_OK otherwise
+
+ @return optimized conditions
+*/
static COND *
optimize_cond(JOIN *join, COND *conds, List<TABLE_LIST> *join_list,
Item::cond_result *cond_value)
@@ -9285,9 +9303,7 @@ optimize_cond(JOIN *join, COND *conds, L
THD *thd= join->thd;
DBUG_ENTER("optimize_cond");
- if (!conds)
- *cond_value= Item::COND_TRUE;
- else
+ if (conds)
{
/*
Build all multiple equality predicates and eliminate equality
=== modified file 'sql/sql_select.h'
--- a/sql/sql_select.h 2010-06-22 20:57:34 +0000
+++ b/sql/sql_select.h 2010-06-30 08:33:05 +0000
@@ -418,7 +418,19 @@ public:
bool need_tmp, hidden_group_fields;
DYNAMIC_ARRAY keyuse;
- Item::cond_result cond_value, having_value;
+ /**
+ Pointers to variables with same names in select_lex. The allowed
+ states are:
+ - COND_UNDEF if the condition was not specified in the query or if it
+ has not been optimized yet
+ - COND_TRUE if the condition is always true.
+ - COND_FALSE if the condition is impossible
+ - COND_OK otherwise
+ If cond_result is set to COND_TRUE or COND_FALSE, conds is also
+ set to NULL. The same applies to the having_result/having variable
+ pair.
+ */
+ Item::cond_result *cond_value, *having_value;
List<Item> all_fields; ///< to store all fields that used in query
///Above list changed to use temporary table
List<Item> tmp_all_fields1, tmp_all_fields2, tmp_all_fields3;
@@ -573,7 +585,7 @@ public:
bool send_row_on_empty_set()
{
return (do_send_rows && tmp_table_param.sum_func_count != 0 &&
- !group_list && having_value != Item::COND_FALSE);
+ !group_list && *having_value != Item::COND_FALSE);
}
bool change_result(select_result *result);
bool is_top_level_join() const
Attachment: [text/bzr-bundle] bzr/jorgen.loland@sun.com-20100630083305-aok5rj05qaa5vl3i.bundle
