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BUG#912513: Wrong result (missing rows) with join_cache_hashed+materialization+semijoin=on

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- equality substitution code was geared towards processing WHERE/ON clauses.
  that is, it assumed that it was doing substitions on the code that 
   = wasn't attached to any particular join_tab yet
   = was going to be fed to make_join_select() which would take the condition
     apart and attach various parts of it to tables inside/outside semi-joins.
- However, somebody added equality substition for ref access. That is, if 
  we have a ref access on TBL.key=expr, they would do equality substition in
  'expr'. This possibility wasn't accounted for.
- Fixed equality substition code by adding a mode that does equality 
  substition under assumption that the processed expression will be 
  attached to a certain particular table TBL.
This commit is contained in:
Sergey Petrunya
2012-01-20 02:11:53 +04:00
parent 8bedf1ea1c
commit 9f60aa27f7
7 changed files with 121 additions and 14 deletions
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51
sql/sql_select.cc
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@ -110,7 +110,8 @@ static COND *build_equal_items(THD *thd, COND *cond,
COND_EQUAL *inherited,
List<TABLE_LIST> *join_list,
COND_EQUAL **cond_equal_ref);
static COND* substitute_for_best_equal_field(COND *cond,
static COND* substitute_for_best_equal_field(JOIN_TAB *context_tab,
COND *cond,
COND_EQUAL *cond_equal,
void *table_join_idx);
static COND *simplify_joins(JOIN *join, List<TABLE_LIST> *join_list,
@ -1225,7 +1226,8 @@ JOIN::optimize()
*/
if (conds)
{
conds= substitute_for_best_equal_field(conds, cond_equal, map2table);
conds= substitute_for_best_equal_field(NO_PARTICULAR_TAB, conds,
cond_equal, map2table);
conds->update_used_tables();
DBUG_EXECUTE("where",
print_where(conds,
@ -1242,7 +1244,8 @@ JOIN::optimize()
{
if (*tab->on_expr_ref)
{
*tab->on_expr_ref= substitute_for_best_equal_field(*tab->on_expr_ref,
*tab->on_expr_ref= substitute_for_best_equal_field(NO_PARTICULAR_TAB,
*tab->on_expr_ref,
tab->cond_equal,
map2table);
(*tab->on_expr_ref)->update_used_tables();
@ -1265,7 +1268,7 @@ JOIN::optimize()
continue;
COND_EQUAL *equals= tab->first_inner ? tab->first_inner->cond_equal :
cond_equal;
ref_item= substitute_for_best_equal_field(ref_item, equals, map2table);
ref_item= substitute_for_best_equal_field(tab, ref_item, equals, map2table);
ref_item->update_used_tables();
if (*ref_item_ptr != ref_item)
{
@ -11446,7 +11449,7 @@ Item *eliminate_item_equal(COND *cond, COND_EQUAL *upper_levels,
else
{
TABLE_LIST *emb_nest;
head= item_equal->get_first(NULL);
head= item_equal->get_first(NO_PARTICULAR_TAB, NULL);
it++;
if ((emb_nest= embedding_sjm(head)))
{
@ -11555,6 +11558,7 @@ Item *eliminate_item_equal(COND *cond, COND_EQUAL *upper_levels,
return cond;
}
/**
Substitute every field reference in a condition by the best equal field
and eliminate all multiple equality predicates.
@ -11569,6 +11573,9 @@ Item *eliminate_item_equal(COND *cond, COND_EQUAL *upper_levels,
After this the function retrieves all other conjuncted
predicates substitute every field reference by the field reference
to the first equal field or equal constant if there are any.
@param context_tab Join tab that 'cond' will be attached to, or
NO_PARTICULAR_TAB. See notes above.
@param cond condition to process
@param cond_equal multiple equalities to take into consideration
@param table_join_idx index to tables determining field preference
@ -11579,11 +11586,37 @@ Item *eliminate_item_equal(COND *cond, COND_EQUAL *upper_levels,
new fields in multiple equality item of lower levels. We want
the order in them to comply with the order of upper levels.
context_tab may be used to specify which join tab `cond` will be
attached to. There are two possible cases:
1. context_tab != NO_PARTICULAR_TAB
We're doing substitution for an Item which will be evaluated in the
context of a particular item. For example, if the optimizer does a
ref access on "tbl1.key= expr" then
= equality substitution will be perfomed on 'expr'
= it is known in advance that 'expr' will be evaluated when
table t1 is accessed.
Note that in this kind of substution we never have to replace Item_equal
objects. For example, for
t.key= func(col1=col2 AND col2=const)
we will not build Item_equal or do equality substution (if we decide to,
this function will need to be fixed to handle it)
2. context_tab == NO_PARTICULAR_TAB
We're doing substitution in WHERE/ON condition, which is not yet
attached to any particular join_tab. We will use information about the
chosen join order to make "optimal" substitions, i.e. those that allow
to apply filtering as soon as possible. See eliminate_item_equal() and
Item_equal::get_first() for details.
@return
The transformed condition
*/
static COND* substitute_for_best_equal_field(COND *cond,
static COND* substitute_for_best_equal_field(JOIN_TAB *context_tab,
COND *cond,
COND_EQUAL *cond_equal,
void *table_join_idx)
{
@ -11612,7 +11645,8 @@ static COND* substitute_for_best_equal_field(COND *cond,
Item *item;
while ((item= li++))
{
Item *new_item= substitute_for_best_equal_field(item, cond_equal,
Item *new_item= substitute_for_best_equal_field(context_tab,
item, cond_equal,
table_join_idx);
/*
This works OK with PS/SP re-execution as changes are made to
@ -11659,7 +11693,8 @@ static COND* substitute_for_best_equal_field(COND *cond,
List_iterator_fast<Item_equal> it(cond_equal->current_level);
while((item_equal= it++))
{
cond= cond->transform(&Item::replace_equal_field, (uchar *) item_equal);
REPLACE_EQUAL_FIELD_ARG arg= {item_equal, context_tab};
cond= cond->transform(&Item::replace_equal_field, (uchar *) &arg);
}
cond_equal= cond_equal->upper_levels;
}