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BUG#834534: Assertion `0' failed in replace_where_subcondition with semijoin subquery in HAVING

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- The problem was that the code that made the check whether the subquery is an AND-part of the WHERE 
  clause didn't work correctly for nested subqueries. In particular, grand-child subquery in HAVING was 
  treated as if it was in the WHERE, which eventually caused an assert when replace_where_subcondition
  looked for the subquery predicate in the WHERE and couldn't find it there.

- The fix: Removed implementation of "thd_marker approach". thd->thd_marker was used to determine the 
  location of subquery predicate: setup_conds() would set accordingly it when making the 

    {where|on_expr}->fix_fields(...)

  call so that AND-parts of the WHERE/ON clauses can determine they are the AND-parts. 
  Item_cond_or::fix_fields(), Item_func::fix_fields(), Item_subselect::fix_fields (this one was missed),
  and all other items-that-contain-items had to reset thd->thd_marker before calling fix_fields() for 
  their children items, so that the children can see they are not AND-parts of WHERE/ON.
- The "thd_marker approach" required that a lot of code in different locations maintains correct value of
  thd->thd_marker, so it was replaced with:
- The new approach with mark_as_condition_AND_part does not keep context in thd->thd_marker. Instead, 
  setup_conds() now calls

    {where|on_expr}->mark_as_condition_AND_part()

  and implementations of that function make sure that: 
   - parts of AND-expressions get the mark_as_condition_AND_part() call
   - Item_in_subselect objects record that they are AND-parts of WHERE/ON
This commit is contained in:
Sergey Petrunya 2011-08-29 19:57:41 +04:00
commit 945a595aa3
14 changed files with 96 additions and 36 deletions
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15
sql/item_cmpfunc.cc
View file

@ -4076,15 +4076,12 @@ Item_cond::fix_fields(THD *thd, Item **ref)
DBUG_ASSERT(fixed == 0);
List_iterator<Item> li(list);
Item *item;
TABLE_LIST *save_emb_on_expr_nest= thd->thd_marker.emb_on_expr_nest;
#ifndef EMBEDDED_LIBRARY
uchar buff[sizeof(char*)]; // Max local vars in function
#endif
not_null_tables_cache= used_tables_cache= 0;
const_item_cache= 1;
if (functype() != COND_AND_FUNC)
thd->thd_marker.emb_on_expr_nest= NULL;
/*
and_table_cache is the value that Item_cond_or() returns for
not_null_tables()
@ -4144,7 +4141,6 @@ Item_cond::fix_fields(THD *thd, Item **ref)
maybe_null=1;
}
thd->lex->current_select->cond_count+= list.elements;
thd->thd_marker.emb_on_expr_nest= save_emb_on_expr_nest;
fix_length_and_dec();
fixed= 1;
return FALSE;
@ -4414,6 +4410,17 @@ void Item_cond::neg_arguments(THD *thd)
}
void Item_cond_and::mark_as_condition_AND_part(TABLE_LIST *embedding)
{
List_iterator<Item> li(list);
Item *item;
while ((item=li++))
{
item->mark_as_condition_AND_part(embedding);
}
}
/**
Evaluation of AND(expr, expr, expr ...).