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Fixed bug#19077: A nested materialized derived table is used before being populated.

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The convert_constant_item() function converts constant items to ints on
prepare phase to optimize execution speed. In this case it tries to evaluate
subselect which contains a derived table and is contained in a derived table. 
All derived tables are filled only after all derived tables are prepared.
So evaluation of subselect with derived table at the prepare phase will
return a wrong result.

A new flag with_subselect is added to the Item class. It indicates that
expression which this item represents is a subselect or contains a subselect.
It is set to 0 by default. It is set to 1 in the Item_subselect constructor
for subselects.
For Item_func and Item_cond derived classes it is set after fixing any argument
in Item_func::fix_fields() and Item_cond::fix_fields accordingly.
The convert_constant_item() function now doesn't convert a constant item
if the with_subselect flag set in it.
This commit is contained in:
evgen@moonbone.local
2006-05-18 00:55:28 +04:00
parent 1e6c14d687
commit 1d820585ae
9 changed files with 65 additions and 5 deletions
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29
sql/item_cmpfunc.cc
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@@ -204,10 +204,28 @@ longlong Item_func_nop_all::val_int()
/*
Convert a constant expression or string to an integer.
This is done when comparing DATE's of different formats and
also when comparing bigint to strings (in which case the string
is converted once to a bigint).
Convert a constant item to an int and replace the original item
SYNOPSIS
convert_constant_item()
thd thread handle
field item will be converted using the type of this field
item [in/out] reference to the item to convert
DESCRIPTION
The function converts a constant expression or string to an integer.
On successful conversion the original item is substituted for the
result of the item evaluation.
This is done when comparing DATE/TIME of different formats and
also when comparing bigint to strings (in which case strings
are converted to bigints).
NOTES
This function is called only at prepare stage.
As all derived tables are filled only after all derived tables
are prepared we do not evaluate items with subselects here because
they can contain derived tables and thus we may attempt to use a
table that has not been populated yet.
RESULT VALUES
0 Can't convert item
@@ -216,7 +234,7 @@ longlong Item_func_nop_all::val_int()
static bool convert_constant_item(THD *thd, Field *field, Item **item)
{
if ((*item)->const_item())
if (!(*item)->with_subselect && (*item)->const_item())
{
/* For comparison purposes allow invalid dates like 2000-01-32 */
ulong orig_sql_mode= field->table->in_use->variables.sql_mode;
@@ -2578,6 +2596,7 @@ Item_cond::fix_fields(THD *thd, Item **ref)
const_item_cache= FALSE;
}
with_sum_func= with_sum_func || item->with_sum_func;
with_subselect|= item->with_subselect;
if (item->maybe_null)
maybe_null=1;
}