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Bug #46175: NULL read_view and consistent read assertion

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The SE API requires mysql to notify the storage engine that
it's going to read certain tables at the beginning of the 
statement (by calling start_stmt(), store_lock() or
external_lock()).
These are typically called by the lock_tables(). 
However SHOW CREATE TABLE is not pre-locking the tables
because it's not expected to access the data at all.
But for some view definitions (that include comparing a
date/datetime/timestamp column to a string returning
scalar subquery) the JOIN::prepare may still access data
when materializing the scalar non-correlated subquery
in Arg_comparator::can_compare_as_dates().
Fixed by not materializing the subquery when the function
is called in a SHOW/EXPLAIN/CREATE VIEW
This commit is contained in:
Georgi Kodinov
2009-11-04 13:54:28 +02:00
parent b7ceeccdbe
commit 43d7fb43cd
3 changed files with 76 additions and 2 deletions
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10
sql/item_cmpfunc.cc
View File

@@ -785,15 +785,21 @@ Arg_comparator::can_compare_as_dates(Item *a, Item *b, ulonglong *const_value)
if (cmp_type != CMP_DATE_DFLT)
{
THD *thd= current_thd;
/*
Do not cache GET_USER_VAR() function as its const_item() may return TRUE
for the current thread but it still may change during the execution.
Don't use cache while in the context analysis mode only (i.e. for
EXPLAIN/CREATE VIEW and similar queries). Cache is useless in such
cases and can cause problems. For example evaluating subqueries can
confuse storage engines since in context analysis mode tables
aren't locked.
*/
if (cmp_type != CMP_DATE_WITH_DATE && str_arg->const_item() &&
if (!thd->is_context_analysis_only() &&
cmp_type != CMP_DATE_WITH_DATE && str_arg->const_item() &&
(str_arg->type() != Item::FUNC_ITEM ||
((Item_func*)str_arg)->functype() != Item_func::GUSERVAR_FUNC))
{
THD *thd= current_thd;
ulonglong value;
bool error;
String tmp, *str_val= 0;