From abe72e7c6711a1fd2aaf1f658da90b91da289a9f Mon Sep 17 00:00:00 2001 From: Dmitry Shulga Date: Fri, 12 Mar 2021 11:06:18 +0700 Subject: MDEV-25108: Running of the EXPLAIN EXTENDED statement produces extra warning in case it is executed in PS (prepared statement) mode The EXPLAIN EXTENDED statement run as a prepared statement can produce extra warning comparing with a case when EXPLAIN EXTENDED statement is run as a regular statement. For example, the following test case CREATE TABLE t1 (c int); CREATE TABLE t2 (d int); EXPLAIN EXTENDED SELECT (SELECT 1 FROM t2 WHERE d = c) FROM t1; produces the extra warning "Field or reference 'c' of SELECT #2 was resolved in SELECT #1" in case the above mentioned "EXPLAIN EXTENDED" statement is executed in PS mode, that is by submitting the following statements: PREPARE stmt FROM "EXPLAIN EXTENDED SELECT (SELECT 1 FROM t2 WHERE d = c) FROM t1"; EXECUTE stmt; The reason of the extra warning emittion is in a way items are handled (being fixed) during execution of the JOIN::prepare() method. The method Item_field::fix_fields() calls the find_field_in_tables() function in case a field hasn't been associated yet with the item. Implementation of the find_field_in_tables() function first checks whether a table containing the required field was already opened and cached. It is done by checking the data member item->cached_table. This data member is set on handling the PRERARE FROM statement and checked on executing the EXECUTE statement. If the data member item->cached_table is set the find_field_in_tables() function invoked and the mark_select_range_as_dependent() function called if the field is an outer referencee. The mark_select_range_as_dependent() function calls the mark_as_dependent() function that finally invokes the push_warning_printf() function that produces extra warning. To fix the issue, calling of push_warning_printf() is elimited in case it was run indirectly in result of hanlding already opened table from the Item_field::fix_fields() method. --- sql/item_subselect.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'sql/item_subselect.h') diff --git a/sql/item_subselect.h b/sql/item_subselect.h index 9116238c640..de21f00143f 100644 --- a/sql/item_subselect.h +++ b/sql/item_subselect.h @@ -279,7 +279,8 @@ public: friend bool Item_ref::fix_fields(THD *, Item **); friend void mark_select_range_as_dependent(THD*, st_select_lex*, st_select_lex*, - Field*, Item*, Item_ident*); + Field*, Item*, Item_ident*, + bool); friend bool convert_join_subqueries_to_semijoins(JOIN *join); }; -- cgit v1.2.1