Bug #38691: segfault/abort in ``UPDATE ...JOIN'' while

          ``FLUSH TABLES WITH READ LOCK''

Concurrent execution of 1) multitable update with a
NATURAL/USING join and 2) a such query as "FLUSH TABLES
WITH READ LOCK" or "ALTER TABLE" of updating table led
to a server crash.


The mysql_multi_update_prepare() function call is optimized
to lock updating tables only, so it postpones locking to
the last, and if locking fails, it does cleanup of modified
syntax structures and repeats a query analysis.  However,
that cleanup procedure was incomplete for NATURAL/USING join
syntax data: 1) some Field_item items pointed into freed
table structures, and 2) the TABLE_LIST::join_columns fields
was not reset.

Major change:
  short-living Field *Natural_join_column::table_field has
  been replaced with long-living Item*.

1 files changed, 1 insertions, 0 deletions

diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc
index 0cf7c11b447..ba9c0e93134 100644
--- a/sql/sql_lex.cc
+++ b/sql/sql_lex.cc
@@ -1205,6 +1205,7 @@ void st_select_lex::init_query()
   subquery_in_having= explicit_limit= 0;
   is_item_list_lookup= 0;
   first_execution= 1;
+  first_natural_join_processing= 1;
   first_cond_optimization= 1;
   parsing_place= NO_MATTER;
   exclude_from_table_unique_test= no_wrap_view_item= FALSE;