Fix for Bug#5034 "prepared "select 1 into @arg15", second

execute crashes server": we were deleting lex->result
after each execute, but prepared statements assumed that
it's left intact.
The fix adds cleanup() method to select_result hierarchy,
so that result objects can be reused.
Plus we now need to delete result objects more wisely.


mysql-test/r/ps.result:
  Test results fixed: test case for bug#5034
mysql-test/t/ps.test:
  A test case for bug#5034, few followups
sql/sql_class.cc:
  - fix warning in THD::THD
  - implementation of cleanup() for select_result hierarchy
  - select_export::send_eof was identical to 
    select_dump::send_eof: moved to the base class select_to_file.
  - Statement::end_statement() to end lex, free items, and
    delete possible select_result
sql/sql_class.h:
  - select_result::cleanup() declaration
  -
sql/sql_insert.cc:
  - implementation of select_insert::cleanup(): currently
    we always create a new instance of select_insert/
    select_create on each execute.
sql/sql_lex.cc:
  - with more complicated logic of freeing lex->result it's 
    easier to have it non-zero only if it points to a valid
    result.
sql/sql_lex.h:
  Now st_lex::st_lex is not empty.
sql/sql_parse.cc:
  mysql_execute_command():
  - delete select_result *result only if it was created in
    this function.
  - use end_statement() to cleanup lex and thd in the end of
    each statement.
  - no need to save THD::lock if this is explain. This save
    apparently left from times when derived tables were 
    materialized here, not in open_and_lock_tables.
sql/sql_prepare.cc:
  - call result->cleanup() in reset_stmt_for_execute
  - now Statement is responsible for freeing its lex->result.
sql/sql_select.cc:
  handle_select():
  - don't delete result, it might be needed
    for next executions
  - result is never null

2 files changed, 38 insertions, 1 deletions

diff --git a/mysql-test/r/ps.result b/mysql-test/r/ps.result
index 0523143f91d..98095930669 100644
--- a/mysql-test/r/ps.result
+++ b/mysql-test/r/ps.result
@@ -226,3 +226,18 @@ a	b
 execute stmt1;
 a	b
 deallocate prepare stmt1;
+drop table t1;
+prepare stmt1 from "select 1 into @var";
+execute stmt1;
+execute stmt1;
+prepare stmt1 from "create table t1 select 1 as i";
+execute stmt1;
+drop table t1;
+execute stmt1;
+prepare stmt1 from "insert into t1 select i from t1";
+execute stmt1;
+execute stmt1;
+prepare stmt1 from "select * from t1 into outfile 'f1.txt'";
+execute stmt1;
+deallocate prepare stmt1;
+drop table t1;
diff --git a/mysql-test/t/ps.test b/mysql-test/t/ps.test
index 9d23c795e05..8b9704f2a06 100644
--- a/mysql-test/t/ps.test
+++ b/mysql-test/t/ps.test
@@ -209,7 +209,7 @@ drop table t1;
 
 #
 # Bug#4912 "mysqld crashs in case a statement is executed a second time":
-# negation elimination should and prepared statemens
+# negation elimination should work once and not break prepared statements
 # 
 
 create table t1(a varchar(2), b varchar(3));
@@ -217,4 +217,26 @@ prepare stmt1 from "select a, b from t1 where (not (a='aa' and b < 'zzz'))";
 execute stmt1;
 execute stmt1;
 deallocate prepare stmt1;
+drop table t1;
+
+#
+# Bug#5034 "prepared "select 1 into @arg15", second execute crashes
+# server".
+# Check that descendands of select_result can be reused in prepared 
+# statements or are correctly created and deleted on each execute
+#
 
+prepare stmt1 from "select 1 into @var";
+execute stmt1;
+execute stmt1;
+prepare stmt1 from "create table t1 select 1 as i";
+execute stmt1;
+drop table t1;
+execute stmt1;
+prepare stmt1 from "insert into t1 select i from t1";
+execute stmt1;
+execute stmt1;
+prepare stmt1 from "select * from t1 into outfile 'f1.txt'";
+execute stmt1;
+deallocate prepare stmt1;
+drop table t1;