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

1 files changed, 1 insertions, 1 deletions

diff --git a/sql/sql_lex.h b/sql/sql_lex.h
index 053c85166f6..9c7918a400f 100644
--- a/sql/sql_lex.h
+++ b/sql/sql_lex.h
@@ -639,7 +639,7 @@ typedef struct st_lex
     list of those tables after they are opened.
   */
   TABLE_LIST *time_zone_tables_used;
-  st_lex() {}
+  st_lex();
   inline void uncacheable(uint8 cause)
   {
     safe_to_cache_query= 0;