Bug#30333 (Performance, expressions lists in the parser)

Before this patch, the parser would execute:
- Select->expr_list.push_front()
- Select->expr_list.pop()
when parsing expressions lists, in the following rules:
- udf_expr_list
- expr_list
- ident_list

This is unnecessary, and introduces overhead due to the memory allocations
performed with Select->expr_list

With this patch, this code has been removed.
The list being parsed is maintained in the parser stack instead.

Also, 'udf_expr_list' has been renamed 'opt_udf_expr_list', since this
production can be empty.


sql/sql_lex.cc:
  Removed unused attribute expr_list
sql/sql_lex.h:
  Removed unused attribute expr_list
sql/sql_yacc.yy:
  Improved performances when parsing expression lists

1 files changed, 0 insertions, 2 deletions

diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc
index 78b4f034f98..7fe2ed04d51 100644
--- a/sql/sql_lex.cc
+++ b/sql/sql_lex.cc
@@ -323,7 +323,6 @@ void lex_start(THD *thd)
   lex->length=0;
   lex->part_info= 0;
   lex->select_lex.in_sum_expr=0;
-  lex->select_lex.expr_list.empty();
   lex->select_lex.ftfunc_list_alloc.empty();
   lex->select_lex.ftfunc_list= &lex->select_lex.ftfunc_list_alloc;
   lex->select_lex.group_list.empty();
@@ -1555,7 +1554,6 @@ void st_select_lex::init_select()
   options= 0;
   sql_cache= SQL_CACHE_UNSPECIFIED;
   braces= 0;
-  expr_list.empty();
   interval_list.empty();
   ftfunc_list_alloc.empty();
   inner_sum_func_list= 0;