Changed database, tablename and alias to be LEX_CSTRING

This was done in, among other things:
- thd->db and thd->db_length
- TABLE_LIST tablename, db, alias and schema_name
- Audit plugin database name
- lex->db
- All db and table names in Alter_table_ctx
- st_select_lex db

Other things:
- Changed a lot of functions to take const LEX_CSTRING* as argument
  for db, table_name and alias. See init_one_table() as an example.
- Changed some function arguments from LEX_CSTRING to const LEX_CSTRING
- Changed some lists from LEX_STRING to LEX_CSTRING
- threads_mysql.result changed because process list_db wasn't always
  correctly updated
- New append_identifier() function that takes LEX_CSTRING* as arguments
- Added new element tmp_buff to Alter_table_ctx to separate temp name
  handling from temporary space
- Ensure we store the length after my_casedn_str() of table/db names
- Removed not used version of rename_table_in_stat_tables()
- Changed Natural_join_column::table_name and db_name() to never return
  NULL (used for print)
- thd->get_db() now returns db as a printable string (thd->db.str or "")

1 files changed, 2 insertions, 2 deletions

diff --git a/sql/item_create.cc b/sql/item_create.cc
index d73a5327d25..19a8f2b138e 100644
--- a/sql/item_create.cc
+++ b/sql/item_create.cc
@@ -3253,7 +3253,7 @@ Create_qfunc::create_func(THD *thd, LEX_CSTRING *name, List<Item> *item_list)
 {
   LEX_CSTRING db;
 
-  if (! thd->db && ! thd->lex->sphead)
+  if (! thd->db.str && ! thd->lex->sphead)
   {
     /*
       The proper error message should be in the lines of:
@@ -3271,7 +3271,7 @@ Create_qfunc::create_func(THD *thd, LEX_CSTRING *name, List<Item> *item_list)
     return NULL;
   }
 
-  if (thd->lex->copy_db_to(&db.str, &db.length))
+  if (thd->lex->copy_db_to(&db))
     return NULL;
 
   return create_with_db(thd, &db, name, false, item_list);