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/session_tracker.cc b/sql/session_tracker.cc
index ff9780a9531..51888913983 100644
--- a/sql/session_tracker.cc
+++ b/sql/session_tracker.cc
@@ -974,7 +974,7 @@ bool Current_schema_tracker::store(THD *thd, String *buf)
     It saves length of database name and name of database name +
     length of saved length of database length.
   */
-  length= db_length= thd->db_length;
+  length= db_length= thd->db.length;
   length += net_length_size(length);
 
   compile_time_assert(SESSION_TRACK_SCHEMA < 251);
@@ -991,7 +991,7 @@ bool Current_schema_tracker::store(THD *thd, String *buf)
   buf->q_net_store_length(length);
 
   /* Length and current schema name */
-  buf->q_net_store_data((const uchar *)thd->db, thd->db_length);
+  buf->q_net_store_data((const uchar *)thd->db.str, thd->db.length);
 
   reset();