SHOW EXPLAIN: merge to 10.0-base.

sql/sql_lex.h

@@ -194,6 +194,7 @@ enum enum_sql_command {
   SQLCOM_SHOW_RELAYLOG_EVENTS, 
   SQLCOM_SHOW_USER_STATS, SQLCOM_SHOW_TABLE_STATS, SQLCOM_SHOW_INDEX_STATS,
   SQLCOM_SHOW_CLIENT_STATS,
+  SQLCOM_SHOW_EXPLAIN,
 
   /*
     When a command is added here, be sure it's also added in mysqld.cc
@@ -357,6 +358,8 @@ typedef uchar index_clause_map;
 #define INDEX_HINT_MASK_ALL (INDEX_HINT_MASK_JOIN | INDEX_HINT_MASK_GROUP | \
                              INDEX_HINT_MASK_ORDER)
 
+class select_result_sink;
+
 /* Single element of an USE/FORCE/IGNORE INDEX list specified as a SQL hint  */
 class Index_hint : public Sql_alloc
 {
@@ -717,6 +720,8 @@ public:
   friend int subselect_union_engine::exec();
 
   List<Item> *get_unit_column_types();
+  int print_explain(select_result_sink *output, uint8 explain_flags,
+                    bool *printed_anything);
 };
 
 typedef class st_select_lex_unit SELECT_LEX_UNIT;
@@ -777,6 +782,12 @@ public:
     those converted to jtbm nests. The list is emptied when conversion is done.
   */
   List<Item_in_subselect> sj_subselects;
+  
+  /*
+    Needed to correctly generate 'PRIMARY' or 'SIMPLE' for select_type column
+    of EXPLAIN
+  */
+  bool have_merged_subqueries;
 
   List<TABLE_LIST> leaf_tables;
   List<TABLE_LIST> leaf_tables_exec;
@@ -1001,7 +1012,7 @@ public:
   bool is_part_of_union() { return master_unit()->is_union(); }
   bool optimize_unflattened_subqueries(bool const_only);
   /* Set the EXPLAIN type for this subquery. */
-  void set_explain_type();
+  void set_explain_type(bool on_the_fly);
   bool handle_derived(LEX *lex, uint phases);
   void append_table_to_list(TABLE_LIST *TABLE_LIST::*link, TABLE_LIST *table);
   bool get_free_table_map(table_map *map, uint *tablenr);
@@ -1025,8 +1036,10 @@ public:
 
   bool save_leaf_tables(THD *thd);
   bool save_prep_leaf_tables(THD *thd);
-  bool is_merged_child_of(st_select_lex *ancestor);
 
+  bool is_merged_child_of(st_select_lex *ancestor);
+  int print_explain(select_result_sink *output, uint8 explain_flags, 
+                    bool *printed_anything);
   /*
     For MODE_ONLY_FULL_GROUP_BY we need to maintain two flags:
      - Non-aggregated fields are used in this select.
@@ -2348,7 +2361,7 @@ struct LEX: public Query_tables_list
   char *backup_dir;				/* For RESTORE/BACKUP */
   char* to_log;                                 /* For PURGE MASTER LOGS TO */
   char* x509_subject,*x509_issuer,*ssl_cipher;
-  String *wild;
+  String *wild; /* Wildcard in SHOW {something} LIKE 'wild'*/ 
   sql_exchange *exchange;
   select_result *result;
   Item *default_value, *on_update_value;