SQL: optimize FOR SYSTEM_TIME ALL queries [closes #85]

sql/sql_select.cc

@@ -676,11 +676,9 @@ vers_setup_select(THD *thd, TABLE_LIST *tables, COND **where_expr, SELECT_LEX *s
   TABLE_LIST *table;
   int versioned_tables= 0;
   Query_arena *arena= 0, backup;
-  bool is_prepare= thd->stmt_arena->is_stmt_prepare();
 
-  if (!thd->stmt_arena->is_conventional()
-    && !is_prepare
-    && !thd->stmt_arena->is_sp_execute())
+  if (!thd->stmt_arena->is_conventional() &&
+      !thd->stmt_arena->is_stmt_prepare() && !thd->stmt_arena->is_sp_execute())
   {
     // statement is already prepared
     DBUG_RETURN(0);
@@ -702,6 +700,11 @@ vers_setup_select(THD *thd, TABLE_LIST *tables, COND **where_expr, SELECT_LEX *s
     DBUG_RETURN(0);
   }
 
+  if (slex->vers_conditions.type == FOR_SYSTEM_TIME_ALL)
+  {
+    DBUG_RETURN(0);
+  }
+
   /* For prepared statements we create items on statement arena,
      because they must outlive execution phase for multiple executions. */
   arena= thd->activate_stmt_arena_if_needed(&backup);

sql/sql_yacc.yy

@@ -8749,13 +8749,7 @@ opt_for_system_time_clause:
           }
         | FOR_SYSTEM_TIME_SYM ALL
           {
-            static MYSQL_TIME min= { TIMESTAMP_MIN_YEAR, 1, 1, 0, 0, 0, 0, false, MYSQL_TIMESTAMP_DATETIME };
-            static MYSQL_TIME max= { TIMESTAMP_MAX_YEAR, 12, 31, 23, 59, 59, 0, false, MYSQL_TIMESTAMP_DATETIME };
-            Item *t0= new (thd->mem_root) Item_datetime_literal(thd, &min);
-            Item *t1= new (thd->mem_root) Item_datetime_literal(thd, &max);
-            if (!t0 || !t1)
-              MYSQL_YYABORT;
-            Lex->current_select->vers_conditions.init(FOR_SYSTEM_TIME_BETWEEN, UNIT_TIMESTAMP, t0, t1);
+            Lex->current_select->vers_conditions.init(FOR_SYSTEM_TIME_ALL, UNIT_TIMESTAMP);
           }
         | FOR_SYSTEM_TIME_SYM
           FROM

sql/table.h

@@ -1817,7 +1817,8 @@ enum vers_range_type_t
   FOR_SYSTEM_TIME_UNSPECIFIED = 0,
   FOR_SYSTEM_TIME_AS_OF,
   FOR_SYSTEM_TIME_FROM_TO,
-  FOR_SYSTEM_TIME_BETWEEN
+  FOR_SYSTEM_TIME_BETWEEN,
+  FOR_SYSTEM_TIME_ALL
 };
 
 enum vers_range_unit_t
@@ -1843,7 +1844,7 @@ struct vers_select_conds_t
   void init(
     vers_range_type_t t,
     vers_range_unit_t u,
-    Item * s,
+    Item * s= NULL,
     Item * e= NULL)
   {
     type= t;