MDEV-17613 MIN/MAX Optimization (Select tables optimized away) does not work

Prune to now-partition when there is no FOR SYSTEM_TIME clause.

mysql-test/suite/versioning/r/partition.result

@@ -546,6 +546,17 @@ t1	CREATE TABLE `t1` (
 #
 create or replace table t1 (f int) with system versioning partition by hash(f);
 insert delayed into t1 values (1);
+#
+# MDEV-17613 MIN/MAX Optimization (Select tables optimized away) does not work
+#
+create or replace table t1 (pk int primary key) with system versioning
+partition by system_time (
+partition p1 history,
+partition pn current);
+insert into t1 values (1), (2);
+explain select max(pk) from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Select tables optimized away
 # Test cleanup
 drop database test;
 create database test;

mysql-test/suite/versioning/r/partition_rotation.result

@@ -44,7 +44,7 @@ i
 6
 explain partitions select * from t1;
 id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	pn_pnsp0,pn_pnsp1	ALL	NULL	NULL	NULL	NULL	2	Using where
+1	SIMPLE	t1	pn_pnsp0,pn_pnsp1	ALL	NULL	NULL	NULL	NULL	2	
 explain partitions select * from t1 for system_time as of '2001-02-04 10:20:30';
 id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	p1_p1sp0,p1_p1sp1,p0_p0sp0,p0_p0sp1,p2_p2sp0,p2_p2sp1,pn_pnsp0,pn_pnsp1	ALL	NULL	NULL	NULL	NULL	#	Using where

mysql-test/suite/versioning/t/partition.test

@@ -497,6 +497,27 @@ create or replace table t1 (f int) with system versioning partition by hash(f);
 --error 0,ER_DELAYED_NOT_SUPPORTED
 insert delayed into t1 values (1);
 
+--echo #
+--echo # MDEV-17613 MIN/MAX Optimization (Select tables optimized away) does not work
+--echo #
+--disable_query_log
+set @saved_storage_engine= @@default_storage_engine;
+if ($MTR_COMBINATION_HEAP)
+{
+  # This case does not work with HEAP
+  set default_storage_engine= myisam;
+}
+--enable_query_log
+create or replace table t1 (pk int primary key) with system versioning
+partition by system_time (
+  partition p1 history,
+  partition pn current);
+insert into t1 values (1), (2);
+explain select max(pk) from t1;
+--disable_query_log
+set default_storage_engine= @saved_storage_engine;
+--enable_query_log
+
 --echo # Test cleanup
 drop database test;
 create database test;

sql/sql_select.cc

@@ -721,6 +721,19 @@ void vers_select_conds_t::print(String *str, enum_query_type query_type) const
   }
 }
 
+/**
+  Setup System Versioning conditions
+
+  Add WHERE condition according to FOR SYSTEM_TIME clause.
+
+  If the table is partitioned by SYSTEM_TIME and there is no FOR SYSTEM_TIME
+  clause, then select now-partition instead of modifying WHERE condition.
+
+  @retval
+    -1    on error
+  @retval
+    0     on success
+*/
 int SELECT_LEX::vers_setup_conds(THD *thd, TABLE_LIST *tables)
 {
   DBUG_ENTER("SELECT_LEX::vers_setup_cond");
@@ -788,12 +801,13 @@ int SELECT_LEX::vers_setup_conds(THD *thd, TABLE_LIST *tables)
     vers_select_conds_t &vers_conditions= table->vers_conditions;
 
 #ifdef WITH_PARTITION_STORAGE_ENGINE
-      /*
-        if the history is stored in partitions, then partitions
-        themselves are not versioned
-      */
-      if (table->partition_names && table->table->part_info->vers_info)
+    Vers_part_info *vers_info;
+    if (table->table->part_info && (vers_info= table->table->part_info->vers_info))
+    {
+      if (table->partition_names)
       {
+        /* If the history is stored in partitions, then partitions
+            themselves are not versioned. */
         if (vers_conditions.is_set())
         {
           my_error(ER_VERS_QUERY_IN_PARTITION, MYF(0), table->alias.str);
@@ -802,6 +816,16 @@ int SELECT_LEX::vers_setup_conds(THD *thd, TABLE_LIST *tables)
         else
           vers_conditions.init(SYSTEM_TIME_ALL);
       }
+      else if (!vers_conditions.is_set())
+      {
+        table->partition_names= newx List<String>;
+        String *s= newx String(vers_info->now_part->partition_name,
+                               system_charset_info);
+        table->partition_names->push_back(s);
+        table->table->file->change_partitions_to_open(table->partition_names);
+        vers_conditions.init(SYSTEM_TIME_ALL);
+      }
+    }
 #endif
 
     if (outer_table && !vers_conditions.is_set())
@@ -951,6 +975,7 @@ int SELECT_LEX::vers_setup_conds(THD *thd, TABLE_LIST *tables)
   DBUG_RETURN(0);
 #undef newx
 }
+#undef newx
 
 /*****************************************************************************
   Check fields, find best join, do the select and output fields.