MDEV-16783 Assertion `!conds' failed in mysql_delete upon 2nd execution of SP with DELETE HISTORY

* remove assertion
* do not setup `conds` if it's already cached

Fixes #823

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

@@ -100,5 +100,11 @@ ERROR 42S02: 'v' is a view
 unlock tables;
 drop view v;
 drop table t;
+create table t1 (i int) with system versioning;
+create procedure pr() delete history from t1 before system_time now();
+call pr;
+call pr;
+drop procedure pr;
+drop table t1;
 drop database test;
 create database test;

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

@@ -107,5 +107,15 @@ unlock tables;
 drop view v;
 drop table t;
 
+#
+# MDEV-16783 Assertion `!conds' failed in mysql_delete upon 2nd execution of SP with DELETE HISTORY
+#
+create table t1 (i int) with system versioning;
+create procedure pr() delete history from t1 before system_time now();
+call pr;
+call pr;
+drop procedure pr;
+drop table t1;
+
 drop database test;
 create database test;

sql/sql_delete.cc

@@ -323,13 +323,17 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
     DBUG_ASSERT(table);
 
     DBUG_ASSERT(!conds || thd->stmt_arena->is_stmt_execute());
+
+    // conds could be cached from previous SP call
+    if (!conds)
+    {
       if (select_lex->vers_setup_conds(thd, table_list))
         DBUG_RETURN(TRUE);
 
-    DBUG_ASSERT(!conds);
       conds= table_list->on_expr;
       table_list->on_expr= NULL;
     }
+  }
 
   if (mysql_handle_list_of_derived(thd->lex, table_list, DT_MERGE_FOR_INSERT))
     DBUG_RETURN(TRUE);