MDEV-37207: dumping tables for multi delete query doesn't work always

It was observed that, when doing multiple DELETE on tables:
-> if there was duplicate data to delete, then no ddls were dumped to the trace.
-> However, when tested with no data being deleted from the tables,
   then ddls of the tables were getting dumped to the trace.

The problem is that store_tables_context_in_trace() is not getting
invoked, from mysql_execute_command() in all the situations.

The reason is that multi-table DELETE returned error when it had deleted duplicate rows.
Multi-table DELETE actually finds record combinations to delete,
and when it has found let's say {t1.rowX, t2.rowY, t3.rowZ}, it will attempt to
save t1.rowX in the temptable for t1, t2.rowY in the temptable for t2 and so forth.
When saving the row to be deleted, in the temp table, it can encounter error
121 (HA_ERR_FOUND_DUPP_KEY), and it is propagated to the caller.

As a fix, I have marked that there is no error when HA_ERR_FOUND_DUPP_KEY error_code is
noticed in the multi_delete::send_data()

Author: bsrikanth-mariadb

mysql-test/main/opt_trace_store_ddls.result

@@ -477,4 +477,40 @@ CREATE TABLE `t1` (
 ) ENGINE=MyISAM AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci
 drop table t1;
 drop table t2;
+#
+# MDEV-37207: test multi delete of 2 tables
+# trace result should have the ddls for both the tables
+#
+create table t1(id1 int not null auto_increment primary key);
+create table t2(id2 int not null);
+insert into t1 values (1),(2);
+insert into t2 values (1),(1),(2),(2);
+delete t1.*, t2.* from t1, t2 where t1.id1 = t2.id2;
+set @ddls= (select json_detailed(json_extract(trace, '$**.ddl')) from information_schema.optimizer_trace);
+select ddl
+from json_table(@ddls, '$[*]' columns(ddl text path '$')) as jt;
+ddl
+CREATE TABLE `t2` (
+  `id2` int(11) NOT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci
+CREATE TABLE `t1` (
+  `id1` int(11) NOT NULL AUTO_INCREMENT,
+  PRIMARY KEY (`id1`)
+) ENGINE=MyISAM AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci
+# rerun the same delete query
+# Now, trace result should have the ddls for all 2 tables,
+# even though no data is deleted
+delete t1.*, t2.* from t1, t2 where t1.id1 = t2.id2;
+set @ddls= (select json_detailed(json_extract(trace, '$**.ddl')) from information_schema.optimizer_trace);
+select ddl
+from json_table(@ddls, '$[*]' columns(ddl text path '$')) as jt;
+ddl
+CREATE TABLE `t2` (
+  `id2` int(11) NOT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci
+CREATE TABLE `t1` (
+  `id1` int(11) NOT NULL AUTO_INCREMENT,
+  PRIMARY KEY (`id1`)
+) ENGINE=MyISAM AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci
+drop table t1, t2;
 drop database db1;

mysql-test/main/opt_trace_store_ddls.test

@@ -361,4 +361,32 @@ select ddl from json_table(@ddls, '$[*]' columns(ddl text path '$')) as jt;
 drop table t1;
 drop table t2;
 
+--echo #
+--echo # MDEV-37207: test multi delete of 2 tables
+--echo # trace result should have the ddls for both the tables
+--echo #
+
+create table t1(id1 int not null auto_increment primary key);
+create table t2(id2 int not null);
+
+insert into t1 values (1),(2);
+insert into t2 values (1),(1),(2),(2);
+
+delete t1.*, t2.* from t1, t2 where t1.id1 = t2.id2;
+
+set @ddls= (select json_detailed(json_extract(trace, '$**.ddl')) from information_schema.optimizer_trace);
+select ddl
+from json_table(@ddls, '$[*]' columns(ddl text path '$')) as jt;
+
+--echo # rerun the same delete query
+--echo # Now, trace result should have the ddls for all 2 tables,
+--echo # even though no data is deleted
+delete t1.*, t2.* from t1, t2 where t1.id1 = t2.id2;
+
+set @ddls= (select json_detailed(json_extract(trace, '$**.ddl')) from information_schema.optimizer_trace);
+select ddl
+from json_table(@ddls, '$[*]' columns(ddl text path '$')) as jt;
+ 
+drop table t1, t2;
+
 drop database db1;

sql/sql_delete.cc

@@ -1419,6 +1419,8 @@ int multi_delete::send_data(List<Item> &values)
               }
               found++;
           }
+          else
+            error= 0; /* Clear HA_ERR_FOUND_DUPP_{KEY,UNIQUE} error */
       }
     }
   }