MDEV-14907 FEDERATEDX doesn't respect DISTINCT

Federated and Federatex cannot be used with ROR scans

Federated::position() and Federatex::position() is storing in 'ref' a
pointer into a local result set buffer. This means that one cannot
compare 'ref' from different handler instances to see if they point to the
same physical record.

This bug caused federated.federatedx to return wrong results when the
optimizer tried to use index_merge to resolve some queries.

Fixed by introducing table flag HA_NON_COMPARABLE_ROWID and using this
with the above handlers.

Todo:
- Fix multi_delete(), multi_update and read_records() to use primary key
  instead of 'ref' if case HA_NON_COMPARABLE_ROWID is set. The current
  code only works if we have only one range (like table scan) for the
  tables that will be updated in the second pass.
- Enable DBUG_ASSERT() in ha_federated::cmp_ref() and
  ha_federatedx::cmp_ref().

2 files changed, 91 insertions, 0 deletions

diff --git a/mysql-test/suite/federated/optimizer.result b/mysql-test/suite/federated/optimizer.result
new file mode 100644
index 00000000000..5d7072e0b35
--- /dev/null
+++ b/mysql-test/suite/federated/optimizer.result
@@ -0,0 +1,52 @@
+connect  master,127.0.0.1,root,,test,$MASTER_MYPORT,;
+connect  slave,127.0.0.1,root,,test,$SLAVE_MYPORT,;
+connection master;
+CREATE DATABASE federated;
+connection slave;
+CREATE DATABASE federated;
+connection default;
+#
+# MDEV-14907 FEDERATEDX doesn't respect DISTINCT
+#
+CREATE TABLE t1 (
+`foo_id` bigint(20) unsigned NOT NULL,
+`foo_name` varchar(255) DEFAULT NULL,
+`parent_foo_id` bigint(20) unsigned DEFAULT NULL,
+PRIMARY KEY (`foo_id`),
+KEY `foo_name` (`foo_name`),
+KEY `parent_foo_id` (`parent_foo_id`)
+) DEFAULT CHARSET=utf8;
+CREATE TABLE `fed_t1` ENGINE=FEDERATED DEFAULT CHARSET=utf8 CONNECTION='mysql://root@127.0.0.1:MASTER_PORT/test/t1';
+INSERT INTO t1 VALUES (968903, 'STRING - 0', 822857);
+INSERT INTO t1 VALUES (968953, 'STRING - 1', 822857);
+INSERT INTO t1 VALUES (971603, 'STRING - 2', 822857);
+INSERT INTO t1 VALUES (971803, 'STRING - 3', 822857);
+INSERT INTO t1 VALUES (975103, 'STRING - 4', 822857);
+INSERT INTO t1 VALUES (822857, 'STRING', NULL);
+select foo_id,parent_foo_id,foo_name from t1 where parent_foo_id = 822857 or foo_name like 'STRING%';
+foo_id	parent_foo_id	foo_name
+968903	822857	STRING - 0
+968953	822857	STRING - 1
+971603	822857	STRING - 2
+971803	822857	STRING - 3
+975103	822857	STRING - 4
+822857	NULL	STRING
+explain
+select foo_id,parent_foo_id,foo_name from fed_t1 where parent_foo_id = 822857 or foo_name like 'STRING%';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	fed_t1	ALL	foo_name,parent_foo_id	NULL	NULL	NULL	6	Using where
+select foo_id,parent_foo_id,foo_name from fed_t1 where parent_foo_id = 822857 or foo_name like 'STRING%';
+foo_id	parent_foo_id	foo_name
+968903	822857	STRING - 0
+968953	822857	STRING - 1
+971603	822857	STRING - 2
+971803	822857	STRING - 3
+975103	822857	STRING - 4
+822857	NULL	STRING
+DROP TABLE fed_t1, t1;
+connection master;
+DROP TABLE IF EXISTS federated.t1;
+DROP DATABASE IF EXISTS federated;
+connection slave;
+DROP TABLE IF EXISTS federated.t1;
+DROP DATABASE IF EXISTS federated;
diff --git a/mysql-test/suite/federated/optimizer.test b/mysql-test/suite/federated/optimizer.test
new file mode 100644
index 00000000000..4263060fab5
--- /dev/null
+++ b/mysql-test/suite/federated/optimizer.test
@@ -0,0 +1,39 @@
+#
+#Test optimizer flags related to federated tables
+#
+
+--source have_federatedx.inc
+--source include/federated.inc
+
+connection default;
+
+--echo #
+--echo # MDEV-14907 FEDERATEDX doesn't respect DISTINCT
+--echo #
+
+CREATE TABLE t1 (
+  `foo_id` bigint(20) unsigned NOT NULL,
+  `foo_name` varchar(255) DEFAULT NULL,
+  `parent_foo_id` bigint(20) unsigned DEFAULT NULL,
+  PRIMARY KEY (`foo_id`),
+  KEY `foo_name` (`foo_name`),
+  KEY `parent_foo_id` (`parent_foo_id`)
+) DEFAULT CHARSET=utf8;
+ 
+--replace_result $MASTER_MYPORT MASTER_PORT
+eval CREATE TABLE `fed_t1` ENGINE=FEDERATED DEFAULT CHARSET=utf8 CONNECTION='mysql://root@127.0.0.1:$MASTER_MYPORT/test/t1';
+INSERT INTO t1 VALUES (968903, 'STRING - 0', 822857);
+INSERT INTO t1 VALUES (968953, 'STRING - 1', 822857);
+INSERT INTO t1 VALUES (971603, 'STRING - 2', 822857);
+INSERT INTO t1 VALUES (971803, 'STRING - 3', 822857);
+INSERT INTO t1 VALUES (975103, 'STRING - 4', 822857);
+INSERT INTO t1 VALUES (822857, 'STRING', NULL);
+
+select foo_id,parent_foo_id,foo_name from t1 where parent_foo_id = 822857 or foo_name like 'STRING%';
+
+explain
+select foo_id,parent_foo_id,foo_name from fed_t1 where parent_foo_id = 822857 or foo_name like 'STRING%';
+select foo_id,parent_foo_id,foo_name from fed_t1 where parent_foo_id = 822857 or foo_name like 'STRING%';
+DROP TABLE fed_t1, t1;
+
+source include/federated_cleanup.inc;