Result rows duplicated by spider engine

Question

I've two mysql server 'G0' and 'G1'. And there is a one row test table on them respectively.

G0:

mysql> select * from test.t1;
+----+--------+
| id | node   |
+----+--------+
|  1 | DB-G0  |
+----+--------+
1 rows in set (0.00 sec)

G1:

mysql> select * from test.t1;
+----+--------+
| id | node   |
+----+--------+
|  2 | DB-G1  |
+----+--------+
1 rows in set (0.00 sec)

I'm then using the spider engine offered by MariaDB 10.4 (mysqld Ver 10.4.12-MariaDB-1:10.4.12+maria~bionic-log for debian-linux-gnu on x86_64 (mariadb.org binary distribution)) to combine them like this:

CREATE TABLE t1 (
   id BIGINT PRIMARY KEY,
   node TEXT
) ENGINE=Spider
COMMENT='wrapper "mysql"'
PARTITION BY HASH (id) (
 PARTITION par0 COMMENT = 'srv "G0", tbl "t1"',
 PARTITION par1 COMMENT = 'srv "G1", tbl "t1"'
);

It's working well for a simple query like this:

MariaDB [(none)]> select * from test.t1;
+-----+--------+
| id  | node   |
+-----+--------+
|   1 | DB-G0  |
|   2 | DB-G1  |
+-----+--------+
2 rows in set (0.013 sec)

But it doubled the results when using this condition:

MariaDB [(none)]> select * from test.t1 where id != 0;
+-----+--------+
| id  | node   |
+-----+--------+
|   1 | DB-G0  |
|   2 | DB-G1  |
|   1 | DB-G0  |
|   2 | DB-G1  |
+-----+--------+
4 rows in set (0.017 sec)

Here is my Spider related settings:

#
# * Spider
#
spider_bulk_update_mode      = 2
spider_bulk_update_size      = 512K
spider_bulk_size             = 512K
spider_conn_wait_timeout     = 5
spider_connect_timeout       = 3
spider_direct_dup_insert     = 1
spider_direct_order_limit    = 1
spider_multi_split_read      = 1
spider_net_read_timeout      = 5
spider_net_write_timeout     = 5
spider_quick_mode            = 3
spider_quick_page_size       = 1000
spider_remote_trx_isolation  = 1
spider_support_xa            = 0

spider_remote_time_zone        = +00:00
spider_remote_access_charset   = utf8mb4
spider_remote_autocommit       = 1
spider_remote_default_database = 0

spider_general_log          = 1
spider_internal_sql_log_off = 0
spider_log_result_errors    = 4

I commented out all the above settings and tried again, the results are same. Is there something wrong with me or it is a bug?

Result rows duplicated by spider engine

0 Answers0