MySQL GTID Replication and lower_case_table_names ~ datablogs

Friday, January 3, 2020

MySQL GTID Replication and lower_case_table_names

Error 'Table 'EMPLOYEES.POSITION' doesn't exist' on query. Default database: 'employees'. Query: 'ALTER TABLE EMPLOYEES.POSITION ADD COLUMN phone VARCHAR(15)'
Interesting , table exist on slave server . But we are getting above error frequently and unable to broken the replication because database size is too big


We are having environment as GTID replication setup with windows server (Master) to Ubuntu Linux machine (Slave) . When we dig into all the findings , concluded its may be with case sensitivity issue . Lower_case_table_names variable value is same on both servers . But as per MySQL documents 
Database and table names are not case-sensitive in Windows , but are case-sensitive in most varieties of Unix.Column,index,stored routine, and event names are not case-sensitive on any platform,nor are column aliases
So , decided to tackle the current situation without data loss in slave server . Changing the lower_case_table_names is not best practice and it will corrupt case_sensitive names data files . 

we have stopped the slave , executed all the DML and DDL statements in slave server to match the schema deployments with master server .

And followed GTID replication error skipping process to skip the transactions manually handled in slave servers 

Capture the error GTID with master binlog files
root@master:/var/log/mysql# mysqlbinlog --start-position=904 mysql-bin.000004
/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=1*/;
/*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/;
DELIMITER /*!*/;
# at 4
#200102 11:35:24 server id 1 end_log_pos 123 CRC32 0x14c9c2f7 Start: binlog v 4, server v 5.7.28-0ubuntu0.16.04.2-log created 200102 11:35:24
# Warning: this binlog is either in use or was not closed properly.
BINLOG '
fNUNXg8BAAAAdwAAAHsAAAABAAQANS43LjI4LTB1YnVudHUwLjE2LjA0LjItbG9nAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAEzgNAAgAEgAEBAQEEgAAXwAEGggAAAAICAgCAAAACgoKKioAEjQA
AffCyRQ=
'/*!*/;
# at 904
#200102 12:06:51 server id 1 end_log_pos 969 CRC32 0x3564eba7 GTID last_committed=4 sequence_number=5 rbr_only=yes
/*!50718 SET TRANSACTION ISOLATION LEVEL READ COMMITTED*//*!*/;
SET @@SESSION.GTID_NEXT= '69b98063-2d31-11ea-9586-12b321a8670d:78'/*!*/;
# at 969
#200102 12:06:51 server id 1 end_log_pos 1042 CRC32 0xb527b5d3 Query thread_id=328 exec_time=0 error_code=0
Skipped the binlog position 904 transactions in slave server
mysql> stop slave;
Query OK, 0 rows affected (0.00 sec)
mysql> SET @@SESSION.GTID_NEXT= '69b98063-2d31-11ea-9586-12b321a8670d:78';
Query OK, 0 rows affected (0.00 sec)
mysql> begin ; commit;
Query OK, 0 rows affected (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
mysql> SET gtid_next=automatic;
Query OK, 0 rows affected (0.00 sec)
mysql> start slave;
Query OK, 0 rows affected (0.00 sec)

Finally , GTID Replication begins to sync pending SQL threads and upto date the data with Master server !!!


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