Pt table checksum

The optional DSN specifies the master host. Percona Toolkit, and it is widely used to identify data differences between masters and slaves. Therefore, as Percona Support Engineers we have customers often asking questions related to the pt-table-checksum errors and warnings produced.

This is because the developers of Galera at Codership added a hook to disable any replication mode other than ROW. One of those tools is pt-table-checksum , which works by dividing table rows into chunks of rows. The size of a chunk changes dynamically during the operation to avoid overloading the server. This is called the DSN (data source name), which is a coma separated string. We can store this information in a dedicated database called percona in a table called dsns.

If specifie pt-table-checksum doesn’t checksum any tables. It checks replicas for differences found by previous checksumming, and then exits. Running pt-table-checksum on a table in. The information about this bug in Launchpad is automatically pulled daily from the remote bug.

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Compare Prices Online And Save Today! Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. To test pt-table-checksum I removed a row from the Tickets table in my test database on the slave. I have verified that this row is indeed missing but still present on the master.

When pt - table - checksum performs a comparison, it compares chunk by chunk instead of record by record. So we can divide the 1records into chunks, with each chunk containing records. The comparison progresses one chunk after another until the comparison for all chunks are completed. We see that pt - table - checksum waits for some slave that it knows and cares (that can not be properly identified by hostname in my case, as all instances run on the same host) to start. This is expecte as this tool works by running statements on master (and rely on statement-based logging for its connection to master) that are expected to be replicated to slaves and produce different (chunk checksums) there if the data are different on specific slave.

CHECKSUM TABLE requires the SELECT privilege for the table. The table row format affects the checksum value. If the row format changes, the checksum will change. You can use this statement to verify that the contents are the same before and after a backup, rollback, or other operation that is intended to put the data back to a known state. This statement requires the SELECT privilege for the table.

As of percona-toolkit 3. Waiting to check replicas for differences : 00:remain I recently came across an issue where the task was to checksum databases using Percona’s pt-table-checksum. Although pt - table - checksum is intelligent, it introduces some issues to the server. Usually it is not used on the master server unless it is the only option. For data consistency checks, we usually make comparisons on two slave servers.

If the two slave servers are okay, the consistency is regarded as okay. Run it periodically against your master schemas or the entire instance if you like. It will store checksums of all of your tables in a special checksum table.

The data from this table then will propagate through replication to all of your connected slaves. MySQL非主从环境下数据一致性校验及修复程序.