Steps to drop the columns:
- Make sure maintenance has finished and data has been migrated
- Change PK:
ALTER TABLE pagelinks DROP PRIMARY KEY, ADD PRIMARY KEY (`pl_from`, `pl_target_id`);
- Stop writing to the old columns
- Make communications if needed
- Drop the columns and indexes:
ALTER TABLE pagelinks DROP COLUMN pl_namespace, DROP COLUMN pl_title; DROP INDEX pl_namespace ON pagelinks; DROP INDEX pl_backlinks_namespace ON pagelinks; optimize table pagelinks;
Progress of PK change:
- s1: Done
- s2: Done
- s3: Done
- s4: Done
- s5: Done
- s6: Done
- s7: Done
- s8: Done
- labtestwiki
Progress of dropping the columns:
- s1: Done
- s2: Done
- s3: Done
- s4: Done
- s5: Done
- s6: Done
- s7: Done
- s8: Done
- labtestwiki
Impact:
- Changing PK:
- s1: Drops ~150GB from each replica
- s2: Drops ~140GB from each replica https://grafana.wikimedia.org/d/000000377/host-overview?orgId=1&var-server=db2097&var-datasource=thanos&var-cluster=mysql&viewPanel=28&from=1716915163036&to=1716957116422
- s5: Drops ~80GB from each replica.
- s3: 150-160GB dropped from each replica.
- s4: ~90GB dropped from each replica.
- s6: ~90GB dropped from each replica.
- s7: ~170GB dropped from each replica (https://grafana.wikimedia.org/d/000000377/host-overview?orgId=1&var-server=db2121&var-datasource=thanos&var-cluster=mysql&viewPanel=28&from=1711369820705&to=1711461258205)
- s8: ~110GB dropped from each replica.
- Dropping the columns
- s1: ~190GB (https://grafana.wikimedia.org/d/000000377/host-overview?orgId=1&var-server=db1169&var-datasource=thanos&var-cluster=mysql&viewPanel=28&from=1717624369265&to=1717658823840)
- s2: ~140GB (https://grafana.wikimedia.org/d/000000377/host-overview?orgId=1&var-server=db1156&var-datasource=thanos&var-cluster=mysql&viewPanel=28&from=1718177818352&to=1718207720515)
- s4: ~80GB
- s3: ~170GB
- s7:
- 410GB(!) in some cases: https://grafana.wikimedia.org/d/000000377/host-overview?orgId=1&var-server=db1158&var-datasource=thanos&var-cluster=mysql&viewPanel=28&from=1715577932535&to=1715612286365
- 210GB in some other cases: https://grafana.wikimedia.org/d/000000377/host-overview?orgId=1&var-server=db1171&var-datasource=thanos&var-cluster=mysql&viewPanel=28&from=1715644015704&to=1715711476748
- 360GB in some https://grafana.wikimedia.org/d/000000377/host-overview?orgId=1&var-server=db1181&var-datasource=thanos&var-cluster=mysql&viewPanel=28&from=1715723772661&to=1715762273882
- s6: 200GB: https://grafana.wikimedia.org/d/000000377/host-overview?orgId=1&var-server=db1165&var-datasource=thanos&var-cluster=mysql&viewPanel=28&from=1715872431625&to=1715887861908
- s5: 70GB: https://grafana.wikimedia.org/d/000000377/host-overview?orgId=1&var-server=db1161&var-datasource=thanos&var-cluster=mysql&viewPanel=28&from=1716211638129&to=1716223263703
- s8: 160GB: https://grafana.wikimedia.org/d/000000377/host-overview?orgId=1&var-server=db1167&var-datasource=thanos&var-cluster=mysql&viewPanel=28&from=1717407538879&to=1717464355750