Change 382693 had a related patch set uploaded (by Ladsgroup; owner: Amir Sarabadani):
[mediawiki/extensions/Wikibase@master] Drop wb_entity_per_page table if it exists

https://gerrit.wikimedia.org/r/382693

Change 382693 merged by jenkins-bot:
[mediawiki/extensions/Wikibase@master] Drop wb_entity_per_page table if it exists

https://gerrit.wikimedia.org/r/382693

Hi @Ladsgroup - I am a bit confused with this ticket.
Is this something you will do? Or something the DBAs have to do (and hence the Schema-change-in-production )?

This is something for the DBAs, this patch only does it for the beta cluster, I was thinking do you need .sql file or you can directly do "DROP TABLE foo" too?

In T177601#3665456, @Ladsgroup wrote:

This is something for the DBAs, this patch only does it for the beta cluster, I was thinking do you need .sql file or you can directly do "DROP TABLE foo" too?

We don't strictly need it no.
So as this is merged, is this ok to be started then, right?

It's merged but not deployed, we should wait for a week if train doesn't get stuck (more if it does)

In T177601#3665510, @Ladsgroup wrote:

It's merged but not deployed, we should wait for a week if train doesn't get stuck (more if it does)

Sounds good - can you ping us once we are good to proceed?

Sure. Thanks!

Add Schema-change-in-production, that way we will know it is ready :-)

@Ladsgroup just to be clear, it needs to be dropped everywhere except from wikidatawiki (s5) and testwikidatawiki (s3)?

@Marostegui : No, it's the other way around. It needs to be dropped in these two wikis only because it's a repo database and the table doesn't exist in client wikis.

In T177601#3689891, @Ladsgroup wrote:

@Marostegui : No, it's the other way around. It needs to be dropped in these two wikis only because it's a repo database and the table doesn't exist in client wikis.

Then the original task description is a bit confusing:

We want the table to be dropped (after the patch got deployed, meaning wmf-3).

It's only needed on wikibase repos (wikidatawiki (s5), testwikidatawiki (s3))

By "It" I meant the dropping, I'm sorry for the confusion, will update the task description.

In T177601#3690074, @Ladsgroup wrote:

By "It" I meant the dropping, I'm sorry for the confusion, will update the task description.

Clear now! Sorry for making you re-write it, but better be safe than sorry :)

Does this need to be backuped or can it just be dropped?
Ideally I will rename it on a production slave and leave it like that for a few days before killing it.

In T177601#3698864, @Marostegui wrote:

Does this need to be backuped or can it just be dropped?
Ideally I will rename it on a production slave and leave it like that for a few days before killing it.

If we really wanted/ needed to, we could easily re-generate the data from the page table… but that's not going to be needed.

A backup would be great, all crazy things can happen. One thing that would be great to know is to see if it's being read / written at all, I know it can be tricky and if it's too much hassle, let's move forward with back up in hand just in case.

@hoo, you are right but re-generating it might take some time.

In T177601#3698866, @Ladsgroup wrote:

A backup would be great, all crazy things can happen. One thing that would be great to know is to see if it's being read / written at all, I know it can be tricky and if it's too much hassle, let's move forward with back up in hand just in case.

That is the idea behind the rename.
If it is being written, replication will break. If it is being read, we should see some errors on logtash.
Backups have been taken and left at:

root@dbstore1001:/srv/tmp/T177601# pwd
/srv/tmp/T177601
root@dbstore1001:/srv/tmp/T177601# ls -lh
total 1.2G
-rw-r--r-- 1 root root 3.2M Oct 20 08:53 s3_wb_entity_per_page.sql
-rw-r--r-- 1 root root 1.2G Oct 20 08:53 s5_wb_entity_per_page.sql

Mentioned in SAL (#wikimedia-operations) [2017-10-23T08:09:17Z] <marostegui> Rename wb_entity_per_page table on s5 db1092 and s3 db1077 - T177601

I have renamed this table on the following servers

s5: wikidatawiki: db1092

root@db1092[wikidatawiki]> set session sql_log_bin=0;
Query OK, 0 rows affected (0.00 sec)

root@db1092[wikidatawiki]> rename table wb_entity_per_page to T177601_wb_entity_per_page;
Query OK, 0 rows affected (0.01 sec)

To revert this change, connect to db1092 and execute:

use wikidatawiki;
set session sql_log_bin=0;
rename table T177601_wb_entity_per_page to wb_entity_per_page;

s3: testwikidatawiki: db1077

root@db1077[testwikidatawiki]> set session sql_log_bin=0;
Query OK, 0 rows affected (0.00 sec)

root@db1077[testwikidatawiki]> rename table wb_entity_per_page to T177601_wb_entity_per_page;
Query OK, 0 rows affected (0.00 sec)

To revert this change, connect to db1077 and execute:

use testwikidatawiki;
set session sql_log_bin=0;
rename table T177601_wb_entity_per_page to wb_entity_per_page;

There have been no errors so I will be dropping this table on Monday (because I do not want to drop stuff on a Friday :-) )

Mentioned in SAL (#wikimedia-operations) [2017-10-30T09:08:42Z] <marostegui> Drop wb_entity_per_page page from s3 and s5 - T177601