[Wikidata-bugs] [Maniphest] [Commented On] T159718: Evaluate if it is possbile to add an empty column for full entity ID to wb_terms without affecting wikidata.org users

Mon, 06 Mar 2017 13:17:37 -0800

jcrespo added a comment.

So the comments:

  • do not defer the creation of the indexes- those are extra alter tables and do no make things easier in any way- just create the indexes from the start- assuming they will be used.
  • Renaming columns is a big no- specially to an already existent name. Always add a new column and stop using the previous one at some point. We then can drop the old one with a lower precedence. Think not only as a bad practice in general with code- some applications that are not mediawiki, like labs, may break in bad ways.

So my suggestion would be:

  1. Create a new column with new indexes
  2. Populate new column at the same time than the current one (ideally with code, but if you do not want to touch code, it can even be made with a trigger) + populate old values with maintenance
  3. Deploy the new code using only the new column
  4. At some point in the future, drop the old column (it can be made all null and it will save space already) -low priority

If you are changing an int for a string in a trivial way, that mysql would be compatible with (1234 -> '1234'), it could even be done in a single blow, but I assume it is not the case, probably something more on the lines of 1234 -> 'Q1234', am I right?

This simplifies the process, and less schema changes is not only less work for us- it is also you getting less blocked by us.

This is not an absolute thing- I am open to criticism, as you may know more details that I don't. It is ok to keep ids like term_entity_id_s, reusing identifiers is a bit frowned upon.


TASK DETAIL
https://phabricator.wikimedia.org/T159718

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To: jcrespo
Cc: jcrespo, Marostegui, Lydia_Pintscher, Aklapper, daniel, WMDE-leszek, Minhnv-2809, D3r1ck01, Izno, Luke081515, Wikidata-bugs, aude, Mbch331, Jay8g, Krenair
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