Avoid storing last_changed in the database if its the same as last_updated

[bdraco]

Proposed change

Data PR home-assistant/data.home-assistant#214

Since last_updated and last_changed are stored as strings in the database they take up
quite a bit of space.

In testing various production instances, ~75%-96% of last_changed was the same as last_updated

sqlite> select count(*) from states where last_updated == last_changed;
1353902
sqlite> select count(*) from states where last_updated != last_changed;
44720

sqlite> select count(*) from states where last_updated == last_changed;
1308420
sqlite> select count(*) from states where last_updated != last_changed;
351063

Type of change

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Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request: Document last_changed is not stored when its the same as last_updated data.home-assistant#214

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[bdraco]

Need to write docs for this.

[balloob]

Nice! I think that we can also leverage this on the frontend and not send both over if they are the same.

[bdraco]

Nice! I think that we can also leverage this on the frontend and not send both over if they are the same.

Thats a good idea. I think we can cleanup https://github.com/home-assistant/frontend/blob/dev/src/data/history.ts#L260 a bit more once home-assistant/frontend#12662 merges but I don't want to make it any bigger

[bdraco]

Nice! I think that we can also leverage this on the frontend and not send both over if they are the same.

#71886