Stop hammering ir_translation id sequence

[gracinet]

Description of the issue/feature this PR addresses: startup failures due to ir_translation_id_seq overflow (DataError)

Current behavior before PR: ir_translation_id_seq grows by big steps, can reach 2**31 in months

Desired behavior after PR is merged: ir_translation_id_seq grows only if new translations appear

(I have NOT signed Odoo CLA)

We've had some instances actually reaching the 2**31 limit, because
the temporary table used to prepare potential insertions used the same
id sequence as the main table, hence each insert in the temporary table
bumps the sequence.

Aggravations:

• if one hits the wall, the instance won't start
• if one resets the sequence too close from an existing id, it won't start either
• the existing ids are spread across the whole spectrum, making it hard to find
  a safe range to reset the sequence.

Yes this probably means instances that restart too much, but that's another issue.

The whole system is questionable at best [1] but this fix should have no impact, and
improve a bit startup performance and PostgreSQL health. On the other hand, we can't
guarantee without a long analysis that's out of our scope that even changing
ir_translation to a bigint would have no impact, yet alone give this the full rewrite
it certainly deserves.

[1] for starters, why use the DB at all in preparation, and use a temporary table
that's logically tied to a specific connection ?

[ccomb]

Looks nice. But could you explain a way to reproduce the issue and see the id_seq grow? Could you also point to the version on which this issue was seen? (oca? odoo? branch? commit?)

[gracinet]

Target version: the one I'm doing the PR against !
To reproduce, just start Odoo on a database that's already initialized and compare growth of the sequence on one hand, and the highest value that's been actually used in a psql console.
(be sure to avoid developer tricks or modules that precisely avoid reloading PO files)

In my case:

mybase => select nextval('ir_translation_id_seq'); select max(id) from ir_translation;
 nextval 
---------
   63407
(1 row)

  max  
-------
 63362

Then start odoo (and stop it if you like):

bin/start_odoo -d mybase --stop-after-init

And check the values again:

mybase => select nextval('ir_translation_id_seq'); select max(id) from ir_translation;
 nextval 
---------
   67703
(1 row)

  max  
-------
 63362

Conclusion: no actual value has been used, but the sequence has been updated more than 300 times. The more addons you have, the worst it is.

After the fix, you'd see a delta of 1 for nextval (due to the measurement itself)

[gracinet]

I've been a bit imprecise in my wording : it occurred in production on a tagged version of that branch but it affects most probably all versions since 2011. We can check that afterwards if you like