Re: changing primary key col(s) with minimal impact

Hi Joe,

> I have a need to provide a way to change a table's primary key
> columns, in the possible presence of foreign keys, and with concurrent
> use (as much as possible).
>
> The best way I have come up with is roughly:
> a. create the to-be-new-pk index concurrently
> b. "demote" the old pk to be a unique constraint
> c. alter table add constraint new pk using existing index
>
> Step b. involves (in one transaction):
> - --------------------------------------
> * update pg_class row for the table
> relhaspkey false
> * update pg_constraint row for the original pk
> contype = 'u'
> conname = 'some_new_name'
> * update pg_index row for the original pk index
> indisprimary = false
> * alter index original pk rename to some_new_name
> - --------------------------------------
> I have tested this (minimally) and as far as I can tell it works.
>
> Questions:
> 1) any major holes in this approach?
> 2) any better ideas?
> 3) should we consider an ALTER TABLE ALTER CONSTRAINT command
> (or some such) to allow demotion of a PRIMARY KEY to a UNIQUE
> constraint?
>
> Thanks for any thoughts/comments.
>

Hi Joe,

I already did something like it once, but to rebuild a bloated PK index
with minimal locks. I still waiting for 'REINDEX CONCURRENTLY' :-)

At that time I didn't have no trouble with this approach.

Regards,

--
Fabrízio de Royes Mello
Consultoria/Coaching PostgreSQL
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