|From:||Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>|
|To:||Andrew Dunstan <andrew(at)dunslane(dot)net>|
|Cc:||Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Harshal Dhumal <harshal(dot)dhumal(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org|
|Subject:||Re: [postgresSQL] [bug] Two or more different types of constraints with same name creates ambiguity while drooping.|
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Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
> On 03/30/2016 10:21 AM, Tom Lane wrote:
>> I think that if we want to ensure uniqueness of constraint names, this
>> is really approaching it the wrong way, as it still fails to provide
>> any guarantees (consider concurrent index creation, for example).
>> What we need is a unique index on pg_constraint.
> +1, but does that mean people will have to change constraint names to be
> compliant before running pg_upgrade?
Yeah, but I think the situation is pretty uncommon, because we already
reject duplicate constraint names in most cases. As far as I could see
in testing it earlier, these cases all fail already:
* create index constraint when same-named index constraint exists already
* create FK constraint when same-named index constraint exists already
* create FK constraint when same-named FK constraint exists already
* create check constraint when same-named check constraint exists already
* create FK constraint when same-named check constraint exists already
I think that the case Amit's patch plugged, namely create index constraint
when same-named FK or check constraint exists already, may be about the
only missing check. I just want a unique index to be sure we are covering
Note also that because pg_dump prefers to create indexes before FK
constraints (for obvious reasons), I believe that such a case would
fail to dump/restore or pg_upgrade already.
regards, tom lane
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