From: Jerry Sievers <gsievers19@comcast.net>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Laurenz Albe <laurenz.albe@cybertec.at>,
  Shrikant Bhende <shrikantpostgresql@gmail.com>,
  pgsql-admin@lists.postgresql.org
Subject: Re: Alter command getting stuck on a table
References: 
 <CAMTQpJALSF2EvBqmdYCqKnXx-o2VQZ4+KRn1TsstudQukC0Ryg@mail.gmail.com>
	<70527e5e5ca140cd0950c1e8c63e19221a207ddc.camel@cybertec.at>
	<4965.1578401074@sss.pgh.pa.us>
Date: Tue, 07 Jan 2020 13:04:19 -0600
In-Reply-To: <4965.1578401074@sss.pgh.pa.us> (Tom Lane's message of "Tue, 07
	Jan 2020 07:44:34 -0500")
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Tom Lane <tgl@sss.pgh.pa.us> writes:

> Laurenz Albe <laurenz.albe@cybertec.at> writes:
>
>> On Tue, 2020-01-07 at 14:58 +0530, Shrikant Bhende wrote:
>>> I am trying to add a column to a table but it's not working, I have also tried
>>> reindex and drop on the same table but those commands are also getting stuck.
>
>> There is a concurrent session which has an open transaction which
>> holds some lock on the table in question.
>
> Yes, that looks like the cause.  The pg_locks view could help you
> find the culprit session.

Yeah, and IMO the pg_blocking_pids($blocked-guys-pid) function is pretty
snazzy too :-)


> 			regards, tom lane
>
>
>

-- 
Jerry Sievers
Postgres DBA/Development Consulting
e: postgres.consulting@comcast.net