From: Tom Lane <tgl@sss.pgh.pa.us>
To: Laurenz Albe <laurenz.albe@cybertec.at>
cc: Shrikant Bhende <shrikantpostgresql@gmail.com>,
        pgsql-admin@lists.postgresql.org
Subject: Re: Alter command getting stuck on a table
In-reply-to: <70527e5e5ca140cd0950c1e8c63e19221a207ddc.camel@cybertec.at>
References: 
 <CAMTQpJALSF2EvBqmdYCqKnXx-o2VQZ4+KRn1TsstudQukC0Ryg@mail.gmail.com>
 <70527e5e5ca140cd0950c1e8c63e19221a207ddc.camel@cybertec.at>
Comments: In-reply-to Laurenz Albe <laurenz.albe@cybertec.at>
	message dated "Tue, 07 Jan 2020 10:57:41 +0100"
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Date: Tue, 07 Jan 2020 07:44:34 -0500
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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 als=
o 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.

			regards, tom lane