From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
cc: kunert@cms.hu-berlin.de, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #16162: create index using gist_trgm_ops leads to panic
In-reply-to: <20191212125023.vpk6zbbeldzmyerc@development>
References: <16162-45d21b7b6c1a3105@postgresql.org>
 <20191212125023.vpk6zbbeldzmyerc@development>
Comments: In-reply-to Tomas Vondra <tomas.vondra@2ndquadrant.com>
	message dated "Thu, 12 Dec 2019 13:50:23 +0100"
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Date: Thu, 12 Dec 2019 08:44:22 -0500
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Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
> This only happens on some runs (in my case the CREATE INDEX passed 8x
> without any issue and failed on 9th iteration), so there has to be some
> random element affecting this.

As far as that goes, gistchoose() intentionally makes random choices
when two insertion paths seem equally good.  So failing only sometimes
isn't very surprising.

> so maybe the GIST stack is stale, not updated, or something like that. I
> think I've seen an issue mentioning that recently ... yep, found it [1].
> And I see Tom came to about the same conclusion, pointing to the same
> place in gistfinishsplit. It's only a couple days old, I don't think
> I've seen any proposed fixes yet.

Good that we seem to have just one bug there not two :-(.  I've not
looked any further than my previous message, though.

I wonder if this could be a recently-introduced bug?  I do not
recall seeing complaints like this before v12.

			regards, tom lane