Re: BUG #16162: create index using gist_trgm_ops leads to panic

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
Cc: kunert(at)cms(dot)hu-berlin(dot)de, pgsql-bugs(at)lists(dot)postgresql(dot)org
Subject: Re: BUG #16162: create index using gist_trgm_ops leads to panic
Date: 2019-12-12 13:44:22
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Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)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

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