Re: assertion failure 9.3.4

So, from top to bottom I see the following elements:

* backend is executing a query
* this query is getting captured by pg_stat_statements
* the query is also getting captured by autoexplain, in chain from
pg_stat_statements
* autoexplain runs the query, which invokes a plpgsql function
* this plpgsql function runs another query, and this one is captured by
pg_stat_statements
* and also by autoexplain
* The autoexplain run of this inner query invokes a trigger
* .. which is a FK trigger, and therefore runs ri_PerformCheck which
runs another query
* This FK check query gets captured by pg_stat_statements
* and also by autoexplain, which runs it
* this autoexplain run of the third query invokes SeqNext
* this does a heap access, which uses HeapTupleSatisfiesMVCC
* this one tries to read the update XID and gets an assertion failure.

Oh my.

Would it be possible for you to provide a self-contained setup that
behaves like this? I think a "bt full" would be useful since it'd
provide the queries at each of the three stages.

I'm not quite clear on why the third query, the one in ri_PerformCheck,
is invoking a sequence. AFAICS it's this:

/* ----------
* The query string built is
* SELECT 1 FROM ONLY <pktable> x WHERE pkatt1 = $1 [AND ...]
* FOR KEY SHARE OF x
* The type id's for the $ parameters are those of the
* corresponding FK attributes.
* ----------
*/
so either I'm misreading the whole thing, or there is something very odd
going on here.

Are you aware of something unusual in the FK setups?

--
Álvaro Herrera http://www.2ndQuadrant.com/
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