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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