Re: [HACKERS] Something is rotten in the state of Denmark...

2015-04-02 Thread Tom Lane
Robert Haas robertmh...@gmail.com writes: On Thu, Apr 2, 2015 at 3:59 PM, Tom Lane t...@sss.pgh.pa.us wrote: Perhaps the difference has to do with whether pg_am's pg_class tuple is on a page that hasn't got enough room for a HOT update? But I definitely tried it several times and consistently

Re: [HACKERS] Something is rotten in the state of Denmark...

2015-04-02 Thread Tom Lane
Robert Haas robertmh...@gmail.com writes: On Thu, Apr 2, 2015 at 2:55 PM, Tom Lane t...@sss.pgh.pa.us wrote: Actually, now that I think it through, the could not open relation error is pretty odd in itself. If we are trying to open pg_am using a stale catalog snapshot, it seems like we ought

Re: [HACKERS] Something is rotten in the state of Denmark...

2015-04-02 Thread Robert Haas
On Wed, Apr 1, 2015 at 7:05 PM, Tom Lane t...@sss.pgh.pa.us wrote: I've been able to reproduce this. The triggering event seems to be that the VACUUM FULL pg_am in vacuum.sql has to happen while another backend is starting up. With a ten-second delay inserted at the bottom of

Re: [HACKERS] Something is rotten in the state of Denmark...

2015-04-02 Thread Tom Lane
Robert Haas robertmh...@gmail.com writes: On Thu, Apr 2, 2015 at 2:40 PM, Tom Lane t...@sss.pgh.pa.us wrote: However, I'm having second thoughts about whether we've fully diagnosed this. Three out of the four failures we've seen in the buildfarm reported cache lookup failed for access method

Re: [HACKERS] Something is rotten in the state of Denmark...

2015-04-02 Thread Robert Haas
On Thu, Apr 2, 2015 at 2:55 PM, Tom Lane t...@sss.pgh.pa.us wrote: Robert Haas robertmh...@gmail.com writes: On Thu, Apr 2, 2015 at 2:40 PM, Tom Lane t...@sss.pgh.pa.us wrote: However, I'm having second thoughts about whether we've fully diagnosed this. Three out of the four failures we've

Re: [HACKERS] Something is rotten in the state of Denmark...

2015-04-02 Thread Tom Lane
Robert Haas robertmh...@gmail.com writes: On Wed, Apr 1, 2015 at 7:05 PM, Tom Lane t...@sss.pgh.pa.us wrote: I've not fully tracked it down, but I think that the blame falls on the MVCC-snapshots-for-catalog-scans patch; it appears that it's trying to read pg_am's pg_class entry with a

Re: [HACKERS] Something is rotten in the state of Denmark...

2015-04-02 Thread Tom Lane
Robert Haas robertmh...@gmail.com writes: On Thu, Apr 2, 2015 at 12:54 PM, Tom Lane t...@sss.pgh.pa.us wrote: It looks to me like an appropriate fix would be as attached; thoughts? Hmm, that fix doesn't reach as far as what I did. My proposal would regard a catalog snapshot as immediately

Re: [HACKERS] Something is rotten in the state of Denmark...

2015-04-02 Thread Robert Haas
On Thu, Apr 2, 2015 at 2:40 PM, Tom Lane t...@sss.pgh.pa.us wrote: Robert Haas robertmh...@gmail.com writes: On Thu, Apr 2, 2015 at 12:54 PM, Tom Lane t...@sss.pgh.pa.us wrote: It looks to me like an appropriate fix would be as attached; thoughts? Hmm, that fix doesn't reach as far as what I

Re: [HACKERS] Something is rotten in the state of Denmark...

2015-04-02 Thread Robert Haas
On Thu, Apr 2, 2015 at 12:54 PM, Tom Lane t...@sss.pgh.pa.us wrote: Robert Haas robertmh...@gmail.com writes: On Wed, Apr 1, 2015 at 7:05 PM, Tom Lane t...@sss.pgh.pa.us wrote: I've not fully tracked it down, but I think that the blame falls on the MVCC-snapshots-for-catalog-scans patch; it

Re: [HACKERS] Something is rotten in the state of Denmark...

2015-04-02 Thread Robert Haas
On Thu, Apr 2, 2015 at 3:59 PM, Tom Lane t...@sss.pgh.pa.us wrote: Robert Haas robertmh...@gmail.com writes: On Thu, Apr 2, 2015 at 2:55 PM, Tom Lane t...@sss.pgh.pa.us wrote: Actually, now that I think it through, the could not open relation error is pretty odd in itself. If we are trying to

Re: [HACKERS] Something is rotten in the state of Denmark...

2015-04-01 Thread Tom Lane
I wrote: Observe these recent buildfarm failures: http://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=muledt=2015-03-21%2000%3A30%3A02 http://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=guaibasaurusdt=2015-03-23%2004%3A17%3A01