Suggests nothing in particular, I'm afraid, because this isn't my area of expertise ;) It's probably an 8-hour bug, so it could be a while before I can devote an entire day to tracking back into it. It would be ideal to have a smaller query that does the same thing.
On Sun, Mar 21, 2010 at 12:58 PM, Mike Leahy <mgle...@alumni.uwaterloo.ca> wrote: > Paul, > > Thanks for looking into it - at least I know it's not just me (for the array > size limit at least). > > What does a cleanly trapped error like this suggest to you? If you try > different variations on the where condition at the end of the statement, are > you able to get a segfault? > > Mike > > On Sunday 21 March 2010 12:57:03 Paul Ramsey wrote: >> As I was installing KUbuntu, I realized I should try the query on my >> own system, and under OS/X 10.6 I see the array error, though it seems >> to be cleanly trapped, there is no segfault. >> >> crashdb=# \i ./crashing.sql >> psql:./crashing.sql:36: ERROR: array size exceeds the maximum allowed >> (134217727) >> crashdb=# >> >> >> P. >> >> On Sat, Mar 20, 2010 at 9:29 PM, Mike Leahy <mgle...@alumni.uwaterloo.ca> > wrote: >> > Leo/Regina, >> > >> > In response to your earlier message, I did find that report of the >> > identical error message. However, as I'm sure you noticed, there is no >> > apparent investigation that followed after it. That was why I went to >> > the PostgreSQL IRC channel first...they walked me through generating a >> > core dump, which is what then pointed to it being a problem related to >> > PostGIS. So while it's certainly the same error being reported, the >> > source of the problem in this case appears PostGIS-specific - likely due >> > to the logic that you note was borrowed from the array_agg that caused >> > the problem in the previous report. >> > >> > As for looking at the different query plans for working/non-working >> > versions of the statement with different where conditions, I've attached >> > several results in text files. Two examples that worked, one that >> > segfaults, and one that produces the 'array size exceeds...' error >> > message. All of these are the same query, just with variations in the >> > where condition. The query plan is a but much for me to interpret though >> > - what does this look like to the experts? >> > >> > Mike >> > >> > On Saturday 20 March 2010 23:35:32 Paragon Corporation wrote: >> >> Mike, >> >> Another thought. I suppose it could be the more or less two identical >> >> subselects both with array_aggs >> >> Just to give Paul something hopefully shorter to work with. Does this >> >> fail too? >> >> >> >> SELECT csls.chat_id, csls.ugeom >> >> FROM ( >> >> >> >> SELECT '[stuff]' AS selection, st_union(geom) AS ugeom, csl1.chat_id >> >> FROM testdb.user_selections AS us1 >> >> INNER JOIN testdb.chat_selection_links AS csl1 ON us1.id = >> >> csl1.selection_id >> >> WHERE (not us1.user_drawing and not csl1.deleted) >> >> GROUP BY chat_id >> >> >> >> ) AS csls >> >> >> >> LEFT JOIN ( >> >> >> >> SELECT '[stuff]' AS drawing, st_union(geom) AS ugeom, csl2.chat_id >> >> FROM testdb.user_selections AS us2 >> >> INNER JOIN testdb.chat_selection_links AS csl2 ON us2.id = >> >> csl2.selection_id >> >> WHERE (us2.user_drawing and us2.deleted and not csl2.deleted) >> >> GROUP BY chat_id >> >> >> >> ) AS csld ON csls.chat_id = csld.chat_id >> >> >> >> Leo and Regina, >> >> http://www.postgis.us >> >> >> >> -----Original Message----- >> >> From: postgis-users-boun...@postgis.refractions.net >> >> [mailto:postgis-users-boun...@postgis.refractions.net] On Behalf Of >> >> Paragon Corporation >> >> Sent: Saturday, March 20, 2010 11:29 PM >> >> To: 'PostGIS Users Discussion'; mgle...@alumni.uwaterloo.ca >> >> Subject: Re: [postgis-users] ERROR: array size exceeds >> >> themaximumallowed(134217727) >> >> >> >> Mike, >> >> Actually scanning thru the archives that 13... is a common number so >> >> suspect that is an OS limit. >> >> >> >> This could be very well a bug in PostgreSQL 8.4. >> >> >> >> Have you tried this on other PostgreSQL 8.4 installs on other your >> >> Fedoras - you mentioned trying on older installs? >> >> >> >> Your problem sounds exactly like this guy's and he wasn't using PostGIS >> >> at all but array_agg (which is logic that PostGIS borrowed from to >> >> implement the faster collecting ST_Union behavior)i >> >> http://archives.postgresql.org/pgsql-hackers/2009-06/msg01171.php >> >> >> >> If you haven't already probably good to check the plan difference >> >> between the two queries (one with addtional WHERE and one without). It >> >> could be doing something nuts like running the sub select for each >> >> record you have in the outer only when your extra WHERE condition is >> >> added and doing more or less the sane thing when you take it out. >> >> >> >> We've had some odd behavior in 8.4 with the planner doing strange things >> >> that we haven't been able to pin down and had to implement workaround >> >> for. As we described in this article.. Its probably unrelated though but >> >> just a thought to throw out at the wind. >> >> >> >> http://www.postgresonline.com/journal/index.php?/archives/149-Forcing-th >> >>e-p l anners-hand-with-set-enable_seqscan-off-WTF.html >> >> >> >> Leo and Regina, >> >> http://www.postgis.us >> >> >> >> -----Original Message----- >> >> From: postgis-users-boun...@postgis.refractions.net >> >> [mailto:postgis-users-boun...@postgis.refractions.net] On Behalf Of Paul >> >> Ramsey >> >> Sent: Saturday, March 20, 2010 8:23 PM >> >> To: mgle...@alumni.uwaterloo.ca; PostGIS Users Discussion >> >> Subject: Re: [postgis-users] ERROR: array size exceeds the >> >> maximumallowed(134217727) >> >> >> >> Mike >> >> >> >> Well, if you can reduce it to a small db dump and query that exercises >> >> it, I can install a 64bit ubuntu VM and see if it happens here too. >> >> >> >> P >> >> >> >> On Sat, Mar 20, 2010 at 3:30 PM, Mike Leahy >> >> <mgle...@alumni.uwaterloo.ca> >> >> >> >> wrote: >> >> > FWIW, if I remove the entire where clause at the end of the >> >> > statement, it works again (with st_union()) and is virtually >> >> >> >> instantaneous. >> >> >> >> > On Saturday 20 March 2010 18:10:38 Mike Leahy wrote: >> >> >> Hey, >> >> >> >> >> >> The query (when it works) is virtually instantaneous when I use >> >> >> st_memunion() (or when I took out part of the where clause - >> >> >> although now >> >> >> I can't even get that to work, so maybe it was just lucky). Each of >> >> >> the >> >> >> subqueries also work fine without any obvious problem. >> >> >> >> >> >> To me, it seems to be a combination of things that somehow add up to >> >> >> this limitation...I don't see what settings could affect the array >> >> >> size limit >> >> >> (in postgresql.conf). Can anyone point to a config option that >> >> >> might make >> >> >> a difference, or maybe point to another place with settings I can >> >> >> tinker >> >> >> with? >> >> >> >> >> >> Mike >> >> >> >> >> >> On Saturday 20 March 2010 17:53:24 Paragon Corporation wrote: >> >> >> > Mike, >> >> >> > >> >> >> > We apologize, didn't notice this was in a subquery and that you >> >> >> > have a >> >> >> > limit statement in your query. So we presume regardless of your >> >> >> > WHERE >> >> >> > only 26 records are being selected. >> >> >> > >> >> >> > So Paul could be right that you do have data that is hitting some >> >> >> > compiled or variable limit. >> >> >> > >> >> >> > Does running the subquery alone work or you didn't try because it >> >> >> > takes a long time? >> >> >> > >> >> >> > Thanks, >> >> >> > Leo and Regina >> >> >> > http://www.postgis.us >> >> >> > >> >> >> > -----Original Message----- >> >> >> > From: Mike Leahy [mailto:mgl....@gmail.com] On Behalf Of Mike Leahy >> >> >> > Sent: Saturday, March 20, 2010 2:01 PM >> >> >> > To: Paragon Corporation >> >> >> > Cc: 'PostGIS Users Discussion' >> >> >> > Subject: Re: [postgis-users] ERROR: array size exceeds the maximum >> >> >> > allowed(134217727) >> >> >> > >> >> >> > Hi Leo/Regina, >> >> >> > >> >> >> > Thanks for the suggestion. I tried adding the clause 'not geom is >> >> >> >> null' >> >> >> >> >> > to the where statement in each of the two sub-queries that have the >> >> >> > st_union(geom) functions are used, but it still segfaults. >> >> >> > >> >> >> > I also tried this on a fresh database with very little data, and it >> >> >> > doesn't seem to cause problems. But I have two databases with live >> >> >> > data where I can cause this. I have been able to pare one of these >> >> >> > down to remove personal information and reduce unnecessary data, >> >> >> > while still generating the crash with that query. Would someone >> >> >> > be interested in a dump of this db? Of course, that someone would >> >> >> > ideally be able to test this on a 64-bit (K)ubutnu system, in the >> >> >> > hopes that the problem can be replicated. >> >> >> > >> >> >> > Mike >> >> >> > >> >> >> > On Saturday 20 March 2010 11:32:35 Paragon Corporation wrote: >> >> >> > > Paul, >> >> >> > > I doubt array size limit is the issue. He said when he left the >> >> >> > > where condition out it worked. I would think it would definitely >> >> >> > > blow up in that case. >> >> >> > > >> >> >> > > Mike, >> >> >> > > The issue from before was that array aggregate functions did not >> >> >> > > handle NULLs correctly. 64-bit systems were more likely to >> >> >> > > segfault or give strange Errros in this case. >> >> >> > > >> >> >> > > To rule out that we still have some of these issues in the code >> >> >> > > base, can you add a >> >> >> > > >> >> >> > > geom IS NOT NULL >> >> >> > > >> >> >> > > Condition to your WHERE filter. If that works, then the NULL >> >> >> > > issue is probably still lurking somewhere. >> >> >> > > >> >> >> > > Leo and Regina >> >> >> > > http://www.postgis.us >> >> >> > > >> >> >> > > >> >> >> > > -----Original Message----- >> >> >> > > From: postgis-users-boun...@postgis.refractions.net >> >> >> > > [mailto:postgis-users-boun...@postgis.refractions.net] On Behalf >> >> >> > > Of Paul Ramsey >> >> >> > > Sent: Saturday, March 20, 2010 10:56 AM >> >> >> > > To: PostGIS Users Discussion; mgle...@alumni.uwaterloo.ca >> >> >> > > Subject: Re: [postgis-users] ERROR: array size exceeds the >> >> >> > > maximum >> >> >> > > allowed(134217727) >> >> >> > > >> >> >> > > Actually, memunion does the opposite, it passes the resultant and >> >> >> > > preserves mem. The default behavior is fast-but-memory-hungry. >> >> >> > > And has been for some time, though in different forms. There were >> >> >> > > some bugs in the array handling code, but Mark CA killed most of >> >> >> > > them, so the latest 1.5 and 1.4 streams should be good. If it's >> >> >> > > possible that the issue is one of array size, maybe Mike could >> >> >> > > find the dial that controls that maximum, and turn it up and down >> >> >> > > and see if it makes his >> >> >> > >> >> >> > problem go away/happen sooner. >> >> >> > >> >> >> > > P. >> >> >> > > >> >> >> > > On Sat, Mar 20, 2010 at 7:41 AM, strk <s...@keybit.net> wrote: >> >> >> > > > On Sat, Mar 20, 2010 at 05:49:42AM -0400, Mike Leahy wrote: >> >> >> > > >> Hello again, >> >> >> > > >> >> >> >> > > >> It might be of interest to point out that substituting >> >> >> > > >> st_union() with >> >> >> > > >> st_memunion() seems to have worked around this. I'm curious >> >> >> > > >> though, because there is not a great deal of data being >> >> >> > > >> processed, and I am running this on a fairly sturdy system >> >> >> > > >> that that has more capacity than some of the Fedora systems >> >> >> > > >> I'm >> >> >> >> running. >> >> >> >> >> > > > st_memunion builds a big array with all geometries in it.. >> >> >> > > > you were hitting a limit of the array type. >> >> >> > > > st_union should behave better. >> >> >> > > > >> >> >> > > > --strk; >> >> >> > > > >> >> >> > > > () Free GIS & Flash consultant/developer >> >> >> > > > /\ http://strk.keybit.net/services.html >> >> >> > > > _______________________________________________ >> >> >> > > > postgis-users mailing list >> >> >> > > > postgis-users@postgis.refractions.net >> >> >> > > > http://postgis.refractions.net/mailman/listinfo/postgis-users >> >> >> > > >> >> >> > > _______________________________________________ >> >> >> > > postgis-users mailing list >> >> >> > > postgis-users@postgis.refractions.net >> >> >> > > http://postgis.refractions.net/mailman/listinfo/postgis-users >> >> > >> >> > _______________________________________________ >> >> > postgis-users mailing list >> >> > postgis-users@postgis.refractions.net >> >> > http://postgis.refractions.net/mailman/listinfo/postgis-users >> >> >> >> _______________________________________________ >> >> postgis-users mailing list >> >> postgis-users@postgis.refractions.net >> >> http://postgis.refractions.net/mailman/listinfo/postgis-users >> >> >> >> >> >> _______________________________________________ >> >> postgis-users mailing list >> >> postgis-users@postgis.refractions.net >> >> http://postgis.refractions.net/mailman/listinfo/postgis-users >> > >> > _______________________________________________ >> > postgis-users mailing list >> > postgis-users@postgis.refractions.net >> > http://postgis.refractions.net/mailman/listinfo/postgis-users >> > _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
