On Aug 12, 2013, at 11:53 AM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > Matt Solnit <msolnit@xxxxxxxxxx> writes: >> After poring over the code in nodeAgg.c, and looking at the in8inc() >> function, I think I know what the problem is: the typical use of >> AggCheckCallContext() is not compatible with TOAST-able data types. > > That's nonsense. There are several standard aggregates that use > that with array transition values. > > Personally, I'd wonder about the blind-faith assumption in your code that > all the input arrays are exactly the same length, with no NULL elements. > At the very least a check for that would seem advisable. An empty > (zero-dimensional) array could also make this code crash, so I'd be > inclined to put in a check that ARR_NDIM() is 1, too. > > regards, tom lane Thanks for your reply, albeit gruffly-worded :-). I'm certainly a novice to the PostgreSQL source code, so I'm not surprised that my hypothesis was wrong. Regarding the assumptions, I am perfectly okay with them because I have complete control over the inputs. We're using this function with a very precise data set. I did, however, take a moment to verify that *every* value in the table matches my assumptions, and it does. So where do I go from here? Additional information that might helpful: 1. When the crash occurs, and I inspect using gdb, I consistently find that the first array's contents are "garbage". For example: (gdb) print array1->dataoffset $6 = -1795162110 (gdb) print array1->ndim $9 = 989856262 while the second array looks fine: (gdb) print array2->dataoffset $7 = 0 (gdb) print array2->ndim $10 = 1 2. The function seems to work consistently when I do a SELECT SUM(mycol) without any GROUP BY. It's only when I add grouping that the failures happen. I'm not sure if this is a real clue or a red herring. Finally, can you tell me what precisely happens when you call datumCopy() with ArrayType? If it's only returning a copy of the TOAST reference, then how is it safe for the transition function to modify the content? I'm probably *completely* misunderstanding how this works, so I would love to be enlightened :-). Sincerely, Matt Solnit -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
