| From: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | iwebcas(at)gmail(dot)com, pgsql-bugs(at)lists(dot)postgresql(dot)org, Melanie Plageman <melanieplageman(at)gmail(dot)com> |
| Subject: | Re: BUG #18514: Encountering an error invalid DSA memory alloc request size 1811939328 when executing script |
| Date: | 2024-06-18 02:03:31 |
| Message-ID: | CA+hUKGJRp4jezAiLvb0vROjPNWpoaP9zqS8_bcqixgE-FFRKsA@mail.gmail.com |
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| Lists: | pgsql-bugs |
On Tue, Jun 18, 2024 at 8:22 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Probably as a result of switching from custom to generic plan.
> There's not anything exciting about that, but we would like to
> get to the bottom of the DSA allocation failure.
Parallel Hash Right Join is new in 16 (commit 11c2d6fd, whose message
unfortunately focuses on JOIN_FULL but also covered JOIN_RIGHT). I
suspect that the allocation failure might be coming from trying to
allocate a huge array of batches in
ExecParallelHashJoinSetUpBatches(), so large that it exceeds the 1GB
allocation cap. I don't think it's the bucket array, because we avoid
exceeding the cap there. The only other thing it could be is a
massive tuple, which seems unlikely. If that's right, then the
question is: what is it about JOIN_RIGHT that is producing very large
nbatch?
There was a similar report[1] on -hackers. One of the links to
depesz's EXPLAIN viewer shows Parallel Hash Right Join, and the report
includes very high numbers of batches. Hmm.
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