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Re: Don't overwrite scan key in systable_beginscan()

Peter Eisentraut <peter@eisentraut.org>

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From: Peter Eisentraut <peter@eisentraut.org>
To: Justin Pryzby <pryzby@telsasoft.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Noah Misch <noah@leadboat.com>, pgsql-hackers@postgresql.org
Date: 2024-12-03T08:15:18Z
Lists: pgsql-hackers 
On 27.11.24 16:35, Justin Pryzby wrote:
> On Wed, Nov 27, 2024 at 04:33:25PM +0100, Peter Eisentraut wrote:
>> On 26.11.24 14:56, Justin Pryzby wrote:
>>> Since 811af9786b, the palloc'd idxkey's seem to be leaking/accumulating
>>> throughout the command.
>>>
>>> I noticed this on the master branch while running ANALYZE on partitioned
>>> table with 600 attributes, even though only 6 were being analyzed.
>>>
>>> LOG:  level: 3; BuildRelationExtStatistics: 1239963512 total in 278 blocks; 5082984 free (296 chunks); 1234880528 used
>>>
>>> Several indexes are being scanned many thousands of times.
>>
>> Hmm, this patch inserts one additional palloc() call per
>> systable_beginscan().  So it won't have much of an impact for isolated
>> calls, but for thousands of scans you get thousands of small chunks of
>> memory.
>>
>> Does your test case get better if you insert corresponding pfree() calls?
> 
> Yes -- I'd already checked.

Ok, I committed a fix that inserts some pfree() calls.  Thanks for the 
report.

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix temporary memory leak in system table index scans

  2. Don't overwrite scan key in systable_beginscan()

  3. Replace gratuitous memmove() with memcpy()