Re: dsa_allocate() faliure

Rick Otten <rottenwindfish(at)gmail(dot)com> writes:
> I'm wondering if there is anything I can tune in my PG 10.1 database to
> avoid these errors:

> $ psql -f failing_query.sql
> psql:failing_query.sql:46: ERROR: dsa_allocate could not find 7 free pages
> CONTEXT: parallel worker

Hmm. There's only one place in the source code that emits that message
text:

/*
* Ask the free page manager for a run of pages. This should always
* succeed, since both get_best_segment and make_new_segment should
* only return a non-NULL pointer if it actually contains enough
* contiguous freespace. If it does fail, something in our backend
* private state is out of whack, so use FATAL to kill the process.
*/
if (!FreePageManagerGet(segment_map->fpm, npages, &first_page))
elog(FATAL,
"dsa_allocate could not find %zu free pages", npages);

Now maybe that comment is being unreasonably optimistic, but it sure
appears that this is supposed to be a can't-happen case, in which case
you've found a bug.

cc'ing the DSA authors for comment.

regards, tom lane