Re: Reference to - BUG #18349: ERROR: invalid DSA memory alloc request size 1811939328, CONTEXT: parallel worker

On Sun, Sep 22, 2024 at 10:23 PM Thomas Munro <thomas.munro@gmail.com>
wrote:

> On Mon, Sep 23, 2024 at 1:46 PM Thomas Munro <thomas.munro@gmail.com>
> wrote:
> > 432 bytes
>
> Oh, as Tomas pointed out in the referenced thread,


Thanks for working on it and the detailed explanation. I tested set
max_parallel_workers_per_gather = 0 from the original thread and it was
working. We are putting that into the application, for our largest
customers. Set to 0 before the query then back to 2 after.

Your explanation also shows why rewriting of the query works. I reduced the
number of rows being processed much earlier in the query. The query was
written with 1 set of many joins which worked on millions of rows then
reduced to a handful. I broke this into a materialized CTE that forced
Postgres to reduce the rows early then do the joins.  Rewriting the query
is better regardless of this issue.

I am working on getting a stock Postgres in our production protected
enclave with our production database.  Probably a full day of work that I
need to splice in.  We have a similar mechanism in our development
environment. Once working I can help test and debug any changes. I can also
work on a reproducible example.

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