From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Noah Watkins <noahwatkins(at)gmail(dot)com> |
Cc: | pgsql-interfaces(at)postgresql(dot)org |
Subject: | Re: Using threads in FDW for read-ahead |
Date: | 2014-06-10 19:21:01 |
Message-ID: | 3383.1402428061@sss.pgh.pa.us |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-interfaces |
Noah Watkins <noahwatkins(at)gmail(dot)com> writes:
> I have created a FDW for a storage backend and it is working well, and now
> I would like to overlap processing with I/O by performing read-ahead. I
> started by using a thread to do background I/O and this worked, but
> problems started to arise when I tried to do predicate filtering in the
> thread.
> In particular, it seems as though `check_stack_depth` is built to assume a
> single threaded environment (`stack_base_ptr` is global).
That is not even the tip of the iceberg of what will break if you try
to use multiple threads in a Postgres backend. It's not supported.
You might possibly manage to not break things if you keep the extra
threads sufficiently narrowly scoped --- which for starters would include
no use of palloc nor elog. Executing query predicates is right out.
regards, tom lane
From | Date | Subject | |
---|---|---|---|
Next Message | Ian Pye | 2014-06-10 19:23:10 | Re: Using threads in FDW for read-ahead |
Previous Message | Noah Watkins | 2014-06-10 19:10:22 | Using threads in FDW for read-ahead |