Horton

Re: index prefetching

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tomas Vondra <tomas.vondra@enterprisedb.com>
Cc: Robert Haas <robertmhaas@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Georgios <gkokolatos@protonmail.com>
Date: 2023-12-21T15:43:52Z
Lists: pgsql-hackers

Commits

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

  1. aio: io_uring: Trigger async processing for large IOs

  2. read stream: Split decision about look ahead for AIO and combining

  3. read_stream: Only increase read-ahead distance when waiting for IO

  4. read_stream: Prevent distance from decaying too quickly

  5. Reduce ExecSeqScan* code size using pg_assume()

  6. Fix rare bug in read_stream.c's split IO handling.

  7. Fix multiranges to behave more like dependent types.

  8. Add EXPLAIN (MEMORY) to report planner memory consumption

  9. Optimize nbtree backward scan boundary cases.

  10. Increment xactCompletionCount during subtransaction abort.

  11. Add nbtree Valgrind buffer lock checks.

  12. Add nbtree high key "continuescan" optimization.

  13. Reduce pinning and buffer content locking for btree scans.

  14. Teach btree to handle ScalarArrayOpExpr quals natively.

Hi,

On 2023-12-21 16:20:45 +0100, Tomas Vondra wrote:
> On 12/21/23 14:43, Andres Freund wrote:
> >> AFAICS this seems similar to some of the AIO patch, I wonder what that
> >> plans to do. I need to check.
> > 
> > Yes, most of this exists there.  The difference that with the AIO you don't
> > need to prefetch, as you can just initiate the IO for real, and wait for it to
> > complete.
> > 
> 
> Right, although the line where things stop being "prefetch" and becomes
> "async" seems a bit unclear to me / perhaps more a point of view.

Agreed. What I meant with not needing prefetching was that you'd not use
fadvise(), because it's better to instead just asynchronously read data into
shared buffers. That way you don't have the doubling of syscalls and you don't
need to care less about the buffering rate in the kernel.

Greetings,

Andres Freund