Horton

Re: index prefetching

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tomas Vondra <tomas@vondra.me>
Cc: Peter Geoghegan <pg@bowt.ie>, Thomas Munro <thomas.munro@gmail.com>, Nazir Bilal Yavuz <byavuz81@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Melanie Plageman <melanieplageman@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Georgios <gkokolatos@protonmail.com>, Konstantin Knizhnik <knizhnik@garret.ru>, Dilip Kumar <dilipbalaut@gmail.com>
Date: 2025-08-28T16:08:50Z
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 2025-08-26 17:06:11 +0200, Tomas Vondra wrote:
> On 8/26/25 01:48, Andres Freund wrote:
> > Hi,
> > 
> > On 2025-08-25 15:00:39 +0200, Tomas Vondra wrote:
> >> Thanks. Based on the testing so far, the patch seems to be a substantial
> >> improvement. What's needed to make this prototype committable?
> > 
> > Mainly some testing infrastructure that can trigger this kind of stream. The
> > logic is too finnicky for me to commit it without that.
> > 
> 
> So, what would that look like?

I'm thinking of something like an SQL function that accepts a relation and a
series of block numbers, which creates a read stream reading the passed in
block numbers.  Combined with the injection points that are already used in
test_aio, that should allow to test things that I don't know how to test
without that.  E.g. encountering an already-in-progress multi-block IO that
only completes partially.


> Another approach would be to test this at C level, sidestepping the
> query execution entirely. We'd have a "stream generator" that just
> generates a sequence of blocks of our own choosing (could be hard-coded,
> some pattern, read from a file ...), and feed it into a read stream.
> 
> But how would we measure success for these tests? I don't think we want
> to look at query duration, that's very volatile.

Yea, the performance effects would be harder to test, what I care more about
is the error paths. Those are really hard to test interactively.

Greetings,

Andres Freund