Re: index prefetching

Tomas Vondra <tomas@vondra.me>

From: Tomas Vondra <tomas@vondra.me>

To: Andres Freund <andres@anarazel.de>

Cc: Peter Geoghegan <pg@bowt.ie>, Nazir Bilal Yavuz <byavuz81@gmail.com>, Thomas Munro <thomas.munro@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: 2025-07-23T01:19:20Z

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 →

aio: io_uring: Trigger async processing for large IOs
- a9ee66881744 19 (unreleased) landed
read stream: Split decision about look ahead for AIO and combining
- 8ca147d582a5 19 (unreleased) landed
read_stream: Only increase read-ahead distance when waiting for IO
- f63ca3379025 19 (unreleased) landed
read_stream: Prevent distance from decaying too quickly
- 6e36930f9aaf 19 (unreleased) landed
Reduce ExecSeqScan* code size using pg_assume()
- b227b0bb4e03 19 (unreleased) cited
Fix rare bug in read_stream.c's split IO handling.
- b421223172a2 19 (unreleased) cited
Fix multiranges to behave more like dependent types.
- 3e8235ba4f9c 17.0 cited
Add EXPLAIN (MEMORY) to report planner memory consumption
- 5de890e3610d 17.0 cited
Optimize nbtree backward scan boundary cases.
- c9c0589fda0e 17.0 cited
Increment xactCompletionCount during subtransaction abort.
- 90c885cdab8b 14.0 cited
Add nbtree Valgrind buffer lock checks.
- 4a70f829d86c 14.0 cited
Add nbtree high key "continuescan" optimization.
- 29b64d1de7c7 12.0 cited
Reduce pinning and buffer content locking for btree scans.
- 2ed5b87f96d4 9.5.0 cited
Teach btree to handle ScalarArrayOpExpr quals natively.
- 9e8da0f75731 9.2.0 cited

On 7/23/25 02:59, Andres Freund wrote:
> Hi,
> 
> On 2025-07-23 02:50:04 +0200, Tomas Vondra wrote:
>> But I don't see why would this have any effect on the prefetch distance,
>> queue depth etc. Or why decreasing INDEX_SCAN_MAX_BATCHES should improve
>> that. I'd have expected exactly the opposite behavior.
>>
>> Could be bug, of course. But it'd be helpful to see the dataset/query.
> 
> Pgbench scale 500, with the simpler query from my message.
> 

With direct I/O, I guess? I'll take a look tomorrow.


regard

-- 
Tomas Vondra