Re: index prefetching
Jim Nasby <jim.nasby@gmail.com>
Commits
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the thread's linked commits as JSON, with link sources.
API reference →
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aio: io_uring: Trigger async processing for large IOs
- a9ee66881744 19 (unreleased) landed
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read stream: Split decision about look ahead for AIO and combining
- 8ca147d582a5 19 (unreleased) landed
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read_stream: Only increase read-ahead distance when waiting for IO
- f63ca3379025 19 (unreleased) landed
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read_stream: Prevent distance from decaying too quickly
- 6e36930f9aaf 19 (unreleased) landed
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Reduce ExecSeqScan* code size using pg_assume()
- b227b0bb4e03 19 (unreleased) cited
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Fix rare bug in read_stream.c's split IO handling.
- b421223172a2 19 (unreleased) cited
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Fix multiranges to behave more like dependent types.
- 3e8235ba4f9c 17.0 cited
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Add EXPLAIN (MEMORY) to report planner memory consumption
- 5de890e3610d 17.0 cited
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Optimize nbtree backward scan boundary cases.
- c9c0589fda0e 17.0 cited
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Increment xactCompletionCount during subtransaction abort.
- 90c885cdab8b 14.0 cited
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Add nbtree Valgrind buffer lock checks.
- 4a70f829d86c 14.0 cited
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Add nbtree high key "continuescan" optimization.
- 29b64d1de7c7 12.0 cited
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Reduce pinning and buffer content locking for btree scans.
- 2ed5b87f96d4 9.5.0 cited
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Teach btree to handle ScalarArrayOpExpr quals natively.
- 9e8da0f75731 9.2.0 cited
On 1/16/24 2:10 PM, Konstantin Knizhnik wrote: > Amazon RDS is just vanilla Postgres with file system mounted on EBS > (Amazon distributed file system). > EBS provides good throughput but larger latencies comparing with local SSDs. > I am not sure if read-ahead works for EBS. Actually, EBS only provides a block device - it's definitely not a filesystem itself (*EFS* is a filesystem - but it's also significantly different than EBS). So as long as readahead is happening somewheer above the block device I would expect it to JustWork on EBS. Of course, Aurora Postgres (like Neon) is completely different. If you look at page 53 of [1] you'll note that there's two different terms used: prefetch and batch. I'm not sure how much practical difference there is, but batched IO (one IO request to Aurora Storage for many blocks) predates index prefetch; VACUUM in APG has used batched IO for a very long time (it also *only* reads blocks that aren't marked all visble/frozen; none of the "only skip if skipping at least 32 blocks" logic is used). 1: https://d1.awsstatic.com/events/reinvent/2019/REPEAT_1_Deep_dive_on_Amazon_Aurora_with_PostgreSQL_compatibility_DAT328-R1.pdf -- Jim Nasby, Data Architect, Austin TX