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From: vlsi (@vlsi) <[email protected]>
To: pgjdbc/pgjdbc <[email protected]>
Subject: Re: [pgjdbc/pgjdbc] PR #3657: perf: cache composite and simple subqueries
Date: Wed, 02 Jul 2025 15:27:21 +0000
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>

(on benchmarks/src/jmh/java/org/postgresql/benchmark/statement/SelectBatch.java:76)

Frankly speaking, I am afraid it is a suboptimal way of executing the queries.

The suggested SQL would have:
* 1-query statement
* 2-query statement
* 3-query statement
* ...
* 1000-query statement

That would consume n^2 memory.

The typical approach for these type of workloads is to use 2^N splits:

* 1-query statement
* 2-query statement
* 4-query statement
* 8-query statement
* 16-query statement
* 32-query statement
* 64-query statement
* 128-query statement
* 256-query statement
* 512-query statement
* 1024-query statement

Then you would have 11 queries that would be enough to cover any possible number of queries in a range of 1..2047.

For instance executing 356 would require 256+64+32+4=356.

WDYT?

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