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Prevent parallel DecompressChunk in queries with LIMIT #6881

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@svenklemm svenklemm commented May 3, 2024

In queries with LIMIT a parallel plan is quite often less desirable
due to startup cost and changed ordering behaviour.

In queries with LIMIT a parallel plan is quite often less desirable
due to startup cost and changed ordering behaviour.
@svenklemm svenklemm self-assigned this May 3, 2024
@svenklemm svenklemm requested a review from akuzm May 3, 2024 17:46
@svenklemm svenklemm marked this pull request as draft May 3, 2024 18:14
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akuzm commented May 6, 2024

With LIMIT, the slower paths should normally get disabled through the startup cost, right? Maybe we can tweak the costs there so that it works? Our cost model for DecompressChunk is kind of bad already, more special cases probably make it even more difficult to debug (e.g. if we ever want to fix these mysterious plan changes in transparent_decompression test that Erik mentioned recently).

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