I had the same question recently. In addition, I looked at the results of tpch which scale factor is 1 ran on postgres REL_15_STABLE and observed no performance improvement from physical tlist. To be specific, I run two versions of tpch, one with physical tlist enabled and one with physical tlist disabled. The performance improvement of some queries in the former was less than 5%, some queries performed worse than latter, and I think this is a normal range of performance fluctuations which was not caused by physical tlist. I have read the relevant commits, maybe because of my carelessness, I did not find the test queries corresponding to physical tlist. Are there any test queries of physical tlist?
Thanks
On 2023-Jul-26, Jian Guo wrote:
> It looks the columns besides `ps_supplycost` and `ps_availqty` are not
> necessary, but fetched from tuples all at once. For the row-based
> storage such as heap, it looks fine, but for column-based storage, it
> would result into unnecessary overhead and impact performance. Is
> there any plan to optimize here?
I suppose that, at some point, it is going to have to be the table AM
the one that makes the decision. That is, use_physical_tlist would have
to involve some new flag in path->parent->amflags to determine whether
to skip using a physical tlist. Right now, we don't have any columnar
stores, so there's no way to verify an implementation. If you do have a
columnar store implementation, you're welcome to share it.
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Álvaro Herrera PostgreSQL Developer
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