Re: Using indices for UNION.

Hi,

On 2014-01-14 18:10:40 +0900, Kyotaro HORIGUCHI wrote:
> This is cont'd from CF3.
>
> http://www.postgresql.org/message-id/20131122.165927.27412386.horiguchi.kyotaro@lab.ntt.co.jp
>
> The issue in brief is that UNION is never flattened differently
> to UNION ALL so UNION cannot make use of index scan even if
> usable.
>
> This patch flattens UNION likewise currently did for UNION ALL.
>
> This patch needs another 'UNION ALL' patch and further gain with
> even another 'Widening application of indices' patch. ('Ready for
> Commit' now in CF3..)
>
> http://www.postgresql.org/message-id/20140114.180447.145186052.horiguchi.kyotaro@lab.ntt.co.jp
> http://www.postgresql.org/message-id/20140114.180810.122352231.horiguchi.kyotaro@lab.ntt.co.jp
>
>
> You can see the detailed outlines in the message at here,
>
> http://www.postgresql.org/message-id/20131031.194251.12577697.horiguchi.kyotaro@lab.ntt.co.jp
>
> The attached patche is rebased to current 9.4dev HEAD and make
> check at the topmost directory and src/test/isolation are passed
> without error.

I haven't really followed this topic, so please excuse my ignorance.

This is still marked as "needs review" in
https://commitfest.postgresql.org/action/patch_view?id=1374 . But I am
not sure the patch as is is relevant after
a87c729153e372f3731689a7be007bc2b53f1410?

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services