Re: Doubts about pushing LIMIT to MergeAppendPath

Tomas Vondra <tomas.vondra@2ndquadrant.com> wrote:

> OK, so the reason is that when building child paths, we don't keep the
> pathkeys unless it matches the "interesting" pathkeys.
>
> So for example we may have an IndexPath, but with pathkeys=NIL if the
> index does not match the ORDER BY we need.

I don't agree that IndexPath will necessarily have pathkeys set to NIL in such
a case. Even if the index ordering does not match ORDER BY clause of the
query, the path can still be useful, typically for merge join.

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Antonin Houska
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