fix: FilterExec should drop projection when apply projection pushdown

[haohuaijin]

Which issue does this PR close?

• Closesregression: ProjectionPushdown failed with project index 2 out of bounds, max field 2 #21459

Rationale for this change

When a ProjectionExec sits on top of a FilterExec that already carries an explicit projection, the ProjectionPushdown optimizer attempts to swap them via try_swapping_with_projection. The swap replaces the FilterExec's input with the narrower ProjectionExec, but FilterExecBuilder::from(self) carried over the old projection indices (e.g. [0, 1, 2]). After the swap the new input only has the columns selected by the ProjectionExec (e.g. 2 columns), so .build() tries to validate the stale projection against the narrower schema and panics with "project index 2 out of bounds, max field 2".

What changes are included in this PR?

In FilterExec::try_swapping_with_projection, after replacing the input with the narrower ProjectionExec, clear the FilterExec's own projection via .apply_projection(None). The ProjectionExec that is now the input already handles column selection, so the FilterExec no longer needs its own projection.

Are these changes tested?

yes, add test case

Are there any user-facing changes?

[alamb]

Thanks @haohuaijin

the fix makes sense to me, but I think it would be better to try and add some higher level tests if possible

[alamb]

Thanks @haohuaijin

[haohuaijin]

Thanks for your quick reviews @alamb

[alamb]

Gotta love the bug fixes. THanks @haohuaijin

Cna you please make a backport for this issue to branch-53 if you want to include it in the 53 release?

[haohuaijin]

Cna you please make a backport for this issue to branch-53 if you want to include it in the 53 release?

@alamb, thanks @comphead, we already have the backport for this pr #21492, although the pr does not include the tests I would added later in 4937804, but i think it is fine.

[alamb]

Cna you please make a backport for this issue to branch-53 if you want to include it in the 53 release?

@alamb, thanks @comphead, we already have the backport for this pr #21492, although the pr does not include the tests I would added later in 4937804, but i think it is fine.

I agree -- it is fine that the test is not included