MAINT: Tweak push_fields pass

[mtsokol]

Hi @willow-ahrens,

I might be wrong here but I think that reorder/aggregate rule in push_fields pass is never used as ¬issubset(A ∩ B, B) is always false regardless of inputs.

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[willow-ahrens]

notice that we use "issubsequence", not "issubset". I think the intention is to push a reorder through an aggregate when the fields of the reorder are in a different permutation than the fields of the argument, ignoring dropped or expanded dimensions. I'm not sure if we really should care to do this though, because in general we don't usually push reorders through aggregates. Let's wait for #750 to merge, and benchmark this change. I think the intention is to try to avoid permuting the output of an aggregate, if possible.

[mtsokol]

Thanks for an explanation - I'm still a bit confused by the if statement here. One thing would help me: Can you provide some exemplary values here for idxs_1 and idxs_2 so that the statement below evaluates to true?

!issubsequence(intersect(idxs_1, idxs_2), idxs_2)

[willow-ahrens]

I'm happy to remove this rule if it passes tests and causes no regressions.

[mtsokol]

I'm happy to remove this rule if it passes tests and causes no regressions.

Let's first release what we have currently in the main branch (we'll be sure we have latest release without regression).
This weak can wait - I will test it separately, it isn't a priority.

[mtsokol]

Thanks for an explanation - I'm still a bit confused by the if statement here. One thing would help me: Can you provide some exemplary values here for idxs_1 and idxs_2 so that the statement below evaluates to true?

!issubsequence(intersect(idxs_1, idxs_2), idxs_2)

Explained in finch-tensor/finch-tensor-lite#31 (comment) it can evaluate to true (I missed the ordering part).