feat: dist auto step aggr pushdown (#6268)

* wip: steppable aggr fn

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* poc: step aggr query

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* feat: mvp poc stuff

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* test: sqlness

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* chore: import missing

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* feat: support first/last_value

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* fix: check also include first/last value

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* chore: clean up after rebase

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* feat: optimize yes!

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* fix: alias qualifled

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* test: more testcases

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* chore: qualified column

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* chore: per review

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* fix: case when can push down

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* feat: udd/hll_merge is also the same

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* fix: udd/hll_merge args

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* tests: fix sqlness

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* tests: fix sqlness

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* fix: udd/hll merge steppable

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* chore: per review

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* test: REDACTED

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* refactor: per review

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* refactor: more formal transform action

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* feat: support modify child plan too

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src/common/function/src/aggrs/approximate.rs

@@ -14,8 +14,8 @@
 
 use crate::function_registry::FunctionRegistry;
 
-pub(crate) mod hll;
-mod uddsketch;
+pub mod hll;
+pub mod uddsketch;
 
 pub(crate) struct ApproximateFunction;