Nithurshen opened a new pull request, #19445:
URL: https://github.com/apache/datafusion/pull/19445
## Which issue does this PR close?
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- Closes #19064
## Rationale for this change
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the issue then this section is not needed.
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After establishing the high-level API for sort pushdown (#19064), it was
identified that the optimizer did not handle cases where the sort prefix is a
**logical constant** (e.g., due to a filter).
For example, in a query like:
`SELECT * FROM table WHERE region = 'US' ORDER BY region, time`
The column `region` is constant. Previously, the optimizer attempted to push
down `Sort(region, time)`. If the underlying source (e.g., Parquet or a custom
TableProvider) only supported sorting by `time` (or had an index on `time`),
the pushdown would fail or be unsupported.
By stripping the constant prefix, we can push down `Sort(time)`, which the
source is more likely to support, leading to significant performance
improvements (e.g., skipping row groups via dynamic top-k pushdown).
## What changes are included in this PR?
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- Modified the `optimize` method in
`physical-optimizer/src/pushdown_sort.rs`.
- The optimizer now checks the input's `EquivalenceProperties`.
- Any sort expression that is determined to be constant is filtered out from
the `required_ordering` before calling `try_pushdown_sort` on the source.
- Added a new unit test `test_sort_pushdown_prefix_removal` that uses a
`MockPlanWithConstants` to verify that a `SortExec` is correctly removed when
the sort column is constant.
## Are these changes tested?
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- [x] Yes, a new unit test `test_sort_pushdown_prefix_removal` has been
added to `datafusion/physical-optimizer/src/pushdown_sort.rs`.
- [x] Verified that the optimizer successfully strips constant columns and
matches `Exact` pushdown results in the test case.
## Are there any user-facing changes?
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updated before approving the PR.
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- Users may see improved performance for queries involving `ORDER BY` and
`WHERE` clauses on sorted data, as the optimizer can now push down sort
requirements more aggressively.
- No changes to public APIs.
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