Support pushing down empty projections into joins#20191
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- Closes apache#20190. We should push down empty projections into HashJoinExec 1. try_embed_projection should embed empty projections 2. build_batch_empty_build_side should support empty schemas Yes No
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- Closes apache#20190. We should push down empty projections into HashJoinExec 1. try_embed_projection should embed empty projections 2. build_batch_empty_build_side should support empty schemas Yes No
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## Which issue does this PR close? - Closes apache#20190. ## Rationale for this change We should push down empty projections into HashJoinExec ## What changes are included in this PR? 1. try_embed_projection should embed empty projections 2. build_batch_empty_build_side should support empty schemas ## Are these changes tested? Yes ## Are there any user-facing changes? No
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…LoopJoinExec` (apache#23082) ## Which issue does this PR close? <!-- We generally require a GitHub issue to be filed for all bug fixes and enhancements and this helps us generate change logs for our releases. You can link an issue to this PR using the GitHub syntax. For example `Closes #123` indicates that this PR will close issue #123. --> - Closes apache#23083 ## Rationale for this change `HashJoinExec` and `NestedLoopJoinExec` carry `projection: Option<Vec<usize>>` but the proto field is `repeated uint32`. Proto3 can't tell `None` from `Some(vec![])`, and the decoder treats both as `None`. `Some(vec![])` is reachable in real plans — `try_embed_projection` produces it for `SELECT count(1) … JOIN …` (apache#20191) — and after a round-trip the join silently switches from "emit zero columns" to "emit all columns". `FilterExec` has a workaround for the same limitation; these two execs were missed. ## What changes are included in this PR? Encode `Some(vec![])` as the single-element sentinel `[u32::MAX]` (never a valid column index); recognise it on decode. Everything else goes through unchanged. ```rust // encode projection: match exec.projection.as_ref() { None => Vec::new(), Some(v) if v.is_empty() => vec![u32::MAX], Some(v) => v.iter().map(|x| *x as u32).collect(), }, // decode let projection = match hashjoin.projection.as_slice() { [] => None, [u32::MAX] => Some(Vec::new()), indices => Some(indices.iter().map(|i| *i as usize).collect()), }; ``` Applied symmetrically to `HashJoinExec` and `NestedLoopJoinExec`. ## Are these changes tested? yes, add roundtrip test case ## Are there any user-facing changes? <!-- If there are user-facing changes then we may require documentation to be updated before approving the PR. --> <!-- If there are any breaking changes to public APIs, please add the `api change` label. -->
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Which issue does this PR close?
ProjectionExecis not embedded intoHashJoinExecby projection pushdown #20190.Rationale for this change
We should push down empty projections into HashJoinExec
What changes are included in this PR?
Are these changes tested?
Yes
Are there any user-facing changes?
No