feat: backport ASOF JOIN to DF55 - #86
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## Which issue does this PR close? - Part of apache#318. - Umbrella PR: apache#23738. - Follow-up for floating-point equality keys: apache#24375. ## Rationale for this change This is the first layer of the ASOF JOIN stack. It establishes a broadcast-based physical execution contract independently so later floating-point equality, logical-plan, SQL, DataFrame, and serialization changes can be reviewed as smaller follow-up PRs. The initial implementation deliberately favors the simpler broadcast design: the right input must fit in memory and each left partition scans the shared right-side batches. A repartitioned implementation can be evaluated separately without changing the ASOF semantics introduced here. Floating-point equality keys are rejected in this base layer because Arrow's required sort order distinguishes `-0.0` from `+0.0` while join equality does not. apache#24375 adds the required ordering normalization as an independently reviewable layer. ## What changes are included in this PR? - Add `AsOfJoinExec` for left-preserving, Snowflake-style ASOF semantics. - Coalesce and collect the ordered right input once, then share it across all left partitions. - Keep the left input partitioned so each partition can scan independently and preserve the left-side output partitioning. - Preserve merge state across input and output batch boundaries. - Reserve each retained Arrow buffer exactly once, including when right-side batches are zero-copy slices, and expose build, match, and output metrics. - Define output properties and statistics for the broadcast execution model. - Reject floating-point equality keys until apache#24375 supplies a sort/equality contract that handles signed zero correctly. - Add physical operator tests covering match directions, equality groups, batch boundaries, unmatched rows, invalid contracts, shared-buffer memory accounting, multi-partition broadcast execution, and float-key rejection. ## Are these changes tested? Yes: - `cargo fmt --all` - `cargo clippy --all-targets --all-features -- -D warnings` - `cargo test -p datafusion-physical-plan joins::asof_join --all-features` - Extended workspace tests from the contributor guide - FFI integration tests ## Are there any user-facing changes? This adds a new physical operator API. The base operator deliberately rejects floating-point equality keys; apache#24375 adds full Float16, Float32, and Float64 support. SQL and DataFrame APIs are left to later dependent PRs. --------- Co-authored-by: Yongting You <2010youy01@gmail.com>
- Part of apache#318. - Umbrella PR: apache#23738. - Depends on apache#23828 (merged). This is the logical-planning layer of the ASOF JOIN stack. It defines the logical contract and planner behavior separately from the SQL frontend and serialization formats. logical layer. It no longer depends on the optional floating-point follow-up - Add `LogicalPlan::AsOfJoin`, `AsOfJoin`, and `AsOfMatch`. - Validate deterministic expressions, input ownership, supported match operators, equality-key types, and USING constraints. - Add `LogicalPlanBuilder` entry points and schema construction that preserves both qualified `USING` keys while exposing one unqualified wildcard key. - Integrate ASOF joins with tree transforms, display, type coercion, projection pruning, row bounds, and physical planning. - Plan logical ASOF joins to the broadcast-based `AsOfJoinExec` from - Fail closed at proto, SQL unparser, and Substrait boundaries until their owning stack layers add explicit support. - Defer ASOF-specific functional-dependency refinement to apache#24799 and filter pushdown to apache#24801 so each optimization can be reviewed independently. Yes: - `cargo fmt --all` - `cargo clippy --all-targets --all-features -- -D warnings` - `cargo test -p datafusion-expr min_rows_of_joins --all-features` - `cargo test -p datafusion-substrait asof_join_fails_closed_until_substrait_has_an_extension --all-features` - The extended workspace test command from the contributor guide This adds logical-plan and builder APIs for ASOF joins. SQL syntax, DataFrame APIs, and plan serialization are intentionally left to dependent stack PRs. Floating equality keys remain rejected by the merged physical operator unless the independent follow-up apache#24375 is also included. As with any new public `LogicalPlan` variant, downstream exhaustive matches must add an arm. The variant is appended so existing variants retain their `PartialOrd` ordering; maintainers should still treat the enum addition as a Rust source-compatibility break. This PR can be reviewed independently now that apache#23828 has merged. The optimization follow-ups apache#24799 and apache#24801 are not required by the core ASOF stack.
- Part of apache#318. - Umbrella PR: apache#23738. - Builds on apache#23829 and apache#23828, both merged. This is the SQL frontend layer of the ASOF JOIN stack. It adds syntax and unparsing on top of the merged physical and logical contracts. The PR now contains only the isolated SQL frontend diff. - Plan `ASOF JOIN ... MATCH_CONDITION (...)` with optional `ON` or `USING` equality keys. - Reject unsupported match shapes and non-equality `ON` predicates. - Unparse ASOF joins while preserving right-side candidate preselection and nested join scope. - Document the supported SQL syntax and semantics, including qualified `USING` keys, left-partitioned broadcast execution, the full-right memory requirement, repeated scans, and the absence of spill/repartitioned ASOF. - Add SQL integration and sqllogictest coverage for all four match directions, coercion, equality-free joins, USING, invalid contracts, EXPLAIN, boundedness, and optimized-plan round trips. - Verify the broadcast topology with a multi-partition left input: left partitioning is preserved while the right input is single-partitioned. Yes: - `cargo fmt --all` - `./ci/scripts/doc_prettier_check.sh --write --allow-dirty` - `cargo clippy --all-targets --all-features -- -D warnings` - `cargo test -p datafusion --test core_integration asof --all-features` - `cargo test -p datafusion-sqllogictest --test sqllogictests --all-features -- asof_join` - The extended workspace test command from the contributor guide Users can express Snowflake-style ASOF joins in SQL with `MATCH_CONDITION`, optional equality keys, and `<`, `<=`, `>`, or `>=` match directions. With `USING`, wildcard output exposes one unqualified key while both qualified input keys remain addressable. The user guide also documents the initial broadcast strategy and its memory/no-spill limitations. stack and does not depend on the optional floating-point follow-up apache#24375.
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Summary
LogicalPlan::min_rowsAPI that was added upstream after the DF55 branch point.Performance
ASOF uses the upstream specialized
AsOfJoinExec, not a Rustice SQL rewrite or nested-loop/window emulation. The right side is ordered and each left row produces at most one nearest match. There is no per-row scalar conversion layer.Validation
cargo +1.95.0 check -p datafusion -p datafusion-optimizer -p datafusion-protocargo +1.95.0 test -p datafusion --test core_integration asof_join(8 passed)cargo +1.95.0 test -p datafusion-sqllogictest --test sqllogictests -- asof_join(1/1 file passed)cargo +1.95.0 clippy -p datafusion-physical-plan -p datafusion-expr -p datafusion-sql -p datafusion --libcargo +1.95.0 fmt --all -- --check