2010YOUY01 opened a new pull request, #17319:
URL: https://github.com/apache/datafusion/pull/17319
## Which issue does this PR close?
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- Closes #.
## Rationale for this change
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Explaining clearly why changes are proposed helps reviewers understand your
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The following join query now it's using NLJ. Given the equal join operators
like Hash Join, SortMergeJoin supports a special null comparison behavior:
`NULL=NULL` -> `true` instead of the default `NULL`, this query can be safely
re-written to equal join with equi-join operator's `null_equals_null` option
enabled.
Given HJ is faster than NLJ in general, this optimization can make similar
queries more efficient.
```SQL
SELECT *
FROM t1
JOIN t2 ON t1.val IS NOT DISTINCT FROM t2.val;
+---------------+------------------------------------------------------------+
| plan_type | plan
|
+---------------+------------------------------------------------------------+
| physical_plan | ┌───────────────────────────┐
|
| | │ ProjectionExec │
|
| | │ -------------------- │
|
| | │ t1_id: id │
|
| | │ t2_id: id │
|
| | │ val: val │
|
| | └─────────────┬─────────────┘
|
| | ┌─────────────┴─────────────┐
|
| | │ NestedLoopJoinExec ├──────────────┐
|
| | └─────────────┬─────────────┘ │
|
| | ┌─────────────┴─────────────┐┌─────────────┴─────────────┐
|
| | │ DataSourceExec ││ DataSourceExec │
|
| | │ -------------------- ││ -------------------- │
|
| | │ bytes: 288 ││ bytes: 288 │
|
| | │ format: memory ││ format: memory │
|
| | │ rows: 1 ││ rows: 1 │
|
| | └───────────────────────────┘└───────────────────────────┘
|
| |
|
+---------------+------------------------------------------------------------+
```
I've verified that DuckDB is already doing so
```
D explain SELECT *
FROM t1
JOIN t2 ON t1.val IS NOT DISTINCT FROM t2.val;
┌─────────────────────────────┐
│┌───────────────────────────┐│
││ Physical Plan ││
│└───────────────────────────┘│
└─────────────────────────────┘
┌───────────────────────────┐
│ PROJECTION │
│ ──────────────────── │
│ id │
│ val │
│ id │
│ val │
│ │
│ ~18 Rows │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│ HASH_JOIN │
│ ──────────────────── │
│ Join Type: INNER │
│ │
│ Conditions: ├──────────────┐
│ val IS NOT DISTINCT FROM │ │
│ val │ │
│ │ │
│ ~18 Rows │ │
└─────────────┬─────────────┘ │
┌─────────────┴─────────────┐┌─────────────┴─────────────┐
│ SEQ_SCAN ││ SEQ_SCAN │
│ ──────────────────── ││ ──────────────────── │
│ Table: t1 ││ Table: t2 │
│ Type: Sequential Scan ││ Type: Sequential Scan │
│ ││ │
│ Projections: ││ Projections: │
│ val ││ val │
│ id ││ id │
│ ││ │
│ ~6 Rows ││ ~6 Rows │
└───────────────────────────┘└───────────────────────────┘
```
## What changes are included in this PR?
Modified logical optimizer pass `ExtractEquijoinPredicate` to also handle
`IS NOT DISTINCT FROM` case.
INDF expressions will only be extracted to equal join condition, if the join
predicate has 0 equality expr, and several INDF comparisons. See the
implementation for more details.
## Are these changes tested?
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2. Serve as another way to document the expected behavior of the code
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sqllogictests (mostly check the plans include HashJoin if the conversion is
possible)
## Are there any user-facing changes?
No
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updated before approving the PR.
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