mrhhsg opened a new pull request, #66806:
URL: https://github.com/apache/doris/pull/66806
### What problem does this PR solve?
Issue Number: None
Related PR: None
Problem Summary:
A one-sided outer join whose condition folds to `FALSE` or `NULL` still
remained in the logical plan. Although the nullable side can only produce
NULL-padded columns, the optimizer did not expose those columns as uniform NULL
values. Consequently, a later null-rejecting inner-join predicate could fail to
fold to an empty relation and execute very large nested-loop intermediates for
a query whose result is already known to be empty.
This change:
- replaces constant-false/NULL inner and cross joins with an empty relation;
- replaces constant-false/NULL left and right outer joins with a projection
over the preserved child plus typed NULL aliases, while preserving output
expression IDs, names, qualifiers, types, and order;
- reapplies join-condition elimination immediately after constant
propagation rewrites join predicates.
Mark joins, semi/anti joins, full outer joins, and ASOF joins retain their
existing behavior.
### Release note
Improve query performance by eliminating joins whose conditions are constant
`FALSE` or `NULL`.
### Check List (For Author)
- Test:
- Unit Test: `./run-fe-ut.sh --run
org.apache.doris.nereids.rules.rewrite.EliminateJoinConditionTest` (5 tests
passed)
- Regression test: Not run; the focused optimizer unit test covers
inner, left outer, right outer, NULL, FALSE, output preservation, and
cross-rule constant propagation.
- Behavior changed: Yes (semantically redundant joins are removed; query
results are unchanged)
- Does this need documentation: No
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