gengliangwang opened a new pull request #28741:
URL: https://github.com/apache/spark/pull/28741
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### What changes were proposed in this pull request?
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Currently, in the rule`PushPredicateThroughJoin`, if the condition predicate
of `Or` operator can't be entirely pushed down, it will be thrown away.
In fact, the predicates under `Or` operators can be partially pushed down.
For example, says `a` and `b` are able to be pushed into one of the joined
tables, while `c` can't be pushed down, the predicate
`a or (b and c)`
can be converted as
`(a or b) and (a or c)`
We can still push down `(a or b)`.
We can't push down disjunctive predicates only when one of its children is
not partially convertible.
The common way is to convert the condition into conjunctive normal
form(CNF), so that we can find all the predicates that can be pushed down by
going over the CNF predicate.
However, CNF conversion result can be huge, the recursive implementation can
cause stack overflow on complex predicates. There were PRs for it such as
#10444, #15558, #28575.
There is also non-recursive implementation: #28733 . It should be workable
but this PR proposes a simpler implementation.
Essentially, we just need to traverse predicate and extract the convertible
sub-predicates like what we did in https://github.com/apache/spark/pull/24598 .
There is no need to maintain the CNF result set.
### Why are the changes needed?
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Improve query performance. PostgreSQL, Impala and Hive support similiar
feature.
### Does this PR introduce _any_ user-facing change?
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No
### How was this patch tested?
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Unit test and benchmark test.
SQL | Before this PR | After this PR
--- | --- | ---
TPCDS 5T Q13 | 84s | 21s
TPCDS 5T q85 | 66s | 34s
TPCH 1T q19 | 37s | 32s
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