GitHub user liancheng opened a pull request:
https://github.com/apache/spark/pull/3784
[SPARK-4937] Normalizes conjunctions and disjunctions to eliminate common
predicates
This PR is a simplified version of several filter optimization rules
introduced in #3778. Newly introduced optimizations include:
1. `a && a` => `a`
2. `a || a` => `a`
3. `(a || b || c || ...) && (a || b || d || ...)` => `a && b && (c || d ||
...)`
The 3rd rule is particularly useful to optimize the following query, which
is planned into a cartesian product
```sql
SELECT *
FROM t1, t2
WHERE (t1.key = t2.key AND t1.value > 10)
OR (t1.key = t2.key AND t2.value < 20)
```
to the following one, which is planned into an equi-join:
```sql
SELECT *
FROM t1, t2
WHERE t1.key = t2.key
AND (t1.value > 10 OR t2.value < 20)
```
The example above is quite artificial, but common predicates are likely to
appear in real life complex queries (like the one mentioned in #3778.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/liancheng/spark normalize-filters
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/3784.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #3784
----
commit cf95639d6ea9f5027a4a4612088e5cc67c6d3470
Author: Cheng Lian <[email protected]>
Date: 2014-12-24T05:42:39Z
Adds an optimization rule for filter normalization
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