GitHub user liancheng opened a pull request:
https://github.com/apache/spark/pull/3367
[SPARK-4493][SQL] Don't pushdown Eq, NotEq, Lt, LtEq, Gt and GtEq
predicates with nulls for Parquet
Predicates like `a = NULL` and `a < NULL` can't be pushed down since
Parquet `Lt`, `LtEq`, `Gt`, `GtEq` doesn't accept null value. Not that `Eq` and
`NotEq` can only be used with `null` to represent predicates like `a IS NULL`
and `a IS NOT NULL`.
However, normally this issue doesn't cause NPE because any value compared
to `NULL` results `NULL`, and Spark SQL automatically optimizes out `NULL`
predicate in the `SimplifyFilters` rule. Only testing code that intentionally
disables the optimizer may trigger this issue. (That's why this issue is not
marked as blocker and I don't think we need to backport this to branch-1.1
This PR restricts `Lt`, `LtEq`, `Gt` and `GtEq` to non-null values only,
and only uses `Eq` with null value to pushdown `IsNull` and `IsNotNull`. Also,
added support for Parquet `NotEq` filter for completeness and (tiny)
performance gain, it's also used to pushdown `IsNotNull`.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/liancheng/spark filters-with-null
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/3367.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 #3367
----
commit de7de288e3e609feaee1d70b4cfbfcca624edec2
Author: Cheng Lian <l...@databricks.com>
Date: 2014-11-19T15:36:30Z
Adds stricter rules for Parquet filters with null
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