GitHub user piaozhexiu opened a pull request:
https://github.com/apache/spark/pull/7216
[SPARK-6910] [SQL] Support for pushing predicates down to metastore for
partition pruning
This PR supersedes my old one #6921. Since my patch has changed quite a
bit, I am opening a new PR to make it easier to review.
The changes include-
* Implement `toMetastoreFilter()` function in `HiveShim` that takes
`Seq[Expression]` and converts them into a filter string for Hive metastore.
* This functions matches all the `AttributeReference` +
`BinaryComparisonOp` + `Integral/StringType` patterns in `Seq[Expression]` and
fold them into a string.
* Change `hiveQlPartitions` field in `MetastoreRelation` to
`getHiveQlPartitions()` function that takes a filter string parameter.
* Call `getHiveQlPartitions()` in `HiveTableScan` with a filter string.
But there are some cases in which predicate pushdown is disabled-
Case | Predicate pushdown
------- | -----------------------------
Hive integral and string types | Yes
Hive varchar type | No
Hive 0.13 and newer | Yes
Hive 0.12 and older | No
convertMetastoreParquet=false | Yes
convertMetastoreParquet=true | No
In case of `convertMetastoreParquet=true`, predicates are not pushed down
because this conversion happens in an `Analyzer` rule
(`HiveMetastoreCatalog.ParquetConversions`). At this point, `HiveTableScan`
hasn't run, so predicates are not available. But reading the source code, I
think it is intentional to convert the entire Hive table w/ all the partitions
into `ParquetRelation` because then `ParquetRelation` can be cached and reused
for any query against that table. Please correct me if I am wrong.
cc @marmbrus
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/piaozhexiu/spark SPARK-6910-2
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/7216.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 #7216
----
commit dce7abf40003ad36675034e9467a5003f7e551ad
Author: Cheolsoo Park <[email protected]>
Date: 2015-07-03T19:51:03Z
Predicate pushdown into Hive metastore
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