GitHub user budde opened a pull request: https://github.com/apache/spark/pull/16797
[SPARK-19455][SQL] Add option for case-insensitive Parquet field resolution ## What changes were proposed in this pull request? **Summary** - Add spark.sql.parquet.caseInsensitiveResolution config option - Add caseInsensitive option to ParquetReadSupport.clipParquetType - Add ParquetIOSuite test - Disable Parquet filter push-down when using case-insensitive field resolution **Details** [*Copied from SPARK-19455*](https://issues.apache.org/jira/browse/SPARK-19455) [SPARK-16980](https://issues.apache.org/jira/browse/SPARK-16980) removed the schema inferrence from the HiveMetastoreCatalog class when converting a MetastoreRelation to a LoigcalRelation (HadoopFsRelation, in this case) in favor of simply using the schema returend by the metastore. This results in an optimization as the underlying file status no longer need to be resolved until after the partition pruning step, reducing the number of files to be touched significantly in some cases. The downside is that the data schema used may no longer match the underlying file schema for case-sensitive formats such as Parquet. This change initially included a [patch to ParquetReadSupport](https://github.com/apache/spark/blob/6ce1b675ee9fc9a6034439c3ca00441f9f172f84/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetReadSupport.scala#L270-L284) that attempted to remedy this conflict by using a case-insentive fallback mapping when resolving field names during the schema clipping step. [SPARK-1833](https://issues.apache.org/jira/browse/SPARK-18333) later removed this patch after [SPARK-17183](https://issues.apache.org/jira/browse/SPARK-17183) added support for embedding a case-sensitive schema as a Hive Metastore table property. AFAIK the assumption here was that the data schema obtained from the Metastore table property will be case sensitive and should match the Parquet schema exactly. The problem arises when dealing with Parquet-backed tables for which this schema has not been embedded as a table attributes and for which the underlying files contain case-sensitive field names. This will happen for any Hive table that was not created by Spark or created by a version prior to 2.1.0. We've seen Spark SQL return no results for any query containing a case-sensitive field name for such tables. The change we're proposing is to introduce a configuration parameter that will re-enable case-insensitive field name resolution in ParquetReadSupport. This option will also disable filter push-down for Parquet, as the filter predicate constructed by Spark SQL contains the case-insensitive field names which Parquet will return 0 records for when filtering against a case-sensitive column name. I was hoping to find a way to construct the filter on-the-fly in ParquetReadSupport but Parquet doesn't propegate the Configuration object passed to this class to the underlying InternalParquetRecordReader class. ## How was this patch tested? This test re-introduces a unit test to ParquetSchemaSuite.scala to test that case-insensitive schema clipping behaves as expected. It also introduces a ParquetIOSuite unit test that constructs a case-insensitive catalog table and ensures case-sensitive Parquet data can still be queried against. Please review http://spark.apache.org/contributing.html before opening a pull request. You can merge this pull request into a Git repository by running: $ git pull https://github.com/budde/spark SPARK-19455 Alternatively you can review and apply these changes as the patch at: https://github.com/apache/spark/pull/16797.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 #16797 ---- commit 5426271946419a9defb59bb84575501bc8296578 Author: Budde <bu...@amazon.com> Date: 2017-02-02T07:34:15Z [SPARK-19455][SQL] Add option for case-insensitive Parquet field resolution - Add spark.sql.parquet.caseInsensitiveResolution config option - Add caseInsensitive option to ParquetReadSupport.clipParquetType - Add ParquetIOSuite test - Disable Parquet filter push-down when using case-insensitive field resolution ---- --- If your project is set up for it, you can reply to this email and have your reply appear on GitHub as well. If your project does not have this feature enabled and wishes so, or if the feature is enabled but not working, please contact infrastructure at infrastruct...@apache.org or file a JIRA ticket with INFRA. --- --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For additional commands, e-mail: reviews-h...@spark.apache.org