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(Link to Jira: https://issues.apache.org/jira/browse/SPARK-20331) ## What changes were proposed in this pull request? Spark 2.1 introduced scalable support for Hive tables with huge numbers of partitions. Key to leveraging this support is the ability to prune unnecessary table partitions to answer queries. Spark supports a subset of the class of partition pruning predicates that the Hive metastore supports. If a user writes a query with a partition pruning predicate that is *not* supported by Spark, Spark falls back to loading all partitions and pruning client-side. We want to broaden Spark's current partition pruning predicate pushdown capabilities. One of the key missing capabilities is support for disjunctions. For example, for a table partitioned by date, writing a query with a predicate like date = 20161011 or date = 20161014 will result in Spark fetching all partitions. For a table partitioned by date and hour, querying a range of hours across dates can be quite difficult to accomplish without fetching all partition metadata. The current partition pruning support supports only comparisons against literals. We can expand that to foldable expressions by evaluating them at planning time. We can also implement support for the "IN" comparison by expanding it to a sequence of "OR"s. ## How was this patch tested? The `HiveClientSuite` and `VersionsSuite` were refactored and simplified to make Hive client-based, version-specific testing more modular and conceptually simpler. There are now two Hive test suites: `HiveClientSuite` and `HivePartitionFilteringSuite`. These test suites have a single-argument constructor taking a `version` parameter. As such, these test suites cannot be run by themselves. Instead, they have been bundled into "aggregation" test suites which run each suite for each Hive client version. These aggregation suites are called `HiveClientSuites` and `HivePartitionFilteringSuites`. The `VersionsSuite` and `HiveClientSuite` have been refactored into each of these aggregation suites, respectively. `HiveClientSuite` and `HivePartitionFilteringSuite` subclass a new abstract class, `HiveVersionSuite`. `HiveVersionSuite` collects functionality related to testing a single Hive version and overrides relevant test suite methods to display version-specific information. A new trait, `HiveClientVersions`, has been added with a sequence of Hive test versions. Author: Michael Allman <michael@videoamp.com> Closes #17633 from mallman/spark-20331-enhanced_partition_pruning_pushdown. |
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Spark SQL
This module provides support for executing relational queries expressed in either SQL or the DataFrame/Dataset API.
Spark SQL is broken up into four subprojects:
- Catalyst (sql/catalyst) - An implementation-agnostic framework for manipulating trees of relational operators and expressions.
- Execution (sql/core) - A query planner / execution engine for translating Catalyst's logical query plans into Spark RDDs. This component also includes a new public interface, SQLContext, that allows users to execute SQL or LINQ statements against existing RDDs and Parquet files.
- Hive Support (sql/hive) - Includes an extension of SQLContext called HiveContext that allows users to write queries using a subset of HiveQL and access data from a Hive Metastore using Hive SerDes. There are also wrappers that allows users to run queries that include Hive UDFs, UDAFs, and UDTFs.
- HiveServer and CLI support (sql/hive-thriftserver) - Includes support for the SQL CLI (bin/spark-sql) and a HiveServer2 (for JDBC/ODBC) compatible server.