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Chao Sun 3165ca742a [SPARK-33376][SQL] Remove the option of "sharesHadoopClasses" in Hive IsolatedClientLoader 
### What changes were proposed in this pull request?

This removes the `sharesHadoopClasses` flag from `IsolatedClientLoader` in Hive module.

### Why are the changes needed?

Currently, when initializing `IsolatedClientLoader`, users can set the `sharesHadoopClasses` flag to decide whether the `HiveClient` created should share Hadoop classes with Spark itself or not. In the latter case, the client will only load Hadoop classes from the Hive dependencies.

There are two reasons to remove this:
1. this feature is currently used in two cases: 1) unit tests, 2) when the Hadoop version defined in Maven can not be found when `spark.sql.hive.metastore.jars` is equal to "maven", which could be very rare.
2. when `sharesHadoopClasses` is false, Spark doesn't really only use Hadoop classes from Hive jars: we also download `hadoop-client` jar and put all the sub-module jars (e.g., `hadoop-common`, `hadoop-hdfs`) together with the Hive jars, and the Hadoop version used by `hadoop-client` is the same version used by Spark itself. As result, we're mixing two versions of Hadoop jars in the classpath, which could potentially cause issues, especially considering that the default Hadoop version is already 3.2.0 while most Hive versions supported by the `IsolatedClientLoader` is still using Hadoop 2.x or even lower.

### Does this PR introduce _any_ user-facing change?

This affects Spark users in one scenario: when `spark.sql.hive.metastore.jars` is set to `maven` AND the Hadoop version specified in pom file cannot be downloaded, currently the behavior is to switch to _not_ share Hadoop classes, but with the PR it will share Hadoop classes with Spark.

### How was this patch tested?

Existing UTs.

Closes #30284 from sunchao/SPARK-33376.

Authored-by: Chao Sun <sunchao@apple.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
2020-11-10 15:41:04 +00:00
..
catalyst [SPARK-33302][SQL] Push down filters through Expand 2020-11-10 14:40:24 +00:00
core [SPARK-33305][SQL] DSv2: DROP TABLE command should also invalidate cache 2020-11-10 14:37:42 +00:00
hive [SPARK-33376][SQL] Remove the option of "sharesHadoopClasses" in Hive IsolatedClientLoader 2020-11-10 15:41:04 +00:00
hive-thriftserver [SPARK-33352][CORE][SQL][SS][MLLIB][AVRO][K8S] Fix procedure-like declaration compilation warnings in Scala 2.13 2020-11-08 12:51:48 -06:00
create-docs.sh [SPARK-31550][SQL][DOCS] Set nondeterministic configurations with general meanings in sql configuration doc 2020-04-27 17:08:52 +09:00
gen-sql-api-docs.py [SPARK-31474][SQL][FOLLOWUP] Replace _FUNC_ placeholder with functionname in the note field of expression info 2020-04-23 13:33:04 +09:00
gen-sql-config-docs.py [SPARK-31550][SQL][DOCS] Set nondeterministic configurations with general meanings in sql configuration doc 2020-04-27 17:08:52 +09:00
gen-sql-functions-docs.py [SPARK-31562][SQL] Update ExpressionDescription for substring, current_date, and current_timestamp 2020-04-26 11:46:52 -07:00
mkdocs.yml [SPARK-30731] Update deprecated Mkdocs option 2020-02-19 17:28:58 +09:00
README.md [SPARK-30510][SQL][DOCS] Publicly document Spark SQL configuration options 2020-02-09 19:20:47 +09:00

README.md

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 extensions that allow users to write queries using a subset of HiveQL and access data from a Hive Metastore using Hive SerDes. There are also wrappers that allow 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.

Running ./sql/create-docs.sh generates SQL documentation for built-in functions under sql/site, and SQL configuration documentation that gets included as part of configuration.md in the main docs directory.