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Cheng Su 39b3a04bfe [SPARK-35794][SQL] Allow custom plugin for AQE cost evaluator 
### What changes were proposed in this pull request?

Current AQE has cost evaluator to decide whether to use new plan after replanning. The current used evaluator is `SimpleCostEvaluator` to make decision based on number of shuffle in the query plan. This is not perfect cost evaluator, and different production environments might want to use different custom evaluators. E.g., sometimes we might want to still do skew join even though it might introduce extra shuffle (trade off resource for better latency), sometimes we might want to take sort into consideration for cost as well. Take our own setting as an example, we are using a custom remote shuffle service (Cosco), and the cost model is more complicated. So We want to make the cost evaluator to be pluggable, and developers can implement their own `CostEvaluator` subclass and plug in dynamically based on configuration.

The approach is to introduce a new config to allow define sub-class name of `CostEvaluator` - `spark.sql.adaptive.customCostEvaluatorClass`. And add `CostEvaluator.instantiate` to instantiate the cost evaluator class in `AdaptiveSparkPlanExec.costEvaluator`.

### Why are the changes needed?

Make AQE cost evaluation more flexible.

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

No but an internal config is introduced - `spark.sql.adaptive.customCostEvaluatorClass` to allow custom implementation of `CostEvaluator`.

### How was this patch tested?

Added unit test in `AdaptiveQueryExecSuite.scala`.

Closes #32944 from c21/aqe-cost.

Authored-by: Cheng Su <chengsu@fb.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
(cherry picked from commit 044dddf288)
Signed-off-by: Wenchen Fan <wenchen@databricks.com>
2021-07-05 09:06:49 +00:00
..
catalyst [SPARK-35794][SQL] Allow custom plugin for AQE cost evaluator 2021-07-05 09:06:49 +00:00
core [SPARK-35794][SQL] Allow custom plugin for AQE cost evaluator 2021-07-05 09:06:49 +00:00
hive [SPARK-35686][SQL] Not allow using auto-generated alias when creating view 2021-07-01 12:47:38 +00:00
hive-thriftserver [SPARK-35966][SQL] Port HIVE-17952: Fix license headers to avoid dangling javadoc warnings 2021-07-01 18:22:04 +08:00
create-docs.sh [SPARK-34010][SQL][DODCS] Use python3 instead of python in SQL documentation build 2021-01-05 19:48:10 +09:00
gen-sql-api-docs.py [SPARK-34747][SQL][DOCS] Add virtual operators to the built-in function document 2021-03-19 10:19:26 +09:00
gen-sql-config-docs.py [SPARK-32194][PYTHON] Use proper exception classes instead of plain Exception 2021-05-26 11:54:40 +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.