ODIn/spark-instrumented-optimizer
1
0
Fork 0
Code Issues Pull requests Projects Releases Wiki Activity
spark-instrumented-optimizer/sql
History
Wenchen Fan 03042529e3 [SPARK-33273][SQL] Fix a race condition in subquery execution 
### What changes were proposed in this pull request?

If we call `SubqueryExec.executeTake`, it will call `SubqueryExec.execute` which will trigger the codegen of the query plan and create an RDD. However, `SubqueryExec` already has a thread (`SubqueryExec.relationFuture`) to execute the query plan, which means we have 2 threads triggering codegen of the same query plan at the same time.

Spark codegen is not thread-safe, as we have places like `HashAggregateExec.bufferVars` that is a shared variable. The bug in `SubqueryExec` may lead to correctness bugs.

Since https://issues.apache.org/jira/browse/SPARK-33119, `ScalarSubquery` will call `SubqueryExec.executeTake`, so flaky tests start to appear.

This PR fixes the bug by reimplementing https://github.com/apache/spark/pull/30016 . We should pass the number of rows we want to collect to `SubqueryExec` at planning time, so that we can use `executeTake` inside `SubqueryExec.relationFuture`, and the caller side should always call `SubqueryExec.executeCollect`. This PR also adds checks so that we can make sure only `SubqueryExec.executeCollect` is called.

### Why are the changes needed?

fix correctness bug.

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

no

### How was this patch tested?

run `build/sbt "sql/testOnly *SQLQueryTestSuite  -- -z scalar-subquery-select"` more than 10 times. Previously it fails, now it passes.

Closes #30765 from cloud-fan/bug.

Authored-by: Wenchen Fan <wenchen@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2020-12-15 18:29:28 +09:00
..
catalyst [SPARK-33767][SQL][TESTS] Unify v1 and v2 ALTER TABLE .. DROP PARTITION tests 2020-12-15 05:36:57 +00:00
core [SPARK-33273][SQL] Fix a race condition in subquery execution 2020-12-15 18:29:28 +09:00
hive [SPARK-33767][SQL][TESTS] Unify v1 and v2 ALTER TABLE .. DROP PARTITION tests 2020-12-15 05:36:57 +00:00
hive-thriftserver [SPARK-33705][SQL][TEST] Fix HiveThriftHttpServerSuite flakiness 2020-12-14 05:14:38 +00:00
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.