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liwensun f0851e95c6 [SPARK-32776][SS] Limit in streaming should not be optimized away by PropagateEmptyRelation 
### What changes were proposed in this pull request?

PropagateEmptyRelation will not be applied to LIMIT operators in streaming queries.

### Why are the changes needed?

Right now, the limit operator in a streaming query may get optimized away when the relation is empty. This can be problematic for stateful streaming, as this empty batch will not write any state store files, and the next batch will fail when trying to read these state store files and throw a file not found error.

We should not let PropagateEmptyRelation optimize away the Limit operator for streaming queries.

This PR is intended as a small and safe fix for PropagateEmptyRelation. A fundamental fix that can prevent this from happening again in the future and in other optimizer rules is more desirable, but that's a much larger task.

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?
unit tests.

Closes #29623 from liwensun/spark-32776.

Authored-by: liwensun <liwen.sun@databricks.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
2020-09-02 18:05:06 +09:00
..
catalyst [SPARK-32776][SS] Limit in streaming should not be optimized away by PropagateEmptyRelation 2020-09-02 18:05:06 +09:00
core [SPARK-32776][SS] Limit in streaming should not be optimized away by PropagateEmptyRelation 2020-09-02 18:05:06 +09:00
hive [SPARK-32592][SQL] Make DataFrameReader.table take the specified options 2020-08-31 13:21:15 +00:00
hive-thriftserver [SPARK-32733][SQL] Add extended information - arguments/examples/since/notes of expressions to the remarks field of GetFunctionsOperation 2020-08-31 11:03:01 +09:00
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.