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[SPARK-18614][SQL] Incorrect predicate pushdown from ExistenceJoin

Nattavut Sutyanyong authored 8 years ago

## What changes were proposed in this pull request?

ExistenceJoin should be treated the same as LeftOuter and LeftAnti, not InnerLike and LeftSemi. This is not currently exposed because the rewrite of [NOT] EXISTS OR ... to ExistenceJoin happens in rule RewritePredicateSubquery, which is in a separate rule set and placed after the rule PushPredicateThroughJoin. During the transformation in the rule PushPredicateThroughJoin, an ExistenceJoin never exists.

The semantics of ExistenceJoin says we need to preserve all the rows from the left table through the join operation as if it is a regular LeftOuter join. The ExistenceJoin augments the LeftOuter operation with a new column called exists, set to true when the join condition in the ON clause is true and false otherwise. The filter of any rows will happen in the Filter operation above the ExistenceJoin.

Example:

A(c1, c2): { (1, 1), (1, 2) }
// B can be any value as it is irrelevant in this example
B(c1): { (NULL) }

select A.*
from   A
where  exists (select 1 from B where A.c1 = A.c2)
       or A.c2=2

In this example, the correct result is all the rows from A. If the pattern ExistenceJoin around line 935 in Optimizer.scala is indeed active, the code will push down the predicate A.c1 = A.c2 to be a Filter on relation A, which will incorrectly filter the row (1,2) from A.

## How was this patch tested?

Since this is not an exposed case, no new test cases is added. The scenario is discovered via a code review of another PR and confirmed to be valid with peer.

Author: Nattavut Sutyanyong <nsy.can@gmail.com>

Closes #16044 from nsyca/spark-18614.

36006352

36006352 8 years ago

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Apache Spark

Spark is a fast and general cluster computing system for Big Data. It provides high-level APIs in Scala, Java, Python, and R, and an optimized engine that supports general computation graphs for data analysis. It also supports a rich set of higher-level tools including Spark SQL for SQL and DataFrames, MLlib for machine learning, GraphX for graph processing, and Spark Streaming for stream processing.

http://spark.apache.org/

Online Documentation

You can find the latest Spark documentation, including a programming guide, on the project web page and project wiki. This README file only contains basic setup instructions.

Building Spark

Spark is built using Apache Maven. To build Spark and its example programs, run:

build/mvn -DskipTests clean package

(You do not need to do this if you downloaded a pre-built package.)

You can build Spark using more than one thread by using the -T option with Maven, see "Parallel builds in Maven 3". More detailed documentation is available from the project site, at "Building Spark".

For general development tips, including info on developing Spark using an IDE, see http://spark.apache.org/developer-tools.html.

Interactive Scala Shell

The easiest way to start using Spark is through the Scala shell:

./bin/spark-shell

Try the following command, which should return 1000:

scala> sc.parallelize(1 to 1000).count()

Interactive Python Shell

Alternatively, if you prefer Python, you can use the Python shell:

./bin/pyspark

And run the following command, which should also return 1000:

>>> sc.parallelize(range(1000)).count()

Example Programs

Spark also comes with several sample programs in the examples directory. To run one of them, use ./bin/run-example <class> [params]. For example:

./bin/run-example SparkPi

will run the Pi example locally.

You can set the MASTER environment variable when running examples to submit examples to a cluster. This can be a mesos:// or spark:// URL, "yarn" to run on YARN, and "local" to run locally with one thread, or "local[N]" to run locally with N threads. You can also use an abbreviated class name if the class is in the examples package. For instance:

MASTER=spark://host:7077 ./bin/run-example SparkPi

Many of the example programs print usage help if no params are given.

Running Tests

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./dev/run-tests

Please see the guidance on how to run tests for a module, or individual tests.

A Note About Hadoop Versions

Spark uses the Hadoop core library to talk to HDFS and other Hadoop-supported storage systems. Because the protocols have changed in different versions of Hadoop, you must build Spark against the same version that your cluster runs.

Please refer to the build documentation at "Specifying the Hadoop Version" for detailed guidance on building for a particular distribution of Hadoop, including building for particular Hive and Hive Thriftserver distributions.

Configuration

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## Contributing

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