GitHub user JoshRosen opened a pull request:
https://github.com/apache/spark/pull/14907
[SPARK-17351] Refactor JDBCRDD to expose ResultSet -> Seq[Row] utility
methods
This patch refactors the internals of the JDBC data source in order to
allow some of its code to be re-used in an automated comparison testing
harness. Here are the key changes:
- Move the JDBC `ResultSetMetadata` to `StructType` conversion logic from
`JDBCRDD.resolveTable()` to the `JdbcUtils` object (as a new
`getSchema(ResultSet, JdbcDialect)` method), allowing it to be applied on
`ResultSet`s that are created elsewhere.
- Move the `ResultSet` to `InternalRow` conversion methods from `JDBCRDD`
to `JdbcUtils`:
- It makes sense to move the `JDBCValueGetter` type and `makeGetter`
functions here given that their write-path counterparts (`JDBCValueSetter`) are
already in `JdbcUtils`.
- Add an internal `resultSetToSparkInternalRows` method which takes a
`ResultSet` and schema and returns an `Iterator[InternalRow]`. This effectively
extracts the main loop of `JDBCRDD` into its own method.
- Add a public `resultSetToRows` method to `JdbcUtils`, which wraps the
minimal machinery around `resultSetToSparkInternalRows` in order to allow it to
be called from outside of a Spark job.
- Make `JdbcDialect.get` into a `DeveloperApi` (`JdbcDialect` itself is
already a `DeveloperApi`).
Put together, these changes enable the following testing pattern:
```scala
val jdbResultSet: ResultSet = conn.prepareStatement(query).executeQuery()
val resultSchema: StructType = JdbcUtils.getSchema(jdbResultSet,
JdbcDialects.get("jdbc:postgresql"))
val jdbcRows: Seq[Row] = JdbcUtils.resultSetToRows(jdbResultSet,
schema).toSeq
checkAnswer(sparkResult, jdbcRows) // in a test case
```
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/JoshRosen/spark modularize-jdbc-internals
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/14907.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #14907
----
commit 17d770a85e0921a5bfcbe00aead71cf169f76119
Author: Josh Rosen <joshro...@databricks.com>
Date: 2016-08-23T19:02:55Z
Move ResultSet -> Seq[InternalRow] conversion into JdbcUtils
commit 682b5917341a530627a5d873196f6c4a3259a91b
Author: Josh Rosen <joshro...@databricks.com>
Date: 2016-08-23T19:07:44Z
Make new method private[spark]
commit ec49accbf2c532766fb66c3b8910fd7c81563839
Author: Josh Rosen <joshro...@databricks.com>
Date: 2016-08-23T19:18:03Z
Move getCatalystType to JdbcUtils and add new getSchema() method.
commit 025c9d08d485ebfab0dd23f1ed5065e537ad0437
Author: Josh Rosen <joshro...@databricks.com>
Date: 2016-08-23T19:54:54Z
Add public resultSetToRows() method for converting to public rows.
commit 05dfe5276017862dadf8791672de818329d52723
Author: Josh Rosen <joshro...@databricks.com>
Date: 2016-08-24T02:25:35Z
Remove InputMetrics from a public API.
commit fca548ae24bbc60e8c04ea4e6756dfb19942fb61
Author: Josh Rosen <joshro...@databricks.com>
Date: 2016-08-25T00:49:28Z
Open up JdbcDialects.get as developerapi.
commit 43cbef6b4310dd9af08672bcaa01d8114b1fe5fc
Author: Josh Rosen <joshro...@databricks.com>
Date: 2016-09-01T00:32:25Z
Merge remote-tracking branch 'origin/master' into modularize-jdbc-internals
----
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