GitHub user yhuai opened a pull request:
https://github.com/apache/spark/pull/1346
[WIP][SPARK-2179][SQL] Public API for DataTypes and Schema
The current PR contains the following changes:
* Expose `DataType`s in the sql package (internal details are private to
sql).
* Introduce `createSchemaRDD` to create a `SchemaRDD` from an `RDD` with a
provided schema (represented by a `StructType`) and a provided function to
construct `Row`,
* Add a function `simpleString` to every `DataType`. Also, the schema
represented by a `StructType` can be visualized by `printSchema`.
An example of using `createSchemaRDD` is shown below.
```scala
import org.apache.spark.sql._
val sqlContext = new org.apache.spark.sql.SQLContext(sc)
val schema =
StructType(
StructField("name", StringType, false) ::
StructField("age", IntegerType, true) :: Nil)
def createRow(record: String): Row = {
val items = record.split(",")
Row(items(0), items(1).trim.toInt)
}
val people = sc.textFile("examples/src/main/resources/people.txt")
val peopleSchemaRDD = sqlContext.createSchemaRDD(people, schema, createRow)
peopleSchemaRDD.printSchema
// root
// |-- name: string (nullable = false)
// |-- age: integer (nullable = true)
peopleSchemaRDD.registerAsTable("people")
sqlContext.sql("select name from people").collect.foreach(println)
```
I am currently working on the following things.
* Move those general purpose functions introduced by the JSON support to
the type system.
* Add pre-defined `constructRow` functions to help users easily use
`createSchemaRDD` (e.g. applying a schema to a JSON dataset).
* Add a method to let user optionally validate the schema of a `SchemaRDD`
by checking every row.
* Add needed tests.
JIRA: https://issues.apache.org/jira/browse/SPARK-2179
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/yhuai/spark dataTypeAndSchema
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/1346.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 #1346
----
commit 16be3e56e83a406af86b9e7f18059ec7a2595a9e
Author: Yin Huai <[email protected]>
Date: 2014-07-09T18:51:24Z
This commit contains three changes:
* Expose `DataType`s in the sql package (internal details are private to
sql).
* Introduce `createSchemaRDD` to create a `SchemaRDD` from an `RDD` with a
provided schema (represented by a `StructType`) and a provided function to
construct `Row`,
* Add a function `simpleString` to every `DataType`. Also, the schema
represented by a `StructType` can be visualized by `printSchema`.
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