Spark1.1.0 Spark SQL Programming Guide

待我称王封你为后i 2022-08-12 01:23 274阅读 0赞

# Spark SQL Programming Guide #

*  [Overview][]
 *  [Getting Started][]
 *  [Data Sources][]
    
     *  [RDDs][]
        
         *  [Inferring the Schema Using Reflection][]
         *  [Programmatically Specifying the Schema][]
     *  [Parquet Files][]
        
         *  [Loading Data Programmatically][]
         *  [Configuration][]
     *  [JSON Datasets][]
     *  [Hive Tables][]
 *  [Performance Tuning][]
    
     *  [Caching Data In Memory][]
     *  [Other Configuration Options][]
 *  [Other SQL Interfaces][]
    
     *  [Running the Thrift JDBC server][]
     *  [Running the Spark SQL CLI][]
 *  [Compatibility with Other Systems][]
    
     *  [Migration Guide for Shark User][]
        
         *  [Scheduling][]
         *  [Reducer number][]
         *  [Caching][]
     *  [Compatibility with Apache Hive][]
        
         *  [Deploying in Existing Hive Warehouses][]
         *  [Supported Hive Features][]
         *  [Unsupported Hive Functionality][]
 *  [Writing Language-Integrated Relational Queries][]
 *  [Spark SQL DataType Reference][]

# Overview #

*  [**Scala**][Scala]
 *  [**Java**][Java]
 *  [**Python**][Python]

Spark SQL allows relational queries expressed in SQL, HiveQL, or Scala to be executed using Spark. At the core of this component is a new type of RDD, [SchemaRDD][]. SchemaRDDs are composed of [Row][] objects, along with a schema that describes the data types of each column in the row. A SchemaRDD is similar to a table in a traditional relational database. A SchemaRDD can be created from an existing RDD, a [Parquet][] file, a JSON dataset, or by running HiveQL against data stored in [Apache Hive][].

All of the examples on this page use sample data included in the Spark distribution and can be run in the `spark-shell`.

**Spark SQL is currently an alpha component. While we will minimize API changes, some APIs may change in future releases.**

--------------------

# Getting Started #

*  [**Scala**][Scala 1]
 *  [**Java**][Java 1]
 *  [**Python**][Python 1]

The entry point into all relational functionality in Spark is the [SQLContext][] class, or one of its descendants. To create a basic SQLContext, all you need is a SparkContext.

val sc: SparkContext // An existing SparkContext.
    val sqlContext = new org.apache.spark.sql.SQLContext(sc)
    
    // createSchemaRDD is used to implicitly convert an RDD to a SchemaRDD.
    import sqlContext.createSchemaRDD

In addition to the basic SQLContext, you can also create a HiveContext, which provides a superset of the functionality provided by the basic SQLContext. Additional features include the ability to write queries using the more complete HiveQL parser, access to HiveUDFs, and the ability to read data from Hive tables. To use a HiveContext, you do not need to have an existing Hive setup, and all of the data sources available to a SQLContext are still available. HiveContext is only packaged separately to avoid including all of Hive’s dependencies in the default Spark build. If these dependencies are not a problem for your application then using HiveContext is recommended for the 1.2 release of Spark. Future releases will focus on bringing SQLContext up to feature parity with a HiveContext.

The specific variant of SQL that is used to parse queries can also be selected using the `spark.sql.dialect` option. This parameter can be changed using either the `setConf` method on a SQLContext or by using a `SET key=value` command in SQL. For a SQLContext, the only dialect available is “sql” which uses a simple SQL parser provided by Spark SQL. In a HiveContext, the default is “hiveql”, though “sql” is also available. Since the HiveQL parser is much more complete, this is recommended for most use cases.

# Data Sources #

Spark SQL supports operating on a variety of data sources through the `SchemaRDD` interface. A SchemaRDD can be operated on as normal RDDs and can also be registered as a temporary table. Registering a SchemaRDD as a table allows you to run SQL queries over its data. This section describes the various methods for loading data into a SchemaRDD.

## RDDs ##

Spark SQL supports two different methods for converting existing RDDs into SchemaRDDs. The first method uses reflection to infer the schema of an RDD that contains specific types of objects. This reflection based approach leads to more concise code and works well when you already know the schema while writing your Spark application.

The second method for creating SchemaRDDs is through a programmatic interface that allows you to construct a schema and then apply it to an existing RDD. While this method is more verbose, it allows you to construct SchemaRDDs when the columns and their types are not known until runtime.

### Inferring the Schema Using Reflection ###

*  [**Scala**][Scala 2]
 *  [**Java**][Java 2]
 *  [**Python**][Python 2]

The Scala interaface for Spark SQL supports automatically converting an RDD containing case classes to a SchemaRDD. The case class defines the schema of the table. The names of the arguments to the case class are read using reflection and become the names of the columns. Case classes can also be nested or contain complex types such as Sequences or Arrays. This RDD can be implicitly converted to a SchemaRDD and then be registered as a table. Tables can be used in subsequent SQL statements.

// sc is an existing SparkContext.
 val sqlContext = new org.apache.spark.sql.SQLContext(sc)
 // createSchemaRDD is used to implicitly convert an RDD to a SchemaRDD.
 import sqlContext.createSchemaRDD
 
 // Define the schema using a case class.
 // Note: Case classes in Scala 2.10 can support only up to 22 fields. To work around this limit,
 // you can use custom classes that implement the Product interface.
 case class Person(name: String, age: Int)
 
 // Create an RDD of Person objects and register it as a table.
 val people = sc.textFile("examples/src/main/resources/people.txt").map(_.split(",")).map(p => Person(p(0), p(1).trim.toInt))
 people.registerTempTable("people")
 
 // SQL statements can be run by using the sql methods provided by sqlContext.
 val teenagers = sqlContext.sql("SELECT name FROM people WHERE age >= 13 AND age <= 19")
 
 // The results of SQL queries are SchemaRDDs and support all the normal RDD operations.
 // The columns of a row in the result can be accessed by ordinal.
 teenagers.map(t => "Name: " + t(0)).collect().foreach(println)

### Programmatically Specifying the Schema ###

*  [**Scala**][Scala 3]
 *  [**Java**][Java 3]
 *  [**Python**][Python 3]

When case classes cannot be defined ahead of time (for example, the structure of records is encoded in a string, or a text dataset will be parsed and fields will be projected differently for different users), a `SchemaRDD` can be created programmatically with three steps.

1.  Create an RDD of `Row`s from the original RDD;
2.  Create the schema represented by a `StructType` matching the structure of `Row`s in the RDD created in Step 1.
3.  Apply the schema to the RDD of `Row`s via `applySchema` method provided by `SQLContext`.

For example:

// sc is an existing SparkContext.
    val sqlContext = new org.apache.spark.sql.SQLContext(sc)
    
    // Create an RDD
    val people = sc.textFile("examples/src/main/resources/people.txt")
    
    // The schema is encoded in a string
    val schemaString = "name age"
    
    // Import Spark SQL data types and Row.
    import org.apache.spark.sql._
    
    // Generate the schema based on the string of schema
    val schema =
      StructType(
        schemaString.split(" ").map(fieldName => StructField(fieldName, StringType, true)))
    
    // Convert records of the RDD (people) to Rows.
    val rowRDD = people.map(_.split(",")).map(p => Row(p(0), p(1).trim))
    
    // Apply the schema to the RDD.
    val peopleSchemaRDD = sqlContext.applySchema(rowRDD, schema)
    
    // Register the SchemaRDD as a table.
    peopleSchemaRDD.registerTempTable("people")
    
    // SQL statements can be run by using the sql methods provided by sqlContext.
    val results = sqlContext.sql("SELECT name FROM people")
    
    // The results of SQL queries are SchemaRDDs and support all the normal RDD operations.
    // The columns of a row in the result can be accessed by ordinal.
    results.map(t => "Name: " + t(0)).collect().foreach(println)

## Parquet Files ##

[Parquet][] is a columnar format that is supported by many other data processing systems. Spark SQL provides support for both reading and writing Parquet files that automatically preserves the schema of the original data.

### Loading Data Programmatically ###

Using the data from the above example:

*  [**Scala**][Scala 4]
 *  [**Java**][Java 4]
 *  [**Python**][Python 4]

// sqlContext from the previous example is used in this example.
 // createSchemaRDD is used to implicitly convert an RDD to a SchemaRDD.
 import sqlContext.createSchemaRDD
 
 val people: RDD[Person] = ... // An RDD of case class objects, from the previous example.
 
 // The RDD is implicitly converted to a SchemaRDD by createSchemaRDD, allowing it to be stored using Parquet.
 people.saveAsParquetFile("people.parquet")
 
 // Read in the parquet file created above. Parquet files are self-describing so the schema is preserved.
 // The result of loading a Parquet file is also a SchemaRDD.
 val parquetFile = sqlContext.parquetFile("people.parquet")
 
 //Parquet files can also be registered as tables and then used in SQL statements.
 parquetFile.registerTempTable("parquetFile")
 val teenagers = sqlContext.sql("SELECT name FROM parquetFile WHERE age >= 13 AND age <= 19")
 teenagers.map(t => "Name: " + t(0)).collect().foreach(println)

### Configuration ###

Configuration of Parquet can be done using the `setConf` method on SQLContext or by running `SET key=value` commands using SQL.

<table style="max-width:100%; border-collapse:collapse; border-spacing:0px; width:914px; margin-bottom:20px; color:rgb(51,51,51); font-family:'Helvetica Neue',Helvetica,Arial,sans-serif; font-size:14px; line-height:22.399999618530273px"> 
 <tbody> 
 <tr> 
 <th style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Property Name</th> 
 <th style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Default</th> 
 <th style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Meaning</th> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> <code style="padding:0px; font-family:Menlo,'Lucida Console',monospace; font-size:12px; color:rgb(68,68,68); border:none">spark.sql.parquet.binaryAsString</code></td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> false</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Some other Parquet-producing systems, in particular Impala and older versions of Spark SQL, do not differentiate between binary data and strings when writing out the Parquet schema. This flag tells Spark SQL to interpret binary data as a string to provide compatibility with these systems.</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> <code style="padding:0px; font-family:Menlo,'Lucida Console',monospace; font-size:12px; color:rgb(68,68,68); border:none">spark.sql.parquet.cacheMetadata</code></td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> false</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Turns on caching of Parquet schema metadata. Can speed up querying of static data.</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> <code style="padding:0px; font-family:Menlo,'Lucida Console',monospace; font-size:12px; color:rgb(68,68,68); border:none">spark.sql.parquet.compression.codec</code></td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> snappy</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Sets the compression codec use when writing Parquet files. Acceptable values include: uncompressed, snappy, gzip, lzo.</td> 
 </tr> 
 </tbody> 
</table>

## JSON Datasets ##

*  [**Scala**][Scala 5]
 *  [**Java**][Java 5]
 *  [**Python**][Python 5]

Spark SQL can automatically infer the schema of a JSON dataset and load it as a SchemaRDD. This conversion can be done using one of two methods in a SQLContext:

*  `jsonFile` - loads data from a directory of JSON files where each line of the files is a JSON object.
 *  `jsonRdd` - loads data from an existing RDD where each element of the RDD is a string containing a JSON object.

// sc is an existing SparkContext.
 val sqlContext = new org.apache.spark.sql.SQLContext(sc)
 
 // A JSON dataset is pointed to by path.
 // The path can be either a single text file or a directory storing text files.
 val path = "examples/src/main/resources/people.json"
 // Create a SchemaRDD from the file(s) pointed to by path
 val people = sqlContext.jsonFile(path)
 
 // The inferred schema can be visualized using the printSchema() method.
 people.printSchema()
 // root
 // |-- age: IntegerType
 // |-- name: StringType
 
 // Register this SchemaRDD as a table.
 people.registerTempTable("people")
 
 // SQL statements can be run by using the sql methods provided by sqlContext.
 val teenagers = sqlContext.sql("SELECT name FROM people WHERE age >= 13 AND age <= 19")
 
 // Alternatively, a SchemaRDD can be created for a JSON dataset represented by
 // an RDD[String] storing one JSON object per string.
 val anotherPeopleRDD = sc.parallelize(
 """{"name":"Yin","address":{"city":"Columbus","state":"Ohio"}}""" :: Nil)
 val anotherPeople = sqlContext.jsonRDD(anotherPeopleRDD)

## Hive Tables ##

Spark SQL also supports reading and writing data stored in [Apache Hive][]. However, since Hive has a large number of dependencies, it is not included in the default Spark assembly. In order to use Hive you must first run “`sbt/sbt -Phive assembly/assembly`” (or use `-Phive` for maven). This command builds a new assembly jar that includes Hive. Note that this Hive assembly jar must also be present on all of the worker nodes, as they will need access to the Hive serialization and deserialization libraries (SerDes) in order to access data stored in Hive.

Configuration of Hive is done by placing your `hive-site.xml` file in `conf/`.

*  [**Scala**][Scala 6]
 *  [**Java**][Java 6]
 *  [**Python**][Python 6]

When working with Hive one must construct a `HiveContext`, which inherits from `SQLContext`, and adds support for finding tables in in the MetaStore and writing queries using HiveQL. Users who do not have an existing Hive deployment can still create a HiveContext. When not configured by the hive-site.xml, the context automatically creates `metastore_db` and `warehouse` in the current directory.

// sc is an existing SparkContext.
    val sqlContext = new org.apache.spark.sql.hive.HiveContext(sc)
    
    sqlContext.sql("CREATE TABLE IF NOT EXISTS src (key INT, value STRING)")
    sqlContext.sql("LOAD DATA LOCAL INPATH 'examples/src/main/resources/kv1.txt' INTO TABLE src")
    
    // Queries are expressed in HiveQL
    sqlContext.sql("FROM src SELECT key, value").collect().foreach(println)

# Performance Tuning #

For some workloads it is possible to improve performance by either caching data in memory, or by turning on some experimental options.

## Caching Data In Memory ##

Spark SQL can cache tables using an in-memory columnar format by calling `cacheTable("tableName")`. Then Spark SQL will scan only required columns and will automatically tune compression to minimize memory usage and GC pressure. You can call `uncacheTable("tableName")` to remove the table from memory.

Note that if you call `cache` rather than `cacheTable`, tables will *not* be cached using the in-memory columnar format, and therefore `cacheTable` is strongly recommended for this use case.

Configuration of in-memory caching can be done using the `setConf` method on SQLContext or by running `SET key=value` commands using SQL.

## Other Configuration Options ##

The following options can also be used to tune the performance of query execution. It is possible that these options will be deprecated in future release as more optimizations are performed automatically.

<table style="max-width:100%; border-collapse:collapse; border-spacing:0px; width:914px; margin-bottom:20px; color:rgb(51,51,51); font-family:'Helvetica Neue',Helvetica,Arial,sans-serif; font-size:14px; line-height:22.399999618530273px"> 
 <tbody> 
 <tr> 
 <th style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Property Name</th> 
 <th style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Default</th> 
 <th style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Meaning</th> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> <code style="padding:0px; font-family:Menlo,'Lucida Console',monospace; font-size:12px; color:rgb(68,68,68); border:none">spark.sql.autoBroadcastJoinThreshold</code></td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> 10000</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Configures the maximum size in bytes for a table that will be broadcast to all worker nodes when performing a join. By setting this value to -1 broadcasting can be disabled. Note that currently statistics are only supported for Hive Metastore tables where the command `ANALYZE TABLE &lt;tableName&gt; COMPUTE STATISTICS noscan` has been run.</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> <code style="padding:0px; font-family:Menlo,'Lucida Console',monospace; font-size:12px; color:rgb(68,68,68); border:none">spark.sql.codegen</code></td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> false</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> When true, code will be dynamically generated at runtime for expression evaluation in a specific query. For some queries with complicated expression this option can lead to significant speed-ups. However, for simple queries this can actually slow down query execution.</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> <code style="padding:0px; font-family:Menlo,'Lucida Console',monospace; font-size:12px; color:rgb(68,68,68); border:none">spark.sql.shuffle.partitions</code></td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> 200</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Configures the number of partitions to use when shuffling data for joins or aggregations.</td> 
 </tr> 
 </tbody> 
</table>

# Other SQL Interfaces #

Spark SQL also supports interfaces for running SQL queries directly without the need to write any code.

## Running the Thrift JDBC server ##

The Thrift JDBC server implemented here corresponds to the [`HiveServer2`][HiveServer2] in Hive 0.12. You can test the JDBC server with the beeline script that comes with either Spark or Hive 0.12.

To start the JDBC server, run the following in the Spark directory:

./sbin/start-thriftserver.sh

The default port the server listens on is 10000. To listen on customized host and port, please set the `HIVE_SERVER2_THRIFT_PORT` and`HIVE_SERVER2_THRIFT_BIND_HOST` environment variables. You may run `./sbin/start-thriftserver.sh --help` for a complete list of all available options. Now you can use beeline to test the Thrift JDBC server:

./bin/beeline

Connect to the JDBC server in beeline with:

beeline> !connect jdbc:hive2://localhost:10000

Beeline will ask you for a username and password. In non-secure mode, simply enter the username on your machine and a blank password. For secure mode, please follow the instructions given in the [beeline documentation][].

Configuration of Hive is done by placing your `hive-site.xml` file in `conf/`.

You may also use the beeline script that comes with Hive.

## Running the Spark SQL CLI ##

The Spark SQL CLI is a convenient tool to run the Hive metastore service in local mode and execute queries input from the command line. Note that the Spark SQL CLI cannot talk to the Thrift JDBC server.

To start the Spark SQL CLI, run the following in the Spark directory:

./bin/spark-sql

Configuration of Hive is done by placing your `hive-site.xml` file in `conf/`. You may run `./bin/spark-sql --help` for a complete list of all available options.

# Compatibility with Other Systems #

## Migration Guide for Shark User ##

### Scheduling ###

s To set a [Fair Scheduler][] pool for a JDBC client session, users can set the `spark.sql.thriftserver.scheduler.pool` variable:

SET spark.sql.thriftserver.scheduler.pool=accounting;

### Reducer number ###

In Shark, default reducer number is 1 and is controlled by the property `mapred.reduce.tasks`. Spark SQL deprecates this property in favor of`spark.sql.shuffle.partitions`, whose default value is 200. Users may customize this property via `SET`:

SET spark.sql.shuffle.partitions=10;
    SELECT page, count(*) c 
    FROM logs_last_month_cached
    GROUP BY page ORDER BY c DESC LIMIT 10;

You may also put this property in `hive-site.xml` to override the default value.

For now, the `mapred.reduce.tasks` property is still recognized, and is converted to `spark.sql.shuffle.partitions` automatically.

### Caching ###

The `shark.cache` table property no longer exists, and tables whose name end with `_cached` are no longer automatically cached. Instead, we provide `CACHE TABLE` and `UNCACHE TABLE` statements to let user control table caching explicitly:

CACHE TABLE logs_last_month;
    UNCACHE TABLE logs_last_month;

**NOTE:** `CACHE TABLE tbl` is lazy, similar to `.cache` on an RDD. This command only marks `tbl` to ensure that partitions are cached when calculated but doesn’t actually cache it until a query that touches `tbl` is executed. To force the table to be cached, you may simply count the table immediately after executing `CACHE TABLE`:

CACHE TABLE logs_last_month;
    SELECT COUNT(1) FROM logs_last_month;

Several caching related features are not supported yet:

*  User defined partition level cache eviction policy
 *  RDD reloading
 *  In-memory cache write through policy

## Compatibility with Apache Hive ##

Spark SQL is designed to be compatible with the Hive Metastore, SerDes and UDFs. Currently Spark SQL is based on Hive 0.12.0.

#### Deploying in Existing Hive Warehouses ####

The Spark SQL Thrift JDBC server is designed to be “out of the box” compatible with existing Hive installations. You do not need to modify your existing Hive Metastore or change the data placement or partitioning of your tables.

### Supported Hive Features ###

Spark SQL supports the vast majority of Hive features, such as:

* Hive query statements, including:
 
 * `SELECT`
 * `GROUP BY`
 * `ORDER BY`
 * `CLUSTER BY`
 * `SORT BY`
 * All Hive operators, including:
 
 * Relational operators (`=`, `⇔`, `==`, `<>`, `<`, `>`, `>=`, `<=`, etc)
 * Arithmetic operators (`+`, `-`, `*`, `/`, `%`, etc)
 * Logical operators (`AND`, `&&`, `OR`, `||`, etc)
 * Complex type constructors
 * Mathematical functions (`sign`, `ln`, `cos`, etc)
 * String functions (`instr`, `length`, `printf`, etc)
 * User defined functions (UDF)
 * User defined aggregation functions (UDAF)
 * User defined serialization formats (SerDes)
 * Joins
 
 * `JOIN`
 * `{LEFT|RIGHT|FULL} OUTER JOIN`
 * `LEFT SEMI JOIN`
 * `CROSS JOIN`
 * Unions
 * Sub-queries
 
 * `SELECT col FROM ( SELECT a + b AS col from t1) t2`
 * Sampling
 * Explain
 * Partitioned tables
 * All Hive DDL Functions, including:
 
 * `CREATE TABLE`
 * `CREATE TABLE AS SELECT`
 * `ALTER TABLE`
 * Most Hive Data types, including:
 
 * `TINYINT`
 * `SMALLINT`
 * `INT`
 * `BIGINT`
 * `BOOLEAN`
 * `FLOAT`
 * `DOUBLE`
 * `STRING`
 * `BINARY`
 * `TIMESTAMP`
 * `ARRAY<>`
 * `MAP<>`
 * `STRUCT<>`

### Unsupported Hive Functionality ###

Below is a list of Hive features that we don’t support yet. Most of these features are rarely used in Hive deployments.

**Major Hive Features**

*  Spark SQL does not currently support inserting to tables using dynamic partitioning.
 *  Tables with buckets: bucket is the hash partitioning within a Hive table partition. Spark SQL doesn’t support buckets yet.

**Esoteric Hive Features**

* Tables with partitions using different input formats: In Spark SQL, all table partitions need to have the same input format.
 * Non-equi outer join: For the uncommon use case of using outer joins with non-equi join conditions (e.g. condition “`key < 10`”), Spark SQL will output wrong result for the `NULL` tuple.
 * `UNION` type and `DATE` type
 * Unique join
 * Single query multi insert
 * Column statistics collecting: Spark SQL does not piggyback scans to collect column statistics at the moment and only supports populating the sizeInBytes field of the hive metastore.

**Hive Input/Output Formats**

*  File format for CLI: For results showing back to the CLI, Spark SQL only supports TextOutputFormat.
 *  Hadoop archive

**Hive Optimizations**

A handful of Hive optimizations are not yet included in Spark. Some of these (such as indexes) are less important due to Spark SQL’s in-memory computational model. Others are slotted for future releases of Spark SQL.

*  Block level bitmap indexes and virtual columns (used to build indexes)
 *  Automatically convert a join to map join: For joining a large table with multiple small tables, Hive automatically converts the join into a map join. We are adding this auto conversion in the next release.
 *  Automatically determine the number of reducers for joins and groupbys: Currently in Spark SQL, you need to control the degree of parallelism post-shuffle using “`SET spark.sql.shuffle.partitions=[num_tasks];`”.
 *  Meta-data only query: For queries that can be answered by using only meta data, Spark SQL still launches tasks to compute the result.
 *  Skew data flag: Spark SQL does not follow the skew data flags in Hive.
 *  `STREAMTABLE` hint in join: Spark SQL does not follow the `STREAMTABLE` hint.
 *  Merge multiple small files for query results: if the result output contains multiple small files, Hive can optionally merge the small files into fewer large files to avoid overflowing the HDFS metadata. Spark SQL does not support that.

# Writing Language-Integrated Relational Queries #

**Language-Integrated queries are experimental and currently only supported in Scala.**

Spark SQL also supports a domain specific language for writing queries. Once again, using the data from the above examples:

// sc is an existing SparkContext.
 val sqlContext = new org.apache.spark.sql.SQLContext(sc)
 // Importing the SQL context gives access to all the public SQL functions and implicit conversions.
 import sqlContext._
 val people: RDD[Person] = ... // An RDD of case class objects, from the first example.
 
 // The following is the same as 'SELECT name FROM people WHERE age >= 10 AND age <= 19'
 val teenagers = people.where('age >= 10).where('age <= 19).select('name)
 teenagers.map(t => "Name: " + t(0)).collect().foreach(println)

The DSL uses Scala symbols to represent columns in the underlying table, which are identifiers prefixed with a tick (`'`). Implicit conversions turn these symbols into expressions that are evaluated by the SQL execution engine. A full list of the functions supported can be found in the[ScalaDoc][SchemaRDD].

# Spark SQL DataType Reference #

*  Numeric types
    
     *  `ByteType`: Represents 1-byte signed integer numbers. The range of numbers is from `-128` to `127`.
     *  `ShortType`: Represents 2-byte signed integer numbers. The range of numbers is from `-32768` to `32767`.
     *  `IntegerType`: Represents 4-byte signed integer numbers. The range of numbers is from `-2147483648` to `2147483647`.
     *  `LongType`: Represents 8-byte signed integer numbers. The range of numbers is from `-9223372036854775808` to `9223372036854775807`.
     *  `FloatType`: Represents 4-byte single-precision floating point numbers.
     *  `DoubleType`: Represents 8-byte double-precision floating point numbers.
     *  `DecimalType`:
 *  String type
    
     *  `StringType`: Represents character string values.
 *  Binary type
    
     *  `BinaryType`: Represents byte sequence values.
 *  Boolean type
    
     *  `BooleanType`: Represents boolean values.
 *  Datetime type
    
     *  `TimestampType`: Represents values comprising values of fields year, month, day, hour, minute, and second.
 *  Complex types
    
     *  `ArrayType(elementType, containsNull)`: Represents values comprising a sequence of elements with the type of `elementType`.`containsNull` is used to indicate if elements in a `ArrayType` value can have `null` values.
     *  `MapType(keyType, valueType, valueContainsNull)`: Represents values comprising a set of key-value pairs. The data type of keys are described by `keyType` and the data type of values are described by `valueType`. For a `MapType` value, keys are not allowed to have `null`values. `valueContainsNull` is used to indicate if values of a `MapType` value can have `null` values.
     *  `StructType(fields)`: Represents values with the structure described by a sequence of `StructField`s (`fields`).
        
         *  `StructField(name, dataType, nullable)`: Represents a field in a `StructType`. The name of a field is indicated by `name`. The data type of a field is indicated by `dataType`. `nullable` is used to indicate if values of this fields can have `null` values.

*  [**Scala**][Scala 7]
 *  [**Java**][Java 7]
 *  [**Python**][Python 7]

All data types of Spark SQL are located in the package `org.apache.spark.sql`. You can access them by doing

import  org.apache.spark.sql._

<table style="max-width:100%; background-color:transparent; border-collapse:collapse; border-spacing:0px; width:914px; margin-bottom:20px"> 
 <tbody> 
 <tr> 
 <th style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221); width:166px"> Data type</th> 
 <th style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221); width:349px"> Value type in Scala</th> 
 <th style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> API to access or create a data type</th> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> ByteType</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Byte</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> ByteType</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> ShortType</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Short</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> ShortType</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> IntegerType</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Int</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> IntegerType</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> LongType</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Long</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> LongType</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> FloatType</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Float</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> FloatType</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> DoubleType</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Double</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> DoubleType</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> DecimalType</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> scala.math.sql.BigDecimal</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> DecimalType</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> StringType</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> String</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> StringType</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> BinaryType</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Array[Byte]</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> BinaryType</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> BooleanType</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> Boolean</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> BooleanType</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> TimestampType</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> java.sql.Timestamp</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> TimestampType</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> ArrayType</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> scala.collection.Seq</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> ArrayType(elementType, [containsNull]) Note:&nbsp;The default value of&nbsp;containsNull&nbsp;is&nbsp;false.</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> MapType</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> scala.collection.Map</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> MapType(keyType,&nbsp;valueType, [valueContainsNull]) Note:&nbsp;The default value of&nbsp;valueContainsNull&nbsp;is&nbsp;true.</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> StructType</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> org.apache.spark.sql.Row</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> StructType(fields) Note:&nbsp;fields&nbsp;is a Seq of StructFields. Also, two fields with the same name are not allowed.</td> 
 </tr> 
 <tr> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> StructField</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> The value type in Scala of the data type of this field (For example, Int for a StructField with the data type IntegerType)</td> 
 <td style="padding:8px; line-height:20px; vertical-align:top; border-top-width:1px; border-top-style:solid; border-top-color:rgb(221,221,221)"> StructField(name,&nbsp;dataType,&nbsp;nullable)</td> 
 </tr> 
 </tbody> 
</table>

[Overview]: http://spark.apache.org/docs/latest/sql-programming-guide.html#overview
[Getting Started]: http://spark.apache.org/docs/latest/sql-programming-guide.html#getting-started
[Data Sources]: http://spark.apache.org/docs/latest/sql-programming-guide.html#data-sources
[RDDs]: http://spark.apache.org/docs/latest/sql-programming-guide.html#rdds
[Inferring the Schema Using Reflection]: http://spark.apache.org/docs/latest/sql-programming-guide.html#inferring-the-schema-using-reflection
[Programmatically Specifying the Schema]: http://spark.apache.org/docs/latest/sql-programming-guide.html#programmatically-specifying-the-schema
[Parquet Files]: http://spark.apache.org/docs/latest/sql-programming-guide.html#parquet-files
[Loading Data Programmatically]: http://spark.apache.org/docs/latest/sql-programming-guide.html#loading-data-programmatically
[Configuration]: http://spark.apache.org/docs/latest/sql-programming-guide.html#configuration
[JSON Datasets]: http://spark.apache.org/docs/latest/sql-programming-guide.html#json-datasets
[Hive Tables]: http://spark.apache.org/docs/latest/sql-programming-guide.html#hive-tables
[Performance Tuning]: http://spark.apache.org/docs/latest/sql-programming-guide.html#performance-tuning
[Caching Data In Memory]: http://spark.apache.org/docs/latest/sql-programming-guide.html#caching-data-in-memory
[Other Configuration Options]: http://spark.apache.org/docs/latest/sql-programming-guide.html#other-configuration-options
[Other SQL Interfaces]: http://spark.apache.org/docs/latest/sql-programming-guide.html#other-sql-interfaces
[Running the Thrift JDBC server]: http://spark.apache.org/docs/latest/sql-programming-guide.html#running-the-thrift-jdbc-server
[Running the Spark SQL CLI]: http://spark.apache.org/docs/latest/sql-programming-guide.html#running-the-spark-sql-cli
[Compatibility with Other Systems]: http://spark.apache.org/docs/latest/sql-programming-guide.html#compatibility-with-other-systems
[Migration Guide for Shark User]: http://spark.apache.org/docs/latest/sql-programming-guide.html#migration-guide-for-shark-user
[Scheduling]: http://spark.apache.org/docs/latest/sql-programming-guide.html#scheduling
[Reducer number]: http://spark.apache.org/docs/latest/sql-programming-guide.html#reducer-number
[Caching]: http://spark.apache.org/docs/latest/sql-programming-guide.html#caching
[Compatibility with Apache Hive]: http://spark.apache.org/docs/latest/sql-programming-guide.html#compatibility-with-apache-hive
[Deploying in Existing Hive Warehouses]: http://spark.apache.org/docs/latest/sql-programming-guide.html#deploying-in-existing-hive-warehouses
[Supported Hive Features]: http://spark.apache.org/docs/latest/sql-programming-guide.html#supported-hive-features
[Unsupported Hive Functionality]: http://spark.apache.org/docs/latest/sql-programming-guide.html#unsupported-hive-functionality
[Writing Language-Integrated Relational Queries]: http://spark.apache.org/docs/latest/sql-programming-guide.html#writing-language-integrated-relational-queries
[Spark SQL DataType Reference]: http://spark.apache.org/docs/latest/sql-programming-guide.html#spark-sql-datatype-reference
[Scala]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_scala_0
[Java]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_java_0
[Python]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_python_0
[SchemaRDD]: http://spark.apache.org/docs/latest/api/scala/index.html#org.apache.spark.sql.SchemaRDD
[Row]: http://spark.apache.org/docs/latest/api/scala/index.html#org.apache.spark.sql.catalyst.expressions.Row
[Parquet]: http://parquet.io/
[Apache Hive]: http://hive.apache.org/
[Scala 1]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_scala_1
[Java 1]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_java_1
[Python 1]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_python_1
[SQLContext]: http://spark.apache.org/docs/latest/api/scala/index.html#org.apache.spark.sql.SQLContext
[Scala 2]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_scala_2
[Java 2]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_java_2
[Python 2]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_python_2
[Scala 3]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_scala_3
[Java 3]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_java_3
[Python 3]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_python_3
[Scala 4]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_scala_4
[Java 4]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_java_4
[Python 4]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_python_4
[Scala 5]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_scala_5
[Java 5]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_java_5
[Python 5]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_python_5
[Scala 6]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_scala_6
[Java 6]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_java_6
[Python 6]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_python_6
[HiveServer2]: https://cwiki.apache.org/confluence/display/Hive/Setting+Up+HiveServer2
[beeline documentation]: https://cwiki.apache.org/confluence/display/Hive/HiveServer2+Clients
[Fair Scheduler]: http://spark.apache.org/docs/latest/job-scheduling.html#fair-scheduler-pools
[Scala 7]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_scala_7
[Java 7]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_java_7
[Python 7]: http://spark.apache.org/docs/latest/sql-programming-guide.html#tab_python_7