org.apache.spark.sql.connector.catalog

Interface Column

@Evolving
public interface Column

An interface representing a column of a Table. It defines basic properties of a column, such as name and data type, as well as some advanced ones like default column value.

Data Sources do not need to implement it. They should consume it in APIs like TableCatalog.createTable(Identifier, Column[], Transform[], Map), and report it in Table.columns() by calling the static create functions of this interface to create it.

A column cannot have both a default value and a generation expression.

Method Summary

Modifier and Type	Method and Description
String	comment() Returns the comment of this table column.
static Column	create(String name, DataType dataType)
static Column	create(String name, DataType dataType, boolean nullable)
static Column	create(String name, DataType dataType, boolean nullable, String comment, ColumnDefaultValue defaultValue, String metadataInJSON)
static Column	create(String name, DataType dataType, boolean nullable, String comment, String metadataInJSON)
static Column	create(String name, DataType dataType, boolean nullable, String comment, String generationExpression, String metadataInJSON)
DataType	dataType() Returns the data type of this table column.
ColumnDefaultValue	defaultValue() Returns the default value of this table column.
String	generationExpression() Returns the generation expression of this table column.
String	metadataInJSON() Returns the column metadata in JSON format.
String	name() Returns the name of this table column.
boolean	nullable() Returns true if this column may produce null values.

Method Detail

create

static Column create(String name,
                     DataType dataType)

create

static Column create(String name,
                     DataType dataType,
                     boolean nullable)

create

static Column create(String name,
                     DataType dataType,
                     boolean nullable,
                     String comment,
                     String metadataInJSON)

create

static Column create(String name,
                     DataType dataType,
                     boolean nullable,
                     String comment,
                     ColumnDefaultValue defaultValue,
                     String metadataInJSON)

create

static Column create(String name,
                     DataType dataType,
                     boolean nullable,
                     String comment,
                     String generationExpression,
                     String metadataInJSON)

name

String name()

Returns the name of this table column.

dataType

DataType dataType()

Returns the data type of this table column.

nullable

boolean nullable()

Returns true if this column may produce null values.

comment

@Nullable
String comment()

Returns the comment of this table column. Null means no comment.

defaultValue

@Nullable
ColumnDefaultValue defaultValue()

Returns the default value of this table column. Null means no default value.

generationExpression

@Nullable
String generationExpression()

Returns the generation expression of this table column. Null means no generation expression.

The generation expression is stored as spark SQL dialect. It is up to the data source to verify expression compatibility and reject writes as necessary.

metadataInJSON

@Nullable
String metadataInJSON()

Returns the column metadata in JSON format.