Package org.apache.flink.table.api

Class Schema

java.lang.Object

org.apache.flink.table.api.Schema

@PublicEvolving
public final class Schema
extends Object

Schema of a table or view.

A schema represents the schema part of a CREATE TABLE (schema) WITH (options) DDL statement in SQL. It defines columns of different kind, constraints, time attributes, and watermark strategies. It is possible to reference objects (such as functions or types) across different catalogs.

This class is used in the API and catalogs to define an unresolved schema that will be translated to ResolvedSchema. Some methods of this class perform basic validation, however, the main validation happens during the resolution. Thus, an unresolved schema can be incomplete and might be enriched or merged with a different schema at a later stage.

Since an instance of this class is unresolved, it should not be directly persisted. The toString() shows only a summary of the contained objects.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final class	Schema.Builder	A builder for constructing an immutable but still unresolved Schema.
static class	Schema.UnresolvedColumn	Super class for all kinds of columns in an unresolved schema.
static final class	Schema.UnresolvedComputedColumn	Declaration of a computed column that will be resolved to Column.ComputedColumn during schema resolution.
static class	Schema.UnresolvedConstraint	Super class for all kinds of constraints in an unresolved schema.
static final class	Schema.UnresolvedMetadataColumn	Declaration of a metadata column that will be resolved to Column.MetadataColumn during schema resolution.
static final class	Schema.UnresolvedPhysicalColumn	Declaration of a physical column that will be resolved to Column.PhysicalColumn during schema resolution.
static final class	Schema.UnresolvedPrimaryKey	Declaration of a primary key that will be resolved to UniqueConstraint during schema resolution.
static final class	Schema.UnresolvedWatermarkSpec	Declaration of a watermark strategy that will be resolved to WatermarkSpec during schema resolution.

Method Summary

Modifier and Type	Method	Description
static Schema	derived()	Convenience method for stating explicitly that a schema is empty and should be fully derived by the framework.
boolean	equals(Object o)
List<Schema.UnresolvedColumn>	getColumns()
Optional<Schema.UnresolvedPrimaryKey>	getPrimaryKey()
List<Schema.UnresolvedWatermarkSpec>	getWatermarkSpecs()
int	hashCode()
static Schema.Builder	newBuilder()	Builder for configuring and creating instances of Schema.
ResolvedSchema	resolve(SchemaResolver resolver)	Resolves the given Schema to a validated ResolvedSchema.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Details

newBuilder

public static Schema.Builder newBuilder()

Builder for configuring and creating instances of Schema.

derived

public static Schema derived()

Convenience method for stating explicitly that a schema is empty and should be fully derived by the framework.

The semantics are equivalent to calling Schema.newBuilder().build().

Note that derivation depends on the context. Usually, the method that accepts a Schema instance will mention whether schema derivation is supported or not.

getColumns

public List<Schema.UnresolvedColumn> getColumns()

getWatermarkSpecs

public List<Schema.UnresolvedWatermarkSpec> getWatermarkSpecs()

getPrimaryKey

public Optional<Schema.UnresolvedPrimaryKey> getPrimaryKey()

resolve

public ResolvedSchema resolve(SchemaResolver resolver)

Resolves the given Schema to a validated ResolvedSchema.

toString

public String toString()

Overrides:

toString in class Object

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object