org.apache.flink.table.connector.source

Interface LookupTableSource

All Superinterfaces:

DynamicTableSource

All Known Implementing Classes:

HiveLookupTableSource

@PublicEvolving
public interface LookupTableSource
extends DynamicTableSource

A DynamicTableSource that looks up rows of an external storage system by one or more keys during runtime.

Compared to ScanTableSource, the source does not have to read the entire table and can lazily fetch individual values from a (possibly continuously changing) external table when necessary.

Note: Compared to ScanTableSource, a LookupTableSource does only support emitting insert-only changes currently (see also RowKind). Further abilities are not supported.

In the last step, the planner will call getLookupRuntimeProvider(LookupContext) for obtaining a provider of runtime implementation. The key fields that are required to perform a lookup are derived from a query by the planner and will be provided in the given LookupTableSource.LookupContext.getKeys(). The values for those key fields are passed during runtime.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	LookupTableSource.LookupContext Context for creating runtime implementation via a LookupTableSource.LookupRuntimeProvider.
static interface	LookupTableSource.LookupRuntimeProvider Provides actual runtime implementation for reading the data.

Nested classes/interfaces inherited from interface org.apache.flink.table.connector.source.DynamicTableSource

DynamicTableSource.Context, DynamicTableSource.DataStructureConverter

Method Summary

Modifier and Type	Method and Description
LookupTableSource.LookupRuntimeProvider	getLookupRuntimeProvider(LookupTableSource.LookupContext context) Returns a provider of runtime implementation for reading the data.

Methods inherited from interface org.apache.flink.table.connector.source.DynamicTableSource

asSummaryString, copy

Method Detail

getLookupRuntimeProvider

LookupTableSource.LookupRuntimeProvider getLookupRuntimeProvider(LookupTableSource.LookupContext context)

Returns a provider of runtime implementation for reading the data.

There exist different interfaces for runtime implementation which is why LookupTableSource.LookupRuntimeProvider serves as the base interface.

Independent of the provider interface, a source implementation can work on either arbitrary objects or internal data structures (see org.apache.flink.table.data for more information).

The given LookupTableSource.LookupContext offers utilities by the planner for creating runtime implementation with minimal dependencies to internal data structures.

See Also:

LookupFunctionProvider, AsyncLookupFunctionProvider