LookupFunction (Flink : 2.0-SNAPSHOT API)

java.lang.Object
- org.apache.flink.table.functions.UserDefinedFunction
- - org.apache.flink.table.functions.TableFunction<RowData>
  - - org.apache.flink.table.functions.LookupFunction

All Implemented Interfaces:

Serializable, FunctionDefinition

Direct Known Subclasses:

CachingLookupFunction, RetryableLookupFunctionDelegator
```
@PublicEvolving
public abstract class LookupFunction
extends TableFunction<RowData>
```
A wrapper class of TableFunction for synchronously lookup rows matching the lookup keys from external system.
The output type of this table function is fixed as RowData.

See Also:

Serialized Form

Constructor Summary

Constructors
Constructor Description

LookupFunction()

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`eval(Object... keys)`	Invoke `lookup(org.apache.flink.table.data.RowData)` and handle exceptions.
`abstract Collection<RowData>`	`lookup(RowData keyRow)`	Synchronously lookup rows matching the lookup keys.

Methods inherited from class org.apache.flink.table.functions.TableFunction
collect, finish, getKind, getParameterTypes, getResultType, getTypeInference, setCollector

Methods inherited from class org.apache.flink.table.functions.UserDefinedFunction
close, functionIdentifier, open, toString

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.apache.flink.table.functions.FunctionDefinition
getRequirements, isDeterministic, supportsConstantFolding

- Constructor Detail
  - LookupFunction
```
public LookupFunction()
```
- Method Detail
  - lookup
```
public abstract Collection<RowData> lookup(RowData keyRow)
                                    throws IOException
```
    Synchronously lookup rows matching the lookup keys.
    Please note that the returning collection of RowData shouldn't be reused across invocations.
    
    Parameters:
    
    keyRow - - A RowData that wraps lookup keys.
    
    Returns:
    
    A collection of all matching rows in the lookup table.
    
    Throws:
    
    IOException
  - eval
```
public final void eval(Object... keys)
```
    Invoke lookup(org.apache.flink.table.data.RowData) and handle exceptions.