Package org.apache.flink.table.runtime.functions.table.lookup

Class CachingLookupFunction

java.lang.Object

org.apache.flink.table.functions.UserDefinedFunction

org.apache.flink.table.functions.TableFunction<org.apache.flink.table.data.RowData>

org.apache.flink.table.functions.LookupFunction

org.apache.flink.table.runtime.functions.table.lookup.CachingLookupFunction

All Implemented Interfaces:

Serializable, org.apache.flink.table.functions.FunctionDefinition

@Internal
public class CachingLookupFunction
extends org.apache.flink.table.functions.LookupFunction

A wrapper function around user-provided lookup function with a cache layer.

This function will check the cache on lookup request and return entries directly on cache hit, otherwise the function will invoke the actual lookup function, and store the entry into the cache after lookup for later use.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
static String	LOOKUP_CACHE_METRIC_GROUP_NAME

Constructor Summary

Constructors

Constructor	Description
CachingLookupFunction(org.apache.flink.table.connector.source.lookup.cache.LookupCache cache, org.apache.flink.table.functions.LookupFunction delegate)	Create a CachingLookupFunction.

Method Summary

Modifier and Type	Method	Description
void	close()
org.apache.flink.table.connector.source.lookup.cache.LookupCache	getCache()
Collection<org.apache.flink.table.data.RowData>	lookup(org.apache.flink.table.data.RowData keyRow)
void	open(org.apache.flink.table.functions.FunctionContext context)	Open the CachingLookupFunction.

Methods inherited from class org.apache.flink.table.functions.LookupFunction

eval

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

functionIdentifier, 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

Field Detail

LOOKUP_CACHE_METRIC_GROUP_NAME

public static final String LOOKUP_CACHE_METRIC_GROUP_NAME

See Also:

Constant Field Values

Constructor Detail

CachingLookupFunction

public CachingLookupFunction(org.apache.flink.table.connector.source.lookup.cache.LookupCache cache,
                             @Nullable
                             org.apache.flink.table.functions.LookupFunction delegate)

Create a CachingLookupFunction.

Please note that the cache may not be the final instance serving in this function. The actual cache instance will be retrieved from the LookupCacheManager during open(org.apache.flink.table.functions.FunctionContext).

Method Detail

open

public void open(org.apache.flink.table.functions.FunctionContext context)
          throws Exception

Open the CachingLookupFunction.

In order to reduce the memory usage of the cache, LookupCacheManager is used to provide a shared cache instance across subtasks of this function. Here we use UserDefinedFunction.functionIdentifier() as the id of the cache, which is generated by MD5 of serialized bytes of this function. As different subtasks of the function will generate the same MD5, this could promise that they will be served with the same cache instance.

Overrides:

open in class org.apache.flink.table.functions.UserDefinedFunction

Throws:

Exception

See Also:

UserDefinedFunction.functionIdentifier()

lookup

public Collection<org.apache.flink.table.data.RowData> lookup(org.apache.flink.table.data.RowData keyRow)
                                                       throws IOException

Specified by:

lookup in class org.apache.flink.table.functions.LookupFunction

Throws:

IOException

close

public void close()
           throws Exception

Overrides:

close in class org.apache.flink.table.functions.UserDefinedFunction

Throws:

Exception

getCache

@VisibleForTesting
public org.apache.flink.table.connector.source.lookup.cache.LookupCache getCache()