org.apache.flink.table.functions

类 TableFunction<T>

java.lang.Object

org.apache.flink.table.functions.UserDefinedFunction

org.apache.flink.table.functions.TableFunction<T>

类型参数:

T - The type of the output row. Either an explicit composite type or an atomic type that is implicitly wrapped into a row consisting of one field.

所有已实现的接口:

Serializable, FunctionDefinition

直接已知子类:

PythonTableFunction, TemporalTableFunction

@PublicEvolving
public abstract class TableFunction<T>
extends UserDefinedFunction

Base class for a user-defined table function. A user-defined table functions maps zero, one, or multiple scalar values to zero, one, or multiple rows. If an output row consists of only one field, the row can be omitted and a scalar value can be emitted. It will be wrapped into an implicit row by the runtime.

The behavior of a TableFunction can be defined by implementing a custom evaluation method. An evaluation method must be declared publicly, not static, and named eval. Evaluation methods can also be overloaded by implementing multiple methods named eval.

By default, input and output data types are automatically extracted using reflection. This includes the generic argument T of the class for determining an output data type. If the reflective information is not sufficient, it can be supported and enriched with DataTypeHint and FunctionHint annotations.

The following examples show how to specify a table function:

 
   // a function that accepts an arbitrary number of INT arguments and emits them as implicit ROW < INT >
   class FlattenFunction extends TableFunction {
     public void eval(Integer... args) {
       for (Integer i : args) {
         collect(i);
       }
     }
   }

   // a function that accepts either INT or STRING and emits them as implicit ROW < STRING >
   class DuplicatorFunction extends TableFunction {
     public void eval(Integer i) {
       eval(String.valueOf(i));
     }
     public void eval(String s) {
       collect(s);
       collect(s);
     }
   }

   // a function that produces a ROW < i INT, s STRING > from arguments, the function hint helps in
   // declaring the row's fields

另请参阅:

序列化表格

构造器概要

构造器

构造器和说明
TableFunction()

方法概要

限定符和类型	方法和说明
protected void	collect(T row) Emits an (implicit or explicit) output row.
FunctionKind	getKind() Returns the kind of function this definition describes.
org.apache.flink.api.common.typeinfo.TypeInformation<?>[]	getParameterTypes(Class<?>[] signature) 已过时。 This method uses the old type system and is based on the old reflective extraction logic. The method will be removed in future versions and is only called when using the deprecated TableEnvironment.registerFunction(...) method. The new reflective extraction logic (possibly enriched with DataTypeHint and FunctionHint) should be powerful enough to cover most use cases. For advanced users, it is possible to override UserDefinedFunction.getTypeInference(DataTypeFactory).
org.apache.flink.api.common.typeinfo.TypeInformation<T>	getResultType() 已过时。 This method uses the old type system and is based on the old reflective extraction logic. The method will be removed in future versions and is only called when using the deprecated TableEnvironment.registerFunction(...) method. The new reflective extraction logic (possibly enriched with DataTypeHint and FunctionHint) should be powerful enough to cover most use cases. For advanced users, it is possible to override UserDefinedFunction.getTypeInference(DataTypeFactory).
TypeInference	getTypeInference(DataTypeFactory typeFactory) Returns the logic for performing type inference of a call to this function definition.
void	setCollector(org.apache.flink.util.Collector<T> collector) Internal use.

从类继承的方法 org.apache.flink.table.functions.UserDefinedFunction

close, functionIdentifier, open, toString

从类继承的方法 java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

从接口继承的方法 org.apache.flink.table.functions.FunctionDefinition

getRequirements, isDeterministic

构造器详细资料

TableFunction

public TableFunction()

方法详细资料

setCollector

public final void setCollector(org.apache.flink.util.Collector<T> collector)

Internal use. Sets the current collector.

getResultType

@Deprecated
public org.apache.flink.api.common.typeinfo.TypeInformation<T> getResultType()

已过时。 This method uses the old type system and is based on the old reflective extraction logic. The method will be removed in future versions and is only called when using the deprecated TableEnvironment.registerFunction(...) method. The new reflective extraction logic (possibly enriched with DataTypeHint and FunctionHint) should be powerful enough to cover most use cases. For advanced users, it is possible to override UserDefinedFunction.getTypeInference(DataTypeFactory).

Returns the result type of the evaluation method.

getParameterTypes

@Deprecated
public org.apache.flink.api.common.typeinfo.TypeInformation<?>[] getParameterTypes(Class<?>[] signature)

已过时。 This method uses the old type system and is based on the old reflective extraction logic. The method will be removed in future versions and is only called when using the deprecated TableEnvironment.registerFunction(...) method. The new reflective extraction logic (possibly enriched with DataTypeHint and FunctionHint) should be powerful enough to cover most use cases. For advanced users, it is possible to override UserDefinedFunction.getTypeInference(DataTypeFactory).

Returns TypeInformation about the operands of the evaluation method with a given signature.

collect

protected final void collect(T row)

Emits an (implicit or explicit) output row.

If null is emitted as an explicit row, it will be skipped by the runtime. For implicit rows, the row's field will be null.

参数:

row - the output row

getKind

public final FunctionKind getKind()

从接口复制的说明: FunctionDefinition

Returns the kind of function this definition describes.

getTypeInference

public TypeInference getTypeInference(DataTypeFactory typeFactory)

从类复制的说明: UserDefinedFunction

Returns the logic for performing type inference of a call to this function definition.

The type inference process is responsible for inferring unknown types of input arguments, validating input arguments, and producing result types. The type inference process happens independent of a function body. The output of the type inference is used to search for a corresponding runtime implementation.

Instances of type inference can be created by using TypeInference.newBuilder().

See BuiltInFunctionDefinitions for concrete usage examples.

The type inference for user-defined functions is automatically extracted using reflection. It does this by analyzing implementation methods such as eval() or accumulate() and the generic parameters of a function class if present. If the reflective information is not sufficient, it can be supported and enriched with DataTypeHint and FunctionHint annotations.

Note: Overriding this method is only recommended for advanced users. If a custom type inference is specified, it is the responsibility of the implementer to make sure that the output of the type inference process matches with the implementation method:

The implementation method must comply with each DataType.getConversionClass() returned by the type inference. For example, if DataTypes.TIMESTAMP(3).bridgedTo(java.sql.Timestamp.class) is an expected argument type, the method must accept a call eval(java.sql.Timestamp).

Regular Java calling semantics (including type widening and autoboxing) are applied when calling an implementation method which means that the signature can be eval(java.lang.Object).

The runtime will take care of converting the data to the data format specified by the DataType.getConversionClass() coming from the type inference logic.

指定者:

getTypeInference 在接口中 FunctionDefinition

指定者:

getTypeInference 在类中 UserDefinedFunction