Package org.apache.flink.table.annotation

Enum ArgumentTrait

java.lang.Object

java.lang.Enum<ArgumentTrait>

org.apache.flink.table.annotation.ArgumentTrait

All Implemented Interfaces:

Serializable, Comparable<ArgumentTrait>

@PublicEvolving
public enum ArgumentTrait
extends Enum<ArgumentTrait>

Declares traits for ArgumentHint. They enable basic validation by the framework.

Some traits have dependencies to other traits, which is why this enum reflects a hierarchy in which SCALAR, TABLE_AS_ROW, and TABLE_AS_SET are the top-level roots.

Enum Constant Summary

Enum Constants

Enum Constant	Description
OPTIONAL_PARTITION_BY	Defines that a PARTITION BY clause is optional for TABLE_AS_SET.
PASS_COLUMNS_THROUGH	Defines that all columns of a table argument (i.e.
SCALAR	An argument that accepts a scalar value.
TABLE_AS_ROW	An argument that accepts a table "as row" (i.e. with row semantics).
TABLE_AS_SET	An argument that accepts a table "as set" (i.e. with set semantics).

Method Summary

Modifier and Type	Method	Description
boolean	isRoot()
StaticArgumentTrait	toStaticTrait()
static ArgumentTrait	valueOf(String name)	Returns the enum constant of this type with the specified name.
static ArgumentTrait[]	values()	Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

SCALAR

public static final ArgumentTrait SCALAR

An argument that accepts a scalar value. For example: f(1), f(true), f('Some string').

It's the default if no ArgumentHint is provided.

TABLE_AS_ROW

public static final ArgumentTrait TABLE_AS_ROW

An argument that accepts a table "as row" (i.e. with row semantics). This trait only applies to ProcessTableFunction (PTF).

For scalability, input tables are distributed across so-called "virtual processors". A virtual processor, as defined by the SQL standard, executes a PTF instance and has access only to a portion of the entire table. The argument declaration decides about the size of the portion and co-location of data. Conceptually, tables can be processed either "as row" (i.e. with row semantics) or "as set" (i.e. with set semantics).

A table with row semantics assumes that there is no correlation between rows and each row can be processed independently. The framework is free in how to distribute rows across virtual processors and each virtual processor has access only to the currently processed row.

TABLE_AS_SET

public static final ArgumentTrait TABLE_AS_SET

An argument that accepts a table "as set" (i.e. with set semantics). This trait only applies to ProcessTableFunction (PTF).

For scalability, input tables are distributed across so-called "virtual processors". A virtual processor, as defined by the SQL standard, executes a PTF instance and has access only to a portion of the entire table. The argument declaration decides about the size of the portion and co-location of data. Conceptually, tables can be processed either "as row" (i.e. with row semantics) or "as set" (i.e. with set semantics).

A table with set semantics assumes that there is a correlation between rows. When calling the function, the PARTITION BY clause defines the columns for correlation. The framework ensures that all rows belonging to same set are co-located. A PTF instance is able to access all rows belonging to the same set. In other words: The virtual processor is scoped by a key context.

It is also possible not to provide a key (OPTIONAL_PARTITION_BY), in which case only one virtual processor handles the entire table, thereby losing scalability benefits.

OPTIONAL_PARTITION_BY

public static final ArgumentTrait OPTIONAL_PARTITION_BY

Defines that a PARTITION BY clause is optional for TABLE_AS_SET. By default, it is mandatory for improving the parallel execution by distributing the table by key.

PASS_COLUMNS_THROUGH

public static final ArgumentTrait PASS_COLUMNS_THROUGH

Defines that all columns of a table argument (i.e. TABLE_AS_ROW or TABLE_AS_SET) are included in the output of the PTF. By default, only columns of the PARTITION BY clause are passed through.

Given a table t (containing columns k and v), and a PTF f() (producing columns c1 and c2), the output of a SELECT * FROM f(tableArg => TABLE t PARTITION BY k) uses the following order:

     Default: | k | c1 | c2 |
     With pass-through columns: | k | v | c1 | c2 |
 

In case of multiple table arguments, pass-through columns are added according to the declaration order in the PTF signature.

Method Detail

values

public static ArgumentTrait[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (ArgumentTrait c : ArgumentTrait.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static ArgumentTrait valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null

isRoot

public boolean isRoot()

toStaticTrait

public StaticArgumentTrait toStaticTrait()