Package org.apache.qpid.server.query.engine.parsing.expression.set

Class UnionExpression<T>

java.lang.Object

org.apache.qpid.server.query.engine.parsing.expression.AbstractExpressionNode<T,R>

org.apache.qpid.server.query.engine.parsing.expression.set.AbstractSetExpression<T,Stream<Map<String,Object>>>

org.apache.qpid.server.query.engine.parsing.expression.set.UnionExpression<T>

Type Parameters:

T - Input parameter type

All Implemented Interfaces:

Function<T,Stream<Map<String,Object>>>, Expression<T,Stream<Map<String,Object>>>, ExpressionNode<T,Stream<Map<String,Object>>>, SetExpression<T,Stream<Map<String,Object>>>

public class UnionExpression<T>
extends AbstractSetExpression<T,Stream<Map<String,Object>>>

Set UNION expression is used to combine the results of two or more SELECT statements. Every SELECT statement within UNION must have the same number of columns. The UNION operator selects all values by default. To eliminate duplicates, UNION DISTINCT should be used.

Field Summary

Fields inherited from class org.apache.qpid.server.query.engine.parsing.expression.set.AbstractSetExpression

_distinct

Fields inherited from class org.apache.qpid.server.query.engine.parsing.expression.AbstractExpressionNode

_metadata

Constructor Summary

Constructors

Constructor	Description
UnionExpression(boolean distinct, ExpressionNode<T,Stream<Map<String,Object>>> left, ExpressionNode<T,Stream<Map<String,Object>>> right)	Constructor initializes children expression list

Method Summary

Modifier and Type	Method	Description
Stream<Map<String,Object>>	apply(T value)	Performs UNION operation on both set expressions

Methods inherited from class org.apache.qpid.server.query.engine.parsing.expression.set.AbstractSetExpression

getProjections, getSelections

Methods inherited from class org.apache.qpid.server.query.engine.parsing.expression.AbstractExpressionNode

containsAggregation, ctx, evaluateChild, getAggregations, getAlias, getChild, getChildren, getParent, isAccessor, isInstantlyEvaluable, setAlias, setParent, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.qpid.server.query.engine.parsing.expression.Expression

andThen

Methods inherited from interface org.apache.qpid.server.query.engine.parsing.expression.ExpressionNode

containsAggregation, getAggregations, getAlias, getChildren, getParent, isAccessor, isInstantlyEvaluable, setAlias, setParent

Methods inherited from interface java.util.function.Function

andThen, compose

Constructor Detail

UnionExpression

public UnionExpression(boolean distinct,
                       ExpressionNode<T,Stream<Map<String,Object>>> left,
                       ExpressionNode<T,Stream<Map<String,Object>>> right)

Constructor initializes children expression list

Parameters:

distinct - Distinct flag

left - Left expression

right - Right expression

Method Detail

apply

public Stream<Map<String,Object>> apply(T value)

Performs UNION operation on both set expressions

Parameters:

value - Object to handle

Returns:

Stream combining entities from both expressions