Package org.elasticsearch.xpack.esql.core.expression

Class Alias

java.lang.Object

org.elasticsearch.xpack.esql.core.tree.Node<Expression>

org.elasticsearch.xpack.esql.core.expression.Expression

org.elasticsearch.xpack.esql.core.expression.NamedExpression

org.elasticsearch.xpack.esql.core.expression.Alias

All Implemented Interfaces:

NamedWriteable, Writeable, Resolvable

public final class Alias
extends NamedExpression

An Alias is a NamedExpression that gets renamed to something else through the Alias.

For example, in the statement 5 + 2 AS x, x is an alias which is points to ADD(5, 2). And in SELECT col AS x "col" is a named expression that gets renamed to "x" through an alias.

Note on equality: The id is respected in NamedExpression.equals(Object) for Alias because the ReferenceAttribute created by toAttribute() uses it.

Nested Class Summary

Nested classes/interfaces inherited from class org.elasticsearch.xpack.esql.core.expression.Expression

Expression.TypeResolution

Nested classes/interfaces inherited from interface org.elasticsearch.common.io.stream.Writeable

Writeable.Reader<V>, Writeable.Writer<V>

Field Summary

Fields

Modifier and Type	Field	Description
static final NamedWriteableRegistry.Entry	ENTRY

Fields inherited from class org.elasticsearch.xpack.esql.core.tree.Node

TO_STRING_MAX_WIDTH

Constructor Summary

Constructors

Constructor	Description
Alias(StreamInput in)
Alias(Source source, String name, Expression child)
Alias(Source source, String name, Expression child, NameId id)
Alias(Source source, String name, Expression child, NameId id, boolean synthetic)

Method Summary

Modifier and Type	Method	Description
Expression	child()
DataType	dataType()	The DataType returned by executing the tree rooted at this expression.
String	getWriteableName()
protected NodeInfo<Alias>	info()	Normally, you want to use one of the static create methods to implement this.
String	nodeString()
Nullability	nullable()
Alias	replaceChild(Expression child)
Alias	replaceChildren(List<Expression> newChildren)
protected Expression.TypeResolution	resolveType()	The implementation of Expression.typeResolved(), which is just a caching wrapper around this method.
Attribute	toAttribute()	Try to return either this if it is an Attribute, or a ReferenceAttribute to it otherwise.
String	toString()
static Expression	unwrap(Expression e)	If the given expression is an alias, return its child - otherwise return as is.
Alias	withId(NameId id)
void	writeTo(StreamOutput out)

Methods inherited from class org.elasticsearch.xpack.esql.core.expression.NamedExpression

equals, equals, hashCode, hashCode, id, innerEquals, innerHashCode, name, synthetic

Methods inherited from class org.elasticsearch.xpack.esql.core.expression.Expression

canonical, canonicalize, childrenResolved, fold, foldable, propertiesToString, references, resolved, semanticEquals, semanticHash, typeResolved

Methods inherited from class org.elasticsearch.xpack.esql.core.tree.Node

anyMatch, children, collect, collectFirstChildren, collectLeaves, doCollectFirst, forEachDown, forEachDown, forEachDownMayReturnEarly, forEachProperty, forEachPropertyDown, forEachPropertyOnly, forEachPropertyUp, forEachUp, forEachUp, nodeName, nodeProperties, replaceChildrenSameSize, source, sourceLocation, sourceText, transformChildren, transformDown, transformDown, transformDown, transformNodeProps, transformPropertiesDown, transformPropertiesOnly, transformPropertiesUp, transformUp, transformUp, transformUp

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Details

ENTRY

public static final NamedWriteableRegistry.Entry ENTRY

Constructor Details

Alias

public Alias(Source source,
 String name,
 Expression child)

Alias

public Alias(Source source,
 String name,
 Expression child,
 @Nullable
 NameId id)

Alias

public Alias(Source source,
 String name,
 Expression child,
 @Nullable
 NameId id,
 boolean synthetic)

Alias

public Alias(StreamInput in)
      throws IOException

Throws:

IOException

Method Details

withId

public Alias withId(NameId id)

writeTo

public void writeTo(StreamOutput out)
             throws IOException

Throws:

IOException

getWriteableName

public String getWriteableName()

info

protected NodeInfo<Alias> info()

Description copied from class: Node

Normally, you want to use one of the static create methods to implement this.

For QueryPlans, it is very important that the properties contain all of the expressions and references relevant to this node, and that all the properties are used in the provided constructor; otherwise query plan transformations like QueryPlan#transformExpressionsOnly(Function) will not have an effect.

Specified by:

info in class Node<Expression>

replaceChild

public Alias replaceChild(Expression child)

replaceChildren

public Alias replaceChildren(List<Expression> newChildren)

Specified by:

replaceChildren in class Node<Expression>

child

public Expression child()

nullable

public Nullability nullable()

Specified by:

nullable in class Expression

resolveType

protected Expression.TypeResolution resolveType()

Description copied from class: Expression

The implementation of Expression.typeResolved(), which is just a caching wrapper around this method. See it's javadoc for what this method should return.

Implementations will rarely interact with the Expression.TypeResolution class directly, instead usually calling the utility methods on TypeResolutions.

Implementations should fail if Expression.childrenResolved() returns false.

Overrides:

resolveType in class Expression

dataType

public DataType dataType()

Description copied from class: Expression

The DataType returned by executing the tree rooted at this expression. If Expression.typeResolved() returns an error then the behavior of this method is undefined. It may return a valid type. Or it may throw an exception. Or it may return a totally nonsensical type.

Specified by:

dataType in class Expression

toAttribute

public Attribute toAttribute()

Description copied from class: NamedExpression

Try to return either this if it is an Attribute, or a ReferenceAttribute to it otherwise. Return an UnresolvedAttribute if this is unresolved.

Specified by:

toAttribute in class NamedExpression

toString

public String toString()

Overrides:

toString in class NamedExpression

nodeString

public String nodeString()

Overrides:

nodeString in class NamedExpression

unwrap

public static Expression unwrap(Expression e)

If the given expression is an alias, return its child - otherwise return as is.