Attribute Expression

Attribute is a leaf (i.e. no children) named expression.

Note
 A QueryPlan uses Attributes to build the schema of the query (it represents).
Table 1. Attribute Properties and Their Behaviour (Inherited from Expression)
Property Behaviour

references

A one-element collection with itself.

toAttribute

Self-reference

Attribute abstract class defines three additional "builder" methods.

Table 2. Attribute Expression Builder Methods
Name Description

withNullability

Sets

withQualifier

Sets

withName

Sets
Note
 Attribute is the base expression for AttributeReference, UnresolvedAttribute, and PrettyAttribute.

As an optimization, Attribute is marked as to not tolerate nulls, and when given a null input produces a null output.

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