Package dev.frostlake.executor.expressions

Class PriorExpression

java.lang.Object

dev.frostlake.executor.expressions.ColumnReferenceExpression

dev.frostlake.executor.expressions.PriorExpression

All Implemented Interfaces:

Expression

public class PriorExpression
extends ColumnReferenceExpression

PRIOR <column> inside a CONNECT BY predicate: the column's value on the PARENT row of the hierarchy step being considered, as opposed to the candidate child row every other reference reads.

The hierarchy expansion evaluates the predicate against a combined row that carries the candidate's values followed by the parent's, exposed under PRIOR_PREFIX-prefixed column names — so this is modelled as an ordinary ColumnReferenceExpression to that prefixed name and every consumer that pattern-matches on column references (equi-key extraction, GROUP BY resolution, the AST printer) keeps working unchanged. Outside a CONNECT BY the prefixed column does not exist, and the evaluator turns the lookup failure into an explicit "PRIOR is only allowed in a CONNECT BY clause" error.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	PRIOR_PREFIX	Prefix of the synthesized parent-row column names produced by the CONNECT BY expansion.

Constructor Summary

Constructors

Constructor	Description
PriorExpression(String baseColumnName)

Method Summary

Modifier and Type	Method	Description
String	getBaseColumnName()	The column name as written after PRIOR, for error messages.
String	toString()

Methods inherited from class dev.frostlake.executor.expressions.ColumnReferenceExpression

accept, describeStar, getColumnName, getPosition, getPositionalOrdinal, getStarArgument, getTableName, getWrittenName, isQualified, setWrittenName

Methods inherited from class java.lang.Object

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

Field Details

PRIOR_PREFIX

public static final String PRIOR_PREFIX

Prefix of the synthesized parent-row column names produced by the CONNECT BY expansion.

See Also:

• Constant Field Values

Constructor Details

PriorExpression

public PriorExpression(String baseColumnName)

Method Details

getBaseColumnName

public String getBaseColumnName()

The column name as written after PRIOR, for error messages.

toString

public String toString()

Overrides:

toString in class ColumnReferenceExpression