gudusoft.gsqlparser.resolver2.expansion

Class StarColumnExpander

Object

gudusoft.gsqlparser.resolver2.expansion.StarColumnExpander

public class StarColumnExpander
extends Object

Expands SELECT * to explicit column lists.

Star expansion is crucial for: - Understanding exactly which columns are selected - Data lineage tracking - Query refactoring - Schema evolution analysis

Supports multiple star expansion scenarios: 1. Simple star: SELECT * FROM t1 2. Qualified star: SELECT t1.* FROM t1 JOIN t2 3. Multiple stars: SELECT t1.*, t2.* FROM t1 JOIN t2 4. Mixed: SELECT t1.*, t2.id FROM t1 JOIN t2 5. Nested: SELECT * FROM (SELECT * FROM t1) sub

Example:

 -- Input:
 SELECT * FROM employees

 -- Expanded (if metadata available):
 SELECT employees.id, employees.name, employees.salary
 FROM employees
 

Constructor Summary

Constructors

Constructor and Description
StarColumnExpander()
StarColumnExpander(boolean includeTableQualifier, boolean expandSubqueries)

Method Summary

Modifier and Type	Method and Description
ExpansionResult	expandAllStars(List<TResultColumn> resultColumns, List<INamespace> availableNamespaces) Expand all stars in a result column list.
List<ExpandedColumn>	expandQualifiedStar(TResultColumn starColumn, INamespace namespace, String tableAlias) Expand qualified star (e.g., t1.*) to explicit column list.
List<ExpandedColumn>	expandStar(TResultColumn starColumn, INamespace namespace) Expand a star column to explicit column list.

Methods inherited from class Object

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

Constructor Detail

StarColumnExpander

public StarColumnExpander()

StarColumnExpander

public StarColumnExpander(boolean includeTableQualifier,
                          boolean expandSubqueries)

Method Detail

expandStar

public List<ExpandedColumn> expandStar(TResultColumn starColumn,
                                       INamespace namespace)

Expand a star column to explicit column list.

Parameters:

starColumn - the star column (SELECT *)

namespace - the namespace to expand from

Returns:

list of expanded columns, or empty if expansion not possible

expandQualifiedStar

public List<ExpandedColumn> expandQualifiedStar(TResultColumn starColumn,
                                                INamespace namespace,
                                                String tableAlias)

Expand qualified star (e.g., t1.*) to explicit column list.

Parameters:

starColumn - the star column (SELECT t1.*)

namespace - the namespace to expand from

tableAlias - the table qualifier (e.g., "t1")

Returns:

list of expanded columns, or empty if expansion not possible

expandAllStars

public ExpansionResult expandAllStars(List<TResultColumn> resultColumns,
                                      List<INamespace> availableNamespaces)

Expand all stars in a result column list.

Parameters:

resultColumns - the result columns

availableNamespaces - list of available namespaces to expand from

Returns:

expansion result with all expanded columns