gudusoft.gsqlparser.resolver2.model

Class FromScopeIndex

Object

gudusoft.gsqlparser.resolver2.model.FromScopeIndex

public class FromScopeIndex
extends Object

Index structure for fast lookups in FromScope.

This class optimizes O(N) linear scans to O(1) hash lookups for common operations like finding tables by alias/name and finding candidate namespaces for star column inference.

The index is built lazily on first access and cached for subsequent lookups. This avoids the overhead of building the index when it's not needed.

Performance improvement: For queries with N tables and M column references, reduces complexity from O(N*M) to O(N + M).

Since:

3.1.0.9

Constructor Summary

Constructors

Constructor and Description
FromScopeIndex(List<ScopeChild> children) Creates an index from the given list of scope children.

Method Summary

Modifier and Type	Method and Description
ScopeChild	findByAlias(String alias) Finds a ScopeChild by its alias (case-insensitive).
ScopeChild	findByQualifier(String qualifier) Finds a ScopeChild by alias first, then by namespace name (case-insensitive).
INamespace	findCandidateNamespace(String tablePrefix) Finds a candidate namespace for column resolution.
TTable	findTableByQualifier(String qualifier) Gets the TTable from a ScopeChild by qualifier, if the namespace represents a table.
static FromScopeIndex	fromScope(IScope scope) Creates an index from a scope, extracting the FromScope if needed.
int	getChildCount() Gets the total number of children indexed.
INamespace	getPreferredStarNamespace() Gets the first namespace that supports star columns or dynamic inference.
boolean	isEmpty() Checks if the index is empty.
String	toString()

Methods inherited from class Object

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

Constructor Detail

FromScopeIndex

public FromScopeIndex(List<ScopeChild> children)

Creates an index from the given list of scope children.

Parameters:

children - The list of ScopeChild from a FromScope

Method Detail

findByAlias

public ScopeChild findByAlias(String alias)

Finds a ScopeChild by its alias (case-insensitive).

Parameters:

alias - The alias to search for

Returns:

The matching ScopeChild, or null if not found

findByQualifier

public ScopeChild findByQualifier(String qualifier)

Finds a ScopeChild by alias first, then by namespace name (case-insensitive).

Parameters:

qualifier - The qualifier (alias or table name) to search for

Returns:

The matching ScopeChild, or null if not found

findTableByQualifier

public TTable findTableByQualifier(String qualifier)

Gets the TTable from a ScopeChild by qualifier, if the namespace represents a table.

Parameters:

qualifier - The qualifier (alias or table name) to search for

Returns:

The TTable if found and the namespace is a table, null otherwise

getPreferredStarNamespace

public INamespace getPreferredStarNamespace()

Gets the first namespace that supports star columns or dynamic inference. Used for resolving unqualified column references.

Returns:

The preferred star namespace, or null if none exists

findCandidateNamespace

public INamespace findCandidateNamespace(String tablePrefix)

Finds a candidate namespace for column resolution.

If a table prefix is provided, looks up by that prefix. Otherwise, returns the first star/dynamic namespace for unqualified columns.

Parameters:

tablePrefix - The table prefix (alias or name), or null for unqualified columns

Returns:

The candidate namespace, or null if not found

getChildCount

public int getChildCount()

Gets the total number of children indexed.

Returns:

The child count

isEmpty

public boolean isEmpty()

Checks if the index is empty.

Returns:

true if no children are indexed

fromScope

public static FromScopeIndex fromScope(IScope scope)

Creates an index from a scope, extracting the FromScope if needed.

Parameters:

scope - The scope (SelectScope, UpdateScope, or FromScope)

Returns:

A new FromScopeIndex, or null if no FromScope is found

toString

public String toString()

Overrides:

toString in class Object