feat(algo): add Leiden community detection with multi-table support

algo/src/function/CMakeLists.txt

@@ -9,6 +9,7 @@ add_library(lbug_algo_function
         page_rank.cpp
         k_core_decomposition.cpp
         louvain.cpp
+        leiden.cpp
         spanning_forest.cpp
         )
 

algo/src/include/function/leiden.h

@@ -0,0 +1,21 @@
+#pragma once
+
+#include "function/function.h"
+
+namespace lbug {
+namespace algo_extension {
+
+struct LeidenFunction {
+    static constexpr const char* name = "LEIDEN";
+
+    static function::function_set getFunctionSet();
+};
+
+struct LeidenAliasFunction {
+    using alias = LeidenFunction;
+
+    static constexpr const char* name = "LE";
+};
+
+} // namespace algo_extension
+} // namespace lbug

algo/src/main/algo_extension.cpp

@@ -1,6 +1,7 @@
 #include "main/algo_extension.h"
 
 #include "function/algo_function.h"
+#include "function/leiden.h"
 #include "main/client_context.h"
 
 namespace lbug {
@@ -21,6 +22,8 @@ void AlgoExtension::load(main::ClientContext* context) {
     ExtensionUtils::addTableFunc<KCoreDecompositionFunction>(db);
     ExtensionUtils::addTableFuncAlias<KCoreDecompositionAliasFunction>(db);
     ExtensionUtils::addTableFunc<LouvainFunction>(db);
+    ExtensionUtils::addTableFunc<LeidenFunction>(db);
+    ExtensionUtils::addTableFuncAlias<LeidenAliasFunction>(db);
     ExtensionUtils::addTableFunc<SpanningForest>(db);
     ExtensionUtils::addTableFuncAlias<SpanningForestAliasFunction>(db);
 }

algo/test/test_files/leiden.test

@@ -0,0 +1,89 @@
+-DATASET CSV empty
+
+--
+
+-CASE LeidenBasic
+-LOAD_DYNAMIC_EXTENSION algo
+-STATEMENT CREATE NODE TABLE Node(id INT64 PRIMARY KEY);
+---- ok
+-STATEMENT CREATE REL TABLE Edge(FROM Node to Node);
+---- ok
+-STATEMENT CREATE (u0:Node {id: 0}),
+            (u1:Node {id: 1}),
+            (u2:Node {id: 2}),
+            (u3:Node {id: 3}),
+            (u4:Node {id: 4}),
+            (u5:Node {id: 5}),
+            (u6:Node {id: 6}),
+            (u7:Node {id: 7}),
+            (u8:Node {id: 8}),
+            (u9:Node {id: 9}),
+            (u0)-[:Edge]->(u1),
+            (u0)-[:Edge]->(u2),
+            (u1)-[:Edge]->(u2),
+            (u2)-[:Edge]->(u3),
+            (u3)-[:Edge]->(u4),
+            (u5)-[:Edge]->(u6),
+            (u5)-[:Edge]->(u7),
+            (u6)-[:Edge]->(u7),
+            (u7)-[:Edge]->(u8),
+            (u8)-[:Edge]->(u9),
+            (u2)-[:Edge]->(u5),
+            (u4)-[:Edge]->(u9);
+---- ok
+-STATEMENT CALL PROJECT_GRAPH('Graph', ['Node'], ['Edge'])
+---- ok
+
+# RED test: Leiden should return communities (same graph as Louvain test)
+# All 10 nodes must get a community assignment.
+-STATEMENT CALL LEIDEN('Graph') RETURN count(*) AS c;
+---- 1
+10
+
+-CASE LeidenAlias
+-LOAD_DYNAMIC_EXTENSION algo
+-STATEMENT CREATE NODE TABLE Node(id INT64 PRIMARY KEY);
+---- ok
+-STATEMENT CREATE REL TABLE Edge(FROM Node to Node);
+---- ok
+-STATEMENT CREATE (u0:Node {id: 0}),
+            (u1:Node {id: 1}),
+            (u2:Node {id: 2}),
+            (u0)-[:Edge]->(u1),
+            (u1)-[:Edge]->(u2),
+            (u0)-[:Edge]->(u2);
+---- ok
+-STATEMENT CALL PROJECT_GRAPH('Graph', ['Node'], ['Edge'])
+---- ok
+
+-STATEMENT CALL LE('Graph') RETURN count(*) AS c;
+---- 1
+3
+
+-CASE LeidenDisconnected
+-LOAD_DYNAMIC_EXTENSION algo
+-STATEMENT CREATE NODE TABLE Node(id INT64 PRIMARY KEY);
+---- ok
+-STATEMENT CREATE REL TABLE Edge(FROM Node TO Node);
+---- ok
+# Component 1
+-STATEMENT CREATE (:Node {id: 0}), (:Node {id: 1}), (:Node {id: 2});
+---- ok
+-STATEMENT MATCH (a:Node {id: 0}), (b:Node {id: 1}) CREATE (a)-[:Edge]->(b);
+---- ok
+-STATEMENT MATCH (a:Node {id: 1}), (b:Node {id: 2}) CREATE (a)-[:Edge]->(b);
+---- ok
+# Component 2 — isolated
+-STATEMENT CREATE (:Node {id: 10}), (:Node {id: 11}), (:Node {id: 12});
+---- ok
+-STATEMENT MATCH (a:Node {id: 10}), (b:Node {id: 11}) CREATE (a)-[:Edge]->(b);
+---- ok
+-STATEMENT MATCH (a:Node {id: 11}), (b:Node {id: 12}) CREATE (a)-[:Edge]->(b);
+---- ok
+-STATEMENT CALL PROJECT_GRAPH('Graph', ['Node'], ['Edge'])
+---- ok
+
+# Two disconnected components → 2 different community IDs
+-STATEMENT CALL LEIDEN('Graph') WITH community_id, count(*) as cnt RETURN count(distinct community_id) as num_communities;
+---- 1
+2

algo/test/test_files/leiden_heterogeneous.test

@@ -0,0 +1,43 @@
+-DATASET CSV empty
+
+--
+
+# Leiden on a heterogeneous projected graph (two node tables + one edge table).
+# Regression test for the array out-of-bounds assertion that occurred when
+# PhaseState arrays were sized for only the first node table.
+
+-CASE LeidenHeterogeneous
+-LOAD_DYNAMIC_EXTENSION algo
+-STATEMENT CREATE NODE TABLE T(id INT64 PRIMARY KEY, name STRING);
+---- ok
+-STATEMENT CREATE NODE TABLE M(id INT64 PRIMARY KEY, name STRING);
+---- ok
+-STATEMENT CREATE REL TABLE E(FROM T TO M);
+---- ok
+-STATEMENT CREATE (:T {id: 0, name: 't0'}),
+            (:T {id: 1, name: 't1'}),
+            (:T {id: 2, name: 't2'});
+---- ok
+-STATEMENT CREATE (:M {id: 0, name: 'm0'}),
+            (:M {id: 1, name: 'm1'}),
+            (:M {id: 2, name: 'm2'});
+---- ok
+-STATEMENT MATCH (t:T {id: 0}), (m:M {id: 0}), (m2:M {id: 1})
+            CREATE (t)-[:E]->(m), (t)-[:E]->(m2);
+---- ok
+-STATEMENT MATCH (t:T {id: 1}), (m:M {id: 1}), (m2:M {id: 2})
+            CREATE (t)-[:E]->(m), (t)-[:E]->(m2);
+---- ok
+-STATEMENT MATCH (t:T {id: 2}), (m:M {id: 0}), (m2:M {id: 2})
+            CREATE (t)-[:E]->(m), (t)-[:E]->(m2);
+---- ok
+-STATEMENT CALL PROJECT_GRAPH('hg', ['T', 'M'], ['E']);
+---- ok
+# All 6 nodes (3 T + 3 M) must get a community assignment.
+-STATEMENT CALL leiden('hg') RETURN count(*) AS c;
+---- 1
+6
+# Communities must be valid community ids (0 <= id < numNodes).
+-STATEMENT CALL leiden('hg') RETURN max(community_id) < 6 AS valid;
+---- 1
+True