From 5060edbbe1bb40f99a77aba7fe1dc3c6af45dbf8 Mon Sep 17 00:00:00 2001
From: Goun Na <gounna@gmail.com>
Date: Mon, 29 Sep 2025 02:04:16 +0900
Subject: [PATCH] undirected edge

---
 .../scala/org/graphframes/GraphFrame.scala    | 21 +++++++--
 .../org/graphframes/PatternMatchSuite.scala   | 45 +++++++++++++++++++
 2 files changed, 63 insertions(+), 3 deletions(-)

diff --git a/core/src/main/scala/org/graphframes/GraphFrame.scala b/core/src/main/scala/org/graphframes/GraphFrame.scala
index e753d422c..8d5b5b112 100644
--- a/core/src/main/scala/org/graphframes/GraphFrame.scala
+++ b/core/src/main/scala/org/graphframes/GraphFrame.scala
@@ -373,9 +373,11 @@ class GraphFrame private (
    * @group motif
    */
   def find(pattern: String): DataFrame = {
-    val VarLengthPattern = """\((\w+)\)-\[(\w*)\*(\d*)\.\.(\d*)\]->\((\w+)\)""".r
+    val VarLengthPattern = """\((\w+)\)-\[(\w*)\*(\d*)\.\.(\d*)\]-(>?)\((\w+)\)""".r
+    val UndirectedPattern = """\((\w+)\)-\[(\w*)\]-\((\w+)\)""".r
+
     pattern match {
-      case VarLengthPattern(src, name, min, max, dst) =>
+      case VarLengthPattern(src, name, min, max, direction, dst) =>
         if (min.isEmpty || max.isEmpty) {
           throw new InvalidParseException(
             s"Unbounded length patten ${pattern} is not supported! " +
@@ -384,9 +386,22 @@ class GraphFrame private (
         val strToSeq: Seq[String] = (min.toInt to max.toInt).reverse.map { hop =>
           s"($src)-[$name*$hop]->($dst)"
         }
-        strToSeq
+        val strToSeqReverse: Seq[String] = if (direction.isEmpty) {
+          (min.toInt to max.toInt).reverse.map(hop => s"($dst)-[$name*$hop]->($src)")
+        } else {
+          Seq.empty[String]
+        }
+
+        (strToSeq ++ strToSeqReverse)
           .map(findAugmentedPatterns)
           .reduce((a, b) => a.unionByName(b, allowMissingColumns = true))
+
+      case UndirectedPattern(src, name, dst) =>
+        val out: DataFrame = findAugmentedPatterns(s"($src)-[$name]->($dst)")
+        val in: DataFrame = findAugmentedPatterns(s"($dst)-[$name]->($src)")
+
+        out.unionByName(in)
+
       case _ =>
         findAugmentedPatterns(pattern)
     }
diff --git a/core/src/test/scala/org/graphframes/PatternMatchSuite.scala b/core/src/test/scala/org/graphframes/PatternMatchSuite.scala
index bdb413fb7..097c76fd3 100644
--- a/core/src/test/scala/org/graphframes/PatternMatchSuite.scala
+++ b/core/src/test/scala/org/graphframes/PatternMatchSuite.scala
@@ -658,6 +658,51 @@ class PatternMatchSuite extends SparkFunSuite with GraphFrameTestSparkContext {
     assert(varEdge.except(unionEdge).isEmpty && unionEdge.except(varEdge).isEmpty)
   }
 
+  test("undirected edge") {
+    val res = g
+      .find("(u)-[]-(v)")
+      .where("u.id == 0")
+      .select("u.id", "v.id")
+      .collect()
+      .toSet
+
+    val expected = Set(Row(0L, 1L), Row(0L, 2L))
+
+    compareResultToExpected(res, expected)
+  }
+
+  test("undirected with edge name") {
+    val res = g
+      .find("(u)-[e]-(v)")
+      .where("u.id == 0")
+      .select("e.src", "e.dst", "e.relationship")
+      .collect()
+      .toSet
+
+    val expected = Set(Row(0L, 1L, "friend"), Row(1L, 0L, "follow"), Row(2L, 0L, "unknown"))
+
+    compareResultToExpected(res, expected)
+  }
+
+  test("undirected var-length pattern") {
+    val res = g
+      .find("(u)-[e*1..3]-(v)")
+      .where("u.id == 2")
+
+    val df1 = g
+      .find("(u)-[e*1..3]->(v)")
+      .where("u.id == 2")
+
+    val df2 = g
+      .find("(v)-[e*1..3]->(u)")
+      .where("u.id == 2")
+
+    val expected = df1.unionByName(df2, allowMissingColumns = true)
+
+    assert(res.schema === expected.schema)
+    assert(res.except(expected).isEmpty && expected.except(res).isEmpty)
+  }
+
   test("stateful predicates via UDFs") {
     val chain4 = g
       .find("(a)-[ab]->(b); (b)-[bc]->(c); (c)-[cd]->(d)")