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feat: method to transform graph to undirected #705

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Merged
SemyonSinchenko merged 1 commit into from
Sep 24, 2025
Merged

feat: method to transform graph to undirected #705

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20 changes: 20 additions & 0 deletions core/src/main/scala/org/graphframes/GraphFrame.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -656,6 +656,26 @@ class GraphFrame private (
*/
def detectingCycles: DetectingCycles = new DetectingCycles(this)

/**
* Converts the directed graph into an undirected graph by ensuring that all directed edges are
* bidirectional. For every directed edge (src, dst), a corresponding edge (dst, src) is added.
*
* @return
* a new GraphFrame representing the undirected graph.
*/
def asUndirected(): GraphFrame = {
val newEdges = edges
.select(col(SRC), col(DST), nestAsCol(edges, ATTR))
.union(edges
.select(col(DST).alias(SRC), col(SRC).alias(DST), nestAsCol(edges, ATTR)))
.select(SRC, DST, ATTR)
val newColumns = Seq(col(SRC), col(DST)) ++ edges.columns
.filter(c => (c != SRC) && (c != DST))
.map(c => col(ATTR).getField(c).alias(c))
.toSeq
GraphFrame(vertices, newEdges.select(newColumns: _*))
}

// ========= Motif finding (private) =========

/**
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36 changes: 36 additions & 0 deletions core/src/test/scala/org/graphframes/GraphFrameSuite.scala
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Expand Up @@ -413,4 +413,40 @@ class GraphFrameSuite extends SparkFunSuite with GraphFrameTestSparkContext {
.toSeq
assert(Seq(0, 0, 0, 0, 1, 0) == clusters)
}

test("convert directed graph to undirected") {
val v = spark.createDataFrame(Seq((1L, "a"), (2L, "b"), (3L, "c"))).toDF("id", "name")
val e = spark.createDataFrame(Seq((1L, 2L), (2L, 3L))).toDF("src", "dst")
val g = GraphFrame(v, e)
val undirected = g.asUndirected()

// Check edge count doubled
assert(undirected.edges.count() === 2 * g.edges.count())

// Verify reverse edges exist
val edges = undirected.edges.sort("src", "dst").collect()
assert(edges.length === 4)
assert(edges(0).getLong(0) === 1L)
assert(edges(0).getLong(1) === 2L)
assert(edges(1).getLong(0) === 2L)
assert(edges(1).getLong(1) === 1L)
assert(edges(2).getLong(0) === 2L)
assert(edges(2).getLong(1) === 3L)
assert(edges(3).getLong(0) === 3L)
assert(edges(3).getLong(1) === 2L)
}

test("convert directed graph with edge attributes to undirected") {
val v = spark.createDataFrame(Seq((1L, "a"), (2L, "b"))).toDF("id", "name")
val e = spark.createDataFrame(Seq((1L, 2L, "edge1"))).toDF("src", "dst", "attr")
val g = GraphFrame(v, e)
val undirected = g.asUndirected()

val edges = undirected.edges.collect()
assert(edges.length === 2)
assert(
edges.exists(r => r.getLong(0) == 1L && r.getLong(1) == 2L && r.getString(2) == "edge1"))
assert(
edges.exists(r => r.getLong(0) == 2L && r.getLong(1) == 1L && r.getString(2) == "edge1"))
}
}