一些高阶函数可以做到这一点。需要Spark>=2.4。

val df2 = df.withColumn(
    "group_ids", 
    expr("""
        filter(
            transform(
                flatten(
                    transform(
                        group_ids, 
                        x -> arrays_zip(
                            array_repeat(x, size(group_ids)), 
                            group_ids
                        )
                    )
                ), 
                x -> array(x['0'], x['group_ids'])
            ), 
            x -> x[0] < x[1]
        )
    """)
)

df2.show(false)
+-------+------------------------+
|user_id|group_ids               |
+-------+------------------------+
|1      |[[5, 8]]                |
|3      |[[1, 2], [1, 3], [2, 3]]|
|2      |[[1, 4]]                |
+-------+------------------------+

基于 explode 以及 joins 解决方案

val exploded = df.select(col("user_id"), explode(col("group_ids")).as("e"))

// to have combinations
val joined1 = exploded.as("t1")
                      .join(exploded.as("t2"), Seq("user_id"), "outer")
                      .select(col("user_id"), col("t1.e").as("e1"), col("t2.e").as("e2"))

// to filter out redundant combinations
val joined2 = joined1.as("t1")
                     .join(joined1.as("t2"), $"t1.user_id" === $"t2.user_id" && $"t1.e1" === $"t2.e2" && $"t1.e2"=== $"t2.e1")
                     .where("t1.e1 < t2.e1")
                     .select("t1.*")

// group into array
val result = joined2.groupBy("user_id")
                    .agg(collect_set(struct("e1", "e2")).as("group_ids"))

可以得到列的最大大小 group_ids . 然后，在范围内使用组合 (1 - maxSize) 与 when 表达式从原始数组创建子数组组合，并最终从结果数组中筛选空元素：

val maxSize = df.select(max(size($"group_ids"))).first.getAs[Int](0)

val newCol = (1 to maxSize).combinations(2)
  .map(c =>
    when(
      size($"group_ids") >= c(1),
      array(element_at($"group_ids", c(0)), element_at($"group_ids", c(1)))
    )
  ).toSeq

df.withColumn("group_ids", array(newCol: _*))
  .withColumn("group_ids", expr("filter(group_ids, x -> x is not null)"))
  .show(false)

//+-------+------------------------+
//|user_id|group_ids               |
//+-------+------------------------+
//|1      |[[5, 8]]                |
//|3      |[[1, 2], [1, 3], [2, 3]]|
//|2      |[[1, 4]]                |
//+-------+------------------------+