improve performance, address comments

Author: Davies Liu

core/src/main/scala/org/apache/spark/api/python/PythonRDD.scala

@@ -77,30 +77,42 @@ private[spark] case class PythonFunction(
     broadcastVars: JList[Broadcast[PythonBroadcast]],
     accumulator: Accumulator[JList[Array[Byte]]])
 
+/**
+ * A wrapper for chained Python functions (from bottom to top).
+ * @param funcs
+ */
+private[spark] case class ChainedPythonFunctions(funcs: Seq[PythonFunction])
 
-object PythonRunner {
+private[spark] object PythonRunner {
   def apply(func: PythonFunction, bufferSize: Int, reuse_worker: Boolean): PythonRunner = {
-    new PythonRunner(Seq(Seq(func)), bufferSize, reuse_worker, false, Seq(1))
+    new PythonRunner(
+      Seq(ChainedPythonFunctions(Seq(func))), bufferSize, reuse_worker, false, Seq(Seq(0)))
   }
 }
 
 /**
  * A helper class to run Python mapPartition/UDFs in Spark.
+ *
+ * funcs is a list of independent Python functions, each one of them is a list of chained Python
+ * functions (from bottom to top).
  */
 private[spark] class PythonRunner(
-    funcs: Seq[Seq[PythonFunction]],
+    funcs: Seq[ChainedPythonFunctions],
     bufferSize: Int,
     reuse_worker: Boolean,
     isUDF: Boolean,
-    numArgs: Seq[Int])
+    argOffsets: Seq[Seq[Int]])
   extends Logging {
 
+  require(funcs.length == argOffsets.length, "numArgs should have the same length as funcs")
+
   // All the Python functions should have the same exec, version and envvars.
-  private val envVars = funcs.head.head.envVars
-  private val pythonExec = funcs.head.head.pythonExec
-  private val pythonVer = funcs.head.head.pythonVer
+  private val envVars = funcs.head.funcs.head.envVars
+  private val pythonExec = funcs.head.funcs.head.pythonExec
+  private val pythonVer = funcs.head.funcs.head.pythonVer
 
-  private val accumulator = funcs.head.head.accumulator // TODO: support accumulator in multiple UDF
+  // TODO: support accumulator in multiple UDF
+  private val accumulator = funcs.head.funcs.head.accumulator
 
   def compute(
       inputIterator: Iterator[_],
@@ -240,8 +252,8 @@ private[spark] class PythonRunner(
 
     @volatile private var _exception: Exception = null
 
-    private val pythonIncludes = funcs.flatMap(_.flatMap(_.pythonIncludes.asScala)).toSet
-    private val broadcastVars = funcs.flatMap(_.flatMap(_.broadcastVars.asScala))
+    private val pythonIncludes = funcs.flatMap(_.funcs.flatMap(_.pythonIncludes.asScala)).toSet
+    private val broadcastVars = funcs.flatMap(_.funcs.flatMap(_.broadcastVars.asScala))
 
     setDaemon(true)
 
@@ -295,17 +307,20 @@ private[spark] class PythonRunner(
         if (isUDF) {
           dataOut.writeInt(1)
           dataOut.writeInt(funcs.length)
-          funcs.zip(numArgs).foreach { case (fs, numArg) =>
-            dataOut.writeInt(numArg)
-            dataOut.writeInt(fs.length)
-            fs.foreach { f =>
+          funcs.zip(argOffsets).foreach { case (chained, offsets) =>
+            dataOut.writeInt(offsets.length)
+            offsets.foreach { offset =>
+              dataOut.writeInt(offset)
+            }
+            dataOut.writeInt(chained.funcs.length)
+            chained.funcs.foreach { f =>
               dataOut.writeInt(f.command.length)
               dataOut.write(f.command)
             }
           }
         } else {
           dataOut.writeInt(0)
-          val command = funcs.head.head.command
+          val command = funcs.head.funcs.head.command
           dataOut.writeInt(command.length)
           dataOut.write(command)
         }

python/pyspark/worker.py

@@ -63,11 +63,13 @@ def chain(f, g):
 
 
 def wrap_udf(f, return_type):
-    return lambda *a: return_type.toInternal(f(*a))
+    toInternal = return_type.toInternal
+    return lambda *a: toInternal(f(*a))
 
 
 def read_single_udf(pickleSer, infile):
     num_arg = read_int(infile)
+    arg_offsets = [read_int(infile) for i in range(num_arg)]
     row_func = None
     for i in range(read_int(infile)):
         f, return_type = read_command(pickleSer, infile)
@@ -76,27 +78,27 @@ def read_single_udf(pickleSer, infile):
         else:
             row_func = chain(row_func, f)
     # the last returnType will be the return type of UDF
-    return num_arg, wrap_udf(row_func, return_type)
+    return arg_offsets, wrap_udf(row_func, return_type)
 
 
 def read_udfs(pickleSer, infile):
     num_udfs = read_int(infile)
-    udfs = []
-    offset = 0
-    for i in range(num_udfs):
-        num_arg, udf = read_single_udf(pickleSer, infile)
-        udfs.append((offset, offset + num_arg, udf))
-        offset += num_arg
-
     if num_udfs == 1:
-        udf = udfs[0][2]
-
         # fast path for single UDF
-        def mapper(args):
-            return udf(*args)
+        _, udf = read_single_udf(pickleSer, infile)
+        mapper = lambda a: udf(*a)
     else:
-        def mapper(args):
-            return tuple(udf(*args[start:end]) for start, end, udf in udfs)
+        udfs = {}
+        call_udf = []
+        for i in range(num_udfs):
+            arg_offsets, udf = read_single_udf(pickleSer, infile)
+            udfs['f%d' % i] = udf
+            args = ["a[%d]" % o for o in arg_offsets]
+            call_udf.append("f%d(%s)" % (i, ", ".join(args)))
+        # Create function like this:
+        #   lambda a: (f0(a0), f1(a1, a2), f2(a3))
+        mapper_str = "lambda a: (%s)" % (", ".join(call_udf))
+        mapper = eval(mapper_str, udfs)
 
     func = lambda _, it: map(mapper, it)
     ser = AutoBatchedSerializer(PickleSerializer())
@@ -149,8 +151,8 @@ def main(infile, outfile):
                 _broadcastRegistry.pop(bid)
 
         _accumulatorRegistry.clear()
-        is_udf = read_int(infile)
-        if is_udf:
+        is_sql_udf = read_int(infile)
+        if is_sql_udf:
             func, profiler, deserializer, serializer = read_udfs(pickleSer, infile)
         else:
             func, profiler, deserializer, serializer = read_command(pickleSer, infile)

sql/core/src/main/scala/org/apache/spark/sql/execution/python/BatchPythonEvaluation.scala

@@ -18,16 +18,17 @@
 package org.apache.spark.sql.execution.python
 
 import scala.collection.JavaConverters._
+import scala.collection.mutable.ArrayBuffer
 
 import net.razorvine.pickle.{Pickler, Unpickler}
 
 import org.apache.spark.TaskContext
-import org.apache.spark.api.python.{PythonFunction, PythonRunner}
+import org.apache.spark.api.python.{ChainedPythonFunctions, PythonFunction, PythonRunner}
 import org.apache.spark.rdd.RDD
 import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.execution.SparkPlan
-import org.apache.spark.sql.types.{StructField, StructType}
+import org.apache.spark.sql.types.{DataType, StructField, StructType}
 
 
 /**
@@ -45,15 +46,15 @@ case class BatchPythonEvaluation(udfs: Seq[PythonUDF], output: Seq[Attribute], c
 
   def children: Seq[SparkPlan] = child :: Nil
 
-  private def collectFunctions(udf: PythonUDF): (Seq[PythonFunction], Seq[Expression]) = {
+  private def collectFunctions(udf: PythonUDF): (ChainedPythonFunctions, Seq[Expression]) = {
     udf.children match {
       case Seq(u: PythonUDF) =>
-        val (fs, children) = collectFunctions(u)
-        (fs ++ Seq(udf.func), children)
+        val (chained, children) = collectFunctions(u)
+        (ChainedPythonFunctions(chained.funcs ++ Seq(udf.func)), children)
       case children =>
         // There should not be any other UDFs, or the children can't be evaluated directly.
         assert(children.forall(_.find(_.isInstanceOf[PythonUDF]).isEmpty))
-        (Seq(udf.func), udf.children)
+        (ChainedPythonFunctions(Seq(udf.func)), udf.children)
     }
   }
 
@@ -69,30 +70,48 @@ case class BatchPythonEvaluation(udfs: Seq[PythonUDF], output: Seq[Attribute], c
       // combine input with output from Python.
       val queue = new java.util.concurrent.ConcurrentLinkedQueue[InternalRow]()
 
-      val (pyFuncs, children) = udfs.map(collectFunctions).unzip
-      val numArgs = children.map(_.length)
+      val (pyFuncs, inputs) = udfs.map(collectFunctions).unzip
 
-      val pickle = new Pickler
+      // Most of the inputs are primitives, do not use memo for better performance
+      val pickle = new Pickler(false)
       // flatten all the arguments
-      val allChildren = children.flatMap(x => x)
-      val currentRow = newMutableProjection(allChildren, child.output)()
-      val fields = allChildren.map(_.dataType)
-      val schema = new StructType(fields.map(t => new StructField("", t, true)).toArray)
+      val allInputs = new ArrayBuffer[Expression]
+      val dataTypes = new ArrayBuffer[DataType]
+      val argOffsets = inputs.map { input =>
+        input.map { e =>
+          if (allInputs.exists(_.semanticEquals(e))) {
+            allInputs.indexWhere(_.semanticEquals(e))
+          } else {
+            allInputs += e
+            dataTypes += e.dataType
+            allInputs.length - 1
+          }
+        }
+      }
+      val projection = newMutableProjection(allInputs, child.output)()
 
       // Input iterator to Python: input rows are grouped so we send them in batches to Python.
       // For each row, add it to the queue.
-      val inputIterator = iter.grouped(100).map { inputRows =>
-        val toBePickled = inputRows.map { row =>
-          queue.add(row)
-          EvaluatePython.toJava(currentRow(row), schema)
+      val inputIterator = iter.grouped(1024).map { inputRows =>
+        val toBePickled = inputRows.map { inputRow =>
+          queue.add(inputRow)
+          val row = projection(inputRow)
+          val fields = new Array[Any](row.numFields)
+          var i = 0
+          while (i < row.numFields) {
+            val dt = dataTypes(i)
+            fields(i) = EvaluatePython.toJava(row.get(i, dt), dt)
+            i += 1
+          }
+          fields
         }.toArray
         pickle.dumps(toBePickled)
       }
 
       val context = TaskContext.get()
 
       // Output iterator for results from Python.
-      val outputIterator = new PythonRunner(pyFuncs, bufferSize, reuseWorker, true, numArgs)
+      val outputIterator = new PythonRunner(pyFuncs, bufferSize, reuseWorker, true, argOffsets)
         .compute(inputIterator, context.partitionId(), context)
 
       val unpickle = new Unpickler