[SPARK-12935][SQL] DataFrame API for Count-Min Sketch

This PR integrates Count-Min Sketch from spark-sketch into DataFrame. This version resorts to `RDD.aggregate` for building the sketch. A more performant UDAF version can be built in future follow-up PRs.

Author: Cheng Lian <lian@databricks.com>

Closes #10911 from liancheng/cms-df-api.

3 files changed, 56 insertions, 36 deletions

diff --git a/common/sketch/src/main/java/org/apache/spark/util/sketch/BloomFilter.java b/common/sketch/src/main/java/org/apache/spark/util/sketch/BloomFilter.java
index 00378d5851..d392fb187a 100644
--- a/common/sketch/src/main/java/org/apache/spark/util/sketch/BloomFilter.java
+++ b/common/sketch/src/main/java/org/apache/spark/util/sketch/BloomFilter.java
@@ -47,10 +47,12 @@ public abstract class BloomFilter {
   public enum Version {
     /**
      * {@code BloomFilter} binary format version 1 (all values written in big-endian order):
-     * - Version number, always 1 (32 bit)
-     * - Total number of words of the underlying bit array (32 bit)
-     * - The words/longs (numWords * 64 bit)
-     * - Number of hash functions (32 bit)
+     * <ul>
+     *   <li>Version number, always 1 (32 bit)</li>
+     *   <li>Total number of words of the underlying bit array (32 bit)</li>
+     *   <li>The words/longs (numWords * 64 bit)</li>
+     *   <li>Number of hash functions (32 bit)</li>
+     * </ul>
      */
     V1(1);
 
diff --git a/common/sketch/src/main/java/org/apache/spark/util/sketch/CountMinSketch.java b/common/sketch/src/main/java/org/apache/spark/util/sketch/CountMinSketch.java
index 00c0b1b9e2..5692e574d4 100644
--- a/common/sketch/src/main/java/org/apache/spark/util/sketch/CountMinSketch.java
+++ b/common/sketch/src/main/java/org/apache/spark/util/sketch/CountMinSketch.java
@@ -59,16 +59,22 @@ abstract public class CountMinSketch {
   public enum Version {
     /**
      * {@code CountMinSketch} binary format version 1 (all values written in big-endian order):
-     * - Version number, always 1 (32 bit)
-     * - Total count of added items (64 bit)
-     * - Depth (32 bit)
-     * - Width (32 bit)
-     * - Hash functions (depth * 64 bit)
-     * - Count table
-     *   - Row 0 (width * 64 bit)
-     *   - Row 1 (width * 64 bit)
-     *   - ...
-     *   - Row depth - 1 (width * 64 bit)
+     * <ul>
+     *   <li>Version number, always 1 (32 bit)</li>
+     *   <li>Total count of added items (64 bit)</li>
+     *   <li>Depth (32 bit)</li>
+     *   <li>Width (32 bit)</li>
+     *   <li>Hash functions (depth * 64 bit)</li>
+     *   <li>
+     *     Count table
+     *     <ul>
+     *       <li>Row 0 (width * 64 bit)</li>
+     *       <li>Row 1 (width * 64 bit)</li>
+     *       <li>...</li>
+     *       <li>Row {@code depth - 1} (width * 64 bit)</li>
+     *     </ul>
+     *   </li>
+     * </ul>
      */
     V1(1);
 
diff --git a/common/sketch/src/main/java/org/apache/spark/util/sketch/CountMinSketchImpl.java b/common/sketch/src/main/java/org/apache/spark/util/sketch/CountMinSketchImpl.java
index d08809605a..8cc29e4076 100644
--- a/common/sketch/src/main/java/org/apache/spark/util/sketch/CountMinSketchImpl.java
+++ b/common/sketch/src/main/java/org/apache/spark/util/sketch/CountMinSketchImpl.java
@@ -21,13 +21,16 @@ import java.io.DataInputStream;
 import java.io.DataOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
 import java.io.OutputStream;
+import java.io.Serializable;
 import java.io.UnsupportedEncodingException;
 import java.util.Arrays;
 import java.util.Random;
 
-class CountMinSketchImpl extends CountMinSketch {
-  public static final long PRIME_MODULUS = (1L << 31) - 1;
+class CountMinSketchImpl extends CountMinSketch implements Serializable {
+  private static final long PRIME_MODULUS = (1L << 31) - 1;
 
   private int depth;
   private int width;
@@ -37,6 +40,9 @@ class CountMinSketchImpl extends CountMinSketch {
   private double eps;
   private double confidence;
 
+  private CountMinSketchImpl() {
+  }
+
   CountMinSketchImpl(int depth, int width, int seed) {
     this.depth = depth;
     this.width = width;
@@ -55,16 +61,6 @@ class CountMinSketchImpl extends CountMinSketch {
     initTablesWith(depth, width, seed);
   }
 
-  CountMinSketchImpl(int depth, int width, long totalCount, long hashA[], long table[][]) {
-    this.depth = depth;
-    this.width = width;
-    this.eps = 2.0 / width;
-    this.confidence = 1 - 1 / Math.pow(2, depth);
-    this.hashA = hashA;
-    this.table = table;
-    this.totalCount = totalCount;
-  }
-
   @Override
   public boolean equals(Object other) {
     if (other == this) {
@@ -325,27 +321,43 @@ class CountMinSketchImpl extends CountMinSketch {
   }
 
   public static CountMinSketchImpl readFrom(InputStream in) throws IOException {
+    CountMinSketchImpl sketch = new CountMinSketchImpl();
+    sketch.readFrom0(in);
+    return sketch;
+  }
+
+  private void readFrom0(InputStream in) throws IOException {
     DataInputStream dis = new DataInputStream(in);
 
-    // Ignores version number
-    dis.readInt();
+    int version = dis.readInt();
+    if (version != Version.V1.getVersionNumber()) {
+      throw new IOException("Unexpected Count-Min Sketch version number (" + version + ")");
+    }
 
-    long totalCount = dis.readLong();
-    int depth = dis.readInt();
-    int width = dis.readInt();
+    this.totalCount = dis.readLong();
+    this.depth = dis.readInt();
+    this.width = dis.readInt();
+    this.eps = 2.0 / width;
+    this.confidence = 1 - 1 / Math.pow(2, depth);
 
-    long hashA[] = new long[depth];
+    this.hashA = new long[depth];
     for (int i = 0; i < depth; ++i) {
-      hashA[i] = dis.readLong();
+      this.hashA[i] = dis.readLong();
     }
 
-    long table[][] = new long[depth][width];
+    this.table = new long[depth][width];
     for (int i = 0; i < depth; ++i) {
       for (int j = 0; j < width; ++j) {
-        table[i][j] = dis.readLong();
+        this.table[i][j] = dis.readLong();
       }
     }
+  }
+
+  private void writeObject(ObjectOutputStream out) throws IOException {
+    this.writeTo(out);
+  }
 
-    return new CountMinSketchImpl(depth, width, totalCount, hashA, table);
+  private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
+    this.readFrom0(in);
   }
 }