TAJO-916: SubQuery::computeStatFromTasks occasionally fail.

tajo-catalog/tajo-catalog-common/src/main/java/org/apache/tajo/catalog/statistics/TableStats.java

@@ -36,8 +36,6 @@
 import java.util.List;
 
 public class TableStats implements ProtoObject<TableStatsProto>, Cloneable, GsonObject {
-  private TableStatsProto.Builder builder = TableStatsProto.newBuilder();
-
   @Expose private Long numRows = null; // required
   @Expose private Long numBytes = null; // required
   @Expose private Integer numBlocks = null; // optional
@@ -178,7 +176,6 @@ public int hashCode() {
 
   public Object clone() throws CloneNotSupportedException {
     TableStats stat = (TableStats) super.clone();
-    stat.builder = CatalogProtos.TableStatsProto.newBuilder();
     stat.numRows = numRows != null ? numRows : null;
     stat.numBytes = numBytes != null ? numBytes : null;
     stat.numBlocks = numBlocks != null ? numBlocks : null;
@@ -241,11 +238,7 @@ public String toJson() {
 
   @Override
   public TableStatsProto getProto() {
-    if (builder == null) {
-      builder = CatalogProtos.TableStatsProto.newBuilder();
-    } else {
-      builder.clear();
-    }
+    TableStatsProto.Builder builder = CatalogProtos.TableStatsProto.newBuilder();
 
     builder.setNumRows(this.numRows);
     builder.setNumBytes(this.numBytes);

tajo-catalog/tajo-catalog-common/src/test/java/org/apache/tajo/catalog/statistics/TestTableStat.java

@@ -20,11 +20,19 @@
 
 import org.apache.tajo.catalog.Column;
 import org.apache.tajo.catalog.json.CatalogGsonHelper;
+import org.apache.tajo.catalog.proto.CatalogProtos.TableStatsProto;
 import org.apache.tajo.common.TajoDataTypes.Type;
+import org.apache.tajo.datum.TextDatum;
 import org.junit.Test;
 
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicBoolean;
+
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
 
 public class TestTableStat {
   @Test
@@ -76,4 +84,51 @@ public void tableStatEquals(TableStats s1, TableStats s2) {
       assertEquals(s1.getColumnStats().get(i), s2.getColumnStats().get(i));
     }
   }
+
+  @Test
+  public void testGetProtoThreadSafe() throws Exception {
+    final TableStats tableStats = new TableStats();
+
+    List<ColumnStats> columnStatsList = new ArrayList<ColumnStats>();
+    for (int i = 0; i < 3; i++) {
+      Column column = new Column("col_" + (i + 1), Type.TEXT);
+      ColumnStats columnStats = new ColumnStats(column);
+      columnStats.setMinValue(new TextDatum(i + ""));
+      columnStats.setMaxValue(new TextDatum((100 - i) + ""));
+
+      columnStatsList.add(columnStats);
+    }
+    tableStats.setColumnStats(columnStatsList);
+
+    int numThread = 10;
+    final CountDownLatch latch = new CountDownLatch(numThread);
+    final AtomicBoolean success = new AtomicBoolean(true);
+    for (int i = 0; i < numThread; i++) {
+      Thread t = new Thread() {
+        public void run() {
+          for (int j = 0; j < 100; j++) {
+            try {
+              TableStatsProto proto = tableStats.getProto();
+              if (tableStats.getColumnStats().size() != proto.getColStatList().size()) {
+                success.set(false);
+                break;
+              }
+            } catch (Exception e) {
+              success.set(false);
+            }
+          }
+
+          latch.countDown();
+        }
+      };
+
+      t.start();
+    }
+
+    latch.await();
+
+    if (!success.get()) {
+      fail("TableStats returns different column ststs");
+    }
+  }
 }