HIVE-22491 : Use Collections emptyList (David Mollitor via Ashutosh C…

…hauhan) Signed-off-by: Ashutosh Chauhan <[email protected]>
zem13579 · May 10, 2020 · 0bf24c8 · 0bf24c8
1 parent d12a308
commit 0bf24c8
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Showing 22 changed files with 48 additions and 44 deletions.
diff --git a/common/src/java/org/apache/hadoop/hive/common/HiveStatsUtils.java b/common/src/java/org/apache/hadoop/hive/common/HiveStatsUtils.java
@@ -19,6 +19,7 @@
 
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 import org.apache.hadoop.conf.Configuration;
@@ -66,7 +67,7 @@ public static List<FileStatus> getFileStatusRecurse(Path path, int level,  FileS
         // does not exist. But getFileStatus() throw IOException. To mimic the
         // similar behavior we will return empty array on exception. For external
         // tables, the path of the table will not exists during table creation
-        return new ArrayList<>(0);
+        return Collections.emptyList();
       }
       return result;
     }

diff --git a/...log/webhcat/java-client/src/main/java/org/apache/hive/hcatalog/api/HCatClientHMSImpl.java b/...log/webhcat/java-client/src/main/java/org/apache/hive/hcatalog/api/HCatClientHMSImpl.java
@@ -21,6 +21,7 @@
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
@@ -1007,7 +1008,7 @@ public HCatNotificationEvent apply(@Nullable NotificationEvent notificationEvent
           }
         });
       } else {
-        return new ArrayList<HCatNotificationEvent>();
+        return Collections.emptyList();
       }
     } catch (TException e) {
       throw new ConnectionFailureException("TException while getting notifications", e);

diff --git a/...g/webhcat/svr/src/main/java/org/apache/hive/hcatalog/templeton/tool/ZooKeeperCleanup.java b/...g/webhcat/svr/src/main/java/org/apache/hive/hcatalog/templeton/tool/ZooKeeperCleanup.java
@@ -19,7 +19,6 @@
 package org.apache.hive.hcatalog.templeton.tool;
 
 import java.io.IOException;
-import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.Date;
@@ -138,7 +137,7 @@ public List<String> getChildList(CuratorFramework zk) {
     } catch (IOException e) {
       LOG.info("No jobs to check.");
     }
-    return new ArrayList<String>();
+    return Collections.emptyList();
   }
 
   /**

diff --git a/...g/webhcat/svr/src/main/java/org/apache/hive/hcatalog/templeton/tool/ZooKeeperStorage.java b/...g/webhcat/svr/src/main/java/org/apache/hive/hcatalog/templeton/tool/ZooKeeperStorage.java
@@ -20,6 +20,7 @@
 
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 import org.apache.hadoop.hive.common.ZooKeeperHiveHelper;
@@ -280,7 +281,7 @@ public List<String> getAllForType(Type type) {
     try {
       return zk.getChildren().forPath(getPath(type));
     } catch (Exception e) {
-      return new ArrayList<String>();
+      return Collections.emptyList();
     }
   }
 

diff --git a/kudu-handler/src/java/org/apache/hadoop/hive/kudu/KuduPredicateHandler.java b/kudu-handler/src/java/org/apache/hadoop/hive/kudu/KuduPredicateHandler.java
@@ -119,7 +119,7 @@ private static IndexPredicateAnalyzer newAnalyzer(Schema schema) {
   public static List<KuduPredicate> getPredicates(Configuration conf, Schema schema) {
     SearchArgument sarg = ConvertAstToSearchArg.createFromConf(conf);
     if (sarg == null) {
-      return new ArrayList<>();
+      return Collections.emptyList();
     }
     return toKuduPredicates(sarg, schema);
   }

diff --git a/ql/src/java/org/apache/hadoop/hive/ql/exec/SerializationUtilities.java b/ql/src/java/org/apache/hadoop/hive/ql/exec/SerializationUtilities.java
@@ -28,8 +28,8 @@
 import java.nio.charset.StandardCharsets;
 import java.sql.Timestamp;
 import java.time.ZoneId;
-import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.LinkedList;
 import java.util.List;
@@ -694,7 +694,7 @@ public static MapredWork clonePlan(MapredWork plan) {
    */
   public static List<Operator<?>> cloneOperatorTree(List<Operator<?>> roots) {
     if (roots.isEmpty()) {
-      return new ArrayList<>();
+      return Collections.emptyList();
     }
     ByteArrayOutputStream baos = new ByteArrayOutputStream(4096);
     CompilationOpContext ctx = roots.get(0).getCompilationOpContext();

diff --git a/ql/src/java/org/apache/hadoop/hive/ql/exec/Utilities.java b/ql/src/java/org/apache/hadoop/hive/ql/exec/Utilities.java
@@ -4141,7 +4141,7 @@ public static Collection<Class<?>> getClassNamesFromConfig(HiveConf hiveConf, Co
     String[] classNames = org.apache.hadoop.util.StringUtils.getStrings(HiveConf.getVar(hiveConf,
         confVar));
     if (classNames == null) {
-      return new ArrayList<>(0);
+      return Collections.emptyList();
     }
     Collection<Class<?>> classList = new ArrayList<Class<?>>(classNames.length);
     for (String className : classNames) {

diff --git a/ql/src/java/org/apache/hadoop/hive/ql/exec/spark/SparkPlan.java b/ql/src/java/org/apache/hadoop/hive/ql/exec/spark/SparkPlan.java
@@ -20,7 +20,7 @@
 
 import java.io.ByteArrayOutputStream;
 import java.io.PrintStream;
-import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedList;
@@ -31,7 +31,6 @@
 import org.apache.commons.lang3.StringUtils;
 import org.apache.hadoop.hive.conf.HiveConf;
 import org.apache.hadoop.hive.ql.exec.ExplainTask;
-import org.apache.hadoop.hive.ql.exec.Utilities;
 import org.apache.hadoop.hive.ql.parse.ExplainConfiguration;
 import org.apache.hadoop.hive.ql.plan.ExplainWork;
 import org.apache.hadoop.mapred.JobConf;
@@ -226,15 +225,15 @@ public void connect(SparkTran parent, SparkTran child) {
 
   public List<SparkTran> getParents(SparkTran tran) {
     if (!invertedTransGraph.containsKey(tran)) {
-      return new ArrayList<SparkTran>();
+      return Collections.emptyList();
     }
 
     return invertedTransGraph.get(tran);
   }
 
   public List<SparkTran> getChildren(SparkTran tran) {
     if (!transGraph.containsKey(tran)) {
-      return new ArrayList<SparkTran>();
+      return Collections.emptyList();
     }
 
     return transGraph.get(tran);

diff --git a/ql/src/java/org/apache/hadoop/hive/ql/io/HiveFileFormatUtils.java b/ql/src/java/org/apache/hadoop/hive/ql/io/HiveFileFormatUtils.java
@@ -23,6 +23,7 @@
 import java.nio.file.Files;
 import java.nio.file.Paths;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.LinkedList;
@@ -481,7 +482,7 @@ public static List<Operator<? extends OperatorDesc>> doGetWorksFromPath(Map<Path
    **/
   public static List<String> doGetAliasesFromPath(Map<Path, List<String>> pathToAliases, Path dir) {
     if (pathToAliases == null) {
-      return new ArrayList<String>();
+      return Collections.emptyList();
     }
     Path path = getMatchingPath(pathToAliases, dir);
     return pathToAliases.get(path);

diff --git a/ql/src/java/org/apache/hadoop/hive/ql/metadata/Hive.java b/ql/src/java/org/apache/hadoop/hive/ql/metadata/Hive.java
@@ -1625,8 +1625,7 @@ public List<RelOptMaterialization> getPreprocessedMaterializedViewsFromRegistry(
     List<RelOptMaterialization> materializedViews =
         HiveMaterializedViewsRegistry.get().getRewritingMaterializedViews();
     if (materializedViews.isEmpty()) {
-      // Bail out: empty list
-      return new ArrayList<>();
+      return Collections.emptyList();
     }
     // Add to final result
     return filterAugmentMaterializedViews(materializedViews, tablesUsed, txnMgr);
@@ -1772,8 +1771,7 @@ public List<RelOptMaterialization> getPreprocessedMaterializedViews(
     List<Table> materializedViewTables =
         getAllMaterializedViewObjectsForRewriting();
     if (materializedViewTables.isEmpty()) {
-      // Bail out: empty list
-      return new ArrayList<>();
+      return Collections.emptyList();
     }
     // Return final result
     return getValidMaterializedViews(materializedViewTables, tablesUsed, false, txnMgr);
@@ -3819,7 +3817,7 @@ public List<Partition> getPartitionsByFilter(Table tbl, String filter)
   private static List<Partition> convertFromMetastore(Table tbl,
       List<org.apache.hadoop.hive.metastore.api.Partition> partitions) throws HiveException {
     if (partitions == null) {
-      return new ArrayList<Partition>();
+      return Collections.emptyList();
     }
 
     List<Partition> results = new ArrayList<Partition>(partitions.size());

diff --git a/ql/src/java/org/apache/hadoop/hive/ql/metadata/Partition.java b/ql/src/java/org/apache/hadoop/hive/ql/metadata/Partition.java
@@ -21,6 +21,7 @@
 import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -511,7 +512,7 @@ private List<FieldSchema> getColsInternal(boolean forMs) {
           tPartition.getSd().getSerdeInfo().getSerializationLib(), e);
     }
 
-    return new ArrayList<FieldSchema>();
+    return Collections.emptyList();
   }
 
   public String getLocation() {

diff --git a/ql/src/java/org/apache/hadoop/hive/ql/metadata/Table.java b/ql/src/java/org/apache/hadoop/hive/ql/metadata/Table.java
@@ -22,6 +22,7 @@
 import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
@@ -714,7 +715,7 @@ private List<FieldSchema> getColsInternal(boolean forMs) {
     } catch (Exception e) {
       LOG.error("Unable to get field from serde: " + serializationLib, e);
     }
-    return new ArrayList<FieldSchema>();
+    return Collections.emptyList();
   }
 
   /**

diff --git a/ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HivePreFilteringRule.java b/ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HivePreFilteringRule.java
@@ -18,6 +18,7 @@
 package org.apache.hadoop.hive.ql.optimizer.calcite.rules;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
@@ -204,13 +205,13 @@ private static List<RexNode> extractCommonOperands(RexBuilder rexBuilder, RelNod
       for (RexNode conjunction : conjunctions) {
         // We do not know what it is, we bail out for safety
         if (!(conjunction instanceof RexCall) || !HiveCalciteUtil.isDeterministic(conjunction)) {
-          return new ArrayList<>();
+          return Collections.emptyList();
         }
         RexCall conjCall = (RexCall) conjunction;
         Set<Integer> refs = HiveCalciteUtil.getInputRefs(conjCall);
         if (refs.size() != 1) {
           // We do not know what it is, we bail out for safety
-          return new ArrayList<>();
+          return Collections.emptyList();
         }
         RexNode ref = rexBuilder.makeInputRef(input, refs.iterator().next());
         String stringRef = ref.toString();
@@ -227,7 +228,7 @@ private static List<RexNode> extractCommonOperands(RexBuilder rexBuilder, RelNod
       // If we did not add any factor or there are no common factors, we can
       // bail out
       if (refsInAllOperands.isEmpty()) {
-        return new ArrayList<>();
+        return Collections.emptyList();
       }
     }
 

diff --git a/ql/src/java/org/apache/hadoop/hive/ql/plan/PlanUtils.java b/ql/src/java/org/apache/hadoop/hive/ql/plan/PlanUtils.java
@@ -660,7 +660,7 @@ public static List<FieldSchema> getFieldSchemasFromRowSchema(RowSchema row,
   public static List<FieldSchema> getFieldSchemasFromColumnInfo(
       List<ColumnInfo> cols, String fieldPrefix) {
     if ((cols == null) || (cols.size() == 0)) {
-      return new ArrayList<FieldSchema>();
+      return Collections.emptyList();
     }
 
     List<FieldSchema> schemas = new ArrayList<FieldSchema>(cols.size());

diff --git a/ql/src/java/org/apache/hadoop/hive/ql/plan/ReduceSinkDesc.java b/ql/src/java/org/apache/hadoop/hive/ql/plan/ReduceSinkDesc.java
@@ -20,6 +20,7 @@
 
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.EnumSet;
 import java.util.LinkedHashSet;
 import java.util.List;
@@ -575,7 +576,7 @@ public List<String> getKeyColumns() {
       int[] keyColumnMap = vectorReduceSinkInfo.getReduceSinkKeyColumnMap();
       if (keyColumnMap == null) {
         // Always show an array.
-        return new ArrayList<String>();
+        return Collections.emptyList();
       }
       return outputColumnsAndTypesToStringList(
           vectorReduceSinkInfo.getReduceSinkKeyColumnMap(),
@@ -591,7 +592,7 @@ public List<String> getValueColumns() {
       int[] valueColumnMap = vectorReduceSinkInfo.getReduceSinkValueColumnMap();
       if (valueColumnMap == null) {
         // Always show an array.
-        return new ArrayList<String>();
+        return Collections.emptyList();
       }
       return outputColumnsAndTypesToStringList(
           vectorReduceSinkInfo.getReduceSinkValueColumnMap(),

diff --git a/ql/src/java/org/apache/hadoop/hive/ql/stats/StatsUtils.java b/ql/src/java/org/apache/hadoop/hive/ql/stats/StatsUtils.java
@@ -1059,8 +1059,8 @@ public static List<ColStatistics> getTableColumnStats(
   }
 
   private static List<ColStatistics> convertColStats(List<ColumnStatisticsObj> colStats, String tabName) {
-    if (colStats==null) {
-      return new ArrayList<ColStatistics>();
+    if (colStats == null) {
+      return Collections.emptyList();
     }
     List<ColStatistics> stats = new ArrayList<ColStatistics>(colStats.size());
     for (ColumnStatisticsObj statObj : colStats) {

diff --git a/serde/src/java/org/apache/hadoop/hive/serde2/NullStructSerDe.java b/serde/src/java/org/apache/hadoop/hive/serde2/NullStructSerDe.java
@@ -17,7 +17,7 @@
  */
 package org.apache.hadoop.hive.serde2;
 
-import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Properties;
 
@@ -107,7 +107,7 @@ public StructField getStructFieldRef(String fieldName) {
 
     @Override
     public List<NullStructField> getAllStructFieldRefs() {
-      return new ArrayList<NullStructField>();
+      return Collections.emptyList();
     }
 
     @Override
@@ -117,7 +117,7 @@ public Object getStructFieldData(Object data, StructField fieldRef) {
 
     @Override
     public List<Object> getStructFieldsDataAsList(Object data) {
-      return new ArrayList<Object>();
+      return Collections.emptyList();
     }
   }
 

diff --git a/...tore/metastore-common/src/main/java/org/apache/hadoop/hive/metastore/utils/FileUtils.java b/...tore/metastore-common/src/main/java/org/apache/hadoop/hive/metastore/utils/FileUtils.java
@@ -332,7 +332,7 @@ public static List<FileStatus> getFileStatusRecurse(Path base, FileSystem fs) {
       // does not exist. But getFileStatus() throw IOException. To mimic the
       // similar behavior we will return empty array on exception. For external
       // tables, the path of the table will not exists during table creation
-      return new ArrayList<>(0);
+      return Collections.emptyList();
     }
   }
 

diff --git a/...astore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/HiveMetaStore.java b/...astore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/HiveMetaStore.java
@@ -6224,12 +6224,10 @@ public List<String> get_partition_names_ps(final String db_name,
     @Override
     public List<String> partition_name_to_vals(String part_name) throws TException {
       if (part_name.length() == 0) {
-        return new ArrayList<>();
+        return Collections.emptyList();
       }
       LinkedHashMap<String, String> map = Warehouse.makeSpecFromName(part_name);
-      List<String> part_vals = new ArrayList<>();
-      part_vals.addAll(map.values());
-      return part_vals;
+      return new ArrayList<>(map.values());
     }
 
     @Override

diff --git a/...re-server/src/main/java/org/apache/hadoop/hive/metastore/MetastoreDefaultTransformer.java b/...re-server/src/main/java/org/apache/hadoop/hive/metastore/MetastoreDefaultTransformer.java
@@ -26,6 +26,7 @@
 
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -706,17 +707,17 @@ private List<String> diff(final List<String> list1, final List<String> list2) {
       return list1;
 
     if (list1 == null || list1.size() == 0)
-      return new ArrayList<String>();
+      return Collections.emptyList();
 
     if (list2.containsAll(list1))
-      return new ArrayList<String>();
+      return Collections.emptyList();
 
     diffList.addAll(list2);
     LOG.debug("diffList=" + Arrays.toString(diffList.toArray()) + ",master list=" + Arrays.toString(list1.toArray()));
     if (diffList.retainAll(list1)) {
       LOG.debug("diffList=" + Arrays.toString(diffList.toArray()));
       if (diffList.size() == list1.size()) { // lists match
-        return new ArrayList<String>(); // return empty list indicating no missing elements
+        return Collections.emptyList(); // return empty list indicating no missing elements
       } else {
         list1.removeAll(diffList);
         LOG.debug("list1.size():" + list1.size());