HBASE-3082 For ICV gets, first look in MemStore before reading StoreFiles (Prakash via jgray)

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1026910 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -1037,6 +1037,8 @@ Release 0.21.0 - Unreleased
    HBASE-3132  Print TimestampRange and BloomFilters in HFile pretty print
    HBASE-2514  RegionServer should refuse to be assigned a region that use 
    	       LZO when LZO isn't available
+   HBASE-3082  For ICV gets, first look in MemStore before reading StoreFiles
+               (prakash via stack)
 
   NEW FEATURES
    HBASE-1961  HBase EC2 scripts

src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java

@@ -2859,6 +2859,86 @@ public class HRegion implements HeapSize { // , Writable{
     return new Result(result);
   }
 
+  /**
+   * An optimized version of {@link #get(Get)} that checks MemStore first for
+   * the specified query.
+   * <p>
+   * This is intended for use by increment operations where we have the
+   * guarantee that versions are never inserted out-of-order so if a value
+   * exists in MemStore it is the latest value.
+   * <p>
+   * It only makes sense to use this method without a TimeRange and maxVersions
+   * equal to 1.
+   * @param get
+   * @return result
+   * @throws IOException
+   */
+  private List<KeyValue> getLastIncrement(final Get get) throws IOException {
+    InternalScan iscan = new InternalScan(get);
+
+    List<KeyValue> results = new ArrayList<KeyValue>();
+
+    // memstore scan
+    iscan.checkOnlyMemStore();
+    InternalScanner scanner = null;
+    try {
+      scanner = getScanner(iscan);
+      scanner.next(results);
+    } finally {
+      if (scanner != null)
+        scanner.close();
+    }
+
+    // count how many columns we're looking for
+    int expected = 0;
+    Map<byte[], NavigableSet<byte[]>> familyMap = get.getFamilyMap();
+    for (NavigableSet<byte[]> qfs : familyMap.values()) {
+      expected += qfs.size();
+    }
+
+    // found everything we were looking for, done
+    if (results.size() == expected) {
+      return results;
+    }
+
+    // still have more columns to find
+    if (results != null && !results.isEmpty()) {
+      // subtract what was found in memstore
+      for (KeyValue kv : results) {
+        byte [] family = kv.getFamily();
+        NavigableSet<byte[]> qfs = familyMap.get(family);
+        qfs.remove(kv.getQualifier());
+        if (qfs.isEmpty()) familyMap.remove(family);
+        expected--;
+      }
+      // make a new get for just what is left
+      Get newGet = new Get(get.getRow());
+      for (Map.Entry<byte[], NavigableSet<byte[]>> f : familyMap.entrySet()) {
+        byte [] family = f.getKey();
+        for (byte [] qualifier : f.getValue()) {
+          newGet.addColumn(family, qualifier);
+        }
+      }
+      iscan = new InternalScan(newGet);
+    }
+
+    // check store files for what is left
+    List<KeyValue> fileResults = new ArrayList<KeyValue>();
+    iscan.checkOnlyStoreFiles();
+    scanner = null;
+    try {
+      scanner = getScanner(iscan);
+      scanner.next(fileResults);
+    } finally {
+      if (scanner != null)
+        scanner.close();
+    }
+
+    // combine and return
+    results.addAll(fileResults);
+    return results;
+  }
+
   /*
    * Do a get based on the get parameter.
    */
@@ -2905,7 +2985,7 @@ public class HRegion implements HeapSize { // , Writable{
         Get get = new Get(row);
         get.addColumn(family, qualifier);
 
-        List<KeyValue> results = get(get);
+        List<KeyValue> results = getLastIncrement(get);
 
         if (!results.isEmpty()) {
           KeyValue kv = results.get(0);
@@ -2914,7 +2994,7 @@ public class HRegion implements HeapSize { // , Writable{
           result += Bytes.toLong(buffer, valueOffset, Bytes.SIZEOF_LONG);
         }
 
-        // bulid the KeyValue now:
+        // build the KeyValue now:
         KeyValue newKv = new KeyValue(row, family,
             qualifier, EnvironmentEdgeManager.currentTimeMillis(),
             Bytes.toBytes(result));
@@ -2930,7 +3010,7 @@ public class HRegion implements HeapSize { // , Writable{
 
         // Now request the ICV to the store, this will set the timestamp
         // appropriately depending on if there is a value in memcache or not.
-        // returns the
+        // returns the change in the size of the memstore from operation
         long size = store.updateColumnValue(row, family, qualifier, result);
 
         size = this.memstoreSize.addAndGet(size);

src/main/java/org/apache/hadoop/hbase/regionserver/InternalScan.java

@@ -0,0 +1,78 @@
+/**
+ * Copyright 2010 The Apache Software Foundation
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hbase.regionserver;
+
+import org.apache.hadoop.hbase.client.Get;
+import org.apache.hadoop.hbase.client.Scan;
+
+/**
+ * Special internal-only scanner, currently used for increment operations to
+ * allow additional server-side arguments for Scan operations.
+ * <p>
+ * Rather than adding new options/parameters to the public Scan API, this new
+ * class has been created.
+ * <p>
+ * Supports adding an option to only read from the MemStore with
+ * {@link #checkOnlyMemStore()} or to only read from StoreFiles with
+ * {@link #checkOnlyStoreFiles()}.
+ */
+class InternalScan extends Scan {
+  private boolean memOnly = false;
+  private boolean filesOnly = false;
+
+  /**
+   * @param get get to model scan after
+   */
+  public InternalScan(Get get) {
+    super(get);
+  }
+
+  /**
+   * StoreFiles will not be scanned. Only MemStore will be scanned.
+   */
+  public void checkOnlyMemStore() {
+    memOnly = true;
+    filesOnly = false;
+  }
+
+  /**
+   * MemStore will not be scanned. Only StoreFiles will be scanned.
+   */
+  public void checkOnlyStoreFiles() {
+    memOnly = false;
+    filesOnly = true;
+  }
+
+  /**
+   * Returns true if only the MemStore should be checked.  False if not.
+   * @return true to only check MemStore
+   */
+  public boolean isCheckOnlyMemStore() {
+    return (memOnly);
+  }
+
+  /**
+   * Returns true if only StoreFiles should be checked.  False if not.
+   * @return true if only check StoreFiles
+   */
+  public boolean isCheckOnlyStoreFiles() {
+    return (filesOnly);
+  }
+}

src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java

@@ -27,6 +27,7 @@ import org.apache.hadoop.hbase.client.Scan;
 
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.LinkedList;
 import java.util.List;
 import java.util.NavigableSet;
 
@@ -149,11 +150,21 @@ class StoreScanner implements KeyValueScanner, InternalScanner, ChangedReadersOb
    */
   private List<KeyValueScanner> getScanners(Scan scan,
       final NavigableSet<byte[]> columns) throws IOException {
+    boolean memOnly;
+    boolean filesOnly;
+    if (scan instanceof InternalScan) {
+      InternalScan iscan = (InternalScan)scan;
+      memOnly = iscan.isCheckOnlyMemStore();
+      filesOnly = iscan.isCheckOnlyStoreFiles();
+    } else {
+      memOnly = false;
+      filesOnly = false;
+    }
+    List<KeyValueScanner> scanners = new LinkedList<KeyValueScanner>();
     // First the store file scanners
+    if (memOnly == false) {
       List<StoreFileScanner> sfScanners = StoreFileScanner
       .getScannersForStoreFiles(store.getStorefiles(), cacheBlocks, isGet);
-    List<KeyValueScanner> scanners =
-      new ArrayList<KeyValueScanner>(sfScanners.size()+1);
 
       // include only those scan files which pass all filters
       for (StoreFileScanner sfs : sfScanners) {
@@ -161,9 +172,10 @@ class StoreScanner implements KeyValueScanner, InternalScanner, ChangedReadersOb
           scanners.add(sfs);
         }
       }
+    }
 
     // Then the memstore scanners
-    if (this.store.memstore.shouldSeek(scan)) {
+    if ((filesOnly == false) && (this.store.memstore.shouldSeek(scan))) {
         scanners.addAll(this.store.memstore.getScanners());
     }
     return scanners;