HBASE-1823 Ability for Scanners to bypass the block cache

git-svn-id: https://svn.apache.org/repos/asf/hadoop/hbase/trunk@814070 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -41,6 +41,7 @@ Release 0.21.0 - Unreleased
    HBASE-1820  Update jruby from 1.2 to 1.3.1
    HBASE-1687  bin/hbase script doesn't allow for different memory settings for
                each daemon type
+   HBASE-1823  Ability for Scanners to bypass the block cache
 
   OPTIMIZATIONS
 

src/java/org/apache/hadoop/hbase/client/Scan.java

@@ -69,12 +69,16 @@ import org.apache.hadoop.io.WritableFactories;
  * {@link #setMaxVersions(int) setMaxVersions}.
  * <p>
  * To add a filter, execute {@link #setFilter(org.apache.hadoop.hbase.filter.Filter) setFilter}.
+ * <p>
+ * Expert: To explicitly disable server-side block caching for this scan, 
+ * execute {@link #setCacheBlocks(boolean)}.
  */
 public class Scan implements Writable {
   private byte [] startRow = HConstants.EMPTY_START_ROW;
   private byte [] stopRow  = HConstants.EMPTY_END_ROW;
   private int maxVersions = 1;
   private int caching = -1;
+  private boolean cacheBlocks = true;
   private Filter filter = null;
   private RowFilterInterface oldFilter = null;
   private TimeRange tr = new TimeRange();
@@ -448,6 +452,29 @@ public class Scan implements Writable {
     return filter != null || oldFilter != null;
   }
   
+  /**
+   * Set whether blocks should be cached for this Scan.
+   * <p>
+   * This is true by default.  When true, default settings of the table and
+   * family are used (this will never override caching blocks if the block
+   * cache is disabled for that family or entirely).
+   * 
+   * @param cacheBlocks if false, default settings are overridden and blocks
+   * will not be cached
+   */
+  public void setCacheBlocks(boolean cacheBlocks) {
+    this.cacheBlocks = cacheBlocks;
+  }
+  
+  /**
+   * Get whether blocks should be cached for this Scan.
+   * @return true if default caching should be used, false if blocks should not
+   * be cached
+   */
+  public boolean getCacheBlocks() {
+    return cacheBlocks;
+  }
+  
   /**
    * @return String
    */
@@ -518,6 +545,7 @@ public class Scan implements Writable {
     this.stopRow = Bytes.readByteArray(in);
     this.maxVersions = in.readInt();
     this.caching = in.readInt();
+    this.cacheBlocks = in.readBoolean();
     if(in.readBoolean()) {
       this.filter = (Filter)createForName(Bytes.toString(Bytes.readByteArray(in)));
       this.filter.readFields(in);
@@ -550,6 +578,7 @@ public class Scan implements Writable {
     Bytes.writeByteArray(out, this.stopRow);
     out.writeInt(this.maxVersions);
     out.writeInt(this.caching);
+    out.writeBoolean(this.cacheBlocks);
     if(this.filter == null) {
       out.writeBoolean(false);
     } else {

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

@@ -43,6 +43,7 @@ class StoreScanner implements KeyValueScanner, InternalScanner, ChangedReadersOb
   private Store store;
   private ScanQueryMatcher matcher;
   private KeyValueHeap heap;
+  private boolean cacheBlocks;
 
   // Used to indicate that the scanner has closed (see HBASE-1107)
   private final AtomicBoolean closing = new AtomicBoolean(false);
@@ -52,6 +53,7 @@ class StoreScanner implements KeyValueScanner, InternalScanner, ChangedReadersOb
    */
   StoreScanner(Store store, Scan scan, final NavigableSet<byte[]> columns) {
     this.store = store;
+    this.cacheBlocks = scan.getCacheBlocks();
     matcher = new ScanQueryMatcher(scan, store.getFamily().getName(),
         columns, store.ttl, store.comparator.getRawComparator(),
         store.versionsToReturn(scan.getMaxVersions()));
@@ -77,6 +79,7 @@ class StoreScanner implements KeyValueScanner, InternalScanner, ChangedReadersOb
    */
   StoreScanner(Store store, Scan scan, KeyValueScanner [] scanners) {
     this.store = store;
+    this.cacheBlocks = false;
     matcher = new ScanQueryMatcher(scan, store.getFamily().getName(),
         null, store.ttl, store.comparator.getRawComparator(),
         store.versionsToReturn(scan.getMaxVersions()));
@@ -96,6 +99,7 @@ class StoreScanner implements KeyValueScanner, InternalScanner, ChangedReadersOb
       final NavigableSet<byte[]> columns,
       final KeyValueScanner [] scanners) {
     this.store = null;
+    this.cacheBlocks = scan.getCacheBlocks();
     this.matcher = new ScanQueryMatcher(scan, colFamily, columns, ttl, 
         comparator.getRawComparator(), scan.getMaxVersions());
 
@@ -215,7 +219,7 @@ class StoreScanner implements KeyValueScanner, InternalScanner, ChangedReadersOb
         LOG.warn("StoreFile " + sf + " has null Reader");
         continue;
       }
-      s.add(r.getScanner());
+      s.add(r.getScanner(cacheBlocks));
     }
     List<KeyValueScanner> scanners =
       new ArrayList<KeyValueScanner>(s.size()+1);

src/test/org/apache/hadoop/hbase/TestSerialization.java

@@ -359,6 +359,7 @@ public class TestSerialization extends HBaseTestCase {
 
     assertTrue(Bytes.equals(scan.getStartRow(), desScan.getStartRow()));
     assertTrue(Bytes.equals(scan.getStopRow(), desScan.getStopRow()));
+    assertEquals(scan.getCacheBlocks(), desScan.getCacheBlocks());
     Set<byte[]> set = null;
     Set<byte[]> desSet = null;