diff options
Diffstat (limited to 'src/main/java')
| -rw-r--r-- | src/main/java/com/amazon/carbonado/cursor/MergeSortBuffer.java | 65 |
1 files changed, 61 insertions, 4 deletions
diff --git a/src/main/java/com/amazon/carbonado/cursor/MergeSortBuffer.java b/src/main/java/com/amazon/carbonado/cursor/MergeSortBuffer.java index 807a0b6..3f645fb 100644 --- a/src/main/java/com/amazon/carbonado/cursor/MergeSortBuffer.java +++ b/src/main/java/com/amazon/carbonado/cursor/MergeSortBuffer.java @@ -20,6 +20,7 @@ package com.amazon.carbonado.cursor; import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
+import java.io.File;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.EOFException;
@@ -51,6 +52,28 @@ import com.amazon.carbonado.spi.StorableSerializer; * storables to fit in the reserved memory buffer, they are sorted and
* serialized to temporary files.
*
+ * <p>The following system properties can be set to change the default
+ * performance characteristics of the merge sort. Each property name must be
+ * prefixed with "com.amazon.carbonado.MergeSortBuffer."
+ *
+ * <pre>
+ * Property Default Notes
+ * ------------------- ---------- ----------------------------------------------
+ * maxArrayCapacity 8192 Larger value greatly improves performance, but
+ * more memory is used for each running sort.
+ *
+ * maxOpenFileCount 100 Larger value may reduce the amount of file
+ * merges, but there is an increased risk of
+ * running out of file descriptors.
+ *
+ * outputBufferSize 10000 Larger value may improve performance of file
+ * writing, but not by much.
+ *
+ * tmpdir Merge sort files by default are placed in the
+ * Java temp directory. Override to place them
+ * somewhere else.
+ * </pre>
+ *
* @author Brian S O'Neill
* @see SortedCursor
*/
@@ -60,13 +83,43 @@ public class MergeSortBuffer<S extends Storable> extends AbstractCollection<S> private static final int MIN_ARRAY_CAPACITY = 64;
// Bigger means better performance, but more memory is used.
- private static final int MAX_ARRAY_CAPACITY = 8192;
+ private static final int MAX_ARRAY_CAPACITY;
+ private static final int DEFAULT_MAX_ARRAY_CAPACITY = 8192;
// Bigger means better performance, but more file handles may be used.
- private static final int MAX_FILE_COUNT = 100;
+ private static final int MAX_OPEN_FILE_COUNT;
+ private static final int DEFAULT_MAX_OPEN_FILE_COUNT = 100;
// Bigger may improve write performance, but not by much.
- private static final int OUTPUT_BUFFER_SIZE = 10000;
+ private static final int OUTPUT_BUFFER_SIZE;
+ private static final int DEFAULT_OUTPUT_BUFFER_SIZE = 10000;
+
+ private static final String TEMP_DIR;
+
+ static {
+ String prefix = MergeSortBuffer.class.getName() + '.';
+
+ MAX_ARRAY_CAPACITY = Integer.getInteger(prefix + "maxArrayCapacity",
+ DEFAULT_MAX_ARRAY_CAPACITY);
+
+ MAX_OPEN_FILE_COUNT = Integer.getInteger(prefix + "maxOpenFileCount",
+ DEFAULT_MAX_OPEN_FILE_COUNT);
+
+ OUTPUT_BUFFER_SIZE = Integer.getInteger(prefix + "outputBufferSize",
+ DEFAULT_OUTPUT_BUFFER_SIZE);
+
+ // Null means use system temp dir.
+ String tempDir = System.getProperty(prefix + "tmpdir", null);
+
+ if (tempDir != null) {
+ File f = new File(tempDir);
+ if (!f.exists() || !f.isDirectory() || !f.canRead() || !f.canWrite()) {
+ tempDir = null;
+ }
+ }
+
+ TEMP_DIR = tempDir;
+ }
private final Storage<S> mStorage;
private final String mTempDir;
@@ -104,9 +157,13 @@ public class MergeSortBuffer<S extends Storable> extends AbstractCollection<S> * @param tempDir directory to store temp files for merging, or null for default
* @param maxArrayCapacity maximum amount of storables to keep in an array
* before serializing to a file
+ * @throws IllegalArgumentException if storage is null
*/
@SuppressWarnings("unchecked")
public MergeSortBuffer(Storage<S> storage, String tempDir, int maxArrayCapacity) {
+ if (storage == null) {
+ throw new IllegalArgumentException();
+ }
mStorage = storage;
mTempDir = tempDir;
mMaxArrayCapacity = maxArrayCapacity;
@@ -164,7 +221,7 @@ public class MergeSortBuffer<S extends Storable> extends AbstractCollection<S> StorableSerializer<S> serializer = mSerializer;
- if (mFilesInUse.size() < (MAX_FILE_COUNT - 1)) {
+ if (mFilesInUse.size() < (MAX_OPEN_FILE_COUNT - 1)) {
mFilesInUse.add(raf);
int count = 0;
for (S element : mElements) {
|