From 933e60b44df8950bb3df2e8908d991bcb6edfc1a Mon Sep 17 00:00:00 2001
From: Nicolas Capponi <nicolas.capponi@forgerock.com>
Date: Wed, 25 Jun 2014 15:43:38 +0000
Subject: [PATCH] Checkpoint commit for OPENDJ-1471 File based changelog : improve cursor behavior
---
opends/src/server/org/opends/server/replication/server/changelog/file/LogFile.java | 63 +++++++++++++++----------------
1 files changed, 30 insertions(+), 33 deletions(-)
diff --git a/opends/src/server/org/opends/server/replication/server/changelog/file/LogFile.java b/opends/src/server/org/opends/server/replication/server/changelog/file/LogFile.java
index 3b91bfa..c27d38d 100644
--- a/opends/src/server/org/opends/server/replication/server/changelog/file/LogFile.java
+++ b/opends/src/server/org/opends/server/replication/server/changelog/file/LogFile.java
@@ -313,10 +313,9 @@
* Returns a cursor that allows to retrieve the records from this log,
* starting at the first position.
* <p>
- * The returned cursor initially points to record corresponding to the first
- * key, that is {@code cursor.getRecord()} is equals to the record
- * corresponding to the first key before any call to {@code cursor.next()}
- * method.
+ * The returned cursor initially points to no record, that is
+ * {@code cursor.getRecord()} is equals {@code null} before any call to
+ * {@code cursor.next()} method.
*
* @return a cursor on the log records, which is never {@code null}
* @throws ChangelogException
@@ -331,9 +330,10 @@
* Returns a cursor that allows to retrieve the records from this log,
* starting at the position defined by the provided key.
* <p>
- * The returned cursor initially points to record corresponding to the key,
- * that is {@code cursor.getRecord()} is equals to the record corresponding to
- * the key before any call to {@code cursor.next()} method.
+ * The returned cursor initially points to no record, that is
+ * {@code cursor.getRecord()} is equals to {@code null} before any call to
+ * {@code cursor.next()} method. After the first call to {@code cursor.next()}
+ * the cursor points to the record corresponding to the key.
*
* @param key
* Key to use as a start position for the cursor. If key is
@@ -352,10 +352,10 @@
* starting at the position defined by the smallest key that is higher than
* the provided key.
* <p>
- * The returned cursor initially points to record corresponding to the key
- * found, that is {@code cursor.getRecord()} is equals to the record
- * corresponding to the key found before any call to {@code cursor.next()}
- * method.
+ * The returned cursor initially points to no record, that is
+ * {@code cursor.getRecord()} is equals to {@code null} before any call to
+ * {@code cursor.next()} method. After the first call to {@code cursor.next()}
+ * the cursor points to the record corresponding to the key found.
*
* @param key
* Key to use as a start position for the cursor. If key is
@@ -421,7 +421,7 @@
try
{
cursor = getCursor();
- return cursor.getRecord();
+ return cursor.next() ? cursor.getRecord() : null;
}
finally
{
@@ -443,7 +443,7 @@
try
{
cursor = getCursor();
- Record<K, V> record = cursor.getRecord();
+ Record<K, V> record = null;
while (cursor.next())
{
record = cursor.getRecord();
@@ -470,15 +470,9 @@
try
{
cursor = getCursor();
- Record<K, V> record = cursor.getRecord();
- if (record == null)
- {
- return 0L;
- }
- long counter = 1L;
+ long counter = 0L;
while (cursor.next())
{
- record = cursor.getRecord();
counter++;
}
return counter;
@@ -580,8 +574,8 @@
/**
* Implements a repositionable cursor on the log file.
* <p>
- * The cursor initially points to a record, that is {@code cursor.getRecord()}
- * is equals to the first record available from the cursor before any call to
+ * The cursor initially points to no record, that is
+ * {@code cursor.getRecord()} is equals to {@code null} before any call to
* {@code cursor.next()} method.
*/
static final class LogFileCursor<K extends Comparable<K>, V> implements RepositionableCursor<K,V>
@@ -596,6 +590,12 @@
private Record<K,V> currentRecord;
/**
+ * The initial record when starting from a given key. It must be
+ * stored because it is read in advance.
+ */
+ private Record<K,V> initialRecord;
+
+ /**
* Creates a cursor on the provided log.
*
* @param logFile
@@ -607,16 +607,6 @@
{
this.logFile = logFile;
this.reader = logFile.getReader();
- try
- {
- // position to the first record.
- next();
- }
- catch (ChangelogException e)
- {
- close();
- throw e;
- }
}
/**
@@ -638,6 +628,13 @@
@Override
public boolean next() throws ChangelogException
{
+ if (initialRecord != null)
+ {
+ // initial record is used only once
+ currentRecord = initialRecord;
+ initialRecord = null;
+ return true;
+ }
currentRecord = reader.readRecord();
return currentRecord != null;
}
@@ -654,7 +651,7 @@
public boolean positionTo(final K key, boolean findNearest) throws ChangelogException {
final Pair<Boolean, Record<K, V>> result = reader.seekToRecord(key, findNearest);
final boolean found = result.getFirst();
- currentRecord = found ? result.getSecond() : null;
+ initialRecord = found ? result.getSecond() : null;
return found;
}
--
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