From 2278740878264362fd0f51e5f782715a89e4964f Mon Sep 17 00:00:00 2001
From: "Brian S. O'Neill" <bronee@gmail.com>
Date: Tue, 19 Sep 2006 06:07:30 +0000
Subject: Removed all cursor synchronization. It just adds overhead and no real
 (or needed) thread safety.

---
 .../amazon/carbonado/cursor/AbstractCursor.java    |   5 +-
 .../amazon/carbonado/cursor/DifferenceCursor.java  |   6 +-
 .../amazon/carbonado/cursor/FilteredCursor.java    |  70 ++++++--------
 .../com/amazon/carbonado/cursor/GroupedCursor.java | 104 ++++++++++-----------
 .../carbonado/cursor/IntersectionCursor.java       |   6 +-
 .../carbonado/cursor/MultiTransformedCursor.java   |  86 ++++++++---------
 .../com/amazon/carbonado/cursor/SortedCursor.java  |   8 +-
 .../cursor/SymmetricDifferenceCursor.java          |   6 +-
 .../amazon/carbonado/cursor/TransformedCursor.java |  70 ++++++--------
 .../com/amazon/carbonado/cursor/UnionCursor.java   |   6 +-
 10 files changed, 166 insertions(+), 201 deletions(-)

(limited to 'src/main/java/com/amazon/carbonado/cursor')

diff --git a/src/main/java/com/amazon/carbonado/cursor/AbstractCursor.java b/src/main/java/com/amazon/carbonado/cursor/AbstractCursor.java
index cf64a24..fb34617 100644
--- a/src/main/java/com/amazon/carbonado/cursor/AbstractCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/AbstractCursor.java
@@ -64,10 +64,7 @@ public abstract class AbstractCursor<S> implements Cursor<S> {
         return list;
     }
 
-    public synchronized int skipNext(int amount) throws FetchException {
-        // This method is synchronized to avoid potential race conditions
-        // between calls to hasNext and next in the loop below.
-
+    public int skipNext(int amount) throws FetchException {
         if (amount <= 0) {
             if (amount < 0) {
                 throw new IllegalArgumentException("Cannot skip negative amount: " + amount);
diff --git a/src/main/java/com/amazon/carbonado/cursor/DifferenceCursor.java b/src/main/java/com/amazon/carbonado/cursor/DifferenceCursor.java
index 39455c8..8b330ea 100644
--- a/src/main/java/com/amazon/carbonado/cursor/DifferenceCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/DifferenceCursor.java
@@ -59,14 +59,14 @@ public class DifferenceCursor<S> extends AbstractCursor<S> {
         mOrder = order;
     }
 
-    public synchronized void close() throws FetchException {
+    public void close() throws FetchException {
         mLeftCursor.close();
         mRightCursor.close();
         mNext = null;
         mNextRight = null;
     }
 
-    public synchronized boolean hasNext() throws FetchException {
+    public boolean hasNext() throws FetchException {
         if (mNext != null) {
             return true;
         }
@@ -109,7 +109,7 @@ public class DifferenceCursor<S> extends AbstractCursor<S> {
         }
     }
 
-    public synchronized S next() throws FetchException {
+    public S next() throws FetchException {
         if (hasNext()) {
             S next = mNext;
             mNext = null;
diff --git a/src/main/java/com/amazon/carbonado/cursor/FilteredCursor.java b/src/main/java/com/amazon/carbonado/cursor/FilteredCursor.java
index 60b3c81..f426f36 100644
--- a/src/main/java/com/amazon/carbonado/cursor/FilteredCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/FilteredCursor.java
@@ -82,61 +82,53 @@ public abstract class FilteredCursor<S> extends AbstractCursor<S> {
     protected abstract boolean isAllowed(S storable);
 
     public void close() throws FetchException {
-        synchronized (mCursor) {
-            mCursor.close();
-            mNext = null;
-        }
+        mCursor.close();
+        mNext = null;
     }
 
     public boolean hasNext() throws FetchException {
-        synchronized (mCursor) {
-            if (mNext != null) {
-                return true;
-            }
-            try {
-                int count = 0;
-                while (mCursor.hasNext()) {
-                    S next = mCursor.next();
-                    if (isAllowed(next)) {
-                        mNext = next;
-                        return true;
-                    }
-                    interruptCheck(++count);
+        if (mNext != null) {
+            return true;
+        }
+        try {
+            int count = 0;
+            while (mCursor.hasNext()) {
+                S next = mCursor.next();
+                if (isAllowed(next)) {
+                    mNext = next;
+                    return true;
                 }
-            } catch (NoSuchElementException e) {
+                interruptCheck(++count);
             }
-            return false;
+        } catch (NoSuchElementException e) {
         }
+        return false;
     }
 
     public S next() throws FetchException {
-        synchronized (mCursor) {
-            if (hasNext()) {
-                S next = mNext;
-                mNext = null;
-                return next;
-            }
-            throw new NoSuchElementException();
+        if (hasNext()) {
+            S next = mNext;
+            mNext = null;
+            return next;
         }
+        throw new NoSuchElementException();
     }
 
     public int skipNext(int amount) throws FetchException {
-        synchronized (mCursor) {
-            if (amount <= 0) {
-                if (amount < 0) {
-                    throw new IllegalArgumentException("Cannot skip negative amount: " + amount);
-                }
-                return 0;
-            }
-
-            int count = 0;
-            while (--amount >= 0 && hasNext()) {
-                interruptCheck(++count);
-                mNext = null;
+        if (amount <= 0) {
+            if (amount < 0) {
+                throw new IllegalArgumentException("Cannot skip negative amount: " + amount);
             }
+            return 0;
+        }
 
-            return count;
+        int count = 0;
+        while (--amount >= 0 && hasNext()) {
+            interruptCheck(++count);
+            mNext = null;
         }
+
+        return count;
     }
 
     private void interruptCheck(int count) throws FetchException {
diff --git a/src/main/java/com/amazon/carbonado/cursor/GroupedCursor.java b/src/main/java/com/amazon/carbonado/cursor/GroupedCursor.java
index 0b17e50..bf838b1 100644
--- a/src/main/java/com/amazon/carbonado/cursor/GroupedCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/GroupedCursor.java
@@ -113,87 +113,79 @@ public abstract class GroupedCursor<S, G> extends AbstractCursor<G> {
     protected abstract G finishGroup() throws FetchException;
 
     public void close() throws FetchException {
-        synchronized (mCursor) {
-            mCursor.close();
-            mGroupLeader = null;
-            mNextAggregate = null;
-        }
+        mCursor.close();
+        mGroupLeader = null;
+        mNextAggregate = null;
     }
 
     public boolean hasNext() throws FetchException {
-        synchronized (mCursor) {
-            if (mNextAggregate != null) {
-                return true;
-            }
+        if (mNextAggregate != null) {
+            return true;
+        }
 
-            try {
-                int count = 0;
-                if (mCursor.hasNext()) {
-                    if (mGroupLeader == null) {
-                        beginGroup(mGroupLeader = mCursor.next());
-                    }
+        try {
+            int count = 0;
+            if (mCursor.hasNext()) {
+                if (mGroupLeader == null) {
+                    beginGroup(mGroupLeader = mCursor.next());
+                }
 
-                    while (mCursor.hasNext()) {
-                        S groupMember = mCursor.next();
+                while (mCursor.hasNext()) {
+                    S groupMember = mCursor.next();
 
-                        if (mGroupComparator.compare(mGroupLeader, groupMember) == 0) {
-                            addToGroup(groupMember);
-                        } else {
-                            G aggregate = finishGroup();
+                    if (mGroupComparator.compare(mGroupLeader, groupMember) == 0) {
+                        addToGroup(groupMember);
+                    } else {
+                        G aggregate = finishGroup();
 
-                            beginGroup(mGroupLeader = groupMember);
+                        beginGroup(mGroupLeader = groupMember);
 
-                            if (aggregate != null) {
-                                mNextAggregate = aggregate;
-                                return true;
-                            }
+                        if (aggregate != null) {
+                            mNextAggregate = aggregate;
+                            return true;
                         }
-
-                        interruptCheck(++count);
                     }
 
-                    G aggregate = finishGroup();
+                    interruptCheck(++count);
+                }
 
-                    if (aggregate != null) {
-                        mNextAggregate = aggregate;
-                        return true;
-                    }
+                G aggregate = finishGroup();
+
+                if (aggregate != null) {
+                    mNextAggregate = aggregate;
+                    return true;
                 }
-            } catch (NoSuchElementException e) {
             }
-
-            return false;
+        } catch (NoSuchElementException e) {
         }
+
+        return false;
     }
 
     public G next() throws FetchException {
-        synchronized (mCursor) {
-            if (hasNext()) {
-                G next = mNextAggregate;
-                mNextAggregate = null;
-                return next;
-            }
-            throw new NoSuchElementException();
+        if (hasNext()) {
+            G next = mNextAggregate;
+            mNextAggregate = null;
+            return next;
         }
+        throw new NoSuchElementException();
     }
 
     public int skipNext(int amount) throws FetchException {
-        synchronized (mCursor) {
-            if (amount <= 0) {
-                if (amount < 0) {
-                    throw new IllegalArgumentException("Cannot skip negative amount: " + amount);
-                }
-                return 0;
-            }
-
-            int count = 0;
-            while (--amount >= 0 && hasNext()) {
-                interruptCheck(++count);
-                mNextAggregate = null;
+        if (amount <= 0) {
+            if (amount < 0) {
+                throw new IllegalArgumentException("Cannot skip negative amount: " + amount);
             }
+            return 0;
+        }
 
-            return count;
+        int count = 0;
+        while (--amount >= 0 && hasNext()) {
+            interruptCheck(++count);
+            mNextAggregate = null;
         }
+
+        return count;
     }
 
     private void interruptCheck(int count) throws FetchException {
diff --git a/src/main/java/com/amazon/carbonado/cursor/IntersectionCursor.java b/src/main/java/com/amazon/carbonado/cursor/IntersectionCursor.java
index 9d11b2f..58aba0d 100644
--- a/src/main/java/com/amazon/carbonado/cursor/IntersectionCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/IntersectionCursor.java
@@ -58,13 +58,13 @@ public class IntersectionCursor<S> extends AbstractCursor<S> {
         mOrder = order;
     }
 
-    public synchronized void close() throws FetchException {
+    public void close() throws FetchException {
         mLeftCursor.close();
         mRightCursor.close();
         mNext = null;
     }
 
-    public synchronized boolean hasNext() throws FetchException {
+    public boolean hasNext() throws FetchException {
         if (mNext != null) {
             return true;
         }
@@ -107,7 +107,7 @@ public class IntersectionCursor<S> extends AbstractCursor<S> {
         }
     }
 
-    public synchronized S next() throws FetchException {
+    public S next() throws FetchException {
         if (hasNext()) {
             S next = mNext;
             mNext = null;
diff --git a/src/main/java/com/amazon/carbonado/cursor/MultiTransformedCursor.java b/src/main/java/com/amazon/carbonado/cursor/MultiTransformedCursor.java
index 0cfd197..feeb414 100644
--- a/src/main/java/com/amazon/carbonado/cursor/MultiTransformedCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/MultiTransformedCursor.java
@@ -54,73 +54,65 @@ public abstract class MultiTransformedCursor<S, T> extends AbstractCursor<T> {
     protected abstract Cursor<T> transform(S storable) throws FetchException;
 
     public void close() throws FetchException {
-        synchronized (mCursor) {
-            mCursor.close();
-            if (mNextCursor != null) {
-                mNextCursor.close();
-                mNextCursor = null;
-            }
+        mCursor.close();
+        if (mNextCursor != null) {
+            mNextCursor.close();
+            mNextCursor = null;
         }
     }
 
     public boolean hasNext() throws FetchException {
-        synchronized (mCursor) {
-            if (mNextCursor != null) {
-                if (mNextCursor.hasNext()) {
-                    return true;
-                }
-                mNextCursor.close();
-                mNextCursor = null;
+        if (mNextCursor != null) {
+            if (mNextCursor.hasNext()) {
+                return true;
             }
-            try {
-                int count = 0;
-                while (mCursor.hasNext()) {
-                    Cursor<T> nextCursor = transform(mCursor.next());
-                    if (nextCursor != null) {
-                        if (nextCursor.hasNext()) {
-                            mNextCursor = nextCursor;
-                            return true;
-                        }
-                        nextCursor.close();
+            mNextCursor.close();
+            mNextCursor = null;
+        }
+        try {
+            int count = 0;
+            while (mCursor.hasNext()) {
+                Cursor<T> nextCursor = transform(mCursor.next());
+                if (nextCursor != null) {
+                    if (nextCursor.hasNext()) {
+                        mNextCursor = nextCursor;
+                        return true;
                     }
-                    interruptCheck(++count);
+                    nextCursor.close();
                 }
-            } catch (NoSuchElementException e) {
+                interruptCheck(++count);
             }
-            return false;
+        } catch (NoSuchElementException e) {
         }
+        return false;
     }
 
     public T next() throws FetchException {
-        synchronized (mCursor) {
-            if (hasNext()) {
-                return mNextCursor.next();
-            }
-            throw new NoSuchElementException();
+        if (hasNext()) {
+            return mNextCursor.next();
         }
+        throw new NoSuchElementException();
     }
 
     public int skipNext(int amount) throws FetchException {
-        synchronized (mCursor) {
-            if (amount <= 0) {
-                if (amount < 0) {
-                    throw new IllegalArgumentException("Cannot skip negative amount: " + amount);
-                }
-                return 0;
+        if (amount <= 0) {
+            if (amount < 0) {
+                throw new IllegalArgumentException("Cannot skip negative amount: " + amount);
             }
+            return 0;
+        }
 
-            int count = 0;
-            while (hasNext()) {
-                int chunk = mNextCursor.skipNext(amount);
-                count += chunk;
-                if ((amount -= chunk) <= 0) {
-                    break;
-                }
-                interruptCheck(count);
+        int count = 0;
+        while (hasNext()) {
+            int chunk = mNextCursor.skipNext(amount);
+            count += chunk;
+            if ((amount -= chunk) <= 0) {
+                break;
             }
-
-            return count;
+            interruptCheck(count);
         }
+
+        return count;
     }
 
     private void interruptCheck(int count) throws FetchException {
diff --git a/src/main/java/com/amazon/carbonado/cursor/SortedCursor.java b/src/main/java/com/amazon/carbonado/cursor/SortedCursor.java
index 7a728bb..9cee89b 100644
--- a/src/main/java/com/amazon/carbonado/cursor/SortedCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/SortedCursor.java
@@ -198,13 +198,13 @@ public class SortedCursor<S> extends AbstractCursor<S> {
         };
     }
 
-    public synchronized void close() throws FetchException {
+    public void close() throws FetchException {
         mCursor.close();
         mChunkIterator = null;
         mChunkBuffer.close();
     }
 
-    public synchronized boolean hasNext() throws FetchException {
+    public boolean hasNext() throws FetchException {
         prepareNextChunk();
         try {
             if (mChunkIterator.hasNext()) {
@@ -217,7 +217,7 @@ public class SortedCursor<S> extends AbstractCursor<S> {
         return false;
     }
 
-    public synchronized S next() throws FetchException {
+    public S next() throws FetchException {
         prepareNextChunk();
         try {
             return mChunkIterator.next();
@@ -233,7 +233,7 @@ public class SortedCursor<S> extends AbstractCursor<S> {
         }
     }
 
-    public synchronized int skipNext(int amount) throws FetchException {
+    public int skipNext(int amount) throws FetchException {
         if (amount <= 0) {
             if (amount < 0) {
                 throw new IllegalArgumentException("Cannot skip negative amount: " + amount);
diff --git a/src/main/java/com/amazon/carbonado/cursor/SymmetricDifferenceCursor.java b/src/main/java/com/amazon/carbonado/cursor/SymmetricDifferenceCursor.java
index 6851464..1f94e30 100644
--- a/src/main/java/com/amazon/carbonado/cursor/SymmetricDifferenceCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/SymmetricDifferenceCursor.java
@@ -60,7 +60,7 @@ public class SymmetricDifferenceCursor<S> extends AbstractCursor<S> {
         mOrder = order;
     }
 
-    public synchronized void close() throws FetchException {
+    public void close() throws FetchException {
         mLeftCursor.close();
         mRightCursor.close();
         mNextLeft = null;
@@ -76,7 +76,7 @@ public class SymmetricDifferenceCursor<S> extends AbstractCursor<S> {
      * left source cursor, and &gt;0 if next element is from right source
      * cursor.
      */
-    public synchronized int compareNext() throws FetchException {
+    public int compareNext() throws FetchException {
         if (mCompareResult != 0) {
             return mCompareResult;
         }
@@ -105,7 +105,7 @@ public class SymmetricDifferenceCursor<S> extends AbstractCursor<S> {
         }
     }
 
-    public synchronized S next() throws FetchException {
+    public S next() throws FetchException {
         S next;
         int result = compareNext();
         if (result < 0) {
diff --git a/src/main/java/com/amazon/carbonado/cursor/TransformedCursor.java b/src/main/java/com/amazon/carbonado/cursor/TransformedCursor.java
index 0860cf0..9f9efe7 100644
--- a/src/main/java/com/amazon/carbonado/cursor/TransformedCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/TransformedCursor.java
@@ -53,61 +53,53 @@ public abstract class TransformedCursor<S, T> extends AbstractCursor<T> {
     protected abstract T transform(S storable) throws FetchException;
 
     public void close() throws FetchException {
-        synchronized (mCursor) {
-            mCursor.close();
-            mNext = null;
-        }
+        mCursor.close();
+        mNext = null;
     }
 
     public boolean hasNext() throws FetchException {
-        synchronized (mCursor) {
-            if (mNext != null) {
-                return true;
-            }
-            try {
-                int count = 0;
-                while (mCursor.hasNext()) {
-                    T next = transform(mCursor.next());
-                    if (next != null) {
-                        mNext = next;
-                        return true;
-                    }
-                    interruptCheck(++count);
+        if (mNext != null) {
+            return true;
+        }
+        try {
+            int count = 0;
+            while (mCursor.hasNext()) {
+                T next = transform(mCursor.next());
+                if (next != null) {
+                    mNext = next;
+                    return true;
                 }
-            } catch (NoSuchElementException e) {
+                interruptCheck(++count);
             }
-            return false;
+        } catch (NoSuchElementException e) {
         }
+        return false;
     }
 
     public T next() throws FetchException {
-        synchronized (mCursor) {
-            if (hasNext()) {
-                T next = mNext;
-                mNext = null;
-                return next;
-            }
-            throw new NoSuchElementException();
+        if (hasNext()) {
+            T next = mNext;
+            mNext = null;
+            return next;
         }
+        throw new NoSuchElementException();
     }
 
     public int skipNext(int amount) throws FetchException {
-        synchronized (mCursor) {
-            if (amount <= 0) {
-                if (amount < 0) {
-                    throw new IllegalArgumentException("Cannot skip negative amount: " + amount);
-                }
-                return 0;
-            }
-
-            int count = 0;
-            while (--amount >= 0 && hasNext()) {
-                interruptCheck(++count);
-                mNext = null;
+        if (amount <= 0) {
+            if (amount < 0) {
+                throw new IllegalArgumentException("Cannot skip negative amount: " + amount);
             }
+            return 0;
+        }
 
-            return count;
+        int count = 0;
+        while (--amount >= 0 && hasNext()) {
+            interruptCheck(++count);
+            mNext = null;
         }
+
+        return count;
     }
 
     private void interruptCheck(int count) throws FetchException {
diff --git a/src/main/java/com/amazon/carbonado/cursor/UnionCursor.java b/src/main/java/com/amazon/carbonado/cursor/UnionCursor.java
index 7a62678..7e4fde3 100644
--- a/src/main/java/com/amazon/carbonado/cursor/UnionCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/UnionCursor.java
@@ -59,14 +59,14 @@ public class UnionCursor<S> extends AbstractCursor<S> {
         mOrder = order;
     }
 
-    public synchronized void close() throws FetchException {
+    public void close() throws FetchException {
         mLeftCursor.close();
         mRightCursor.close();
         mNextLeft = null;
         mNextRight = null;
     }
 
-    public synchronized boolean hasNext() throws FetchException {
+    public boolean hasNext() throws FetchException {
         if (mNextLeft == null && mLeftCursor.hasNext()) {
             mNextLeft = mLeftCursor.next();
         }
@@ -76,7 +76,7 @@ public class UnionCursor<S> extends AbstractCursor<S> {
         return mNextLeft != null || mNextRight != null;
     }
 
-    public synchronized S next() throws FetchException {
+    public S next() throws FetchException {
         if (hasNext()) {
             S next;
             if (mNextLeft == null) {
-- 
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