From 17f39437744585c656cf37d4515a0b115cc73cc8 Mon Sep 17 00:00:00 2001
From: "Brian S. O'Neill" <bronee@gmail.com>
Date: Mon, 29 Jan 2007 23:24:57 +0000
Subject: Fixed multiple cursor implementations to be extra paranoid and close
 the cursor when an exception is thrown.

---
 .../amazon/carbonado/cursor/AbstractCursor.java    |  85 ++++++---
 .../amazon/carbonado/cursor/DifferenceCursor.java  |  72 +++++---
 .../amazon/carbonado/cursor/FilteredCursor.java    |  45 +++--
 .../com/amazon/carbonado/cursor/GroupedCursor.java |  45 +++--
 .../carbonado/cursor/IntersectionCursor.java       |  84 +++++----
 .../carbonado/cursor/MultiTransformedCursor.java   |  83 ++++++---
 .../com/amazon/carbonado/cursor/SortedCursor.java  |  61 +++++--
 .../cursor/SymmetricDifferenceCursor.java          |  87 +++++----
 .../amazon/carbonado/cursor/ThrottledCursor.java   |  49 +++--
 .../amazon/carbonado/cursor/TransformedCursor.java |  45 +++--
 .../com/amazon/carbonado/cursor/UnionCursor.java   |  62 ++++---
 .../carbonado/repo/indexed/IndexedCursor.java      | 197 ++++++++++++---------
 .../com/amazon/carbonado/repo/jdbc/JDBCCursor.java |  29 ++-
 13 files changed, 637 insertions(+), 307 deletions(-)

(limited to 'src')

diff --git a/src/main/java/com/amazon/carbonado/cursor/AbstractCursor.java b/src/main/java/com/amazon/carbonado/cursor/AbstractCursor.java
index fb34617..5fb0fa8 100644
--- a/src/main/java/com/amazon/carbonado/cursor/AbstractCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/AbstractCursor.java
@@ -37,31 +37,67 @@ public abstract class AbstractCursor<S> implements Cursor<S> {
     }
 
     public int copyInto(Collection<? super S> c) throws FetchException {
-        int originalSize = c.size();
-        while (hasNext()) {
-            c.add(next());
+        try {
+            int originalSize = c.size();
+            while (hasNext()) {
+                c.add(next());
+            }
+            return c.size() - originalSize;
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
-        return c.size() - originalSize;
     }
 
     public int copyInto(Collection<? super S> c, int limit) throws FetchException {
-        int originalSize = c.size();
-        while (--limit >= 0 && hasNext()) {
-            c.add(next());
+        try {
+            int originalSize = c.size();
+            while (--limit >= 0 && hasNext()) {
+                c.add(next());
+            }
+            return c.size() - originalSize;
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
-        return c.size() - originalSize;
     }
 
     public List<S> toList() throws FetchException {
-        List<S> list = new ArrayList<S>();
-        copyInto(list);
-        return list;
+        try {
+            List<S> list = new ArrayList<S>();
+            copyInto(list);
+            return list;
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
+        }
     }
 
     public List<S> toList(int limit) throws FetchException {
-        List<S> list = new ArrayList<S>();
-        copyInto(list, limit);
-        return list;
+        try {
+            List<S> list = new ArrayList<S>();
+            copyInto(list, limit);
+            return list;
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
+        }
     }
 
     public int skipNext(int amount) throws FetchException {
@@ -72,12 +108,21 @@ public abstract class AbstractCursor<S> implements Cursor<S> {
             return 0;
         }
 
-        int count = 0;
-        while (--amount >= 0 && hasNext()) {
-            next();
-            count++;
-        }
+        try {
+            int count = 0;
+            while (--amount >= 0 && hasNext()) {
+                next();
+                count++;
+            }
 
-        return count;
+            return count;
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
+        }
     }
 }
diff --git a/src/main/java/com/amazon/carbonado/cursor/DifferenceCursor.java b/src/main/java/com/amazon/carbonado/cursor/DifferenceCursor.java
index 8b330ea..a04aec0 100644
--- a/src/main/java/com/amazon/carbonado/cursor/DifferenceCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/DifferenceCursor.java
@@ -73,47 +73,65 @@ public class DifferenceCursor<S> extends AbstractCursor<S> {
 
         S nextLeft;
 
-        while (true) {
-            if (mLeftCursor.hasNext()) {
-                nextLeft = mLeftCursor.next();
-            } else {
-                close();
-                return false;
-            }
-            if (mNextRight == null) {
-                if (mRightCursor.hasNext()) {
-                    mNextRight = mRightCursor.next();
+        try {
+            while (true) {
+                if (mLeftCursor.hasNext()) {
+                    nextLeft = mLeftCursor.next();
                 } else {
-                    mNext = nextLeft;
-                    return true;
+                    close();
+                    return false;
                 }
-            }
-
-            while (true) {
-                int result = mOrder.compare(nextLeft, mNextRight);
-                if (result < 0) {
-                    mNext = nextLeft;
-                    return true;
-                } else if (result > 0) {
+                if (mNextRight == null) {
                     if (mRightCursor.hasNext()) {
                         mNextRight = mRightCursor.next();
                     } else {
-                        mNextRight = null;
                         mNext = nextLeft;
                         return true;
                     }
-                } else {
-                    break;
+                }
+
+                while (true) {
+                    int result = mOrder.compare(nextLeft, mNextRight);
+                    if (result < 0) {
+                        mNext = nextLeft;
+                        return true;
+                    } else if (result > 0) {
+                        if (mRightCursor.hasNext()) {
+                            mNextRight = mRightCursor.next();
+                        } else {
+                            mNextRight = null;
+                            mNext = nextLeft;
+                            return true;
+                        }
+                    } else {
+                        break;
+                    }
                 }
             }
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
     }
 
     public S next() throws FetchException {
-        if (hasNext()) {
-            S next = mNext;
-            mNext = null;
-            return next;
+        try {
+            if (hasNext()) {
+                S next = mNext;
+                mNext = null;
+                return next;
+            }
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
         throw new NoSuchElementException();
     }
diff --git a/src/main/java/com/amazon/carbonado/cursor/FilteredCursor.java b/src/main/java/com/amazon/carbonado/cursor/FilteredCursor.java
index f426f36..c25f8db 100644
--- a/src/main/java/com/amazon/carbonado/cursor/FilteredCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/FilteredCursor.java
@@ -101,15 +101,31 @@ public abstract class FilteredCursor<S> extends AbstractCursor<S> {
                 interruptCheck(++count);
             }
         } catch (NoSuchElementException e) {
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
         return false;
     }
 
     public S next() throws FetchException {
-        if (hasNext()) {
-            S next = mNext;
-            mNext = null;
-            return next;
+        try {
+            if (hasNext()) {
+                S next = mNext;
+                mNext = null;
+                return next;
+            }
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
         throw new NoSuchElementException();
     }
@@ -122,13 +138,22 @@ public abstract class FilteredCursor<S> extends AbstractCursor<S> {
             return 0;
         }
 
-        int count = 0;
-        while (--amount >= 0 && hasNext()) {
-            interruptCheck(++count);
-            mNext = null;
-        }
+        try {
+            int count = 0;
+            while (--amount >= 0 && hasNext()) {
+                interruptCheck(++count);
+                mNext = null;
+            }
 
-        return count;
+            return count;
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
+        }
     }
 
     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 202f73a..daf9419 100644
--- a/src/main/java/com/amazon/carbonado/cursor/GroupedCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/GroupedCursor.java
@@ -157,16 +157,32 @@ public abstract class GroupedCursor<S, G> extends AbstractCursor<G> {
                 }
             }
         } catch (NoSuchElementException e) {
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
 
         return false;
     }
 
     public G next() throws FetchException {
-        if (hasNext()) {
-            G next = mNextAggregate;
-            mNextAggregate = null;
-            return next;
+        try {
+            if (hasNext()) {
+                G next = mNextAggregate;
+                mNextAggregate = null;
+                return next;
+            }
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
         throw new NoSuchElementException();
     }
@@ -179,13 +195,22 @@ public abstract class GroupedCursor<S, G> extends AbstractCursor<G> {
             return 0;
         }
 
-        int count = 0;
-        while (--amount >= 0 && hasNext()) {
-            interruptCheck(++count);
-            mNextAggregate = null;
-        }
+        try {
+            int count = 0;
+            while (--amount >= 0 && hasNext()) {
+                interruptCheck(++count);
+                mNextAggregate = null;
+            }
 
-        return count;
+            return count;
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
+        }
     }
 
     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 58aba0d..6eb3179 100644
--- a/src/main/java/com/amazon/carbonado/cursor/IntersectionCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/IntersectionCursor.java
@@ -71,47 +71,65 @@ public class IntersectionCursor<S> extends AbstractCursor<S> {
 
         S nextLeft, nextRight;
 
-        if (mLeftCursor.hasNext()) {
-            nextLeft = mLeftCursor.next();
-        } else {
-            close();
-            return false;
-        }
-        if (mRightCursor.hasNext()) {
-            nextRight = mRightCursor.next();
-        } else {
-            close();
-            return false;
-        }
+        try {
+            if (mLeftCursor.hasNext()) {
+                nextLeft = mLeftCursor.next();
+            } else {
+                close();
+                return false;
+            }
+            if (mRightCursor.hasNext()) {
+                nextRight = mRightCursor.next();
+            } else {
+                close();
+                return false;
+            }
 
-        while (true) {
-            int result = mOrder.compare(nextLeft, nextRight);
-            if (result < 0) {
-                if (mLeftCursor.hasNext()) {
-                    nextLeft = mLeftCursor.next();
+            while (true) {
+                int result = mOrder.compare(nextLeft, nextRight);
+                if (result < 0) {
+                    if (mLeftCursor.hasNext()) {
+                        nextLeft = mLeftCursor.next();
+                    } else {
+                        close();
+                        return false;
+                    }
+                } else if (result > 0) {
+                    if (mRightCursor.hasNext()) {
+                        nextRight = mRightCursor.next();
+                    } else {
+                        close();
+                        return false;
+                    }
                 } else {
-                    close();
-                    return false;
+                    mNext = nextLeft;
+                    return true;
                 }
-            } else if (result > 0) {
-                if (mRightCursor.hasNext()) {
-                    nextRight = mRightCursor.next();
-                } else {
-                    close();
-                    return false;
-                }
-            } else {
-                mNext = nextLeft;
-                return true;
             }
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
     }
 
     public S next() throws FetchException {
-        if (hasNext()) {
-            S next = mNext;
-            mNext = null;
-            return next;
+        try {
+            if (hasNext()) {
+                S next = mNext;
+                mNext = null;
+                return next;
+            }
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
         throw new NoSuchElementException();
     }
diff --git a/src/main/java/com/amazon/carbonado/cursor/MultiTransformedCursor.java b/src/main/java/com/amazon/carbonado/cursor/MultiTransformedCursor.java
index 7606eab..4b4a25a 100644
--- a/src/main/java/com/amazon/carbonado/cursor/MultiTransformedCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/MultiTransformedCursor.java
@@ -64,34 +64,52 @@ public abstract class MultiTransformedCursor<S, T> extends AbstractCursor<T> {
     }
 
     public boolean hasNext() throws FetchException {
-        if (mNextCursor != null) {
-            if (mNextCursor.hasNext()) {
-                return true;
-            }
-            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;
+            if (mNextCursor != null) {
+                if (mNextCursor.hasNext()) {
+                    return true;
+                }
+                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;
+                        }
+                        nextCursor.close();
                     }
-                    nextCursor.close();
+                    interruptCheck(++count);
                 }
-                interruptCheck(++count);
+            } catch (NoSuchElementException e) {
+            }
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
             }
-        } catch (NoSuchElementException e) {
+            throw e;
         }
         return false;
     }
 
     public T next() throws FetchException {
-        if (hasNext()) {
-            return mNextCursor.next();
+        try {
+            if (hasNext()) {
+                return mNextCursor.next();
+            }
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
         throw new NoSuchElementException();
     }
@@ -104,17 +122,26 @@ public abstract class MultiTransformedCursor<S, T> extends AbstractCursor<T> {
             return 0;
         }
 
-        int count = 0;
-        while (hasNext()) {
-            int chunk = mNextCursor.skipNext(amount);
-            count += chunk;
-            if ((amount -= chunk) <= 0) {
-                break;
+        try {
+            int count = 0;
+            while (hasNext()) {
+                int chunk = mNextCursor.skipNext(amount);
+                count += chunk;
+                if ((amount -= chunk) <= 0) {
+                    break;
+                }
+                interruptCheck(count);
             }
-            interruptCheck(count);
-        }
 
-        return count;
+            return count;
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
+        }
     }
 
     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 9cee89b..15a72d9 100644
--- a/src/main/java/com/amazon/carbonado/cursor/SortedCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/SortedCursor.java
@@ -205,28 +205,46 @@ public class SortedCursor<S> extends AbstractCursor<S> {
     }
 
     public boolean hasNext() throws FetchException {
-        prepareNextChunk();
         try {
-            if (mChunkIterator.hasNext()) {
-                return true;
+            prepareNextChunk();
+            try {
+                if (mChunkIterator.hasNext()) {
+                    return true;
+                }
+            } catch (UndeclaredThrowableException e) {
+                throw toFetchException(e);
             }
-        } catch (UndeclaredThrowableException e) {
-            throw toFetchException(e);
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
         close();
         return false;
     }
 
     public S next() throws FetchException {
-        prepareNextChunk();
         try {
-            return mChunkIterator.next();
-        } catch (UndeclaredThrowableException e) {
-            throw toFetchException(e);
-        } catch (NoSuchElementException e) {
+            prepareNextChunk();
+            try {
+                return mChunkIterator.next();
+            } catch (UndeclaredThrowableException e) {
+                throw toFetchException(e);
+            } catch (NoSuchElementException e) {
+                try {
+                    close();
+                } catch (FetchException e2) {
+                    // Don't care.
+                }
+                throw e;
+            }
+        } catch (FetchException e) {
             try {
                 close();
-            } catch (FetchException e2) {
+            } catch (Exception e2) {
                 // Don't care.
             }
             throw e;
@@ -241,13 +259,22 @@ public class SortedCursor<S> extends AbstractCursor<S> {
             return 0;
         }
 
-        int count = 0;
-        while (--amount >= 0 && hasNext()) {
-            next();
-            count++;
-        }
+        try {
+            int count = 0;
+            while (--amount >= 0 && hasNext()) {
+                next();
+                count++;
+            }
 
-        return count;
+            return count;
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
+        }
     }
 
     private void prepareNextChunk() throws FetchException {
diff --git a/src/main/java/com/amazon/carbonado/cursor/SymmetricDifferenceCursor.java b/src/main/java/com/amazon/carbonado/cursor/SymmetricDifferenceCursor.java
index 1f94e30..1cd381a 100644
--- a/src/main/java/com/amazon/carbonado/cursor/SymmetricDifferenceCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/SymmetricDifferenceCursor.java
@@ -68,7 +68,16 @@ public class SymmetricDifferenceCursor<S> extends AbstractCursor<S> {
     }
 
     public boolean hasNext() throws FetchException {
-        return compareNext() != 0;
+        try {
+            return compareNext() != 0;
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
+        }
     }
 
     /**
@@ -81,43 +90,61 @@ public class SymmetricDifferenceCursor<S> extends AbstractCursor<S> {
             return mCompareResult;
         }
 
-        while (true) {
-            if (mNextLeft == null && mLeftCursor.hasNext()) {
-                mNextLeft = mLeftCursor.next();
-            }
-            if (mNextRight == null && mRightCursor.hasNext()) {
-                mNextRight = mRightCursor.next();
-            }
+        try {
+            while (true) {
+                if (mNextLeft == null && mLeftCursor.hasNext()) {
+                    mNextLeft = mLeftCursor.next();
+                }
+                if (mNextRight == null && mRightCursor.hasNext()) {
+                    mNextRight = mRightCursor.next();
+                }
 
-            if (mNextLeft == null) {
-                return mNextRight != null ? 1 : 0;
+                if (mNextLeft == null) {
+                    return mNextRight != null ? 1 : 0;
+                }
+                if (mNextRight == null) {
+                    return -1;
+                }
+
+                if ((mCompareResult = mOrder.compare(mNextLeft, mNextRight)) == 0) {
+                    mNextLeft = null;
+                    mNextRight = null;
+                } else {
+                    return mCompareResult;
+                }
             }
-            if (mNextRight == null) {
-                return -1;
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
             }
+            throw e;
+        }
+    }
 
-            if ((mCompareResult = mOrder.compare(mNextLeft, mNextRight)) == 0) {
+    public S next() throws FetchException {
+        try {
+            S next;
+            int result = compareNext();
+            if (result < 0) {
+                next = mNextLeft;
                 mNextLeft = null;
+            } else if (result > 0) {
+                next = mNextRight;
                 mNextRight = null;
             } else {
-                return mCompareResult;
+                throw new NoSuchElementException();
             }
+            mCompareResult = 0;
+            return next;
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
     }
-
-    public S next() throws FetchException {
-        S next;
-        int result = compareNext();
-        if (result < 0) {
-            next = mNextLeft;
-            mNextLeft = null;
-        } else if (result > 0) {
-            next = mNextRight;
-            mNextRight = null;
-        } else {
-            throw new NoSuchElementException();
-        }
-        mCompareResult = 0;
-        return next;
-    }
 }
diff --git a/src/main/java/com/amazon/carbonado/cursor/ThrottledCursor.java b/src/main/java/com/amazon/carbonado/cursor/ThrottledCursor.java
index 2f4c5a0..d108d95 100644
--- a/src/main/java/com/amazon/carbonado/cursor/ThrottledCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/ThrottledCursor.java
@@ -61,12 +61,30 @@ public class ThrottledCursor<S> extends AbstractCursor<S> {
     }
 
     public boolean hasNext() throws FetchException {
-        return mCursor.hasNext();
+        try {
+            return mCursor.hasNext();
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
+        }
     }
 
     public S next() throws FetchException {
-        throttle();
-        return mCursor.next();
+        try {
+            throttle();
+            return mCursor.next();
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
+        }
     }
 
     public int skipNext(int amount) throws FetchException {
@@ -77,16 +95,25 @@ public class ThrottledCursor<S> extends AbstractCursor<S> {
             return 0;
         }
 
-        int count = 0;
-        while (--amount >= 0) {
-            throttle();
-            if (skipNext(1) <= 0) {
-                break;
+        try {
+            int count = 0;
+            while (--amount >= 0) {
+                throttle();
+                if (skipNext(1) <= 0) {
+                    break;
+                }
+                count++;
             }
-            count++;
-        }
 
-        return count;
+            return count;
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
+        }
     }
 
     private void throttle() throws FetchInterruptedException {
diff --git a/src/main/java/com/amazon/carbonado/cursor/TransformedCursor.java b/src/main/java/com/amazon/carbonado/cursor/TransformedCursor.java
index 70161cc..46dedd1 100644
--- a/src/main/java/com/amazon/carbonado/cursor/TransformedCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/TransformedCursor.java
@@ -74,15 +74,31 @@ public abstract class TransformedCursor<S, T> extends AbstractCursor<T> {
                 interruptCheck(++count);
             }
         } catch (NoSuchElementException e) {
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
         return false;
     }
 
     public T next() throws FetchException {
-        if (hasNext()) {
-            T next = mNext;
-            mNext = null;
-            return next;
+        try {
+            if (hasNext()) {
+                T next = mNext;
+                mNext = null;
+                return next;
+            }
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
         throw new NoSuchElementException();
     }
@@ -95,13 +111,22 @@ public abstract class TransformedCursor<S, T> extends AbstractCursor<T> {
             return 0;
         }
 
-        int count = 0;
-        while (--amount >= 0 && hasNext()) {
-            interruptCheck(++count);
-            mNext = null;
-        }
+        try {
+            int count = 0;
+            while (--amount >= 0 && hasNext()) {
+                interruptCheck(++count);
+                mNext = null;
+            }
 
-        return count;
+            return count;
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
+        }
     }
 
     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 7e4fde3..c2bdd19 100644
--- a/src/main/java/com/amazon/carbonado/cursor/UnionCursor.java
+++ b/src/main/java/com/amazon/carbonado/cursor/UnionCursor.java
@@ -67,39 +67,57 @@ public class UnionCursor<S> extends AbstractCursor<S> {
     }
 
     public boolean hasNext() throws FetchException {
-        if (mNextLeft == null && mLeftCursor.hasNext()) {
-            mNextLeft = mLeftCursor.next();
-        }
-        if (mNextRight == null && mRightCursor.hasNext()) {
-            mNextRight = mRightCursor.next();
+        try {
+            if (mNextLeft == null && mLeftCursor.hasNext()) {
+                mNextLeft = mLeftCursor.next();
+            }
+            if (mNextRight == null && mRightCursor.hasNext()) {
+                mNextRight = mRightCursor.next();
+            }
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
         return mNextLeft != null || mNextRight != null;
     }
 
     public S next() throws FetchException {
-        if (hasNext()) {
-            S next;
-            if (mNextLeft == null) {
-                next = mNextRight;
-                mNextRight = null;
-            } else if (mNextRight == null) {
-                next = mNextLeft;
-                mNextLeft = null;
-            } else {
-                int result = mOrder.compare(mNextLeft, mNextRight);
-                if (result < 0) {
-                    next = mNextLeft;
-                    mNextLeft = null;
-                } else if (result > 0) {
+        try {
+            if (hasNext()) {
+                S next;
+                if (mNextLeft == null) {
                     next = mNextRight;
                     mNextRight = null;
-                } else {
+                } else if (mNextRight == null) {
                     next = mNextLeft;
                     mNextLeft = null;
-                    mNextRight = null;
+                } else {
+                    int result = mOrder.compare(mNextLeft, mNextRight);
+                    if (result < 0) {
+                        next = mNextLeft;
+                        mNextLeft = null;
+                    } else if (result > 0) {
+                        next = mNextRight;
+                        mNextRight = null;
+                    } else {
+                        next = mNextLeft;
+                        mNextLeft = null;
+                        mNextRight = null;
+                    }
                 }
+                return next;
+            }
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
             }
-            return next;
+            throw e;
         }
         throw new NoSuchElementException();
     }
diff --git a/src/main/java/com/amazon/carbonado/repo/indexed/IndexedCursor.java b/src/main/java/com/amazon/carbonado/repo/indexed/IndexedCursor.java
index 892af49..35fc492 100644
--- a/src/main/java/com/amazon/carbonado/repo/indexed/IndexedCursor.java
+++ b/src/main/java/com/amazon/carbonado/repo/indexed/IndexedCursor.java
@@ -63,117 +63,144 @@ class IndexedCursor<S extends Storable> extends AbstractCursor<S> {
         if (mNext != null) {
             return true;
         }
-        while (mCursor.hasNext()) {
-            final Storable indexEntry = mCursor.next();
-
-            S master = mStorage.mMasterStorage.prepare();
-            mGenerator.copyToMasterPrimaryKey(indexEntry, master);
-
-            if (!master.tryLoad()) {
-                LogFactory.getLog(getClass()).warn
-                    ("Master is missing for index entry: " + indexEntry);
-            } else {
-                if (mGenerator.isConsistent(indexEntry, master)) {
-                    mNext = master;
-                    return true;
-                }
-
-                // This index entry is stale. Repair is needed.
-
-                // Insert a correct index entry, just to be sure.
-                try {
-                    final IndexedRepository repo = mStorage.mRepository;
-                    final Storage<?> indexEntryStorage =
-                        repo.getIndexEntryStorageFor(mGenerator.getIndexEntryClass());
-                    Storable newIndexEntry = indexEntryStorage.prepare();
-                    mGenerator.copyFromMaster(newIndexEntry, master);
-
-                    if (newIndexEntry.tryLoad()) {
-                        // Good, the correct index entry exists. We'll see
-                        // the master record eventually, so skip.
-                    } else {
-                        // We have no choice but to return the master, at
-                        // the risk of seeing it multiple times. This is
-                        // better than seeing it never.
-                        LogFactory.getLog(getClass()).warn
-                            ("Inconsistent index entry: " + indexEntry);
+        try {
+            while (mCursor.hasNext()) {
+                final Storable indexEntry = mCursor.next();
+
+                S master = mStorage.mMasterStorage.prepare();
+                mGenerator.copyToMasterPrimaryKey(indexEntry, master);
+
+                if (!master.tryLoad()) {
+                    LogFactory.getLog(getClass()).warn
+                        ("Master is missing for index entry: " + indexEntry);
+                } else {
+                    if (mGenerator.isConsistent(indexEntry, master)) {
                         mNext = master;
+                        return true;
                     }
 
-                    // Repair the stale index entry.
-                    RepairExecutor.execute(new Runnable() {
-                        public void run() {
-                            Transaction txn = repo.enterTransaction();
-                            try {
-                                // Reload master and verify inconsistency.
-                                S master = mStorage.mMasterStorage.prepare();
-                                mGenerator.copyToMasterPrimaryKey(indexEntry, master);
-
-                                if (master.tryLoad()) {
-                                    Storable newIndexEntry = indexEntryStorage.prepare();
-                                    mGenerator.copyFromMaster(newIndexEntry, master);
-
-                                    newIndexEntry.tryInsert();
+                    // This index entry is stale. Repair is needed.
+
+                    // Insert a correct index entry, just to be sure.
+                    try {
+                        final IndexedRepository repo = mStorage.mRepository;
+                        final Storage<?> indexEntryStorage =
+                            repo.getIndexEntryStorageFor(mGenerator.getIndexEntryClass());
+                        Storable newIndexEntry = indexEntryStorage.prepare();
+                        mGenerator.copyFromMaster(newIndexEntry, master);
+
+                        if (newIndexEntry.tryLoad()) {
+                            // Good, the correct index entry exists. We'll see
+                            // the master record eventually, so skip.
+                        } else {
+                            // We have no choice but to return the master, at
+                            // the risk of seeing it multiple times. This is
+                            // better than seeing it never.
+                            LogFactory.getLog(getClass()).warn
+                                ("Inconsistent index entry: " + indexEntry);
+                            mNext = master;
+                        }
 
-                                    indexEntry.tryDelete();
-                                    txn.commit();
-                                }
-                            } catch (FetchException fe) {
-                                LogFactory.getLog(IndexedCursor.class).warn
-                                    ("Unable to check if repair required for " +
-                                     "inconsistent index entry " +
-                                     indexEntry, fe);
-                            } catch (PersistException pe) {
-                                LogFactory.getLog(IndexedCursor.class).error
-                                    ("Unable to repair inconsistent index entry " +
-                                     indexEntry, pe);
-                            } finally {
+                        // Repair the stale index entry.
+                        RepairExecutor.execute(new Runnable() {
+                            public void run() {
+                                Transaction txn = repo.enterTransaction();
                                 try {
-                                    txn.exit();
+                                    // Reload master and verify inconsistency.
+                                    S master = mStorage.mMasterStorage.prepare();
+                                    mGenerator.copyToMasterPrimaryKey(indexEntry, master);
+
+                                    if (master.tryLoad()) {
+                                        Storable newIndexEntry = indexEntryStorage.prepare();
+                                        mGenerator.copyFromMaster(newIndexEntry, master);
+
+                                        newIndexEntry.tryInsert();
+
+                                        indexEntry.tryDelete();
+                                        txn.commit();
+                                    }
+                                } catch (FetchException fe) {
+                                    LogFactory.getLog(IndexedCursor.class).warn
+                                        ("Unable to check if repair required for " +
+                                         "inconsistent index entry " +
+                                         indexEntry, fe);
                                 } catch (PersistException pe) {
                                     LogFactory.getLog(IndexedCursor.class).error
                                         ("Unable to repair inconsistent index entry " +
                                          indexEntry, pe);
+                                } finally {
+                                    try {
+                                        txn.exit();
+                                    } catch (PersistException pe) {
+                                        LogFactory.getLog(IndexedCursor.class).error
+                                            ("Unable to repair inconsistent index entry " +
+                                             indexEntry, pe);
+                                    }
                                 }
                             }
-                        }
-                    });
-                } catch (RepositoryException re) {
-                    LogFactory.getLog(getClass()).error
-                        ("Unable to inspect inconsistent index entry " +
-                         indexEntry, re);
-                }
+                        });
+                    } catch (RepositoryException re) {
+                        LogFactory.getLog(getClass()).error
+                            ("Unable to inspect inconsistent index entry " +
+                             indexEntry, re);
+                    }
 
-                if (mNext != null) {
-                    return true;
+                    if (mNext != null) {
+                        return true;
+                    }
                 }
             }
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
         return false;
     }
 
     public S next() throws FetchException {
-        if (hasNext()) {
-            S next = mNext;
-            mNext = null;
-            return next;
+        try {
+            if (hasNext()) {
+                S next = mNext;
+                mNext = null;
+                return next;
+            }
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
         }
         throw new NoSuchElementException();
     }
 
     public int skipNext(int amount) throws FetchException {
-        if (mNext == null) {
-            return mCursor.skipNext(amount);
-        }
+        try {
+            if (mNext == null) {
+                return mCursor.skipNext(amount);
+            }
 
-        if (amount <= 0) {
-            if (amount < 0) {
-                throw new IllegalArgumentException("Cannot skip negative amount: " + amount);
+            if (amount <= 0) {
+                if (amount < 0) {
+                    throw new IllegalArgumentException("Cannot skip negative amount: " + amount);
+                }
+                return 0;
             }
-            return 0;
-        }
 
-        mNext = null;
-        return 1 + mCursor.skipNext(amount - 1);
+            mNext = null;
+            return 1 + mCursor.skipNext(amount - 1);
+        } catch (FetchException e) {
+            try {
+                close();
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
+        }
     }
 }
diff --git a/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCCursor.java b/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCCursor.java
index f419c0d..fa80fde 100644
--- a/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCCursor.java
+++ b/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCCursor.java
@@ -35,10 +35,10 @@ import com.amazon.carbonado.cursor.AbstractCursor;
  */
 class JDBCCursor<S extends Storable> extends AbstractCursor<S> {
     private final JDBCStorage<S> mStorage;
-    private Connection mConnection;
-    private PreparedStatement mStatement;
-    private ResultSet mResultSet;
+    private final Connection mConnection;
+    private final PreparedStatement mStatement;
 
+    private ResultSet mResultSet;
     private boolean mHasNext;
 
     JDBCCursor(JDBCStorage<S> storage,
@@ -49,7 +49,17 @@ class JDBCCursor<S extends Storable> extends AbstractCursor<S> {
         mStorage = storage;
         mConnection = con;
         mStatement = statement;
-        mResultSet = statement.executeQuery();
+        try {
+            mResultSet = statement.executeQuery();
+        } catch (SQLException e) {
+            try {
+                statement.close();
+                storage.mRepository.yieldConnection(con);
+            } catch (Exception e2) {
+                // Don't care.
+            }
+            throw e;
+        }
     }
 
     public void close() throws FetchException {
@@ -62,6 +72,7 @@ class JDBCCursor<S extends Storable> extends AbstractCursor<S> {
                 throw mStorage.getJDBCRepository().toFetchException(e);
             } finally {
                 mResultSet = null;
+                mHasNext = false;
             }
         }
     }
@@ -75,6 +86,11 @@ class JDBCCursor<S extends Storable> extends AbstractCursor<S> {
             try {
                 mHasNext = rs.next();
             } catch (SQLException e) {
+                try {
+                    close();
+                } catch (FetchException e2) {
+                    // Don't care.
+                }
                 throw mStorage.getJDBCRepository().toFetchException(e);
             }
             if (!mHasNext) {
@@ -93,6 +109,11 @@ class JDBCCursor<S extends Storable> extends AbstractCursor<S> {
             mHasNext = false;
             return obj;
         } catch (SQLException e) {
+            try {
+                close();
+            } catch (FetchException e2) {
+                // Don't care.
+            }
             throw mStorage.getJDBCRepository().toFetchException(e);
         }
     }
-- 
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