From ea1374c003ecc195295dfc42cc68a02f0d47e8af Mon Sep 17 00:00:00 2001
From: "Brian S. O'Neill" <bronee@gmail.com>
Date: Sat, 4 Aug 2007 18:27:54 +0000
Subject: Added convenience method, Query.exists()

---
 src/main/java/com/amazon/carbonado/Query.java            | 10 ++++++++++
 src/main/java/com/amazon/carbonado/qe/EmptyQuery.java    |  7 +++++++
 src/main/java/com/amazon/carbonado/qe/StandardQuery.java |  9 +++++++++
 src/main/java/com/amazon/carbonado/spi/WrappedQuery.java |  4 ++++
 4 files changed, 30 insertions(+)

(limited to 'src/main/java')

diff --git a/src/main/java/com/amazon/carbonado/Query.java b/src/main/java/com/amazon/carbonado/Query.java
index e27e484..a729331 100644
--- a/src/main/java/com/amazon/carbonado/Query.java
+++ b/src/main/java/com/amazon/carbonado/Query.java
@@ -351,6 +351,16 @@ public interface Query<S extends Storable> {
      */
     long count() throws FetchException;
 
+    /**
+     * Returns true if any results are matched by this query.
+     *
+     * @return true if any matches
+     * @throws IllegalStateException if any blank parameters in this query
+     * @throws FetchException if storage layer throws an exception
+     * @since 1.2
+     */
+    boolean exists() throws FetchException;
+
     /**
      * Print the native query to standard out, which is useful for performance
      * analysis. Not all repositories have a native query format. An example
diff --git a/src/main/java/com/amazon/carbonado/qe/EmptyQuery.java b/src/main/java/com/amazon/carbonado/qe/EmptyQuery.java
index 31d9dd3..1a970e0 100644
--- a/src/main/java/com/amazon/carbonado/qe/EmptyQuery.java
+++ b/src/main/java/com/amazon/carbonado/qe/EmptyQuery.java
@@ -106,6 +106,13 @@ public final class EmptyQuery<S extends Storable> extends AbstractQuery<S> {
         return 0;
     }
 
+    /**
+     * Always returns false.
+     */
+    public boolean exists() {
+        return false;
+    }
+
     /**
      * Always throws an IllegalStateException.
      */
diff --git a/src/main/java/com/amazon/carbonado/qe/StandardQuery.java b/src/main/java/com/amazon/carbonado/qe/StandardQuery.java
index ec9bf4e..2d7995e 100644
--- a/src/main/java/com/amazon/carbonado/qe/StandardQuery.java
+++ b/src/main/java/com/amazon/carbonado/qe/StandardQuery.java
@@ -294,6 +294,15 @@ public abstract class StandardQuery<S extends Storable> extends AbstractQuery<S>
         }
     }
 
+    public boolean exists() throws FetchException {
+        Cursor<S> cursor = fetch();
+        try {
+            return cursor.skipNext(1) > 0;
+        } finally {
+            cursor.close();
+        }
+    }
+
     public boolean printNative(Appendable app, int indentLevel) throws IOException {
         try {
             return executor().printNative(app, indentLevel, mValues);
diff --git a/src/main/java/com/amazon/carbonado/spi/WrappedQuery.java b/src/main/java/com/amazon/carbonado/spi/WrappedQuery.java
index ba3c013..bee05f0 100644
--- a/src/main/java/com/amazon/carbonado/spi/WrappedQuery.java
+++ b/src/main/java/com/amazon/carbonado/spi/WrappedQuery.java
@@ -167,6 +167,10 @@ public abstract class WrappedQuery<S extends Storable> implements Query<S> {
         return mQuery.count();
     }
 
+    public boolean exists() throws FetchException {
+        return mQuery.exists();
+    }
+
     public boolean printNative() {
         return mQuery.printNative();
     }
-- 
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