Added convenience method, Query.exists()

4 files changed, 30 insertions, 0 deletions

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
@@ -352,6 +352,16 @@ 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

      * native format is SQL.

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
@@ -107,6 +107,13 @@ public final class EmptyQuery<S extends Storable> extends AbstractQuery<S> {
     }

 

     /**

+     * Always returns false.

+     */

+    public boolean exists() {

+        return false;

+    }

+

+    /**

      * Always throws an IllegalStateException.

      */

     public Query<S> with(int value) {

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();

     }