Support query fetch limits.

6 files changed, 94 insertions, 1 deletions

diff --git a/src/main/java/com/amazon/carbonado/qe/AbstractQuery.java b/src/main/java/com/amazon/carbonado/qe/AbstractQuery.java
index 7639348..767b039 100644
--- a/src/main/java/com/amazon/carbonado/qe/AbstractQuery.java
+++ b/src/main/java/com/amazon/carbonado/qe/AbstractQuery.java
@@ -129,4 +129,26 @@ public abstract class AbstractQuery<S extends Storable> implements Query<S>, App
 

     @Override

     public abstract boolean equals(Object obj);

+

+    /**

+     * Called by sliced fetch to ensure that arguments are valid.

+     *

+     * @return false if from is 0 and to is null

+     * @throws IllegalArgumentException if arguments are invalid

+     * @since 1.2

+     */

+    protected boolean checkSliceArguments(long from, Long to) {

+        if (from < 0) {

+            throw new IllegalArgumentException("Slice from is negative: " + from);

+        }

+        if (to == null) {

+            if (from == 0) {

+                return false;

+            }

+        } else if (from > to) {

+            throw new IllegalArgumentException

+                ("Slice from is more than to: " + from + " > " + to);

+        }

+        return true;

+    }

 }

diff --git a/src/main/java/com/amazon/carbonado/qe/AbstractQueryExecutor.java b/src/main/java/com/amazon/carbonado/qe/AbstractQueryExecutor.java
index dc67fc1..8a8a127 100644
--- a/src/main/java/com/amazon/carbonado/qe/AbstractQueryExecutor.java
+++ b/src/main/java/com/amazon/carbonado/qe/AbstractQueryExecutor.java
@@ -24,6 +24,9 @@ import com.amazon.carbonado.Cursor;
 import com.amazon.carbonado.FetchException;

 import com.amazon.carbonado.Storable;

 

+import com.amazon.carbonado.cursor.LimitCursor;

+import com.amazon.carbonado.cursor.SkipCursor;

+

 import com.amazon.carbonado.filter.FilterValues;

 

 /**

@@ -37,7 +40,25 @@ public abstract class AbstractQueryExecutor<S extends Storable> implements Query
     }

 

     /**

-     * Counts results by opening a cursor and skipping entries.

+     * Produces a slice via skip and limit cursors. Subclasses are encouraged

+     * to override with a more efficient implementation.

+     *

+     * @since 1.2

+     */

+    public Cursor<S> fetch(FilterValues<S> values, long from, Long to) throws FetchException {

+        Cursor<S> cursor = fetch(values);

+        if (from > 0) {

+            cursor = new SkipCursor<S>(cursor, from);

+        }

+        if (to != null) {

+            cursor = new LimitCursor<S>(cursor, to - from);

+        }

+        return cursor;

+    }

+

+    /**

+     * Counts results by opening a cursor and skipping entries. Subclasses are

+     * encouraged to override with a more efficient implementation.

      */

     public long count(FilterValues<S> values) throws FetchException {

         Cursor<S> cursor = fetch(values);

diff --git a/src/main/java/com/amazon/carbonado/qe/DelegatedQueryExecutor.java b/src/main/java/com/amazon/carbonado/qe/DelegatedQueryExecutor.java
index b4bc0a3..3ec209d 100644
--- a/src/main/java/com/amazon/carbonado/qe/DelegatedQueryExecutor.java
+++ b/src/main/java/com/amazon/carbonado/qe/DelegatedQueryExecutor.java
@@ -95,6 +95,10 @@ public class DelegatedQueryExecutor<S extends Storable> implements QueryExecutor
         return applyFilterValues(values).fetch();

     }

 

+    public Cursor<S> fetch(FilterValues<S> values, long from, Long to) throws FetchException {

+        return applyFilterValues(values).fetch(from, to);

+    }

+

     public long count(FilterValues<S> values) throws FetchException {

         return applyFilterValues(values).count();

     }

diff --git a/src/main/java/com/amazon/carbonado/qe/EmptyQuery.java b/src/main/java/com/amazon/carbonado/qe/EmptyQuery.java
index f3d54f5..9754019 100644
--- a/src/main/java/com/amazon/carbonado/qe/EmptyQuery.java
+++ b/src/main/java/com/amazon/carbonado/qe/EmptyQuery.java
@@ -215,11 +215,27 @@ public final class EmptyQuery<S extends Storable> extends AbstractQuery<S> {
     /**

      * Always returns an {@link EmptyCursor}.

      */

+    public Cursor<S> fetch(long from, Long to) {

+        checkSliceArguments(from, to);

+        return EmptyCursor.the();

+    }

+

+    /**

+     * Always returns an {@link EmptyCursor}.

+     */

     public Cursor<S> fetchAfter(S start) {

         return EmptyCursor.the();

     }

 

     /**

+     * Always returns an {@link EmptyCursor}.

+     */

+    public Cursor<S> fetchAfter(S start, long from, Long to) {

+        checkSliceArguments(from, to);

+        return EmptyCursor.the();

+    }

+

+    /**

      * Always throws {@link PersistNoneException}.

      */

     public void deleteOne() throws PersistNoneException {

diff --git a/src/main/java/com/amazon/carbonado/qe/QueryExecutor.java b/src/main/java/com/amazon/carbonado/qe/QueryExecutor.java
index b0ab801..6b5a864 100644
--- a/src/main/java/com/amazon/carbonado/qe/QueryExecutor.java
+++ b/src/main/java/com/amazon/carbonado/qe/QueryExecutor.java
@@ -46,6 +46,13 @@ public interface QueryExecutor<S extends Storable> {
     Cursor<S> fetch(FilterValues<S> values) throws FetchException;

 

     /**

+     * Returns a new cursor using the given filter values and slice.

+     *

+     * @since 1.2

+     */

+    Cursor<S> fetch(FilterValues<S> values, long from, Long to) throws FetchException;

+

+    /**

      * Counts the query results using the given filter values.

      */

     long count(FilterValues<S> values) throws FetchException;

diff --git a/src/main/java/com/amazon/carbonado/qe/StandardQuery.java b/src/main/java/com/amazon/carbonado/qe/StandardQuery.java
index 5596c32..10fdf43 100644
--- a/src/main/java/com/amazon/carbonado/qe/StandardQuery.java
+++ b/src/main/java/com/amazon/carbonado/qe/StandardQuery.java
@@ -217,6 +217,18 @@ public abstract class StandardQuery<S extends Storable> extends AbstractQuery<S>
         }

     }

 

+    public Cursor<S> fetch(long from, Long to) throws FetchException {

+        if (!checkSliceArguments(from, to)) {

+            return fetch();

+        }

+        try {

+            QueryHints hints = QueryHints.emptyHints().with(QueryHint.CONSUME_SLICE);

+            return executorFactory().executor(mFilter, mOrdering, hints).fetch(mValues, from, to);

+        } catch (RepositoryException e) {

+            throw e.toFetchException();

+        }

+    }

+

     public Cursor<S> fetchAfter(S start) throws FetchException {

         OrderingList<S> orderings;

         if (start == null || (orderings = mOrdering).size() == 0) {

@@ -225,6 +237,17 @@ public abstract class StandardQuery<S extends Storable> extends AbstractQuery<S>
         return buildAfter(start, orderings).fetch();

     }

 

+    public Cursor<S> fetchAfter(S start, long from, Long to) throws FetchException {

+        if (!checkSliceArguments(from, to)) {

+            return fetchAfter(start);

+        }

+        OrderingList<S> orderings;

+        if (start == null || (orderings = mOrdering).size() == 0) {

+            return fetch(from, to);

+        }

+        return buildAfter(start, orderings).fetch(from, to);

+    }

+

     private Query<S> buildAfter(S start, OrderingList<S> orderings) throws FetchException {

         Class<S> storableType = getStorableType();

         Filter<S> orderFilter = Filter.getClosedFilter(storableType);