Simplified process for generating table aliases.

2 files changed, 55 insertions, 18 deletions

diff --git a/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCStorage.java b/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCStorage.java
index 9d60741..384f1bc 100644
--- a/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCStorage.java
+++ b/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCStorage.java
@@ -76,7 +76,6 @@ import com.amazon.carbonado.util.QuickConstructorGenerator;
 class JDBCStorage<S extends Storable> extends StandardQueryFactory<S>

     implements Storage<S>, JDBCSupport<S>

 {

-    private static final String TABLE_ALIAS_PREFIX = "T";

     private static final int FIRST_RESULT_INDEX = 1;

 

     final JDBCRepository mRepository;

@@ -298,9 +297,11 @@ class JDBCStorage<S extends Storable> extends StandardQueryFactory<S>
         public QueryExecutor<S> executor(Filter<S> filter, OrderingList<S> ordering)

             throws RepositoryException

         {

+            TableAliasGenerator aliasGenerator = new TableAliasGenerator();

+

             JoinNode jn;

             try {

-                JoinNodeBuilder jnb = new JoinNodeBuilder();

+                JoinNodeBuilder jnb = new JoinNodeBuilder(aliasGenerator);

                 if (filter == null) {

                     jn = new JoinNode(getStorableInfo(), null);

                 } else {

@@ -834,21 +835,20 @@ class JDBCStorage<S extends Storable> extends StandardQueryFactory<S>
             }

         }

 

-        /**

-         * @return new value for aliasCounter

-         */

-        public int addJoin(ChainedProperty<?> chained, int aliasCounter)

+        public void addJoin(ChainedProperty<?> chained, TableAliasGenerator aliasGenerator)

             throws RepositoryException

         {

-            return addJoin(chained, aliasCounter, 0);

+            addJoin(chained, aliasGenerator, 0);

         }

 

-        private int addJoin(ChainedProperty<?> chained, int aliasCounter, int offset)

+        private void addJoin(ChainedProperty<?> chained,

+                             TableAliasGenerator aliasGenerator,

+                             int offset)

             throws RepositoryException

         {

             if ((chained.getChainCount() - offset) <= 0) {

                 // At this point in the chain, there are no more joins.

-                return aliasCounter;

+                return;

             }

             StorableProperty<?> property;

             if (offset == 0) {

@@ -861,10 +861,10 @@ class JDBCStorage<S extends Storable> extends StandardQueryFactory<S>
             if (subNode == null) {

                 JDBCStorableInfo<?> info = mRepository.examineStorable(property.getJoinedType());

                 JDBCStorableProperty<?> jProperty = mRepository.getJDBCStorableProperty(property);

-                subNode = new JoinNode(jProperty, info, TABLE_ALIAS_PREFIX + (++aliasCounter));

+                subNode = new JoinNode(jProperty, info, aliasGenerator.nextAlias());

                 mSubNodes.put(name, subNode);

             }

-            return subNode.addJoin(chained, aliasCounter, offset + 1);

+            subNode.addJoin(chained, aliasGenerator, offset + 1);

         }

 

         public String toString() {

@@ -886,12 +886,12 @@ class JDBCStorage<S extends Storable> extends StandardQueryFactory<S>
      * Filter visitor that constructs a JoinNode tree.

      */

     private class JoinNodeBuilder extends Visitor<S, Object, Object> {

-        private JoinNode mRootJoinNode;

-        private int mAliasCounter;

+        private final TableAliasGenerator mAliasGenerator;

+        private final JoinNode mRootJoinNode;

 

-        JoinNodeBuilder() {

-            mAliasCounter = 1;

-            mRootJoinNode = new JoinNode(getStorableInfo(), TABLE_ALIAS_PREFIX + mAliasCounter);

+        JoinNodeBuilder(TableAliasGenerator aliasGenerator) {

+            mAliasGenerator = aliasGenerator;

+            mRootJoinNode = new JoinNode(getStorableInfo(), aliasGenerator.nextAlias());

         }

 

         public JoinNode getRootJoinNode() {

@@ -909,7 +909,7 @@ class JDBCStorage<S extends Storable> extends StandardQueryFactory<S>
                 if (ordering != null) {

                     for (OrderedProperty<?> orderedProperty : ordering) {

                         ChainedProperty<?> chained = orderedProperty.getChainedProperty();

-                        mAliasCounter = mRootJoinNode.addJoin(chained, mAliasCounter);

+                        mRootJoinNode.addJoin(chained, mAliasGenerator);

                     }

                 }

             } catch (RepositoryException e) {

@@ -932,7 +932,7 @@ class JDBCStorage<S extends Storable> extends StandardQueryFactory<S>
 

         private void visit(PropertyFilter<S> filter) throws RepositoryException {

             ChainedProperty<S> chained = filter.getChainedProperty();

-            mAliasCounter = mRootJoinNode.addJoin(chained, mAliasCounter);

+            mRootJoinNode.addJoin(chained, mAliasGenerator);

         }

     }

 

diff --git a/src/main/java/com/amazon/carbonado/repo/jdbc/TableAliasGenerator.java b/src/main/java/com/amazon/carbonado/repo/jdbc/TableAliasGenerator.java
new file mode 100644
index 0000000..5c73a2b
--- /dev/null
+++ b/src/main/java/com/amazon/carbonado/repo/jdbc/TableAliasGenerator.java
@@ -0,0 +1,37 @@
+/*

+ * Copyright 2007 Amazon Technologies, Inc. or its affiliates.

+ * Amazon, Amazon.com and Carbonado are trademarks or registered trademarks

+ * of Amazon Technologies, Inc. or its affiliates.  All rights reserved.

+ *

+ * Licensed under the Apache License, Version 2.0 (the "License");

+ * you may not use this file except in compliance with the License.

+ * You may obtain a copy of the License at

+ *

+ *     http://www.apache.org/licenses/LICENSE-2.0

+ *

+ * Unless required by applicable law or agreed to in writing, software

+ * distributed under the License is distributed on an "AS IS" BASIS,

+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

+ * See the License for the specific language governing permissions and

+ * limitations under the License.

+ */

+

+package com.amazon.carbonado.repo.jdbc;

+

+/**

+ * Simple non-thread-safe class for generating SQL statement table aliases.

+ *

+ * @author Brian S O'Neill

+ */

+class TableAliasGenerator {

+    private static final String TABLE_ALIAS_PREFIX = "T";

+

+    private int mAliasCounter;

+

+    TableAliasGenerator() {

+    }

+

+    String nextAlias() {

+        return TABLE_ALIAS_PREFIX + (++mAliasCounter);

+    }

+}