Allow caching to be skipped for single record loads, ensure that we don't cache

DepotMigrationHistoryRecord.

src/java/com/samskivert/depot/DepotRepository.java

@@ -271,7 +271,19 @@ public abstract class DepotRepository
     protected <T extends PersistentRecord> T load (Class<T> type, QueryClause... clauses)
         throws DatabaseException
     {
-        return _ctx.invoke(new FindOneQuery<T>(_ctx, type, clauses));
+        return load(type, CacheStrategy.BEST, clauses);
+    }
+
+    /**
+     * Loads the first persistent object that matches the supplied query clauses.
+     *
+     * @throws DatabaseException if any problem is encountered communicating with the database.
+     */
+    protected <T extends PersistentRecord> T load (Class<T> type, CacheStrategy strategy,
+                                                   QueryClause... clauses)
+        throws DatabaseException
+    {
+        return _ctx.invoke(new FindOneQuery<T>(_ctx, type, strategy, clauses));
     }
 
     /**
@@ -1063,7 +1075,8 @@ public abstract class DepotRepository
         DepotMigrationHistoryRecord record;
         while (true) {
             // check to see if the migration has already been completed
-            record = load(DepotMigrationHistoryRecord.class, migration.getIdent());
+            record = load(DepotMigrationHistoryRecord.class, CacheStrategy.NONE,
+                          DepotMigrationHistoryRecord.getKey(migration.getIdent()));
             if (record != null && record.whenCompleted != null) {
                 return; // great, no need to do anything
             }

src/java/com/samskivert/depot/impl/FindOneQuery.java

@@ -45,9 +45,11 @@ import static com.samskivert.depot.Log.log;
  */
 public class FindOneQuery<T extends PersistentRecord> extends Query<T>
 {
-    public FindOneQuery (PersistenceContext ctx, Class<T> type, QueryClause[] clauses)
+    public FindOneQuery (PersistenceContext ctx, Class<T> type,
+                         DepotRepository.CacheStrategy strategy, QueryClause[] clauses)
         throws DatabaseException
     {
+        _strategy = strategy;
         _marsh = ctx.getMarshaller(type);
         _select = new SelectClause<T>(type, _marsh.getFieldNames(), clauses);
         WhereClause where = _select.getWhereClause();
@@ -123,10 +125,14 @@ public class FindOneQuery<T extends PersistentRecord> extends Query<T>
 
     protected CacheKey getCacheKey ()
     {
+        if (_strategy == DepotRepository.CacheStrategy.NONE) {
+            return null;
+        }
         WhereClause where = _select.getWhereClause();
         return (where != null && where instanceof CacheKey) ? (CacheKey)where : null;
     }
 
+    protected DepotRepository.CacheStrategy _strategy;
     protected DepotMarshaller<T> _marsh;
     protected SelectClause<T> _select;
     protected SQLBuilder _builder;