Added support for intervals which would almost be exactly the same except that

Postgres insists that you quote: interval '7 day' and MySQL insists that you
not quote: interval 7 day. Frawesome!

src/java/com/samskivert/depot/expression/IntervalExp.java

@@ -0,0 +1,65 @@
+//
+// $Id$
+//
+// Depot library - a Java relational persistence library
+// Copyright (C) 2006-2009 Michael Bayne and Pär Winzell
+//
+// This library is free software; you can redistribute it and/or modify it
+// under the terms of the GNU Lesser General Public License as published
+// by the Free Software Foundation; either version 2.1 of the License, or
+// (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+
+package com.samskivert.depot.expression;
+
+import java.util.Collection;
+
+import com.samskivert.depot.PersistentRecord;
+import com.samskivert.depot.impl.ExpressionVisitor;
+
+/**
+ * A code for representing a date interval.
+ */
+public class IntervalExp
+    implements SQLExpression
+{
+    /** The units that can be used for an interval. */
+    public enum Unit { YEAR, MONTH, DAY, HOUR, MINUTE, SECOND };
+
+    /** The unit for this interval. */
+    public final Unit unit;
+
+    /** The number of units for this interval. */
+    public final int amount;
+
+    public IntervalExp (Unit unit, int amount)
+    {
+        this.unit = unit;
+        this.amount = amount;
+    }
+
+    // from SQLExpression
+    public Object accept (ExpressionVisitor<?> builder)
+    {
+        return builder.visit(this);
+    }
+
+    // from SQLExpression
+    public void addClasses (Collection<Class<? extends PersistentRecord>> classSet)
+    {
+    }
+
+    @Override
+    public String toString ()
+    {
+        return amount + " " + unit;
+    }
+}

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

@@ -51,6 +51,7 @@ import com.samskivert.depot.clause.WhereClause;
 import com.samskivert.depot.expression.ColumnExp;
 import com.samskivert.depot.expression.EpochSeconds;
 import com.samskivert.depot.expression.FunctionExp;
+import com.samskivert.depot.expression.IntervalExp;
 import com.samskivert.depot.expression.LiteralExp;
 import com.samskivert.depot.expression.SQLExpression;
 import com.samskivert.depot.expression.ValueExp;
@@ -320,6 +321,12 @@ public abstract class BuildVisitor implements ExpressionVisitor<Void>
         return null;
     }
 
+    public Void visit (IntervalExp interval)
+    {
+        _builder.append("interval ").append(interval.amount).append(" ").append(interval.unit);
+        return null;
+    }
+
     public Void visit (Exists<? extends PersistentRecord> exists)
     {
         _builder.append("exists ");

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

@@ -40,6 +40,7 @@ import com.samskivert.depot.clause.WhereClause;
 import com.samskivert.depot.expression.ColumnExp;
 import com.samskivert.depot.expression.EpochSeconds;
 import com.samskivert.depot.expression.FunctionExp;
+import com.samskivert.depot.expression.IntervalExp;
 import com.samskivert.depot.expression.LiteralExp;
 import com.samskivert.depot.expression.SQLExpression;
 import com.samskivert.depot.expression.SQLExpression.NoValue;
@@ -214,6 +215,11 @@ public class ExpressionEvaluator
         return valueExp.getValue();
     }
 
+    public Object visit (IntervalExp interval)
+    {
+        return new NoValue("Cannot evaluate IntervalExp: " + interval);
+    }
+
     public Object visit (WhereClause where)
     {
         Object result = where.getWhereExpression().accept(this);

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

@@ -37,6 +37,7 @@ import com.samskivert.depot.clause.WhereClause;
 import com.samskivert.depot.expression.ColumnExp;
 import com.samskivert.depot.expression.EpochSeconds;
 import com.samskivert.depot.expression.FunctionExp;
+import com.samskivert.depot.expression.IntervalExp;
 import com.samskivert.depot.expression.LiteralExp;
 import com.samskivert.depot.expression.ValueExp;
 
@@ -76,8 +77,9 @@ public interface ExpressionVisitor<T>
     public T visit (OrderBy orderBy);
     public T visit (Join join);
     public T visit (Limit limit);
-    public T visit (LiteralExp literalExp);
-    public T visit (ValueExp valueExp);
+    public T visit (LiteralExp literal);
+    public T visit (ValueExp value);
+    public T visit (IntervalExp interval);
     public T visit (WhereClause where);
     public T visit (Key.Expression<? extends PersistentRecord> key);
     public T visit (Exists<? extends PersistentRecord> exists);

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

@@ -40,6 +40,7 @@ import com.samskivert.depot.PersistentRecord;
 import com.samskivert.depot.annotation.FullTextIndex.Configuration;
 import com.samskivert.depot.annotation.FullTextIndex;
 import com.samskivert.depot.expression.EpochSeconds;
+import com.samskivert.depot.expression.IntervalExp;
 import com.samskivert.depot.operator.FullText;
 
 import static com.samskivert.Log.log;
@@ -53,6 +54,12 @@ public class PostgreSQLBuilder
 
     public class PGBuildVisitor extends BuildVisitor
     {
+        @Override public Void visit (IntervalExp interval) {
+            _builder.append("interval '").append(interval.amount);
+            _builder.append(" ").append(interval.unit).append("'");
+            return null;
+        }
+
         @Override public Void visit (FullText.Match match) {
             appendIdentifier("ftsCol_" + match.getDefinition().getName());
             _builder.append(" @@ to_tsquery('").