From 37295dbcb3c58ac6d694b2ae661e52d8cee70165 Mon Sep 17 00:00:00 2001
From: Michael Bayne <mdb@samskivert.com>
Date: Fri, 7 Aug 2009 01:58:58 +0000
Subject: [PATCH] Added Exps.count() and Exps.countDistinct() and the necessary
 plumbing to sneak a 'distinct' into the argument list of the count()
 invocation.

---
 src/java/com/samskivert/depot/Exps.java       | 21 +++++++++++++++++--
 .../depot/expression/FunctionExp.java         | 21 ++++++++++++++++++-
 .../samskivert/depot/impl/BuildVisitor.java   |  3 +++
 3 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/src/java/com/samskivert/depot/Exps.java b/src/java/com/samskivert/depot/Exps.java
index 05718ee..6db1fad 100644
--- a/src/java/com/samskivert/depot/Exps.java
+++ b/src/java/com/samskivert/depot/Exps.java
@@ -116,11 +116,28 @@ public class Exps
     }
 
     /**
-     * Creates an expression that computes the sum of the supplied expression. This would usually
-     * be used in a FieldOverride and supplied with a ColumnExp.
+     * Creates an expression that computes the absolute value of the supplied expression.
      */
     public static FunctionExp abs (SQLExpression expr)
     {
         return new FunctionExp("abs", expr);
     }
+
+    /**
+     * Creates an expression that counts the number of rows that match the supplied expression.
+     * This would usually be used in a FieldOverride and supplied with a ColumnExp.
+     */
+    public static FunctionExp count (SQLExpression expr)
+    {
+        return new FunctionExp("count", expr);
+    }
+
+    /**
+     * Creates an expression that counts the number of distinct values that match the supplied
+     * expression. This would usually be used in a FieldOverride and supplied with a ColumnExp.
+     */
+    public static FunctionExp countDistinct (SQLExpression expr)
+    {
+        return new FunctionExp("count", "distinct", expr);
+    }
 }
diff --git a/src/java/com/samskivert/depot/expression/FunctionExp.java b/src/java/com/samskivert/depot/expression/FunctionExp.java
index 81886d4..a86c6ba 100644
--- a/src/java/com/samskivert/depot/expression/FunctionExp.java
+++ b/src/java/com/samskivert/depot/expression/FunctionExp.java
@@ -36,8 +36,18 @@ public class FunctionExp extends FluentExp
      * Create a new FunctionExp with the given function and arguments.
      */
     public FunctionExp (String function, SQLExpression... arguments)
+    {
+        this(function, null, arguments);
+        _arguments = arguments;
+    }
+
+    /**
+     * Create a new FunctionExp with the given function, expression annotation and arguments.
+     */
+    public FunctionExp (String function, String annotation, SQLExpression... arguments)
     {
         _function = function;
+        _annotation = annotation;
         _arguments = arguments;
     }
 
@@ -60,6 +70,11 @@ public class FunctionExp extends FluentExp
         return _function;
     }
 
+    public String getAnnotation ()
+    {
+        return _annotation;
+    }
+
     public SQLExpression[] getArguments ()
     {
         return _arguments;
@@ -68,12 +83,16 @@ public class FunctionExp extends FluentExp
     @Override
     public String toString ()
     {
-        return _function + "(" + StringUtil.join(_arguments, ", ") + ")";
+        return _function + "(" + (_annotation == null ? "" : (_annotation + " ")) +
+            StringUtil.join(_arguments, ", ") + ")";
     }
 
     /** The literal name of this function, e.g. FLOOR */
     protected String _function;
 
+    /** An annotation that goes on the function's expression (only used for count(distinct X)) */
+    protected String _annotation;
+
     /** The arguments to this function */
     protected SQLExpression[] _arguments;
 }
diff --git a/src/java/com/samskivert/depot/impl/BuildVisitor.java b/src/java/com/samskivert/depot/impl/BuildVisitor.java
index 757a2be..1c1a6b5 100644
--- a/src/java/com/samskivert/depot/impl/BuildVisitor.java
+++ b/src/java/com/samskivert/depot/impl/BuildVisitor.java
@@ -146,6 +146,9 @@ public abstract class BuildVisitor implements ExpressionVisitor<Void>
     {
         _builder.append(functionExp.getFunction());
         _builder.append("(");
+        if (functionExp.getAnnotation() != null) {
+            _builder.append(functionExp.getAnnotation()).append(" ");
+        }
         SQLExpression[] arguments = functionExp.getArguments();
         for (int ii = 0; ii < arguments.length; ii ++) {
             if (ii > 0) {