It turns out PostgreSQL supports LN(exp) and LOG(exp) in double precision, but not LOG(base, exp). So we're adding an explicit LOG10. I wonder how useful the two-argument one is... maybe we should delete it.

src/java/com/samskivert/depot/Funs.java

@@ -68,7 +68,8 @@ public class Funs
     }
 
     /**
-     * Creates an expression that computes the natural logarithm of the supplied expression.
+     * Creates an expression that computes the natural logarithm of the supplied expression,
+     * which may be double-precision.
      */
     public static Ln ln (SQLExpression exp)
     {
@@ -76,16 +77,18 @@ public class Funs
     }
 
     /**
-     * Creates an expression that computes the base-10 logarithm of the supplied expression.
+     * Creates an expression that computes the base-10 logarithm of the supplied expression,
+     * which may be double-precision.
      */
-    public static LogN log10 (SQLExpression value)
+    public static Log10 log10 (SQLExpression value)
     {
-        return new LogN(Exps.value(10), value);
+        return new Log10(value);
     }
 
     /**
      * Creates an expression that computes the logarithm of the supplied value expression
-     * in the supplied base expression.
+     * in the supplied base expression. Note: Under PostgreSQL, this must evaluate to a simple
+     * numerical, not double precision.
      */
     public static LogN logN (SQLExpression base, SQLExpression value)
     {

src/java/com/samskivert/depot/function/NumericalFun.java

@@ -70,6 +70,15 @@ public abstract class NumericalFun
         }
     }
 
+    public static class Log10 extends OneArgFun {
+        public Log10 (SQLExpression value) {
+            super(value);
+        }
+        public Object accept (ExpressionVisitor<?> visitor) {
+            return visitor.visit(this);
+        }
+    }
+
     public static class LogN extends TwoArgFun {
         public LogN (SQLExpression base, SQLExpression value) {
             super(base, value);

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

@@ -68,6 +68,7 @@ import com.samskivert.depot.function.NumericalFun.Ceil;
 import com.samskivert.depot.function.NumericalFun.Exp;
 import com.samskivert.depot.function.NumericalFun.Floor;
 import com.samskivert.depot.function.NumericalFun.Ln;
+import com.samskivert.depot.function.NumericalFun.Log10;
 import com.samskivert.depot.function.NumericalFun.LogN;
 import com.samskivert.depot.function.NumericalFun.Pi;
 import com.samskivert.depot.function.NumericalFun.Power;
@@ -617,6 +618,11 @@ public abstract class BuildVisitor implements ExpressionVisitor<Void>
         return appendFunctionCall("ln", exp.getArg());
     }
 
+    public Void visit (Log10 exp)
+    {
+        return appendFunctionCall("log", exp.getArg());
+    }
+
     public Void visit (LogN exp)
     {
         return appendFunctionCall("log", exp.getBase(), exp.getValue());

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

@@ -51,6 +51,7 @@ import com.samskivert.depot.function.NumericalFun.Ceil;
 import com.samskivert.depot.function.NumericalFun.Exp;
 import com.samskivert.depot.function.NumericalFun.Floor;
 import com.samskivert.depot.function.NumericalFun.Ln;
+import com.samskivert.depot.function.NumericalFun.Log10;
 import com.samskivert.depot.function.NumericalFun.LogN;
 import com.samskivert.depot.function.NumericalFun.Pi;
 import com.samskivert.depot.function.NumericalFun.Power;
@@ -123,6 +124,7 @@ public interface ExpressionVisitor<T>
     public T visit (Exp exp);
     public T visit (Floor exp);
     public T visit (Ln exp);
+    public T visit (Log10 exp);
     public T visit (LogN exp);
     public T visit (Pi exp);
     public T visit (Power exp);

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

@@ -86,7 +86,8 @@ public class PostgreSQLBuilder
             return null;
         }
 
-        @Override public Void visit (DatePart exp) {
+        @Override public Void visit (DatePart exp)
+        {
             return appendFunctionCall(
                 "date_part", Exps.value(translateDatePart(exp.getPart())), exp.getArg());
         }