From 6f8517d45849761cd20ba790bdc86f20224cea52 Mon Sep 17 00:00:00 2001
From: Ben Ng <me@benng.me>
Date: Sun, 4 May 2014 01:32:56 -0500
Subject: [PATCH] Fix breakage on empty query via .getAssn of a hasMany/through
 relationship

---
 lib/adapters/transformers/sql.js | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/lib/adapters/transformers/sql.js b/lib/adapters/transformers/sql.js
index 837d72af..de0bc210 100644
--- a/lib/adapters/transformers/sql.js
+++ b/lib/adapters/transformers/sql.js
@@ -54,11 +54,17 @@ var sql = utils.mixin(new BaseTransformer(), new (function () {
     return sql;
   };
 
+  /*
+  * Note: please return null on empty operations.
+  * returning empty strings leads to weirdness like
+  * `WHERE ()` appearing in queries, which breaks
+  * postgresql (and possibly others)
+  */
   this.transformOperation = function (op) {
     var self = this
       , ops = [];
     if (op.isEmpty()) {
-      return '';
+      return null;
     }
     else {
       if (op.type == 'not') {
@@ -66,14 +72,26 @@ var sql = utils.mixin(new BaseTransformer(), new (function () {
       }
       else {
         op.forEach(function (o) {
+          var temp;
           if (o instanceof operation.OperationBase) {
-            ops.push(self.transformOperation(o));
+            temp = self.transformOperation(o);
+
+            if(temp)
+              ops.push(temp);
           }
           else {
-            ops.push(self.transformComparison(o));
+            temp = self.transformComparison(o);
+
+            if(temp)
+              ops.push(self.transformComparison(o));
           }
         });
-        return '(' + ops.join(' ' + op.type.toUpperCase() + ' ') + ')';
+
+        if(ops.length)
+          return '(' + ops.join(' ' + op.type.toUpperCase() + ' ') + ')';
+        else
+          return null;
+
       }
     }
   };