From 203296149f7d9d771639cef87555387f4ec07ffa Mon Sep 17 00:00:00 2001
From: Andy Chambers <andy.chambers@fundingcircle.com>
Date: Thu, 23 Apr 2015 23:44:19 -0700
Subject: [PATCH] Add support for exists

---
 .gitignore                    |  1 +
 CHANGES.md                    |  1 +
 src/honeysql/format.clj       | 22 +++++++++++++++-------
 test/honeysql/format_test.clj | 10 ++++++++++
 4 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/.gitignore b/.gitignore
index 2bfb42e..ec625cc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,4 +10,5 @@ pom.xml*
 .lein-plugins
 .classpath
 .project
+.nrepl-port
 bin
diff --git a/CHANGES.md b/CHANGES.md
index 8481996..26e96a0 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,5 +1,6 @@
 ## 0.5.3 In development
 
+* Support exists syntax (@cddr)
 * Support locking selects (@dball)
 * Add sql array type and reader literal (@loganmhb)
 * Allow user to specify where in sort order NULLs fall (@mishok13)
diff --git a/src/honeysql/format.clj b/src/honeysql/format.clj
index 192e22b..8031484 100644
--- a/src/honeysql/format.clj
+++ b/src/honeysql/format.clj
@@ -350,13 +350,18 @@
     (to-sql pred)
     (let [[op & args] pred
           op-name (name op)]
-      (if (= "not" op-name)
-        (str "NOT " (format-predicate* (first args)))
-        (if (#{"and" "or" "xor"} op-name)
-          (paren-wrap
-           (string/join (str " " (string/upper-case op-name) " ")
-                        (map format-predicate* args)))
-          (to-sql (apply call pred)))))))
+      (case op-name
+        "not" (str "NOT " (format-predicate* (first args)))
+
+        ("and" "or" "xor")
+        (paren-wrap
+         (string/join (str " " (string/upper-case op-name) " ")
+                      (map format-predicate* args)))
+
+        "exists"
+        (str "EXISTS " (to-sql (first args)))
+
+        (to-sql (apply call pred))))))
 
 (defmulti format-clause
   "Takes a map entry representing a clause and returns an SQL string"
@@ -370,6 +375,9 @@
 (defmethod format-clause :default [& _]
   "")
 
+(defmethod format-clause :exists [[_ table-expr] _]
+  (str "EXISTS " (to-sql table-expr)))
+
 (defmethod format-clause :select [[_ fields] sql-map]
   (str "SELECT "
        (when (:modifiers sql-map)
diff --git a/test/honeysql/format_test.clj b/test/honeysql/format_test.clj
index ce4a518..e0f8bca 100644
--- a/test/honeysql/format_test.clj
+++ b/test/honeysql/format_test.clj
@@ -34,6 +34,16 @@
   (is (= (format-clause (first {:insert-into [[:foo [:a :b :c]] {:select [:d :e :f] :from [:baz]}]}) nil)
          "INSERT INTO foo (a, b, c) SELECT d, e, f FROM baz")))
 
+(deftest exists-test
+  (is (= (format {:exists {:select [:a] :from [:foo]}})
+         ["EXISTS (SELECT a FROM foo)"]))
+  (is (= (format {:select [:id]
+                  :from [:foo]
+                  :where [:exists {:select [1]
+                                   :from [:bar]
+                                   :where :deleted}]})
+         ["SELECT id FROM foo WHERE EXISTS (SELECT 1 FROM bar WHERE deleted)"])))
+
 (deftest array-test
   (is (= (format {:insert-into :foo
                   :columns [:baz]