Fix up union/intersection operations

Previously the union/intersection operations didn't work when you tried to
select/project/sort/drop/whatever on them. Now they just automatically
introduce a subquery, which means that they can be used in other operations
automatically. (There is a potential for a minor decrease in query speed, but I
think it's worthwhile to maintain the abstraction.)

1 files changed, 12 insertions, 10 deletions

diff --git a/src/clojure_sql/dsl.clj b/src/clojure_sql/dsl.clj
index 015dfda..16bc2e5 100644
--- a/src/clojure_sql/dsl.clj
+++ b/src/clojure_sql/dsl.clj
@@ -370,19 +370,21 @@
        (apply = (map (comp set keys :fields) queries))))
 
 (defn union
-  "Combine the results of two queries"
+  "Combine the results of two queries.
+
+  Will always introduce a subquery."
   [& queries]
   {:pre [(apply union-compatible? queries)]}
-  (assoc (q/->Query)
-    :set-operation :union
-    :queries queries
-    :fields (zipmap (keys (:fields (first queries))) (repeat nil))))
+  (convert-to-subquery (q/map->Query {:set-operation :union
+                                      :queries queries
+                                      :fields (zipmap (keys (:fields (first queries))) (repeat nil))})))
 
 (defn intersection
-  "Take the common rows in two queries"
+  "Take the common rows in two queries.
+
+  Will always introduce a subquery."
   [& queries]
   {:pre [(apply union-compatible? queries)]}
-  (assoc (q/->Query)
-    :set-operation :intersect
-    :queries queries
-    :fields (zipmap (keys (:fields (first queries))) (repeat nil))))
+  (convert-to-subquery (q/map->Query {:set-operation :intersect
+                                      :queries queries
+                                      :fields (zipmap (keys (:fields (first queries))) (repeat nil))})))