From 7831ebed3898e3c30d6e3d18b4b6f906b2b685ce Mon Sep 17 00:00:00 2001
From: Sean Corfield <sean@corfield.org>
Date: Sat, 7 Sep 2019 13:24:46 -0700
Subject: [PATCH] Fixes #128 by adding :truncate / truncate

---
 CHANGES.md                     | 1 +
 README.md                      | 8 ++++++++
 src/honeysql/format.cljc       | 4 ++++
 src/honeysql/helpers.cljc      | 7 +++++++
 test/honeysql/format_test.cljc | 5 +++++
 5 files changed, 25 insertions(+)

diff --git a/CHANGES.md b/CHANGES.md
index 349c73f..48bea9a 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,6 +1,7 @@
 ## Changes coming in 0.9.7
 
 * Fix #248 by treating alias as "not a subquery" when generating SQL for it. (@seancorfield)
+* Fix #128 by adding `truncate` support.
 * Fix #99 by adding a note to the first use of `select` in the README that column names can be keywords or symbols but not strings.
 
 ## 0.9.6
diff --git a/README.md b/README.md
index 0abd54b..a499771 100644
--- a/README.md
+++ b/README.md
@@ -228,6 +228,14 @@ If your database supports it, you can also delete from multiple tables:
     "musical"]
 ```
 
+If you want to delete everything from a table, you can use `truncate`:
+
+```clojure
+(-> (truncate :films)
+    sql/format)
+=> ["TRUNCATE films"]
+```
+
 Queries can be nested:
 
 ```clojure
diff --git a/src/honeysql/format.cljc b/src/honeysql/format.cljc
index 338ab6c..5e5dcbf 100644
--- a/src/honeysql/format.cljc
+++ b/src/honeysql/format.cljc
@@ -219,6 +219,7 @@
    :update 70
    :delete 75
    :delete-from 80
+   :truncate 85
    :columns 90
    :from 110
    :join 120
@@ -629,6 +630,9 @@
 (defmethod format-clause :delete [[_ tables] _]
   (str "DELETE " (comma-join (map to-sql tables))))
 
+(defmethod format-clause :truncate [[_ table] _]
+  (str "TRUNCATE " (to-sql table)))
+
 (defn cte->sql
   [[cte-name query]]
   (str (binding [*subquery?* false]
diff --git a/src/honeysql/helpers.cljc b/src/honeysql/helpers.cljc
index 6d4149c..d177e68 100644
--- a/src/honeysql/helpers.cljc
+++ b/src/honeysql/helpers.cljc
@@ -279,6 +279,13 @@
   ([tables] (delete nil tables))
   ([m tables] (build-clause :delete m tables)))
 
+(defmethod build-clause :truncate [_ m table]
+  (assoc m :truncate table))
+
+(defn truncate
+  ([table] (truncate nil table))
+  ([m table] (build-clause :truncate m table)))
+
 (macros/usetime
  (defhelper with [m ctes]
    (assoc m :with ctes)))
diff --git a/test/honeysql/format_test.cljc b/test/honeysql/format_test.cljc
index 480fd8b..09459e7 100644
--- a/test/honeysql/format_test.cljc
+++ b/test/honeysql/format_test.cljc
@@ -228,6 +228,11 @@
               :where [:= :t1.bar 42]}
              (format :quoting :mysql)))))
 
+(deftest truncate-test
+  (is (= ["TRUNCATE `foo`"]
+         (-> {:truncate :foo}
+             (format :quoting :mysql)))))
+
 (deftest inlined-values-are-stringified-correctly
   (is (= ["SELECT foo, bar, NULL"]
          (format {:select [(honeysql.core/inline "foo")