From e1f15baa02651a383cb298df65a783b73db1f4a2 Mon Sep 17 00:00:00 2001
From: Oleksandr Yakushev <alex@bytopia.org>
Date: Sat, 5 Oct 2024 14:57:47 +0300
Subject: [PATCH] [select] Use transients in select-reducing functions

---
 src/toucan2/jdbc/mysql_mariadb.clj | 2 +-
 src/toucan2/pipeline.clj           | 9 +++++++++
 src/toucan2/select.clj             | 6 +++---
 test/toucan2/execute_test.clj      | 4 ++--
 4 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/toucan2/jdbc/mysql_mariadb.clj b/src/toucan2/jdbc/mysql_mariadb.clj
index 18cb590..f819e1e 100644
--- a/src/toucan2/jdbc/mysql_mariadb.clj
+++ b/src/toucan2/jdbc/mysql_mariadb.clj
@@ -107,7 +107,7 @@
         _              (log/debugf "update-returning-pks workaround: doing SELECT with conditions %s"
                                    conditions-map)
         parsed-args    (update pipeline/*parsed-args* :kv-args merge conditions-map)
-        select-rf      (pipeline/with-init conj [])
+        select-rf      (pipeline/conj-with-init! [])
         xform          (map (model/select-pks-fn model))
         pks            (pipeline/transduce-query (xform select-rf)
                                                  :toucan.query-type/select.instances.fns
diff --git a/src/toucan2/pipeline.clj b/src/toucan2/pipeline.clj
index 12f3a60..842eab8 100644
--- a/src/toucan2/pipeline.clj
+++ b/src/toucan2/pipeline.clj
@@ -326,6 +326,15 @@
     ([x]   (rf x))
     ([x y] (rf x y))))
 
+(defn ^:no-doc conj!-with-init
+  "Returns a reducing function with a zero-arity (initial value arity) that returns transient version of `init`, `conj!`s
+  values into it, and finally returns a persistent collection in 1-arity."
+  [init]
+  (fn
+    ([]      (transient init))
+    ([acc]   (persistent! acc))
+    ([acc y] (conj! acc y))))
+
 (m/defmulti default-rf
   "The default reducing function for queries of `query-type`. Used for non-reducible operations
   like [[toucan2.select/select]] or [[toucan2.execute/query]]."
diff --git a/src/toucan2/select.clj b/src/toucan2/select.clj
index 76f17d0..0111abc 100644
--- a/src/toucan2/select.clj
+++ b/src/toucan2/select.clj
@@ -78,7 +78,7 @@
                [f :conn connectable modelable-columns & kv-args? query?])}
   [f & unparsed-args]
   (let [f     (comp realize/realize f)
-        rf    (pipeline/with-init conj #{})
+        rf    (pipeline/conj-with-init! #{})
         xform (map f)]
     (not-empty (pipeline/transduce-unparsed (xform rf) :toucan.query-type/select.instances.fns unparsed-args))))
 
@@ -98,7 +98,7 @@
                [f :conn connectable modelable-columns & kv-args? query?])}
   [f & unparsed-args]
   (let [f     (comp realize/realize f)
-        rf    (pipeline/with-init conj [])
+        rf    (pipeline/conj-with-init! [])
         xform (map f)]
     (not-empty (pipeline/transduce-unparsed (xform rf) :toucan.query-type/select.instances.fns unparsed-args))))
 
@@ -190,7 +190,7 @@
   [f1 f2 & unparsed-args]
   (let [f1    (comp realize/realize f1)
         f2    (comp realize/realize f2)
-        rf    (pipeline/with-init conj {})
+        rf    (pipeline/conj-with-init! {})
         xform (map (juxt f1 f2))]
     (pipeline/transduce-unparsed (xform rf) :toucan.query-type/select.instances unparsed-args)))
 
diff --git a/test/toucan2/execute_test.clj b/test/toucan2/execute_test.clj
index 5e3dfb4..182ee4b 100644
--- a/test/toucan2/execute_test.clj
+++ b/test/toucan2/execute_test.clj
@@ -186,7 +186,7 @@
                                                          #_query-type :default
                                                          #_model      :default]
   [rf _conn _query-type _model [{k :key}, :as _compiled-query]]
-  (reduce rf (rf) [{k 1} {k 2} {k 3}]))
+  (transduce identity rf [{k 1} {k 2} {k 3}]))
 
 (deftest ^:parallel wow-dont-even-need-to-use-jdbc-test
   (is (= [{:a 1} {:a 2} {:a 3}]
@@ -203,7 +203,7 @@
                                                          #_query-type :default
                                                          #_model      ::model.not-even-jdbc]
   [rf _conn _query-type _model {k :key, :as _compiled-query}]
-  (reduce rf (rf) [{k 4} {k 5} {k 6}]))
+  (transduce identity rf [{k 4} {k 5} {k 6}]))
 
 (deftest ^:parallel wow-dont-even-need-to-use-jdbc-custom-model-test
   (is (= [{:a 4} {:a 5} {:a 6}]