From 42a1da6d2e1fc42090a223d8d086d05b79416762 Mon Sep 17 00:00:00 2001
From: Pavel Abalikhin <anpavl@gmail.com>
Date: Thu, 3 Dec 2015 12:08:02 +0300
Subject: [PATCH] Add transaction support

---
 README.md             | 21 +++++++++++++++++++++
 src/pgpool_worker.erl | 11 ++++++++++-
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index e9f99c8..7411216 100644
--- a/README.md
+++ b/README.md
@@ -111,6 +111,27 @@ Types:
   Params = list()
 ```
 
+##### Transaction
+
+```erlang
+pgpool:transaction(DatabaseName, Fun) -> (see epgsql for reply/error types)
+
+Types:
+  DatabaseName = atom()
+  Fun = fun()
+```
+
+For example:
+
+```erlang
+pgpool:transaction(db1_name,
+                   fun(C) ->
+                           pgpool:squery(C, "DELETE FROM users WHERE foo = true"),
+                           pgpool:squery(C, "UPDATE users SET bar = 100"),
+                           pgpool:squery(C, "SELECT * FROM users")
+                   end).
+```
+
 ## Contributing
 So you want to contribute? That's great! Please follow the guidelines below. It will make it easier to get merged in.
 
diff --git a/src/pgpool_worker.erl b/src/pgpool_worker.erl
index 2f7a914..206f9d2 100644
--- a/src/pgpool_worker.erl
+++ b/src/pgpool_worker.erl
@@ -4,7 +4,7 @@
 
 %% API
 -export([start_link/1]).
--export([squery/2, equery/3]).
+-export([squery/2, equery/3, transaction/2]).
 
 %% gen_server callbacks
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3]).
@@ -43,6 +43,12 @@ equery(DatabaseName, Statement, Params) ->
         gen_server:call(Worker, {equery, Statement, Params})
     end).
 
+-spec transaction(DatabaseName :: atom(), Fun :: fun()) -> any() | {error, no_connection}.
+transaction(DatabaseName, Fun) ->
+    poolboy:transaction(DatabaseName, fun(Worker) ->
+        gen_server:call(Worker, {transaction, Fun})
+    end).
+
 %% ===================================================================
 %% Callbacks
 %% ===================================================================
@@ -102,6 +108,9 @@ handle_call({squery, Sql}, _From, #state{conn = Conn} = State) ->
 handle_call({equery, Statement, Params}, _From, #state{conn = Conn} = State) ->
     {reply, epgsql:equery(Conn, Statement, Params), State};
 
+handle_call({transaction, Fun}, _From, #state{conn = Conn} = State) ->
+    {reply, epgsql:with_transaction(Conn, Fun), State};
+
 handle_call(Request, From, State) ->
     error_logger:warning_msg("Received from ~p an unknown call message: ~p", [Request, From]),
     {reply, undefined, State}.