From 3ff7baa5f827efcbfd9434e27b4251f7c759e2ac Mon Sep 17 00:00:00 2001
From: Brian Lopez <seniorlopez@gmail.com>
Date: Tue, 3 Aug 2010 20:21:51 -0700
Subject: [PATCH] libmysql only allows one query be sent at a time per
 connection, bail early if that's attempted

---
 ext/mysql2/client.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/ext/mysql2/client.c b/ext/mysql2/client.c
index 9573e8f..f7783cd 100644
--- a/ext/mysql2/client.c
+++ b/ext/mysql2/client.c
@@ -225,6 +225,9 @@ static VALUE rb_mysql_client_async_result(VALUE self) {
     return Qnil;
   }
 
+  // we have a result, mark this connection inactive
+  rb_iv_set(self, "@active", Qfalse);
+
   VALUE resultObj = rb_mysql_result_to_obj(result);
   // pass-through query options for result construction later
   rb_iv_set(resultObj, "@query_options", rb_obj_dup(rb_iv_get(self, "@query_options")));
@@ -240,13 +243,22 @@ static VALUE rb_mysql_client_query(int argc, VALUE * argv, VALUE self) {
   fd_set fdset;
   int fd, retval;
   int async = 0;
-  VALUE opts, defaults;
+  VALUE opts, defaults, active;
   MYSQL *client;
 
   Data_Get_Struct(self, MYSQL, client);
   REQUIRE_OPEN_DB(client);
   args.mysql = client;
 
+  active = rb_iv_get(self, "@active");
+  // see if this connection is still waiting on a result from a previous query
+  if (NIL_P(active) || active == Qfalse) {
+    // mark this connection active
+    rb_iv_set(self, "@active", Qtrue);
+  } else {
+    rb_raise(cMysql2Error, "This connection is still waiting for a result, try again once you have the result");
+  }
+
   defaults = rb_iv_get(self, "@query_options");
   if (rb_scan_args(argc, argv, "11", &args.sql, &opts) == 2) {
     opts = rb_funcall(defaults, intern_merge, 1, opts);