Bug #30989042 GETTING CDK ERROR: REPLY BLOCKED BY A PREVIOUS ONE.

Fixes an error in reply processing logic which in case of a reply with multiple rsets could incorrectly deregister cdk reply object after reading the first rset, while more rsets from the server are pending.

Author: rsomla1

common/result.cc

@@ -322,14 +322,23 @@ bool Result_impl::load_cache(row_count_t prefetch_size)
   m_cursor->wait();
 
   /*
-    Cleanup after reading all rows.
+    Cleanup after reading all rows: close the cursor if whole rset has
+    been consumed (or error happend, in which case server won't sent more
+    data).
   */
 
   if (!m_pending_rows || m_reply->entry_count() > 0)
   {
     m_cursor->close();
-    m_sess->deregister_result(this);
     m_pending_rows = false;
+
+    /*
+      If there are no more rsets in the reply, deregister the result so that
+      session is unlocked for the next command.
+    */
+
+    if (m_reply->end_of_reply())
+      m_sess->deregister_result(this);
   }
 
   return !m_result_cache.back().empty();

devapi/tests/bugs-t.cc

@@ -42,6 +42,55 @@ class Bugs : public mysqlx::test::Xplugin
 };
 
 
+TEST_F(Bugs,bug30989042_cdk_reply_error)
+{
+  SKIP_IF_NO_XPLUGIN;
+
+  // Create procedure that returns 2 row sets
+
+  sql("DROP PROCEDURE IF EXISTS test.p");
+  sql(
+    "CREATE PROCEDURE test.p(error INT)"
+    "BEGIN"
+    "  SELECT 1;"
+    "  IF error = 0 THEN"
+    "    SELECT 2;"
+    "  ELSE"
+    "    SELECT 1/point(1,0);"    // trigger error
+    "  END IF;"
+    "END"
+  );
+
+  auto res = sql("CALL test.p(0)");
+
+  // res.count() will consume the first row set, but another
+  // one is pending.
+
+  EXPECT_EQ(1,res.count());
+
+  // As we execute new statement, all remaining rows from the previous
+  // reply should be cached. It was not the case before bug was fixed,
+  // and the next statement was throwing error, because previous reply
+  // was not fully consumed.
+
+  EXPECT_NO_THROW(sql("select 1"));
+
+  // Check that remaining rows from the reply to CALL are cached
+  // and still available.
+
+  EXPECT_TRUE(res.nextResult());
+  EXPECT_EQ(1,res.count());
+
+  // Check that in case of error, it is reported only when moving to
+  // the next result in the reply (should not be reported while accessing
+  // the first result).
+
+  res = sql("CALL test.p(1)");
+  EXPECT_EQ(1, res.count());
+  EXPECT_THROW(res.nextResult(), Error);
+}
+
+
 TEST_F(Bugs, failover_error)
 {