Disable PostgreSQL JIT and parallel workers in middle

They are known to have problems with the int arrays.

See #1045

src/middle-pgsql.cpp

@@ -554,6 +554,14 @@ void middle_pgsql_t::start()
     }
 
     if (m_append) {
+        // Disable JIT and parallel workers as they are known to cause
+        // problems when accessing the intarrays.
+        // Update pg_settings instead of using SET because it does not yield
+        // errors on older versions of Postgres where the settings are not
+        // implemented.
+        m_db_connection.set_config("jit_above_cost", "-1");
+        m_db_connection.set_config("max_parallel_workers_per_gather", "0");
+
         // Prepare queries for updating dependent objects
         for (auto &table : m_tables) {
             if (!table.m_prepare_intarray.empty()) {

src/pgsql.cpp

@@ -41,6 +41,14 @@ pg_result_t pg_conn_t::query(ExecStatusType expect,
     return query(expect, sql.c_str());
 }
 
+void pg_conn_t::set_config(char const *setting, char const *value) const
+{
+    auto const sql =
+        "UPDATE pg_settings SET setting = '{}' WHERE name = '{}'"_format(
+            setting, value);
+    query(PGRES_TUPLES_OK, sql);
+}
+
 void pg_conn_t::exec(char const *sql) const { query(PGRES_COMMAND_OK, sql); }
 
 void pg_conn_t::exec(std::string const &sql) const

src/pgsql.hpp

@@ -123,6 +123,8 @@ class pg_conn_t
 
     pg_result_t query(ExecStatusType expect, std::string const &sql) const;
 
+    void set_config(char const *setting, char const *value) const;
+
     void exec(char const *sql) const;
 
     void exec(std::string const &sql) const;