Re: optimizing pg_upgrade's once-in-each-database steps

> On 9 Jul 2024, at 05:33, Nathan Bossart <nathandbossart(at)gmail(dot)com> wrote:

> The code is still very rough and nowhere near committable, but this at
> least gets the patch set into the editing phase.

First reaction after a read-through is that this seems really cool, can't wait
to see how much v18 pg_upgrade will be over v17. I will do more testing and
review once back from vacation, below are some comments from reading which is
all I had time for at this point:

+static void
+conn_failure(PGconn *conn)
+{
+ pg_log(PG_REPORT, "%s", PQerrorMessage(conn));
+ printf(_("Failure, exiting\n"));
+ exit(1);
+}

Any particular reason this isn't using pg_fatal()?

+static void
+dispatch_query(const ClusterInfo *cluster, AsyncSlot *slot,
....
+ pg_free(query);
+}

A minor point, perhaps fueled by me not having played around much with this
patchset. It seems a bit odd that dispatch_query is responsible for freeing
the query from the get_query callback. I would have expected the output from
AsyncTaskGetQueryCB to be stored in AsyncTask and released by async_task_free.

+static void
+sub_process(DbInfo *dbinfo, PGresult *res, void *arg)
+{
....
+ fprintf(state->script, "The table sync state \"%s\" is not allowed for database:\"%s\" subscription:\"%s\" schema:\"%s\" relation:\"%s\"\n",
+ PQgetvalue(res, i, 0),
+ dbinfo->db_name,
+ PQgetvalue(res, i, 1),

With the query being in a separate place in the code from the processing it
takes a bit of jumping around to resolve the columns in PQgetvalue calls like
this. Using PQfnumber() calls and descriptive names would make this easier. I
know this case is copying old behavior, but the function splits make it less
useful than before.

+ char *query = pg_malloc(QUERY_ALLOC);

Should we convert this to a PQExpBuffer?

--
Daniel Gustafsson