Re: PATCH: logical_work_mem and logical streaming of large in-progress transactions

On Wed, Oct 30, 2019 at 9:38 AM vignesh C <vignesh21(at)gmail(dot)com> wrote:
>
I have noticed one more problem in the logic of setting the logical
decoding work mem from the create subscription command. Suppose in
subscription command we don't give the work mem then it sends the
garbage value to the walsender and the walsender overwrite its value
with the garbage value. After investigating a bit I have found the
reason for the same.

@@ -406,6 +406,9 @@ libpqrcv_startstreaming(WalReceiverConn *conn,
appendStringInfo(&cmd, "proto_version '%u'",
options->proto.logical.proto_version);

+ appendStringInfo(&cmd, ", work_mem '%d'",
+ options->proto.logical.work_mem);

I think the problem is we are unconditionally sending the work_mem as
part of the CREATE REPLICATION SLOT, without checking whether it's
valid or not.

--- a/src/backend/catalog/pg_subscription.c
+++ b/src/backend/catalog/pg_subscription.c
@@ -71,6 +71,7 @@ GetSubscription(Oid subid, bool missing_ok)
sub->name = pstrdup(NameStr(subform->subname));
sub->owner = subform->subowner;
sub->enabled = subform->subenabled;
+ sub->workmem = subform->subworkmem;

Another problem is that there is no handling if the subform->subworkmem is NULL.

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com