Re: Minimal logical decoding on standbys

On Tue, Mar 23, 2021 at 10:18 AM Fabrízio de Royes Mello <
fabriziomello(at)gmail(dot)com> wrote:
>
> LGTM too... Reviewing new changes now to move it forward and make this
patch set ready for commiter review.
>

According to the feature LGTM and all tests passed. Documentation is also
OK. Some minor comments:

+ <para>
+ A logical replication slot can also be created on a hot standby. To
prevent
+ <command>VACUUM</command> from removing required rows from the system
+ catalogs, <varname>hot_standby_feedback</varname> should be set on the
+ standby. In spite of that, if any required rows get removed, the slot
gets
+ dropped. Existing logical slots on standby also get dropped if
wal_level
+ on primary is reduced to less than 'logical'.
+ </para>

Remove extra space before "Existing logical slots..."

+ pg_stat_get_db_conflict_logicalslot(D.oid) AS
confl_logicalslot,

Move it to the end of pg_stat_database_conflicts columns

+ * is being reduced. Hence this extra check.

Remove extra space before "Hence this..."

+ /* Send the other backend, a conflict recovery signal */
+
+ SetInvalidVirtualTransactionId(vxid);

Remove extra empty line

+ if (restart_lsn % XLOG_BLCKSZ != 0)
+ elog(ERROR, "invalid replay pointer");

Add an empty line after this "IF" for code readability

+void
+ResolveRecoveryConflictWithLogicalSlots(Oid dboid, TransactionId xid,
+ char *conflict_reason)
+{
+ int i;
+ bool found_conflict = false;
+
+ if (max_replication_slots <= 0)
+ return;

What about adding an "Assert(max_replication_slots >= 0);" before the
replication slots check?

One last thing is about the name of TAP tests, we should rename them
because there are other TAP tests starting with 022_ and 023_. It should be
renamed to:

src/test/recovery/t/022_standby_logical_decoding_xmins.pl ->
src/test/recovery/t/024_standby_logical_decoding_xmins.pl
src/test/recovery/t/023_standby_logical_decoding_conflicts.pl
-> src/test/recovery/t/025_standby_logical_decoding_conflicts.pl

Regards,

--
Fabrízio de Royes Mello
PostgreSQL Developer at OnGres Inc. - https://ongres.com