Horton

Re: Minimal logical decoding on standbys

Fabrízio de Royes Mello <fabriziomello@gmail.com>

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From: Fabrízio de Royes Mello <fabriziomello@gmail.com>
To: "Drouvot, Bertrand" <bdrouvot@amazon.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, Andres Freund <andres@anarazel.de>, tushar <tushar.ahuja@enterprisedb.com>, "[pgdg] Robert Haas" <robertmhaas@gmail.com>, Amit Khandekar <amitdkhan.pg@gmail.com>, Rahila Syed <rahila.syed@2ndquadrant.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2021-03-23T14:29:41Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Reduce the log level in 035_standby_logical_decoding.pl.

  2. 035_standby_logical_decoding: Add missing waits for replication

  3. For cascading replication, wake physical and logical walsenders separately

  4. Handle logical slot conflicts on standby

  5. Support invalidating replication slots due to horizon and wal_level

  6. Prevent use of invalidated logical slot in CreateDecodingContext()

  7. Replace replication slot's invalidated_at LSN with an enum

  8. Pass down table relation into more index relation functions

  9. Assert only valid flag bits are passed to visibilitymap_set()

  10. Remove unused _bt_delitems_delete() argument.

  11. Add xl_btree_delete optimization.

On Tue, Mar 23, 2021 at 10:18 AM Fabrízio de Royes Mello <
fabriziomello@gmail.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