RE: Logical replication timeout problem

Dear Wang,

> Attached a new patch that addresses following improvements I have got so far as
> comments:
> 1. Consider other changes that need to be skipped(truncate, DDL and function
> calls pg_logical_emit_message). [suggestion by Ajin, Amit]
> (Add a new function SendKeepaliveIfNecessary for trying to send keepalive
> message.)
> 2. Set the threshold conservatively to a static value of 10000.[suggestion by Amit,
> Kuroda-San]
> 3. Reset sendTime in function WalSndUpdateProgress when send_keep_alive is
> false. [suggestion by Amit]

Thank you for giving a good patch! I'll check more detail later,
but it can be applied my codes and passed check world.
I put some minor comments:

```
+ * Try to send keepalive message
```

Maybe missing "a"?

```
+ /*
+ * After continuously skipping SKIPPED_CHANGES_THRESHOLD changes, try to send a
+ * keepalive message.
+ */
```

This comments does not follow preferred style:
https://www.postgresql.org/docs/devel/source-format.html

```
@@ -683,12 +683,12 @@ OutputPluginWrite(struct LogicalDecodingContext *ctx, bool last_write)
* Update progress tracking (if supported).
*/
void
-OutputPluginUpdateProgress(struct LogicalDecodingContext *ctx)
+OutputPluginUpdateProgress(struct LogicalDecodingContext *ctx, bool send_keep_alive)
```

This function is no longer doing just tracking.
Could you update the code comment above?

```
if (!is_publishable_relation(relation))
return;
```

I'm not sure but it seems that the function exits immediately if relation
is a sequence, view, temporary table and so on. Is it OK? Does it never happen?

```
+ SendKeepaliveIfNecessary(ctx, false);
```

I think a comment is needed above which clarifies sending a keepalive message.

Best Regards,
Hayato Kuroda
FUJITSU LIMITED