RE: Pgoutput not capturing the generated columns

Dear Shubham,

Thanks for updating the patch! I checked your patches briefly. Here are my comments.

01. API

Since the option for test_decoding is enabled by default, I think it should be renamed.
E.g., "skip-generated-columns" or something.

02. ddl.sql

```
+-- check include-generated-columns option with generated column
+CREATE TABLE gencoltable (a int PRIMARY KEY, b int GENERATED ALWAYS AS (a * 2) STORED);
+INSERT INTO gencoltable (a) VALUES (1), (2), (3);
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'include-generated-columns', '1');
+ data
+-------------------------------------------------------------
+ BEGIN
+ table public.gencoltable: INSERT: a[integer]:1 b[integer]:2
+ table public.gencoltable: INSERT: a[integer]:2 b[integer]:4
+ table public.gencoltable: INSERT: a[integer]:3 b[integer]:6
+ COMMIT
+(5 rows)
```

We should test non-default case, which the generated columns are not generated.

03. ddl.sql

Not sure new tests are in the correct place. Do we have to add new file and move tests to it?
Thought?

04. protocol.sgml

Please keep the format of the sgml file.

05. protocol.sgml

The option is implemented as the streaming option of pgoutput plugin, so they should be
located under "Logical Streaming Replication Parameters" section.

05. AlterSubscription

```
+ if (IsSet(opts.specified_opts, SUBOPT_GENERATED_COLUMN))
+ {
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("toggling generated_column option is not allowed.")));
+ }
```

If you don't want to support the option, you can remove SUBOPT_GENERATED_COLUMN
macro from the function. But can you clarify the reason why you do not want?

07. logicalrep_write_tuple

```
- if (!column_in_column_list(att->attnum, columns))
+ if (!column_in_column_list(att->attnum, columns) && !att->attgenerated)
+ continue;
+
+ if (att->attgenerated && !publish_generated_column)
continue;
```

I think changes in v2 was reverted or wrongly merged.

08. test code

Can you add tests that generated columns are replicated by the logical replication?

Best Regards,
Hayato Kuroda
FUJITSU LIMITED
https://www.fujitsu.com/