RE: Logical replication row filter loses unchanged toasted columns

Dear Hou,

> Here is the patch (on HEAD) for the suggested approach. I extended
> extractReplicaIdentity
> to also extract unchanged toasted columns, as it fits best there, we only need
> to log unchanged toast columns when the replica identity changes.

Thanks for posting the patch.
I cannot find any the conceptual issues. I considered the alternative that new
tuple can have un-changed toasted values, but it seems not good for the crash
recovery: the code uses the tuple in the WAL as-is, so we should have the pointer
to the toast table. Few small comments:

```
+#include "catalog/pg_publication.h"
```

I could compile the code without the inclusion, maybe because we use
RelationHasPubRowFilterForUpdate() to obtain the rf_exists_for_update.

```
+ * to protect unchanged, non-replica-identity, TOASTed column values that
```

Not sure the term "protect" correct. How about "preserve"? Because we try to keep
the toast value on the memory in heap_update().

Best regards,
Hayato Kuroda
FUJITSU LIMITED