Re: row filtering for logical replication

On Wed, Oct 6, 2021 at 2:33 PM Ajin Cherian <itsajin@gmail.com> wrote:
>
> On Sat, Oct 2, 2021 at 5:44 PM Ajin Cherian <itsajin@gmail.com> wrote:
> >
> > I have for now also rebased the patch and merged the first 5 patches
> > into 1, and added my changes for the above into the second patch.
>
> I have split the patches back again, just to be consistent with the
> original state of the patches. Sorry for the inconvenience.

Thanks for the updated version of the patch, I was looking into the
latest version and I have a few comments.


+        if ((att->attlen == -1 &&
VARATT_IS_EXTERNAL_ONDISK(tmp_new_slot->tts_values[i])) &&
+                (!old_slot->tts_isnull[i] &&
+                    !(VARATT_IS_EXTERNAL_ONDISK(old_slot->tts_values[i]))))
+        {
+            tmp_new_slot->tts_values[i] = old_slot->tts_values[i];
+            newtup_changed = true;
+        }

If the attribute is stored EXTERNAL_ONDIS on the new tuple and it is
not null in the old tuple then it must be logged completely in the old
tuple, so instead of checking
!(VARATT_IS_EXTERNAL_ONDISK(old_slot->tts_values[i]), it should be
asserted,


+    heap_deform_tuple(newtuple, desc, new_slot->tts_values,
new_slot->tts_isnull);
+    heap_deform_tuple(oldtuple, desc, old_slot->tts_values,
old_slot->tts_isnull);
+
+    if (newtup_changed)
+        tmpnewtuple = heap_form_tuple(desc, tmp_new_slot->tts_values,
new_slot->tts_isnull);
+
+    old_matched = pgoutput_row_filter(relation, NULL, oldtuple, entry);
+    new_matched = pgoutput_row_filter(relation, NULL,
+                                      newtup_changed ? tmpnewtuple :
newtuple, entry);

I do not like the fact that, first we have deformed the tuples and we
are again using the HeapTuple
for expression evaluation machinery and later the expression
evaluation we do the deform again.

So why don't you use the deformed tuple as it is to store as a virtual tuple?

Infact, if newtup_changed is true then you are forming back the tuple
just to get it deformed again
in the expression evaluation.

I think I have already given this comment on the last version.


-- 
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com