RE: [Patch] Use *other* indexes on the subscriber when REPLICA IDENTITY is FULL

Dear Önder,

Thank you for giving comments! The author's comment is quite helpful for us.

>
When I last dealt with the same issue, I was examining it from a slightly broader perspective. I think
my conclusion was that RelationFindReplTupleByIndex() is designed for the constraints of UNIQUE INDEX
and Primary Key.
>

I see. IIUC that's why you have added tuples_equal() in the RelationFindReplTupleByIndex().

>
I think we should also be mindful about tuples_equal() function. When an index returns more than
one tuple, we rely on tuples_equal() function to make sure non-relevant tuples are skipped.

For btree indexes, it was safe to rely on that function as the columns that are indexed using btree
always have equality operator. I think we can safely assume the same for hash indexes.

However, say we indexed "point" type using "gist" index. Then, if we let this logic to kick in,
I think tuples_equal() would fail saying that there is no equality operator exists.
>

Good point. Actually I have tested for "point" datatype but it have not worked well.
Now I understand the reason.
It seemed that when TYPECACHE_EQ_OPR_FINFO is reuqesed to lookup_type_cache(),
it could return valid value only if the datatype has operator class for Btree or Hash.
So tuples_equal() might not be able to use if tuples have point box circle types.

BTW, I have doubt that the restriction is not related with your commit.
In other words, if the table has attributes which the datatype is not for operator
class of Btree, we could not use REPLICA IDENTITY FULL. IIUC it is not documented.
Please see attched script to reproduce that. The final DELETE statement cannot be
replicated at the subscriber on my env.

>
For the specific notes you raised about strategy numbers / operator classes, I need to
study a bit :) Though, I'll be available to do that early next week.
>

Thanks! I'm looking forward to see your opinions...

Best Regards,
Hayato Kuroda
FUJITSU LIMITED