Re: Column Filtering in Logical Replication

From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
To: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Cc: vignesh C <vignesh21(at)gmail(dot)com>, Rahila Syed <rahilasyed90(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Peter Smith <smithpb2250(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Column Filtering in Logical Replication
Date: 2021-09-27 12:23:49
Message-ID: 202109271223.pw2dggvhq2mz@alvherre.pgsql
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On 2021-Sep-27, Amit Kapila wrote:

> I am not sure what makes you say that we can't distinguish the above
> cases when there is already a separate rule for CURRENT_SCHEMA? I
> think you can distinguish by tracking the previous objects as we are
> already doing in the patch. But one thing that is not clear to me is
> is the reason to introduce a new type PUBLICATIONOBJ_CURRSCHEMA when
> distinguish all cases of CURRENT_SCHEMA. Alvaro might have something
> in mind for this which is not apparent and that might have caused
> confusion to you as well?

My issue is what happens if you have a schema that is named
CURRENT_SCHEMA. In the normal case where you do ALL TABLES IN SCHEMA
"CURRENT_SCHEMA" you would end up with a String containing
"CURRENT_SCHEMA", so how do you distinguish that from ALL TABLES IN
SCHEMA CURRENT_SCHEMA, which does not refer to the schema named
"CURRENT_SCHEMA" but in Vignesh's proposal also uses a String containing

Now you could say "but who would be stupid enough to do that??!", but it
seems easier to dodge the problem entirely. AFAICS our grammar never
uses String "CURRENT_SCHEMA" to represent CURRENT_SCHEMA, but rather
some special enum value.

Álvaro Herrera 39°49'30"S 73°17'W —

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