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Date: Fri, 04 Sep 1998 11:03:00 +0800
From: Vadim Mikheev <vadim@krs.ru>
Organization: OJSC Rostelecom (Krasnoyarsk)
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To: "D'Arcy J.M. Cain" <darcy@druid.net>
CC: "Thomas G. Lockhart" <lockhart@alumni.caltech.edu>, hackers@postgreSQL.org
Subject: Re: [HACKERS] Adding PRIMARY KEY info
References: <m0zEaoV-00006JC@druid.net>
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D'Arcy J.M. Cain wrote:
>
> Thus spake Vadim Mikheev
> > Imho, indices should be used/created for FOREIGN keys and so pg_index
> > is good place for both PRIMARY and FOREIGN keys infos.
>
> Are you sure? I don't know about implementing it but it seems more
> like an attribute thing rather than an index thing. Certainly from a
> database design viewpoint you want to refer to the fields, not the
> index on them. If you put it into the index then you have to do
> an extra join to get the information.
>
> Perhaps you have to do the extra join anyway for other purposes so it
> may not matter. All I want is to be able to be able to extract the
> field that the designer specified as the key. As long as I can design
> a select statement that gives me that I don't much care how it is
> implemented. I'll cache the information anyway so it won't have a
> huge impact on my programs.
First, let me note that you have to add int28 field to pg_class,
not just oid field, to know what attributeS are in primary key
(we support multi-attribute primary keys).
This could be done...
But what about foreign and unique (!) keys ?
There may be _many_ foreign/unique keys defined for one table!
And so foreign/unique keys info have to be stored somewhere else,
not in pg_class.
pg_index is good place for all _3_ key types because of:
1. index should be created for each foreign key -
just for performance.
2. pg_index already has int28 field for key attributes.
3. pg_index already has indisunique (note that foreign keys
may reference unique keys, not just primary ones).
- so we have just add two fields to pg_index:
bool indisprimary;
oid indreferenced;
^^^^^^^^^^^^^^^^^^
this is for foreign keys: oid of referenced relation'
primary/unique key index.
I agreed that indices are just implementation...
If you don't like to store key infos in pg_index then
new pg_key relation have to be added...
Comments ?
Vadim
From owner-pgsql-hackers@hub.org Sat Sep 5 02:01:13 1998
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