Re: Table partition with primary key in 11.3

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От Simon Riggs
Тема Re: Table partition with primary key in 11.3
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Msg-id CANP8+j+Yxyb8q0wHepRuW1WxJyOyoak7Pmfx_HfAFnhvLat03g@mail.gmail.com
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Ответ на Re: Table partition with primary key in 11.3  (Alvaro Herrera <alvherre@2ndquadrant.com>)
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On Thu, 6 Jun 2019 at 18:03, Alvaro Herrera <alvherre@2ndquadrant.com> wrote:
On 2019-Jun-06, Alex V. wrote:

> I think that your position about primary keys in partitional tables is
> not right.
>
> If we see regular table, one-field primary key is cross-table unique.
> In partitional tables for users view we MUST also seen unique
> one-field primary key because this is user requirement and another
> keys can destroy logic between regular and partitional tables and
> functionality of partitioning becomes useless.
> For administrators of table we not-MAY, but MUST see one-field unique
> primary key in cross-table realisation.
> All another realizations are plugging holes in a hurry and non-logical
> at global review of engine.

If you are saying that you think that Postgres should support primary
keys that don't necessarily overlap partition keys, then I agree with
you.  Please send a patch to implement that capability.

The point is that unique indexes that overlap partition keys are rather cheap because they can be made from a set of local indexes.

A unique index that doesn't overlap partition keys would be
* unfeasibly huge
* likely to hit the 32TB limit on relations
* unable to cope with dropping partitions

It sounds like you want it, cos its just a line of DDL, but in practice your colleagues wouldn't want those things. 

--
Simon Riggs                http://www.2ndQuadrant.com/
PostgreSQL Solutions for the Enterprise

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