Re: EXPIRE as a statement

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От David G Johnston
Тема Re: EXPIRE as a statement
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Msg-id CAKFQuwbFmRRVRhGjBtKvR1LUN7T0qu01weAMegcwkUm-JKB4uQ@mail.gmail.com
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Ответ на Re: EXPIRE as a statement  (Tom Lane <tgl@sss.pgh.pa.us>)
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On Sun, May 4, 2014 at 10:06 PM, Tom Lane-2 [via PostgreSQL] <[hidden email]> wrote:
David G Johnston <[hidden email]> writes:
> Blagoj Petrushev wrote
>> I know for example that redis has this feature, the EXPIRE / EXPIREAT
>> / TTL commands.
>> http://redis.io/commands/expire

One thought here is that recent versions of the SQL standard contain some
temporal-data features, which might well be usable for the purposes
envisioned here.  I'd much rather see us implementing SQL-spec features
than randomly invented ones, so please take a look into the spec before
going too far with EXPIRE.


​Slightly different semantics between data valid over a period - but maintained indefinitely - and data that is intentionally desired to be physically removed from the database after a certain point.  

And the temporal features require, from my recollection, require a specified "AT point-in-time" clause whereas expiration would generally be invisible from the viewpoint of a SELECT writer - hence why polluting existing queries is so high a risk.

Since expires seems easier I'm not sure that, if one were to go here first, we'd want decisions made to support the "expires" capability to bleed into a future temporal implementation.

David J.




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