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From: Vik Fearing <[email protected]>
To: Surafel Temesgen <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: WIP: System Versioned Temporal Table
Date: Fri, 25 Oct 2019 21:45:46 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <CALAY4q8xpuU7Qz7qy+5F8bh=GPAwR-pyscorAzTpyTQGyZbqtQ@mail.gmail.com>
References: <CALAY4q-cXCD0r4OybD=w7Hr7F026ZUY6=LMsVPUe6yw_PJpTKQ@mail.gmail.com>
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On 25/10/2019 11:56, Surafel Temesgen wrote:
>
>
> On Thu, Oct 24, 2019 at 6:49 PM Vik Fearing
> <[email protected] <mailto:[email protected]>> wrote:
>
>     On 24/10/2019 16:54, Surafel Temesgen wrote:
>     >
>     > hi Vik,
>     > On Wed, Oct 23, 2019 at 9:02 PM Vik Fearing
>     > <[email protected]
>     <mailto:[email protected]>
>     <mailto:[email protected]
>     <mailto:[email protected]>>> wrote:
>     >  
>     >
>     >
>     >     If we're going to be implicitly adding stuff to the PK, we also
>     >     need to
>     >     add that stuff to the other unique constraints, no?  And I
>     think it
>     >     would be better to add both the start and the end column to
>     these
>     >     keys. 
>     >     Most of the temporal queries will be accessing both.
>     >
>     >  
>     > yes it have to be added to other constraint too but adding both
>     system
>     > time 
>     > to PK will violate constraint because it allow multiple data in
>     > current data
>
>
>     I don't understand what you mean by this.
>
>
>
> The primary purpose of adding row end time to primary key is to allow
> duplicate value to be inserted into a table with keeping constraint in
> current data but it can be duplicated in history data. Adding row
> start time column to primary key will eliminate this uniqueness for
> current data which is not correct  


How?  The primary/unique keys must always be unique at every point in time.

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