From: | Gavin Flower <GavinFlower(at)archidevsys(dot)co(dot)nz> |
---|---|
To: | David G Johnston <david(dot)g(dot)johnston(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: "RETURNING PRIMARY KEY" syntax extension |
Date: | 2014-06-09 07:06:30 |
Message-ID: | 53955CF6.3090107@archidevsys.co.nz |
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Lists: | pgsql-hackers |
On 09/06/14 17:47, David G Johnston wrote:
> Ian Barwick wrote
>> Hi,
>>
>> The JDBC API provides the getGeneratedKeys() method as a way of retrieving
>> primary key values without the need to explicitly specify the primary key
>> column(s). This is a widely-used feature, however the implementation has
>> significant
>> performance drawbacks.
>>
>> Currently this feature is implemented in the JDBC driver by appending
>> "RETURNING *" to the supplied statement. However this means all columns of
>> affected rows will be returned to the client, which causes significant
>> performance problems, particularly on wide tables. To mitigate this, it
>> would
>> be desirable to enable the JDBC driver to request only the primary key
>> value(s).
> Seems like a good idea.
>
>
>> ERROR: Relation does not have any primary key(s)
> "Relation does not have a primary key."
> or
> "Relation has no primary key." (preferred)
>
> By definition it cannot have more than one so it must have none.
>
> It could have multiple unique constraints but I do not believe they are
> considered if not tagged as primary.
>
> David J.
>
>
>
>
>
> --
> View this message in context: http://postgresql.1045698.n5.nabble.com/RETURNING-PRIMARY-KEY-syntax-extension-tp5806462p5806463.html
> Sent from the PostgreSQL - hackers mailing list archive at Nabble.com.
>
>
From memory all unique keys can be considered 'candidate primary keys',
but only one can be designated 'the PRIMARY KEY'.
I also like your preferred error message, and to the full extent of my
decidedly Non-Authority, I hereby authorise it! :-)
Cheers,
Gavin
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