Re: "RETURNING PRIMARY KEY" syntax extension

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.

Also,

I did see where you account for auto-updatable views but what about complex
views with instead of triggers?

These can still be the target of DML queries but are not guaranteed (though
can possibly) to return a well-defined primary key.  At worse an explicit
error about the view itself, not the apparent lack of primary key, should be
emitted.

David J.



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