Re: Replication identifiers, take 3

On Sat, Sep 27, 2014 at 12:11 PM, Steve Singer <steve@ssinger.info> wrote:
> If we were now increasing the WAL record size anyway for some unrelated
> reason, would we be willing to increase it by a further 2 bytes for the node
> identifier?

Obviously not.  Otherwise Andres would be proposing to put an OID in
there instead of a kooky 16-bit identifier.

> If the answer is 'no' then I don't think we can justify using the 2 padding
> bytes just because they are there and have been unused for years.  But if
> the answer is yes, we feel this important enough to justfiy a slightly (2
> byte) larger WAL record header then we shouldn't use the excuse of maybe
> needing those 2 bytes for something else.   When something else comes along
> that needs the WAL space we'll have to increase the record size.
>
> To say that if some other patch comes along that needs the space we'll redo
> this feature to use the method Robert describes is unrealistic.  If we think
> that the replication identifier  isn't general/important/necessary to
> justify 2 bytes of WAL header space then we should start out with something
> that doesn't use the WAL header,

I lean in that direction too, but would welcome more input from others.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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