Re: remote database queries - Mailing list pgsql-hackers

From Bruce Momjian
Subject Re: remote database queries
Date
Msg-id 200106141648.f5EGmlF09097@candle.pha.pa.us
Whole thread Raw
In response to remote database queries  ("Joe Conway" <joe.conway@mail.com>)
List pgsql-hackers
Added to /contrib.  Thanks.

> > Until we fix that (maybe for 7.2, maybe not) your existing hack is
> > probably pretty reasonable.  You could save some cycles by avoiding
> > conversion to text, though --- instead return an opaque datum that is
> > pointer-to-tuple-slot and let the dblink_tok function extract fields
> > from the tuple.  Look at SQL function support and the FieldSelect
> > expression node type for inspiration.
> >
> 
> I changed the dblink() function to return a pointer instead of concatenated
> text, and dblink_tok() to use the pointer. FWIW, a query on a small (85
> tuples) remote (a second PC on a 100baseT subnet) table takes about 34
> milliseconds (based on show_query_stats) versus about 4 milliseconds when
> run locally. It actually takes a bit longer (~65 milliseconds) when run
> against a second database on the same PC. The original text parsing version
> was about 25% slower.
> 
> Although shifting from text parsing to pointer passing is more efficient, I
> have one more question regarding this -- for now ;) -- is there any way to
> check the pointer passed to dblink_tok() to be sure it came from dblink()?
> 
> Thanks,
> 
> -- Joe
> 

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--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
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