On Wednesday, June 13, 2012 05:18:22 PM Robert Haas wrote: > On Wed, Jun 13, 2012 at 11:06 AM, Andres Freund <and...@2ndquadrant.com> wrote: > > On Wednesday, June 13, 2012 05:03:38 PM Robert Haas wrote: > >> On Wed, Jun 13, 2012 at 10:35 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > >> > Robert Haas <robertmh...@gmail.com> writes: > >> >> On Tue, Jun 12, 2012 at 9:52 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > >> >>> The code for this is as attached. Note that I'd rip out the > >> >>> normal-path tracking of line boundaries; it seems better to have a > >> >>> second scan of the data in the error case and save the cycles in > >> >>> non-error cases. > >> >> > >> >> Really?! > >> > > >> > Um ... do you have a problem with that idea, and if so what? It would > >> > be considerably more complicated to do it without a second pass. > >> > >> Could you explain how it's broken now, and why it will be hard to fix? > >> People may well want to use a cast to JSON within an exception block > >> as a way of testing whether strings are valid JSON. We should not > >> assume that the cost of an exception is totally irrelevant, because > >> this might be iterated. > > > > Exception blocks/subtransctions already are considerably expensive. I > > have a hard time believing this additional cost would be measureable. > > According to my testing, the main cost of an exception block catching > a division-by-zero error is that of generating the error message, > primarily sprintf()-type stuff. The cost of scanning a multi-megabyte > string seems likely to be much larger. True. I ignored that there doesn't have to be an xid assigned yet... I still think its not very relevant though.
Andres -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
