On Tue, Jun 17, 2014 at 10:08 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Robert Haas <robertmh...@gmail.com> writes: >> On Mon, Jun 16, 2014 at 8:10 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >>> On a micro-optimization level, it might be worth passing the TID as >>> ItemPointer not ItemPointerData (ie, pass a pointer until we get to >>> the point of actually inserting the TID into the index tuple). >>> I'm not sure that copying odd-size structs should be assumed to be >>> efficient. > >> Yeah, true. Checking existing precedent, it looks like we usually >> pass ItemPointer rather than ItemPointerData, so it's probably a good >> idea to do this that way too for reasons of style if nothing else. I >> kind of wonder whether it's really more efficient to pass an 8-byte >> pointer to a 6-byte structure than to just pass the structure itself, >> but it might be. > > The pointer will certainly be passed in a register, or whatever passes for > registers on the particular machine architecture. Weird-size structs, > though, tend to have arcane and not-so-efficient rules for being passed > by value. It's not unlikely that what the compiler will do under the hood > is pass a pointer anyhow, and then do a memcpy to make a local copy in > the called function.
OK, committed with the suggested changes. (Thanks to Abhijit for pinging me about this, and more generally for his active and effective management of this CommitFest!) -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
