Greg Stark wrote: > There's another API question I have. To implement Consistent I need to > call the hash function which in the case of functions like hashtext > could be fairly expensive and I even need to generate multiple hash > values(though currently I'm slicing them all from the integer hash > value so that's not too bad) and then test each of those bits. It > would be natural to call hashtext once at the start of the scan and > possibly build a bitmap and compare all of them in a single & > operation. But afaict there's no way to hook the beginning of the scan > and opaque is not associated with the specific scan so I don't think I > can cache the hash value of the scan key there safely. Is there a good > way to do it with the current API?
I'm not sure why you say opaque is not associated with the specific scan. Are you thinking we could reuse opaque for a future scan? I think we could consider that opaque *is* the place to cache things such as the hashed value of the qual constants or whatever. > On a side note I'm curious about something, I was stepping through the > my code in gdb and discovered that a single row insert appeared to > construct a new summary then union it into the existing summary > instead of just calling AddValue on the existing summary. Is that > intentional? What led to that? That's to test the Union procedure; if you look at the code, it's just used in assert-enabled builds. Now that I think about it, perhaps this can turn out to be problematic for your bloom filter opclass. I considered the idea of allowing the opclass to disable this testing procedure, but it isn't done (yet.) -- Álvaro Herrera 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
