On Sun, Oct 02, 2005 at 09:46:07PM -0400, Tom Lane wrote: > Fredrik Olsson <[EMAIL PROTECTED]> writes: > > To allow indexes to be inherited so unique, foreign keys and such works > > properly with inheritance has been on the todo for quite some time. I > > thought that most probably it is a very non trivial thing, perhaps > > completely rethinking how indexes are done. > > Yup, you're right. There are a couple of major problems, to my mind: > > 1. A cross-table index would need to store a table OID as well as the > existing block/offset information in order to tell you what an entry is > pointing at. An extra 4 bytes per index entry (8 bytes if MAXALIGN is > 8) is a lot of overhead, so you'd not want to pay that all the time. > Which means two index tuple header formats to support, which looks > painful. How can that be handled cleanly and efficiently?
Wouldn't it make more sense to use a smaller pointer to a table of OIDs that that index covers? I don't know off-hand how much padding there currently is in index tuples, but hopefully this would allow bringing the space usage under control for common cases involving less than a few dozen tables. Another possibility is optimizing for the special case of indexing on a partitioning key. In this case, index values would be very localized to one table, so just storing the table info on each index page (or something similar) would work well. -- Jim C. Nasby, Sr. Engineering Consultant [EMAIL PROTECTED] Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461 ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly