Heikki Linnakangas <[EMAIL PROTECTED]> writes: >> Here's a patch that implements page at a time index scans discussed at >> pgsql-hackers earlier. See proposal 1 at: >> http://archives.postgresql.org/pgsql-hackers/2006-03/msg01237.php
One potential performance lossage from this is that it partially defeats the keys_are_unique optimization: bt_checkkeys will be run across all the matching tuples on the index page even if the waiting caller is going to stop after the first live one. (I don't see any way to avoid that without breaking the entire concept, since we can't know which of the index entries the caller will think is live.) I suspect this is not a deal-breaker, but we have to test to make sure that case isn't getting markedly worse. The thing to look at would be unique indexes with expensive comparison functions (eg, text in a non-C locale). regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match