Hi, On Aug 25, 2004, at 4:22 AM, Mark Kirkwood wrote:
> select > pav1.person_id > from > person_attributes_vertical pav1 > where > ( pav1.attribute_id = 1 > and pav1.value_id in (2,3)) > or ( pav1.attribute_id = 2 > and pav1.value_id in (2,3)) > [...] Why not combine attribute_id and value_id? Then you have nothing but an OR (or IN). It should, AFAICS, give you much better selectivity on your indexes: There will be a lot of attributes with the same ID; there will also be a lot of attributes with the same value. However, there should be much less attributes with a specific combination of (ID/Value). Right now I think it will be very hard to determine which field has a better selectivity: attribute_id or value_id. The combined attribute/value field could be an int8 or so, where the upper 4 bytes are for attribute_id and the lower 4 bytes for value_id. Depending on the number of attributes and possible values a smaller datatype and / or a different split can be made. A smaller datatype will result in faster access. What difference does that make? regards, --Tim ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings
