Useful explanation of PostgreSQL index format: http://www.faqs.org/docs/ppbook/c13329.htm I think you are aiming for the wrong thing. The worst possible index is one with every value the same. The second worst (still basically useless) is one with only two values. The greater the differentiation of the data, the more workload is reduced on a search. Since it isn't a straight binary tree, I don't think that having highly dissimilar data in the index should be a problem. Do you have data or experience that shows otherwise? -----Original Message----- From: pgsql-general-owner@xxxxxxxxxxxxxx [mailto:pgsql-general-owner@xxxxxxxxxxxxxx] On Behalf Of TJ O'Donnell Sent: Tuesday, January 25, 2005 2:19 PM To: pgsql-general@xxxxxxxxxxxxxx Cc: tjo@xxxxxxx Subject: visualizing B-tree index coverage Does anyone know of a tools that allows one to visualize the tree created by a multi-column B-tree index? A picture of a tree with branches, showing how "branchy" the tree is would be great. I'm wondering how well I've "clustered" the data in my table using the multi-column index. In other words, do my multi-columns sufficiently but not overly discriminate rows from each other? Do I have too many with the same index? (not enough branches) Do I have a unique index for each row? (way too many branches) Thanks, TJ ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org
