Eddy Escardo-Raffo <eescardo@xxxxxxxxxx> writes: > The table used in this query is called "users", and it has columns "userid" > (primary key) and "location". > The "location" column is indexed. > The users table has 1 million rows, and all rows have integer typed value > '-1' for "location" column, except for 2 rows that have the integer value > '76543'. Oh, after poking at it a bit more, I realize the problem: the planner doesn't want to use an indexscan because it assumes there's a significant probability that the search will be for -1 (in which case the indexscan would be slower than a seqscan, as indeed your results prove). Even though it could know in this particular case that the comparison value isn't -1, I doubt that teaching it that would help your real queries where it will probably be impossible to determine the comparison values in advance. I would suggest considering using NULL rather than inventing a dummy value for unknown locations. The estimation heuristics will play a lot nicer with that choice. regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
