I understand that COUNT queries are expensive.  So I'm looking for advice on 
displaying paginated query results.

I display my query results like this:

  Displaying 1 to 50 of 2905.
  1-50 | 51-100 | 101-150 | etc.

I do this by executing two queries.  One is of the form:

  SELECT <select list> FROM <view/table list> WHERE <filter> LIMIT m OFFSET n

The other is identical except that I replace the select list with COUNT(*).

I'm looking for suggestions to replace that COUNT query.  I cannot use the 
method of storing the number of records in a separate table because my queries 
(a) involve joins, and (b) have a WHERE clause.

And an unrelated question:
I'm running PG 7.2.2 and want to upgrade to 7.4.1.  I've never upgraded PG 
before and I'm nervous.  Can I simply run pg_dumpall, install 7.4.1, and then 
feed the dump into psql?  I'm planning to use pg_dumpall rather than pg_dump 
because I want to preserve the users I've defined.  My database is the only one 
on the system.

-David (who would love to go to Bruce Momjian's boot camp)

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TIP 9: the planner will ignore your desire to choose an index scan if your
      joining column's datatypes do not match

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