Dror Matalon <[EMAIL PROTECTED]> writes: > Actually what finally sovled the problem is repeating the > dtstamp > last_viewed > in the sub select
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That will at least convince the optimizer to use an index range lookup. But it still will have to scan every record that matches channel==$1, link==$2, and dtstamp>$3. The trick of using limit 1 will be faster still as it only has to retrieve a single record using the index. But you have to be sure to convince it to use the index and the way to do that is to list exactly the same columns in the ORDER BY as are in the index definition. Even if some of the leading columns are redundant because they'll be constant for all of the records retrieved. The optimizer doesn't know to ignore those. > > (This is the thing i pointed out previously in > > <[EMAIL PROTECTED]> on Feb 13th 2003 on pgsql-general) -- greg ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
