On Wed, 2004-10-20 at 08:06, Dan Pelleg wrote:
> I'm trying to access a table with about 120M rows. It's a vertical version
> of a table with 360 or so columns. The new columns are: original item col,
> original item row, and the value.
>
> I created an index:
>
> CREATE INDEX idx on table (col, row)
>
> however, selects are still very slow. It seems it still needs a sequential
> scan:
>
> EXPLAIN SELECT * FROM table WHERE col=1 AND row=10;
> QUERY PLAN
> ------------------------------------------------------------------------------
> Seq Scan on table (cost=100000000.00..102612533.00 rows=1 width=14)
> Filter: ((col = 1) AND ("row" = 10))
>
> What am I doing wrong?
What type are row and col? If they're bigint (i.e. not int / int4) then
you might need to quote the value to get the query to use an index:
SELECT * FROM table WHERE col='1' AND row='10';
also, have you vacuumed / analyzed the table? I'm assuming yes.
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TIP 8: explain analyze is your friend
