Re: Problem with inserts from subselects

Can you try in this way:

INSERT INTO table_a (session, sent, data_row, direction_id, instrument,
price, size)
  select tmp.session, tmp.sent, tmp.data_row, tmp.direction_id, i.id,
tmp.price, tmp.size
  FROM table_b tmp
  INNER JOIN table_c i ON i.symbol_id = tmp.symbol_id AND i.route_id =
tmp.route_id
  LIMIT 10 ;

This is without ( ).

Banghe


Tyler Ward wrote:

>
>
>
> I'm using postgres 7.3.x (the default installed on Fedora Core 1) and
> I'm running into a serious
> bug in the insert performance.
>
> When I try a query like this...
>
> <snip>
>
> INSERT INTO table_a (session, sent, data_row, direction_id,
> instrument, price, size)
> (
>   select tmp.session, tmp.sent, tmp.data_row, tmp.direction_id, i.id,
> tmp.price, tmp.size
>   FROM table_b tmp
>   INNER JOIN table_c i ON i.symbol_id = tmp.symbol_id AND i.route_id =
> tmp.route_id
>   LIMIT 10
> );
>
> </snip>
>
> the performance is really slow, that query takes about 10 seconds to
> run. If I raise the limit to 100, it takes
> 10 times longer, etc.... It is basically so slow that we can't use our
> database at all. However, if I just run the
> inner select, like this....
>
> <snip>
>   select tmp.session, tmp.sent, tmp.data_row, tmp.direction_id, i.id,
> tmp.price, tmp.size
>   FROM table_b tmp
>   INNER JOIN table_c i ON i.symbol_id = tmp.symbol_id AND i.route_id =
> tmp.route_id
>   LIMIT 10
> </snip>
>
> The result returns basically instantly, in less than half a second.
>
> If I just insert the data by hand....
>
> <snip>
> INSERT INTO table_a (session, sent, data_row, direction_id,
> instrument, price, size) VALUES (1, NOW(), 820183, 1, 852, 1.0, 10);
> INSERT INTO table_a (session, sent, data_row, direction_id,
> instrument, price, size) VALUES (1, NOW(), 820184, 1, 852, 1.0, 10);
> INSERT INTO table_a (session, sent, data_row, direction_id,
> instrument, price, size) VALUES (1, NOW(), 820185, 1, 852, 1.0, 10);
> INSERT INTO table_a (session, sent, data_row, direction_id,
> instrument, price, size) VALUES (1, NOW(), 820186, 1, 852, 1.0, 10);
> INSERT INTO table_a (session, sent, data_row, direction_id,
> instrument, price, size) VALUES (1, NOW(), 820187, 1, 852, 1.0, 10);
> INSERT INTO table_a (session, sent, data_row, direction_id,
> instrument, price, size) VALUES (1, NOW(), 820188, 1, 852, 1.0, 10);
> INSERT INTO table_a (session, sent, data_row, direction_id,
> instrument, price, size) VALUES (1, NOW(), 820189, 1, 852, 1.0, 10);
> INSERT INTO table_a (session, sent, data_row, direction_id,
> instrument, price, size) VALUES (1, NOW(), 820190, 1, 852, 1.0, 10);
> INSERT INTO table_a (session, sent, data_row, direction_id,
> instrument, price, size) VALUES (1, NOW(), 820191, 1, 852, 1.0, 10);
> INSERT INTO table_a (session, sent, data_row, direction_id,
> instrument, price, size) VALUES (1, NOW(), 820192, 1, 852, 1.0, 10);
> </snip>
>
> then it's fast again. The above query finishes all ten inserts in less
> than half a second.
>
> So it seems that the problem only occurs when inserting data from a
> select clause, what's going on? And more importantly, how can I
> fix it?
>
>
> -Tyler
> tjw19@columbia.edu
>
>
>
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