-> Index Scan using transaction_stopped on
"transaction" t (cost=0.00..79787.90 rows=1747458 width=8) (actual
time=0.149..2905.861 rows=1682003 loops=1)
Index Cond: (('2005-10-25 15:00:00'::timestamp
without time zone <
On 2 Nov 2005, at 21:13, Scott Lamb wrote:
I want to retrieve all the events during a timespan in one list;
typical timespans will involve up to a couple rows.
Err, I meant up to a couple million rows. With two rows, I wouldn't
be so concerned about performance. ;)
--
Scott Lamb
Merlin Moncure wrote:
hmm, try pushing the union into a subquery...this is better style
because it's kind of ambiguous if the ordering will apply before/after
the union.
Seems to be a little slower. There's a new "subquery scan" step.
explain analyze
selectq.when_happened from (
to take
my first plunge into looking at a database query planner.
Regards,
Scott
--
Scott Lamb <http://www.slamb.org/>
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each element of the union and then merging
that, compared to the cost of grabbing the union and then ordering
it. In this case, the former cost is about 0 - it already has
independently ordered them, and the merge algorithm is trivial.
<http://en.wikipedia.org/wiki/Merge_algorithm&g
7; and value = 'oid080505';
# DELETE FROM "tmp_table2" WHERE id IN
# (SELECT at.id FROM "tmp_table2" at, "tmp_table2" a
# WHERE at.id=a.id and a.name='obsid' and a.value='oid080505');
and this?
delete from tmp_table2 where name = '
On Nov 14, 2005, at 3:52 PM, Steve Wampler wrote:
Scott Lamb wrote:
On Nov 14, 2005, at 2:07 PM, Steve Wampler wrote:
# SELECT at.id FROM "tmp_table2" at, "tmp_tabl2e" a
# WHERE at.id=a.id and a.name='obsid' and a.value='oid080505';
Isn't this
you have to get them:
(1) sort the values into an array
(2) use each value's array index as its key
It reduces to the problem you're trying to use it to solve.
--
Scott Lamb <http://www.slamb.org/>
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about anything.Interesting. If you abandon the idea that collisions should be impossible (they're not indexes) or extremely rare (they're not hashes), it's pretty easy to come up with a decent hint to avoid a lot of dereferences. --Scott Lamb <http://www.slamb.org/>
n. So no real way
to do this.
Regards,
Scott
--
Scott Lamb <http://www.slamb.org/>
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th
the client-side solution we came up with.
--
Scott Lamb <http://www.slamb.org/>
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where latest.regn_no = even_later.regn_no
and latest.transfer_date < even_later.transfer_date)
and latest.flock_no = '1359'
There's no MAX() or DISTINCT here, so maybe this is easier to optimize?
--
Scott Lamb <http://www.slamb.org/>
--
Peter, I compared these using the data you supplied on my PostgreSQL
8.1.4 system:
On Aug 17, 2006, at 12:09 PM, Scott Lamb wrote:
On Aug 16, 2006, at 3:51 PM, Tom Lane wrote:
/* Select all sheep who's most recent transfer was into the
subject flock */
SELECT DISTINCT f1.regn_n
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