On Sat, Oct 18, 2014 at 2:25 PM, Feng Tian wrote:
> Hi, David,
>
> Yes, switch sorting order would loose an interesting order so if user
> dictates order by t, i; planner need to resort to its cost model.
> Estimating cardinality of groupby is a much bigger topic than this thread.
>
>
Well I don'
On Sat, Oct 18, 2014 at 5:27 AM, Greg Stark wrote:
> That's interesting but I think it's mostly a quirk of your example.
> Afaics the difference is only that the en_US locale ignores
> punctuation like : and / (or at least treats them as less significant
> than alphabetic characters). If you had
On Sat, Oct 18, 2014 at 3:10 AM, Peter Geoghegan wrote:
> So the first eight bytes of the first string is 0x131F1F1B221E,
> and the second 0x131F1F1B220C. The last byte is different.
That's interesting but I think it's mostly a quirk of your example.
Afaics the difference is only that the
On Fri, Oct 17, 2014 at 6:25 PM, Feng Tian wrote:
> I feel sorting string as if it is bytea is particularly interesting. I am
> aware Peter G's patch and I think it is great, but for this sort agg case,
> first, I believe it is still slower than sorting bytea, and second, Peter
> G's patch depend
Hi, David,
Yes, switch sorting order would loose an interesting order so if user
dictates order by t, i; planner need to resort to its cost model.
Estimating cardinality of groupby is a much bigger topic than this thread.
I feel sorting string as if it is bytea is particularly interesting. I am
On Sat, Oct 18, 2014 at 12:35 PM, Tatsuo Ishii wrote:
> > The query,
> > select count(distinct j) from t group by t, i;
> >
> > runs for 35 seconds. However, if I change the query to,
> > select count(distinct j) from t group by i, t; -- note switching the
> > ordering
> > select count(distinct
On Sat, Oct 18, 2014 at 5:10 AM, Feng Tian wrote:
> Hi,
>
> Consider the following queries.
>
> create table t(i int, j int, k int, t text);
> insert into t select i, i % 100, i % 1000, 'AABBCCDD' || i from
> generate_series(1, 100) i;
>
> ftian=# explain select count(distinct j) from t group
> The query,
> select count(distinct j) from t group by t, i;
>
> runs for 35 seconds. However, if I change the query to,
> select count(distinct j) from t group by i, t; -- note switching the
> ordering
> select count(distinct j) from t group by decode(t, 'escape'), i; -- convert
> t to bytea
>
Hi,
Consider the following queries.
create table t(i int, j int, k int, t text);
insert into t select i, i % 100, i % 1000, 'AABBCCDD' || i from
generate_series(1, 100) i;
ftian=# explain select count(distinct j) from t group by t, i;
QUERY PLAN
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