How does PostgreSQL recognise "deleted" tuples by using xmax ?
I want to test the optimizer of postgresql.
Can anyone give me any idea about which kinds of query I should test?
large query for path an geqo?
subquery?
Yeah, the problem is when I test large join, the plan considered by geqo is
large than path. (3000+ vs 500+). However, the time used in optimizer of
geqo is 1/4 of path. By the way, I use the same query.
Another thing is for the join of 2 tables, geqo consider 60-90 plans.
In general, I think for l
Is it a reasonable idea to add a counter to set_cheapest? I think this
function evaluate the cheapest path. Therefore, it means how many complete
plans have been considered, doesn't it?
2009/10/12 纪晓曦
> What I want to count is the number of plans that have been considered
> ch
What I want to count is the number of plans that have been considered
cheapest_path. Since if a path is considered to be a cheapest_path, the
postgres optimizer need to spent time on comparison. I think this is what I
want.
2009/10/4 Martijn van Oosterhout
> On Sat, Oct 03, 2009 at 04:20:59PM
Since I also need to consider gego, is this the best way to do it?
2009/9/30 Tom Lane
> =?UTF-8?B?57qq5pmT5pum?= writes:
> > Where can I add a integer counter to count the plans considered by
> planner.
>
> Well, you could count the number of calls to add_path, but a path is
> hardly the same
I think there no better way you can get around this problem. You need to
check the disk periodically and it is not to hard.
2009/10/1 Dave Huber
> I am inserting 250 rows of data (~2kbytes/row) every 5 seconds into a
> table (the primary key is a big serial). I need to be able to limit the size
Where can I add a integer counter to count the plans considered by planner.
In my opinion, it is in the src/backend/optimizer/path directorty.
Thank you very much, I think I need to stady more about trigger.
2009/9/28 A. Kretschmer
> In response to ? :
> > Yes, you are right. That maybe a bad example. what I want to say maybe
> like
> > this:
> >
> > create table a (
> > id integer,
> > room varchar(32),
> >
create table a(
name varchar(32);
);
create talbe b(
name1 varchar(32);
name2 varchar(32);
);
How to write a constraint to check name1, name2 in the table a without
change table defination?
ALTER TABLE b ADD CHECK( ??? );
To be precise,
The difference between
create table a (
foreign key (id) referenced by b(name),
);
create table b(
id integer referenced by b(name),
);
I want detail usage introduction about constraint,such as how to constrain a
string to be exactly 4 character and start with 'z'.Where can I find the
reference of CHECK? detail usage.
Well I don't think the result would keep if you run a "hot" test. However,
in one SELECT clause, maybe it can be optimised .
2009/9/3 Allan Kamau
> Hi,
> I do have a query which make use of the results of an aggregate
> function (for example bit_or) several times in the output column list
> of
Thank you very much. It seems it is better to save it on file system.
2009/9/9 Yaroslav Tykhiy
> On 09/09/2009, at 10:43 AM, John R Pierce wrote:
>
> 纪晓曦 wrote:
>>
>>> Can I save images in the postgres? How to define? Does the format
>>> matters? Can I save JP
Can I save images in the postgres? How to define? Does the format matters?
Can I save JPG/PNG?How?
How can I do a moving avg by only using SQL?
Consider the following relational schema about daily stock prices.
StockPrice (stockid; timeid; price)
We make the simplifying assumption that timeid is an integer that count the
number
of days from a particular date in the past (that is, the stock prices on the
x-th day can
be found by a simple se
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