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Thread: Table Sorting and Limit Question

Table Sorting and Limit Question

From
Dawn Hollingsworth
Date:

Currently we have a table with a sequence number( id ) as a primary key,
a date field which is indexed and several other columns. The user
interface allows the user to sort the data by date and limits the result
set to 100 rows. 

The question is: 
The user interface needs the capability to sort the table by date but
pull out the hundred row set that contains id say...542 for example. 

What would be the best way to do this taking into account this table is
several hundred thousand rows? 


Dawn Hollingsworth 
Principal Engineer 
AirDefense, Inc.

Re: Table Sorting and Limit Question

From
Ludwig Lim
Date:
--- Dawn Hollingsworth <dmh@airdefense.net> wrote:
> 
> 
> Currently we have a table with a sequence number( id
> ) as a primary key,
> a date field which is indexed and several other
> columns. The user
> interface allows the user to sort the data by date
> and limits the result
> set to 100 rows. 
> 
> The question is: 
> The user interface needs the capability to sort the
> table by date but
> pull out the hundred row set that contains id
> say...542 for example. 
> 
> What would be the best way to do this taking into
> account this table is
> several hundred thousand rows? 

try also to index the id.

Try :
Select *
from <table>
where id=<id>
order by date
limit <limit no>

In this case you <limit no> is 100 since you want to
return at most 100 rows.

hope that helps.

ludwig.


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Re: Table Sorting and Limit Question

From
Dawn Hollingsworth
Date:
Since the id is a sequence type it should be unique. In this case it
also happens to be my primary key into this table which will also make
it unique. So the query below would only return 1 row. 

The part I'm missing is the offset number of the limit. Is there any way
to figure out which offset into the query would contain the id I'm
interested in.

Dawn Hollingsworth 
Principal Engineer 
AirDefense, Inc.


On Thu, 2002-08-08 at 21:42, Ludwig Lim wrote:
> 
> --- Dawn Hollingsworth <dmh@airdefense.net> wrote:
> > 
> > 
> > Currently we have a table with a sequence number( id
> > ) as a primary key,
> > a date field which is indexed and several other
> > columns. The user
> > interface allows the user to sort the data by date
> > and limits the result
> > set to 100 rows. 
> > 
> > The question is: 
> > The user interface needs the capability to sort the
> > table by date but
> > pull out the hundred row set that contains id
> > say...542 for example. 
> > 
> > What would be the best way to do this taking into
> > account this table is
> > several hundred thousand rows? 
> 
> try also to index the id.
> 
> Try :
> Select *
> from <table>
> where id=<id>
> order by date
> limit <limit no>
> 
> In this case you <limit no> is 100 since you want to
> return at most 100 rows.
> 
> hope that helps.
> 
> ludwig.
> 
> 
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update on a large table

From
"Aaron Held"
Date:
I need to do an UPDATE on a large (100 million record) table.  Is there
any way to speed up the process (Like turning off the transaction log)?

So far postgres has been handling the large database exceptionally well
(large \copy imports and WHERE clauses w/ multiple params) but it is
killing me on UPDATES.  It takes about 4 hours to run an UPDATE (the WHERE
clause is against an INDEX) but about 50 sec for a similar SELECT.

Thank You,
-Aaron Held