What is faster? C++ vector sort or sort in database

[JerryJ]

hi there,

I have to fetch values from a database and store them in a vector in
my c++ application.

What is faster? if i fetch the values sorted from the database with a
'order by' clause in the sql-statement or if i fetch them into the
vector unsorted and sort the vector then?
Thanx for your help
Greetz

Jens

[Simon Hayes]

"JerryJ" <je****@gmx.de> wrote in message
news:e9**************************@posting.google.c om...

hi there,

I have to fetch values from a database and store them in a vector in
my c++ application.

What is faster? if i fetch the values sorted from the database with a
'order by' clause in the sql-statement or if i fetch them into the
vector unsorted and sort the vector then?
Thanx for your help
Greetz

Jens

Well, the easiest thing to do would be to test it, of course, but there's
probably no point in writing your own sorting code when the database will do
it for you. Unless perhaps you have some unusual sorting logic which can't
be handled in the database.

Simon

[Dan Guzman]

To add to Simon's response, a lot of work has gone into database sorting
algorithms over the years so database sorting is fairly efficient. One of
the advantages the DBMS has over your code is that it may be able to exploit
indexes to facilitate the task.

This isn't to say that you can't sometimes sort faster in code but I would
specify the ORDER BY unless you have critical performance requirements and
your performance testing shows that sorting in your application is the best
method..

--
Hope this helps.

Dan Guzman
SQL Server MVP

"JerryJ" <je****@gmx.de> wrote in message
news:e9**************************@posting.google.c om...

hi there,

I have to fetch values from a database and store them in a vector in
my c++ application.

What is faster? if i fetch the values sorted from the database with a
'order by' clause in the sql-statement or if i fetch them into the
vector unsorted and sort the vector then?
Thanx for your help
Greetz

Jens

[Erland Sommarskog]

Dan Guzman (da*******@nospam-earthlink.net) writes:

To add to Simon's response, a lot of work has gone into database sorting
algorithms over the years so database sorting is fairly efficient. One
of the advantages the DBMS has over your code is that it may be able to
exploit indexes to facilitate the task.

This isn't to say that you can't sometimes sort faster in code but I
would specify the ORDER BY unless you have critical performance
requirements and your performance testing shows that sorting in your
application is the best method..

One argument for sorting client-side it scales better. But this would
only be relevant you are retrieving a lot of data, and there are many users
who are make concurrent retrievals.

Another factor is that the server may be better equipped with CPU than
the client, and thus be faster.

In the general case, I definitely agree with the recommendation to use
ORDER BY.

--
Erland Sommarskog, SQL Server MVP, so****@algonet.se

Books Online for SQL Server SP3 at
http://www.microsoft.com/sql/techinf...2000/books.asp

[Yvan]

I'd like to know your opinion about the following:

cache a hashmap of all the objects with their ID being the key
when you make your query with the order by, only fetch the IDs, and
create a new Vector by retrieving the elements from the HashMap

it seems to me that it benefits the database sorting capacities, while
avoiding the overhead of recreating the objects every time

of course it incurs some caching management on the client side, but I
think it would be worth it

let me know what you think

Yvan