ibatis-user-java mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Eric Williams <er...@sandiego.com>
Subject RE: queryForPaginatedList, stored procedures and output parameter s
Date Mon, 20 Dec 2004 22:32:58 GMT
That's not the design approach we wanted to use, but I guess we have no
choice when you consider the following factors:

1.) iBATIS ignores Sun's recommendation for compatibility when it tries to
grab output parameters before processing result sets. The response from MS
SQL Server, for example, packages output parameters *after* result sets and
row counts, so you can't grab an output param when you're sitting on a
result set. I believe the logic behind queryForList could be modified,
though it seems queryForPaginatedList could not.

2.) Either jTDS or iBATIS or both have trouble creating scrollable result
sets when I use queryForList, and the forward only cursor iBATIS uses
requires manually moving over each skipped record. With the amount of data
we'll be handling, this is a show-stopper.

Thanks to everyone who offered suggestions on this problem. I appreciate it.

Regards,
    Eric

-----Original Message-----
From: Larry Meadors [mailto:Larry.Meadors@plumcreek.com]
Sent: Sunday, December 19, 2004 6:30 AM
To: ibatis-user-java@incubator.apache.org; ericw@sandiego.com
Subject: RE: queryForPaginatedList, stored procedures and output
parameter s


Maybe I am being naive here.

If you are using a stored procedure already...why not make it return
just the data you want, one page at a time?

Every sql-based language i have used allows this, and it would be
faster, lighter-weight, clearer, and just plain easier for everyone.

Larry

>>> Eric Williams <ericw@sandiego.com> 12/17/04 3:20 PM >>>
queryForList has the same problem unless I pull the whole list at once,
which I can't (huge result sets). But it seems to me that the behavior
of
queryForList could be modified to call getMoreResults, since the result
set
is no longer needed once you get your last row.

Even so, it looks like the result set that is created when using
queryForList is not forward only, so in SqlExecutor.handleResults it
can't
use rs.absolute(skipResults) to jump ahead, and has to go one-by-one
over
the rows I want to skip (which could be a very large number of rows).
I'm
not sure why the result set is not forward only, or what I can do to
ensure
that it is. But again, if iBATIS won't go to the end of the result set
or
call getMoreResults before trying to get output parameters, queryForList
is
no better than queryForPaginatedList.

Is there anything else I can do? I really like iBATIS and want to move
away
from our home-grown JDBC code.

Regards,
	Eric

-----Original Message-----
From: Brandon Goodin [mailto:brandon.goodin@gmail.com]
Sent: Friday, December 17, 2004 12:10 PM
To: Eric Williams
Cc: ibatis-user-java@incubator.apache.org
Subject: Re: queryForPaginatedList, stored procedures and output
parameter s


Perhaps we could make this an optional setting for using PaginatedList
in concert with a Stored Procedure that has return parameters.
Although the performance gain that you are receiving from the
PaginatesList is diminished by having to traverse the whole resultset
in order to retrieve your output parameters. Why not use a
queryForList and handle the paging manually for now?

Brandon


On Fri, 17 Dec 2004 11:04:40 -0800, Eric Williams <ericw@sandiego.com>
wrote:
> I've been investigating this problem further, and I've found more
> information but I'm still somewhat lost as to what to do. This may or
may
> not be a bug in iBATIS.
> 
> From what I can tell, JDBC expects (or at least recommends) that all
rows
in
> a result set be processed before output parameters are grabbed. As
stated
in
> the java.sql.CallableStatement documentation: "For maximum
portability, a
> call's ResultSet objects and update counts should be processed prior
to
> getting the values of output parameters."
>
(http://java.sun.com/j2se/1.5.0/docs/api/java/sql/CallableStatement.html)
> 
> Please correct me if I'm wrong, but my debugging indicates that iBATIS
does
> not do this. When using queryForPaginatedList, a scrollable result set
is
> created, n results are grabbed for the first "page", then output
parameters
> are processed before the end of the result set has been reached, while
it
is
> still open (this assumes, of course, that you have more than one
"page" of
> results, which I do).
> 
> I'm using the jTDS driver for SQL Server. Its FAQ discusses this very
issue.
> After quoting the JDBC documentation as I have above, it states:
"Although
> this means that a 'good' driver could 'fix' this behavior, fixing it
would
> imply caching the whole server response, equaling a huge performance
drop.
> The exception is thrown because it's better to warn the user that the
output
> parameters are not yet set instead of leaving the impression that all
is
ok
> and cause other, harder to detect problems."
> (http://jtds.sourceforge.net/faq.html#callableStatementOutput)
> 
> The JDBC docs do mention "portability", and maybe its the case that
SQL
> Server is the issue here because it packages up its response in this
order:
> ResultSets, update counts, output parameters, return values.
> 
> So, I assume either:
>        1) You have a driver that processes all results and returns the
> output parameters, even if you're trying to use a scrollable result
set,
> which as the jTDS documentation asserts could result in a huge
performance
> loss, or
>        2) You have a driver like jTDS that won't allow this and throws
an
> error (my problem), or
>        3) You don't use output parameters (not an option for me), or
>        4) You use another driver/database combo (not happening)
> 
> I don't know if this is a bug in iBATIS, per se, but it does appear
that
> iBATIS does not follow the letter of the law (or is it simply a
> recommendation?) when it tries to get output parameters before it has
> reached the end of a result set.
> 
> Any ideas on this? Even if I don't use iBATIS (which if I can't solve
this
> problem will very unfortunately be the case), I'm going to have to
deal
with
> this in my own JDBC code. Basically, it means implementing paging
inside
my
> stored procedures, which is a less elegant solution than scrollable
result
> sets (at least for my application).
> 
> Regards,
>        Eric
> 
> -----Original Message-----
> From: Eric Williams [mailto:ericw@sandiego.com]
> Sent: Wednesday, December 15, 2004 12:13 PM
> To: ibatis-user-java@incubator.apache.org
> Subject: queryForPaginatedList, stored procedures and output
parameters
> 
> I'm having trouble building PaginatedLists from stored procedures that
use
> output parameters. If I don't use output parameters, the problems
don't
> occur.
> 
> I'm getting this error:
> 
>        java.sql.SQLException: Output parameters have not yet been
> processed. Call getMoreResults()
> 
> I assume IBatis must be calling getMoreResults() when I use
queryForObject
> because I use procs with output params there, too. Only
> queryForPaginatedList fails.
> 
> Any help with this issue would be much appreciated. Thanks!
> 
> Regards,
>        Eric
>

Mime
View raw message