Re: How to read parent session data - without forcing a commit in the parent

From: Ed Prochak <edprochak_at_gmail.com>
Date: Tue, 21 Oct 2008 11:18:20 -0700 (PDT)
Message-ID: <a7fdceef-198d-4792-922c-f3f8464dc243@75g2000hso.googlegroups.com>

On Oct 21, 8:18 am, nis..._at_gmail.com wrote:
> Hi Folks,
>
> I have an interesting problem. Basically, I have an oracle job that I
> need to speed up as we are exceeding our allocated time window. The
> oracle job consists of a large number of small changes across multiple
> 'source' tables and then one of my functions is called to try and
> process this source data in the fastest possible time - in order to
> create a single huge table from the uncommitted data. If there is an
> error in my processing, I simply raise an exception that causes a
> rollback of the source data. So far so good.
>
> Now here's the problem. The 'huge' table that I am building consists
> of 2 distinct sets of SELECT queries on the uncomitted source data
> tables. There is no problem in doing this serially - other than it
> takes us 4 hours which is too long. To speed things up, I wanted to
> run the 2 distinct SELECT queries in parallel - and therein lies the
> problem. I cannot get parallel SELECT functions to run without them
> forcing the source data to become committed. Is there any way to get
> around this?? Below is a cut down version of the top level function
> that I used to kick off the parallel functions that build the huge
> table from the source tables. It works - but we cannot rollback
> because the parallel functions force the source data to become
> comitted!!! is there no way for a child session to have access to its
> parents uncomitted data?
>
> Thanks folks..
> Nis.
>
> PROCEDURE testParallel
>   IS
>
>     p_ba varchar2(100) :='CSR';
>     p_no number :=100;
>
>     v_command1 varchar2(200):= 'nis_test_parallel.func1(' || '''' ||
> '''' || p_ba || '''' || '''' || ',' || p_no || ')';
>     v_command2 varchar2(200):= 'nis_test_parallel.func2(' || '''' ||
> '''' || p_ba || '''' || '''' || ',' || p_no || ')';
>
>   BEGIN
>
>     -- When this function is called, then at this point we have got
> uncomitted data in tables. These tables are
>     -- need to be read by
>
>     -- The start_background_job command uses the
> dbms_scheduler.create_job command to kick off the thread
>     start_background_job( 'BUILD_TABLE_PART1',
>                           v_command1,
>                           'Background Job to build part1 of the
> results table');
>
>     start_background_job( 'BUILD_TABLE_PART2',
>                           v_command2,
>                           'Background Job to build part2 of the
> results table');
>
>   END testParallel;

Have you considered using some staging tables?

0. truncate staging tables.
1. parent commits the tentative data to the staging tables
2. parallel jobs create the results data based on the staging table

data
3. if all looks good, the staging table data is copied to the real tables and the results and stage data are committed.

Something like that should work.
  Ed Received on Tue Oct 21 2008 - 13:18:20 CDT