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RE: Hunting down (possible) memory leak in DBD::Oracle ** EXTERNAL**

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Fennell, Brian
December 18, 2017 15:30
RE: Hunting down (possible) memory leak in DBD::Oracle ** EXTERNAL**
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Thanks for the reply, Howard,

I am using the exact same database - a test database that has copies of the production data put into it once a day - besides that it doesn't change much (if at all) during the day.

The SQL I am using doesn't leave out a "bad guy" - I thought of that and actually had an off-by-one gap in some of my early tests.  Closed that hole by changing a ">" to a ">=".

Here is the SQL (with the original table and field names changed to allow for sharing

        SELECT /*+ FULL(A) PARALLEL(A 6) */
            rownum ROW_NUMBER,
            A.field1 f1 ,
            A.field2 f2,
            A.field3 f3,
            A.field4 f4,
            B.field5 f5
            tableA A,
            tableB B
                B.field6      IN      ( 'TOK3', 'TOK4', 'TOK5' )
            AND B.field7      LIKE    'A%'
            AND B.field8      IN      ('TOK1', 'TOK2')
            AND B.fkfield1    =       A.field1
        ORDER BY
            1, 2, 3, 4, 5
      ) d
        d.row_number <  2020000
    AND d.row_number >= 1000000

-----Original Message-----
From: Howard, Chris [] 
Sent: Monday, December 18, 2017 9:21 AM
To: Fennell, Brian <>;
Subject: RE: Hunting down (possible) memory leak in DBD::Oracle ** EXTERNAL **

Same database... do you mean the actual very same data source?

What is the Oracle error? 

To eliminate problems based on data (implicit conversions, that kind of thing) can you do a run from row 500,000 to 1,500,000 ?  (I think you have this covered, but maybe that row right at the breaking spot is somehow a bad guy.)

-----Original Message-----
From: Fennell, Brian []
Sent: Saturday, December 16, 2017 3:19 PM
Subject: Hunting down (possible) memory leak in DBD::Oracle ** EXTERNAL **

Dear DBI people - 

I am trying to port some old perl code to a new box.  (see Details below) Needless to say the original box and code works fine, but the new box (and old code) does not.
Specifically what I am seeing is that when I select slightly over a million records from a specific join of two tables (to be dumped one row at a time into a TSV file) we get strange ORA-NNNNN errors that don't really make any sense in this context.
The Same database and same table works fine on the original box with the large number of records.  2 million records always causes errors but two groups of 1million (divided up by ROWNUM - the EXACT same rows) causes no errors.  I am using a test database with little activity do I am reasonably certain that the queries deal with the same rows.
So I am thinking the problem is data volume and not any specific piece of data (originally I thought it might be an odd string/data related error, but I am starting to think it is a memory leak of some kind).
The error always happens inside of fetchrow_array - and "$dbh->trace( 4 , $filename )" shows that the error originates inside the DBD::Oracle module while reading field 3 of 6.  
Researching the ORA-NNNNNN error gives a perfectly sane description that makes no sense at all in the context of reading a specific field.  

We are going thru an Audit and tightening up security so there are some things (like REAL hostnames and REAL column/table names) that I cannot share - but I will try to share as much as I can.

The Host I am calling "prod" below is the only one NOT exhibiting this issue.

Things I want to try - 

1) recompile the DBD::Oracle module on Host "sandbox" with "perl Makefile.PL -g" and then use Valgrind.  I haven't used Valgrind before, but I guess it is time to learn.
2) Anything else this list suggests. 


Host: prod
OS: Red Hat Enterprise Linux AS release 4 (Nahant Update 4)
Perl: 5.8.8 built for x86_64-linux
DBI: 1.53
DBD::Oracle: 1.19

Host: dev
OS: Red Hat Enterprise Linux Server release 6.5 (Santiago)
Perl: 5.16.1  built for x86_64-linux
DBI: 1.631
DBD::Oracle: 1.74

Host: prodnew
OS: Red Hat Enterprise Linux Server release 6.5 (Santiago)
Perl: 5.16.1  built for x86_64-linux
DBI: 1.631
DBD::Oracle: 1.70

Host: sandbox
OS: CentOS Linux release 7.4.1708 (Core)
Perl: 5.16.3  built for x86_64-linux-thread-multi
DBI: 1.637
DBD::Oracle: 1.74

Brian Fennell, Software Engineer | Radial
O: 610 491 7308 | M: 484 354 1699

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