Re: Distributed Join
This is a multi-part message in MIME format. ---------------------------------13897900730428 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii >We have just finished evaluating DB Integrator against an RDB 6.1 >database and were very disappointed in the performance of this tool. >As an example the program before dbi took about 10 seconds to load >some initial information and display the opening menu. The only changes >made were to create a DBI database that pointed to the original >database. All data resided in the same database as before but the >program pointed to the dbi database and the same test takes over 2 >minutes and 30 seconds. All other tests show about a 35% increase in >elapsed time to perform tests. >Do you have any ideas on what we might do to improve on this quite dismal >performance problem. DBI will add some overhead in comparison to accessing rdb directly. The overhead is in attaching to its catalog database to obtain the metadata, and the attach to the underlying rdb database containing data. But, this is only an attach time cost. Even so, your attach time appears to be unusually high. Also, first time any table is queried, DBI does incremental metadata loading, the overhead of which is not that significant, but subsequent query execution against that table should be relatively fast. In you case, 35% appears to be very high. I suspect that your setup may need to be tuned. If you can provide me some info, I can try and help. What version of DBI are you using? How many tables have you imported into DBI? Also, turn on the EXPLAIN tracing, and send me the output along with the queries you are running? - vishu ---------------------------------13897900730428 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain From: houghjejr@ornl.gov (John E. Hough) Newsgroups: comp.databases,comp.databases.informix,comp.databases.ingres,comp.databases.ms-access,comp.databases.object,comp.databas= es.oracle,comp.databases.paradox,comp.databases.pick,comp.databases.rdb,comp.databases.sybase,comp.databases.theory Subject: Re: Distributed Join Date: Thu, 8 Jun 1995 14:44:26 GMT Organization: C&TS Message-ID: <houghjejr.99.2FD70CC9@ornl.gov> References: <3qdt5t$l2h@lantana.singnet.com.sg> <3ql38p$6cq@raisinet.cs.umd.edu> <MAL.95Jun3100013@yavanna> <802275189snz@copse.demo= n.co.uk> <james.lawrence.45.0012036C@EPAMAIL.EPA.GOV> <1995Jun7.130349.10170@eisner> In article <1995Jun7.130349.10170@eisner> armstrong@eisner.decus.org (Borden Armstrong, United Airlines) writes: >From: armstrong@eisner.decus.org (Borden Armstrong, United Airlines) >Subject: Re: Distributed Join >Date: 7 Jun 95 13:03:49 -0400 >In article <james.lawrence.45.0012036C@EPAMAIL.EPA.GOV>, james.lawrence@EPAMAIL.EPA.GOV writes: >> However anyone considering this for production systems should be aware >> that nobody is optimizing distributed joins yet. Unfortunately this >> means that there is no value in making it transparent, since it wouldn't >> perform worth a shit. >Not entirely true. Examine Digital's DBIntegrator. And since DBI can >front-end both Sybase & Oracle7 (as well as DB2, Oracle Rdb and a number of >other databases) it is possible to perform optimised distributed joins across >database platforms, not just across databases. >Disclaimer: I do not work for Digital, but I did beta-test the product. >Borden Armstrong United Airlines - SFOKI >Sr. Staff Analyst - Database Design San Francisco International Airport >Armstrong@Eisner.Decus.Org San Francisco, CA 94128 >[Disclaimer: All opinions herein are my own and not those of my employer. All >advice herein is worth exactly what you paid for it.] Borden: We have just finished evaluating DB Integrator against an RDB 6.1 database and were very disappointed in the performance of this tool. As an example the program before dbi took about 10 seconds to load some initial information and display the opening menu. The only changes made were to create a DBI database that pointed to the original database. All data resided in the same database as before but the program pointed to the dbi database and the same test takes over 2 minutes and 30 seconds. All other tests show about a 35% increase in elapsed time to perform tests. Do you have any ideas on what we might do to improve on this quite dismal performance problem. Thanks, John Hough ---------------------------------13897900730428--