How to migrate from Oracle to MongoDB?

[Sandra Schlichting]

Hi everyone.

Are there a way to do a quick analysis on ones Oracle database to tell
how the same data would perform on MongoDB?

If so, what would the migration path be? Does there exist a tutorial
for migrating from Oracle to MongoDB?

Hugs,
Sandra

[Andreas Jung]

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Sandra Schlichting wrote:
> Hi everyone.
>
> Are there a way to do a quick analysis on ones Oracle database to
> tell how the same data would perform on MongoDB?

What do you mean with same data? Since a RDBMS schema is different from
the documented approach in MongoDB there is no one-to-one mapping.

>
> If so, what would the migration path be? Does there exist a tutorial

> for migrating from Oracle to MongoDB.

First you have to think about a proper database design for MongoDB
and then check your out-of-the-box options (like CSV or JSON import)
or writing a migration script according to your needs and data.

- -aj
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[Sandra Schlichting]

> What do you mean with same data? Since a RDBMS schema is different from
> the documented approach in MongoDB there is no one-to-one mapping.

I mean, without modifying the fundamental way the application talks to
the Oracle database. So it would more or less be a matter of replacing
the database layer.

Are the things where you can say, if you use this feature in Oracle,
then the migration will be hard?

Or are things where you can say, if you only use these features in
Oracle, then the migration will be easy?

> First you have to think about a proper database design for MongoDB
> and then check your out-of-the-box options (like CSV or JSON import)
> or writing a migration script according to your needs and data.

I can do that. But I am afraid that when I am done, the end is slower,
because I hadn't identified performance killers.

So I am looking for a check list so to speak of things I should be
aware of, before I begin migrating the data.

[Andreas Jung]

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Sandra Schlichting wrote:
>> What do you mean with same data? Since a RDBMS schema is different
>> from the documented approach in MongoDB there is no one-to-one
>> mapping.
>
> I mean, without modifying the fundamental way the application talks
> to the Oracle database. So it would more or less be a matter of
> replacing the database layer.

I am under the impression that you think that MongoDB would be a
fully-fledged replacement for a RDBMS, right?

- -aj
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[Dan Cook]

Sandra,

How isolated is your application from the database layer? 
(Are database keys exposed in the application layer?   What about views?)

Is your current application tied a specific schema?  Does it expect a particular relationships to hold true, like referential integrity?

Can your existing schema be expressed in terms of documents and collections efficiently/sufficiently in MongoDB?

What are your goals with using MongoDB?  (performance, sharding, etc..)
How constrained are you with application changes?

Dan

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[Chris Westin]

The short answer is "no, there isn't a way to do a quick analysis."
Unless your use of an RDBMS is extremely simple, it is almost certain
that MongoDB cannot be a drop-in replacement, and that you will have
to invest in rewriting parts of your application to make the switch.

Re later questions in the thread, a couple of major differences
between MongoDB and any RDBMS is that as a NoSQL store, MongoDB has
neither transactions, nor joins. You would have to look at your
application and see where you depend on these, and find ways to
rewrite your application to avoid needing them. In some cases, both
can be avoided by using embedded documents to model master-details
situations. But if you need to model many-to-many relationships,
you're going to have to add logic to your application to deal with
that, because NoSQL stores don't do that.

In general MongoDB gets its performance gains through simplicity. It
provides less functionality than an RDBMS, and in exchange, a number
of other things emerge. Schema evolution is doable. Data can be
sharded under the covers. In short, features that make building large
scalable web sites easier.

You might want to check out some of the introductory talks on the
10gen site to see what this is all about: http://www.10gen.com/presentations
.

Chris


On Aug 8, 11:22 am, Sandra Schlichting <littlesandr...@gmail.com>
wrote:

[trac...@gmail.com]

Hi,

 

you may check a tool called mongodbpumper for oracle. As far as I know this tool can perform a quick data migration from oracle to mongodb. thus, you will be able to compare oracle and mongodb in terms of performance.

 

cheers,

tracer

 

[Ger Hartnett]

Apollo did such a migration and published it as a whitepaper recently. They documented performance and the process they followed. You'll find it at:

http://mongodb.com/lp/whitepaper/nosql-oracle-migration-mongodb

/ger.

[s.molinari]

Um, not really. From what I read, Apollo imported only a small subset of the Oracle data using a python script and formed it to fit in a single collection to see how well Mongo can perform. There is no real details of a migration/ import and no real comparisons to Oracle's performance, other than noting Mongo performed as well or better than their (20 year old?) Oracle system. That white paper is mostly about their findings while testing Mongo. Still, it is an interesting read, but I think will disappoint Sandra, as it doesn't really answer her questions. Some of the things they mention though are also pluses for Mongo like 

Ease of use

Quick implementation

Ability to handle failover well

Great support

Easy to learn for application devs, dev ops and DBAs

and so on and so forth.  

Scott

[Rajeshwar Reddy]

Hi Sandra,

There is a tool called "Pelica Migrator" that can migrate data from Oracle to MongoDB. The tool is available for trail and it can migrate data from almost any RDBMS to MongoDB. Here is the url: http://www.techgene.com/pelica-migrator/

[s.molinari]

From the MongoDB site, they have this listed in their tools section. http://www.spviewer.com/mongodbpumper.html

Scott