show the factors beyond your control this :-

By Philip Howard, Bloor Research
Published Thursday 24th March 2005 15:23 GMT
I have espoused the cause of Ingres for some time and, especially, I
have commended Computer Associates' decision to take the Ingres
database into the open source community.

Now, I dare say that at some point CA will tell me all about its "open
source challenge" and how successful that has been in developing new
facilities for Ingres. And they will also tell me about how many
downloads there have been (though I am cynical about the utility of
such a figure). But this article is about one company, Datallegro,
which has adopted Ingres as its database.

Datallegro is a vendor in the data warehouse space that develops and
markets an appliance-based solution. That is, a combination of
hardware and software similar in concept (if not in method) to that
which underpinned the original development of Teradata. The company is
headed up by Stuart Frost, who was the founder and CEO of Select
Software and subsequently chairman of Avellino.

Datallegro is an open source based product to the extent that it runs
on Linux and uses Ingres as its database. However, it wasn't always
like that. Originally, it was developed using MySQL. For performance
reasons, this was quite quickly replaced with PostgreSQL. Bear in mind
that at this time, Ingres was not available as an open source product.
When it became available, Datallegro evaluated Ingres and rapidly made
the decision to jump ship from PostgreSQL to Ingres (not too difficult,
as they share common origins). This says quite a lot about the relative
robustness, performance, scalability, and so on of MySQL versus
PostgreSQL versus Ingres.

You would not normally mention Ingres and data warehousing in the same
breath, yet Datallegro has tuned the product up to the extent that it
is offering one of the best (the best if you listen to Datallegro, but
I'll hedge my bets until some benchmarks have been published)
price/performance offerings on the market.

The key to this is that the core functionality and the architecture
were already in place within Ingres (not to mention flexibility), on
which Datallegro has been able to build. What is more, it is clear from
talking to Datallegro, just how committed CA is to open source.

Stuart Frost is extremely complimentary about the help that CA has
provided throughout the company's developments, describing it in
superlative terms. That is good to hear and should be music to the ears
of any other companies thinking of taking on major developments in
conjunction with CA and Ingres. ®

It's not too likely for the current stable MySQL, because PostgreSQL has
a substantial number of SQL language features that MySQL (4.1) does not.
You would have to have a PostgreSQL database that used no views, no
stored procedures, no triggers, and no rewrite rules.

Views (derived tables) are kind of the killer.  Every view would have to
be translated into a piece of application code that performed the
corresponding SELECT statement.

For MySQL 5.0, you might be able to do more, because it does include
views, subselects, and triggers.  I'm not familiar with the specific
limitations on these, though ....

Hi Robb,

This company claims to support migrations between PostgreSQL & MySQL
... http://www.swissql.com/

I have not used it myself for a migration, I usually transfer data with
a custom written tool in Perl DBI, that also takes into account special
transformation considerations as I migrate the database.

Regards,

Josh