
AWS Database Migration Service (Preview) - runesoerensen
https://aws.amazon.com/dms/
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apetresc
Genuinely curious how it's possible to port things like triggers from one
engine to the next, when they may have fundamentally different syntax and
semantics.

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cbsmith
That's been a "thing" for a while now. It's tricky, has some rough edges, but
doable.

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apetresc
Neat. How does it work? Like, do they compile one system's triggers to some
sort of intermediate language, and then compile that back to the target
system's language?

Does the resulting code resemble something a human would write?

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cbsmith
It's a combination of that (usually the intermediate language is ANSI SQL) and
also used stored procs & UDT's to provide "work alike" behaviors.

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Tomdarkness
Wonder if it's possible to use this to upgrade Amazon RDS instances?

At the moment you can't upgrade an existing postgres 9.3 RDS instance to 9.4
without dumping all the data and importing it into a new 9.4 RDS instance.

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dangrossman
That's possible according to the page:

> AWS Database Migration Service can migrate on-premises databases to Amazon
> RDS or Amazon EC2, databases running on EC2 to RDS, or vice versa, as well
> as migrate an RDS database to another RDS database.

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Tomdarkness
Excellent, will look forward to testing it out when it's available in eu-
west-1. We'd like to use some of the new features in postgres 9.4 but our
production DBs on RDS are stuck on 9.3 at the moment.

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wahnfrieden
Does this help with online schema migrations too? Maybe for blue/green
deployment of DB schema changes?

