[Scons-users] database builder

[Philipp Kraus]

Hi Gary,


Am 13.04.2013 um 15:51 schrieb Gary Oberbrunner:


> While this is a cool idea, I don't think SCons would actually be that helpful.  I'd start by looking at how Rails migrations work.  Schema updates should be defined by the db developer; I don't think trying to diff schemas (with SCons or any tool) will actually get you where you need. 


At the moment I do this like env.Command("database", "mysqlfile.sql", "mysql.... $SOURCE")
It works, but IMHO it's not a good solution, because the parameters can be different on different OS / versions, so I need different switches for calling the database client.
Bruce has describe Liquidbase, so in this case for the developers of a project can be this a solution, but I would like to use Scons also on update procedure on
the userside. But in this view I can not tell the user "you need to install liquidbase and scons and database driver.... for updating your database", also on server
systems there are often installed not all packages eg Java, Python. Some packaging programs with GUI are don't run in a console.
So "one tool (Scons) for everything" can be a nice idea, but for database there must be more abstraction, I think about UML specification and the model transformation.


>  There's often queries that need to be run when updating a schema for instance, to compute values for a new column or set the default value or other things.  


Yes eg you set a field to a "non null" before update it can store null values, so I must set in a preprocess the values to other values. So IMHO a short call eg alter table
is not enough, so there must be more processing.
The update process of a database is also a dependency graph, because the calls of changes are ordered. 



> You could certainly *drive* the migration process out of SCons, but even there I don't think SCons's dependency analysis will be all that helpful -- I'd just use os.system() to kick off your migration script (or make it be a python function and just execute it straight out of your SConstruct).



For developer yes, but I would like to use scons also on the userside and than I need an easy call, but not in all system I can use a GUI based package.

It is only an idea and I would like thinking about it, because the Python structure of Scons can be helpfull.

Thanks

Phil



> 

> 

> On Sat, Apr 13, 2013 at 5:34 AM, Philipp Kraus <philipp.kraus at flashpixx.de> wrote:

> Hi,

> 

> I'm searching for database support in Scons something like databse installation and updating. I'm often work with database and do the installation with SQL scripts,

> but the client is compiled and installed with Scons, so can be this an idea for Scons? Do you think this is a good & meningful feature?

> At the moment I run env.Command with the database command-line client, but the updating process can not work / can only work with deleting & creating the database.

> 

> I think a feature like this

> env.CreateDatabase("localhost:5432", databse="testdb", user"=myself", password="1234", type="postgresql", source="database.sql.scons")

> 

> should be nice, also an env.UpdateDatabase which updates the database without deleting tables, it creates only alter statements and run these statements for the update process.

> Scons can handle this calls in an transaction for atomic calls and uses Pythons database packages. The database script should be more than a plain text file, so Scons can

> check the database and create individual statements during the update process.

> 

> My idea is, that the Scons database.sql.scons file is a XML files which descriptes tables, indicies, references datatypes (validation via XSD)....

> On the createdatabase Scons transform this data with XSLT into SQL or walk through the XML tree and creates on-fly the statements and send it over Python Database API

> The update is more difficult, because I must create a diff between installed tables and new table definition. I think a post- / preprocessing should be also in it, so the user

> can run some codes before / after the update for modifying datasets.

> 

> Hope for some comments :-)

> Have a nice weekend

> 

> Phil

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> 

> 

> -- 

> Gary

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