RE: Discussion Topic #2 Databases

You might want to check out One$DB - aka daffodil.  This is a full featured, pure Java DB that's also pure JDBC.  Probably one of the nicest things in open source I've seen in quite a while (besides SmartFrog, of course).

-----Original Message-----
From: smartfrog-developer-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org [mailto:smartfrog-developer-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org] On Behalf Of Steve Loughran
Sent: Thursday, January 19, 2006 7:23 AM
To: smartfrog-developer
Subject: [Smartfrog-developer] Discussion Topic #2 Databases


Hello,

This is just a note to start some discussion on the mailing list as to
what people out there think SmartFrog needs in terms of database support
in the next year.

-We have a MySQL component from the seed project that we are thinking of
moving in to the SourceForge repository; I don't know what
tests/documentation it has. Are there any interested users who could
help with those?

-for demos and testing, HSQLDB is probably adequate, as it is the
simplest of the pure-java datastores. It could have a component to
configure it without too much effort.

-I haven't looked at Apache Derby at all.

I don't want to try and define generic database deployment components,
because it only creates the illusion that you can switch database
engines on the fly, which everyone knows is even less sensible than
switching app servers between installations. But we might benefit from
having some components whose aim in life is to create and issue SQL
commands against JDBC bindings

It would have the following (probably syntactically incorrect) components

-JdbcBinding to declare a JDBC binding
-SqlTransaction for a SQL XA.
-SqlLiveness to issue a select against a DB for liveness, failing with
an error  or if the result count is more/less than expected, maybe even
a different value

-SqlDeployment to issue different commands/XAs when
deploying/undeploying something. So at deploy time you could create a
table, and at undeploy time it could be dropped.

The JDBC binding would look like this

mysql extends JdbcBinding {
   classpath "optional-extra-jars";
   classname "com.mysql.JdbcDriver";
   url TBD;
   user TBD;
   password TBD;

   options  [["name","value"],["name2","value2"]];
}

With a sql transaction a very thin wrapper around the java.sql API:

insert extends SqlTransaction {
	
	id TBD;
	date TBD;
	text "";

	command "insert into table events values(?,?,?);"
	arguments [id,date,text];

}

doInsert extends insert {
	db LAZY mysql;
	id "f324";
  	date "2006-01-19;
	text "test";
}

A component to have both deploy and undeploy commands would just be an
extension, taking two
SqlDeployment  extends Prim {
	db TBD;
	deploy extends SqlTransaction {  .. }
	
	undeploy extends SqlTransaction {  .. }
}

The only complication there is that I would not want the nested
transactions to bind to anything other than the outer jdbc binding,
which is going to be fiddly to make implicit.

The liveness would just be a way of defining the health of a database if
a select operation succeeds with the # of values returned in the
expected range, possibly with a list of values that get checked too.
That would appear to be the simplest way to do database health checks.

Comments?

-Steve


	







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