Re: Mckoi 2.0 work in progress download

Toby,

I've reviewed the work you've done for the new version of McKoi and I
found some things I like (like the new treestore, although I haven't
got how it is attached to the rest of the system) and some things I
like less (like the replacement of the interpret package with
Operation classes)...

One thing I didn't find at all was the class Database.java :D
Hope you will include in the next version...

Anyway, thank you again for the effort!
John


On Tue, Mar 4, 2008 at 4:35 AM, Tobias Downer <[email protected]> wrote:
> Hi all,
>
> I have just uploaded a work in progress release of Mckoi 2.  You can
> download it here;
>
> http://www.mckoi.com/database/ver2/mckoi20wip01.zip
>
> I will be continuing to add releases to this directory as development
> continues.
>
> Please be aware this release is a work in progress and it's missing some
> important features.  First I'll quickly describe what is complete and
> I'm most interested in getting feedback on at the moment.
>
> The Mckoi 2.0 data store;  I expect the new snapshot data store engine
> and API will be the main focus of the 2 release.  The data store is the
> part of a database engine that deals with modeling structures for
> storing and indexing data in a database and mapping this data to a
> storage medium (such as in a persistent local file system or a transient
> heap).  Version 2.0 provides developers with a fairly straight forward
> API for modeling and manipulating primitive data structures freely in a
> strict snapshot transactional environment.  The problems of caching,
> memory allocation/deallocation, transaction management and structural
> representation are dealt with by the data store engine.
>
> One way to think of the data store engine in 2.0 is a file system that
> is designed for database software and so supports strict isolation
> enforcement, discrete and controllable commit states, and supports files
> of various sizes and quantities with efficient creation and deletion.
> Most importantly, the data store supports very efficient copying of data
> and very efficient shifting of data inside a file.  These primitive
> operations are the base on which any type of more sophisticated data
> structure can be built.  For example, to implement an insert function on
> a list of 64 bit values you could implement a simple binary search and
> insert sort algorithm over a file.  You find the position in the file
> where the value is to be inserted, shift the data in the file by 64 bits
> and write the value at the sorted position.  The data store is designed
> to be able to handle these types of operations very efficiently on very
> large data sets (larger than the available heap memory).
>
> The API will provide reference implementations for common data
> structures using the data store model.
>
> Another useful feature of the new data store engine is the ability to
> copy data without actually replicating the data - the only thing that is
> replicated in a copy operation is the meta structure that organizes the
> data which is many times smaller than the actual data.  This means you
> can make a copy of a file that logically looks and works as if you have
> multiple copies but only one actual copy may be stored in the physical
> representation.  This leads to many elegant optimizations especially in
> a versioning RDBMS that needs to manage multiple versions of mostly
> identical data.
>
> The new data store is feature complete.  I appreciate all feedback,
> comments, testing, questions on this part of the database.  Any feedback
> on this you give me will help me greatly with documentation and making
> sure I'm heading in the right direction with the API.  The relevant
> package is 'com.mckoi.treestore'.  Check out
> src/com/mckoi/tests/Main.java for examples on how to create a
> KeyObjectDatabase for either a heap or file system data store to get you
> started.  If you don't understand something about it then feel free to
> email me.
>
> The SQL engine;  The Mckoi 2.0 SQL engine has been almost completely
> rewritten to make use of the features provided by the new data store
> engine.  We now have a proper cost based query optimizer and planner in
> 2.0 (an EXPLAIN command is now available for analysis of query plans).
> The JDBC driver supports updatable result sets and this feature is
> implemented as a first class operation by the driver (updating
> information in a result set will not cause any SQL operations to be
> parsed or interpreted).  JDBC BLOB/CLOB support is also complete.
>
> SQL features that are currently finished - you can CREATE and DROP
> tables, indexes and sequences, define integrity constraints but they are
> not enforced correctly yet.  The standard SQL functions are mostly
> finished, but there is no hook yet for defining user defined functions.
>  Most SELECT features are working but there's currently no flatting of
> nested queries so nested queries can not make full use of all indexes
> available and are not costed correctly by the planner.
>
> Basically, if you are going to try out the SQL stuff you'll probably
> find something that doesn't work properly yet.  I'm still interested in
> getting feedback on the SQL code though, but you can expect lots of new
> SQL features added and the code tidied up this month.
>
> Thanks, hope you like the direction we are taking,
> Toby.
>
>
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