Fawzi Mohamed wrote:
On 3-apr-11, at 19:28, Piotr Szturmaj wrote:
Fawzi Mohamed wrote:
Looking more maybe I was a bit too harsh, if you define clearly the
goals of your API then yes it might be a good project.
The api doesn't have to be defined yet, but a more detailed definition
of its goals should be there, maybe with code example of some usages.
Questions that should be answered:
I know your response is'nt to me, but please let me answer these
questions from my point of view, based on my recent work on ddb.
I think that your responses are very relevant, as it seems to me that
your work is nice, and I find that if a GSoC is done in that direction
it should definitely work together with the good work that is already
done, let's don't create multiple competing projects if people are
willing to work together.
I'm ready to cooperate :)
* support for static and dynamic types.
how access of dynamic and static types differs, should be as little as
possible, and definitely the access one uses for dynamic types should
work without changes on static types
If you mean statically or dynamically typed data row then I can say my
DBRow support both.
yes but as I said I find the support for dynamic data rows weak.
I've just added row["column"] bracket syntax for dynamic rows.
* class or struct for row object
I'm using struct, because I think row received from database is a
value type rather than reference. If one selects rows from one table
then yes, it is possible to do some referencing based on primary key,
but anyway I think updates should be done explicitly, because row
could be deleted in the meantime. In more complex queries, not all of
selected rows are materialized, i.e. they may be from computed
columns, view columns, aggregate functions and so on. Allocation
overhead is also lower for structs.
* support for table specific classes?
Table specific classes may be written by user and somehow wrap
underlying row type.
well with the current approach it is ugly because your calls would be
another type, thus either you remove all typing or you can't have
generic functions, accepting rows, everything has to be a template,
looping on a table or a row you always need a template.
Could you elaborate? I don't know what do you mean.
* reference to description of the table (to be able to get also dynamic
types by column name, but avoid using too much memory for the structure)
My PostgreSQL client already supports that. Class PGCommand has member
"fields", which contain information about returned columns. You can
even check what columns will be returned from a query, before actually
executing it.
ok that is nice, and my point is that the type that the user sees by
default should automatically take advantage of that
* Nice to define table structure, and what happens if the db has another
structure.
This is a problem for ORM, but at first, we need standard query API.
I am not so sure about this, yes these (also classes for tables) are
part of the ORM, but the normal users will more often be at the ORM
level I think, and how exactly we want the things look like that the
object level can influence the choice of the best low level interface.
A "defined" DBRow or static one, if used on result which has inequal
number of columns or their types aren't convertible to row fields then
it's an error. But, if someone uses a static fields, he should also take
care that the query result is consistent with those fields.
* you want to support only access or also db creation and modification?
First, I'm preparing base "traditional" API. Then I want to write
simple object-relational mapping. I've already written some code that
generated CREATE TABLE for structs at compile time. Static typing of
row fields is very helpful here.
Very good I think that working on getting the API right there and having
it nice to use is important.
Maybe you are right and the current DBRow is indeed the best
abstraction, but I am not yet 100% sure, to me it looks like it isn't
the best end user abstraction (but it might be an excellent low level
object)
I should state here, that end-user usability is very important to me. I
should also clarify that my code isn't completely finished and of course
it is a subject to change. Any suggestions and critics are welcome :)
