MagmaCollectionReader behavior

[Miguel Cobá]

2009/4/1 Chris Muller <ma.chris.m at gmail.com>:
> Hi again!  I'd just like to say one more thing; In Smalltalk, Strings
> do not have any upper-bound size-limit, so they are as flexible as a
> CLOBS in a RDBMS.  The premise of your indexing comparison would seem
> require an RDBMS to index and search entire CLOB values, which I don't
> think they can do without application-developer help.  (Please correct
> me if I'm wrong, I haven't used RDBMS in years..)

Oh, yes, that explains the problem. I was comparing a string in
Smalltalk to a varchar with a fixed lenght.
And indeed, reading the documentation for indexes on MySQL, for
example, the index creation over text fields (blobs alike for strings)
*requires* a index prefix to create the index. Something analogous to
the MagmaIndexes for strings.

>
> OTOH, if you define a indexed VARCHAR column, you are specifying an
> upper-bound on the size of the strings it can index (not to mention,
> store!).  To me, this is analagous to specifying a key-size..
>
> If you are willing in your application, to restrict the length of
> e-mail addresses to the length of whatever you would make the VARCHAR
> column, then you can choose an appropriate key-size to handle that
> length and not have to do the post-detect.

I don't want to create a new class for the index, so my options are:

- limit the size of the input string for the #email field and choose a
keySize for the MagmaIndex that have enough meaningful characters
- use the post-detect to obtain the wanted value from the collection.


>
> Finally,
>
>> I think that this is a point where the requirements for the developers can
>> be a little too much. See it this way, we are only indexing a string. It
>> shouldn't be necessary to implement a hash code for converting them to
>> numbers.
>
> As you get deeper into it, I hope you'll find the MaByteSequenceIndex
> hierarchy included in the base Magma package is flexible enough for
> use "out of the box" (but if not, it isn't hard to define your own
> custom index type).
>
> But yes, the key point of this whole thread is the post-detect:
> required to index "CLOB" values (read: Smalltalk Strings), which is
> what I would do rather than restricting the user..
>

I agree, I prefer no to limit the user and do a post-detect.

> Regards,
>  Chris

Regards,
Miguel Cobá