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Re: preserve value order with referential integrity overlay?
Thanks for this short but clear information which is as long as needed!
The difference here between relational database and LDAP is we cannot
design LDAP so we begin to expect more from LDAP, e.g. in case of
favorite drink order, a table can be designed more complex to preserve
order, but LDAP structure cannot be designed. However I think this is
again my mistake, because LDAP structure CAN be "designed" by changing
value format. I can "design" the client must not directly store the name
of drinks, it should store the drinks in a format a number followed by
the drink. e.g.
favoriteDrink: 1 coke
favoriteDrink: 2 beer
So here I used to think "usuall values in db can be presented to user
as-is", with this new format, the client remove the leading digit after
sorted values and present the result to users. The change of table
structure in RDBMS map to the change of value format in LDAP, this is
the part that people don't get fast and easily.
But having gone this far, my solution is already very close to that of
Chu, so I get the idea of Chu's design now. I am very happy and thankful
that openldap already implemented Chu's solution so that I have less to
do on the client (the client code for sorting and re-calculating index
numbers of values are no longer needed). What easily frastrates
administrator and developers is if some problems don't have a solution
at all, e.g. in my case companyRepresentative order is vital and total
number is unknown, the db by itself provided no solution and you cannot
re-design the database! I am glad I am wrong, there is a solution.
Change value format needs to update client, but it's better than I can
do nothing about it.
And thanks for your time!
å 2007-08-14äç 22:28 +0200ïPierangelo Masaratiåéï
> I don't want to make this longer than necessary, but if you have a table
> person_id, drink
> 'ando' 'coke'
> 'ando' 'beer'
> and you
> "delete from favourite_drink where person_id='ando' and drink='coke';"
> "insert into favourite_drink (person_id,drink) values ('ando','wine');"
> I'm pretty confident 'wine' will not come before 'beer', even if 'wine' is
> what I really prefer.
> In this sense, I think LDAP was designed to be almost as dumb as most
> applications (and application developers) but not dumber. So, values with
> the very same importance go into sets, and values with special importance
> go into specific attributes, possibly with SINGLE-VALUE constraint if
> appropriate, as I explained in my previous message.
> As a general rule, don't ask software to do what can be better done by
> yourself, and viceversa :)
> Ing. Pierangelo Masarati
> OpenLDAP Core Team
> SysNet s.r.l.
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