Re: Qualify unique values from a tale column

Hi, Sigthor,

On May 23, 2006, at 8:28 AM, Sigþór Hrafnsson wrote:
> Thanks Jerry
>
> I thought I might have to go down there, thanks for the confirmation.

My response was to meet your stated requirement: "...but I don't want  
to fetch all the tables to memory, I want to qualify them at the DB  
level."

Before my WO-Dev buds start accusing me of recommending that you drop  
to the level of raw SQL and result sets unnecessarily (something I  
overtly try to avoid) let me suggest another option.

Any time you drop down to raw rows, you're increasing the complexity  
of your program (thereby increasing the maintenance burden). May I  
suggest that you try the raw rows approach and also try simply  
bringing all the rows as EOs into an NSSet. Let the set cull out the  
non-unique records, turn the set back into an array and time the two  
approaches.

Unless you have a large table (on the order of a few megabytes or  
more) and a large percentage of duplicate records (say, 40% or more  
as a guess), I think you'll find the difference in time will not be  
all that significant. I could be wrong, but I would do a time test  
before I ever dropped down to raw SQL.

On the other hand, if avoiding raw SQL pushed me into lots of extra  
memory management, explicit calls to the GC and such, then I would  
just use the raw SQL approach.

Regards,
Jerry

>
> At 12:25 23.5.2006, you wrote:
>> Hi, Sigthor,
>>
>> I think that the only way you're going to pull this one off is to use
>> the EOUtilities method:
>>
>>   public static NSArray rawRowsForSQL(EOEditingContext ec,
>>                                     String modelName,
>>                                     String sqlString,
>>                                     NSArray keys)
>>
>> Then supply a sqlString with "SELECT DISTINCT" to obtain unique
>> values for that given column (ip).
>>
>> You can turn the returned raw row NSDictionaries into full fledged
>> EOs using the EOEditingContext method:
>>
>>    public EOEnterpriseObject faultForRawRow(NSDictionary row,
>>                                          String entityName,
>>                                          EOEditingContext context)
>>
>> Regards,
>> Jerry
>>
>> On May 23, 2006, at 7:12 AM, Sigþór Hrafnsson wrote:
>>
>>> This is completely eluding me.
>>>
>>> I want to qualify based on unique values from a column in a table,
>>> like
>>>
>>> Have a table User with a column ipAddress, in the table there can
>>> be more that one user by the same name with the same
>>> ipAddress but a different table id.
>>>
>>> User Table example
>>>
>>> User john ip 111 id 1 (simplified for demonstration)
>>> User Bart ip 222 id 2
>>> User Elsa ip 333 id 3
>>> User john ip 111 id 4
>>>
>>> With the EOQualifier, I would like to get the result for table id's
>>> 1, 2 and 3 but not 4, or it could also be id's 2, 3 and 4 but not 1.
>>>
>>> I know how to do the sort in memory, but I don't want to fetch all
>>> the tables to memory, I want to qualify them at the DB level.
>>>
>>> Thanks
>>>
>>> Sigthor
>>>
>>> _______________________________________________
>>> WebObjects-dev mailing list
>>> [email protected]
>>> http://www.omnigroup.com/mailman/listinfo/webobjects-dev
>>
>>
>> --
>> __ Jerry W. Walker,
>>    WebObjects Developer/Instructor for High Performance Industrial
>> Strength Internet Enabled Systems
>>
>>     [email protected]
>>     203 278-4085        office
>>
>>
>


--
__ Jerry W. Walker,
    WebObjects Developer/Instructor for High Performance Industrial  
Strength Internet Enabled Systems

     [email protected]
     203 278-4085        office