implementing a large table over a database

[Dave Mason]

Hi,
Hope you dont mind a follow-up to this, I'm still getting handle on 
these methods.  I prefer the MibTable subclass approach, since the data 
I'm working with is owned by an existing MibTable subclass produced by 
AgentGen.  It would be pretty simple to add some new code there.  Any 
extra detail about the update() method and Request accessors will help. 
 I see the parameter is a Request*, which must have a varbind with the 
table's OID.  If the request is for one row only I guess the OID would 
have the row's index appended?  In any case, as you say I need to read a 
subset of the rows, stuff into memory for the rest of agent++, free the 
memory when done, and repeat till all rows are read.  The comments for 
update() say it only gets called once, so I'm not sure how to use it. 
 When I pre-populate a table, do I need to explitly generate each 
MibTableRow, create the columnar objects, and set the values?

Also, we wrote a simple database with the Gnu gdbm library instead of 
using MySql.  libgdbm is not thread safe or reentrant, but I believe I 
should be OK if I protect my database access with start_sync and end_sync?

Thanks again,
Dave

Frank Fock wrote:

> Hi Dave,
>
> There have been several AGENT++ users that integrated
> database access as part of table implementaions.
> I recommend that you implement some generic approach
> in your own MibComplexEntry or MibTable subclass.
> You should use MibTable, if you users should be able to
> create rows in the table. In other cases both approaches
> have pros and cons.
> If you choose to use MibTable, then you should overwrite
> its update Method to create a view of a small (required)
> portion of the table from the database when a request is
> being processed. You will have to take some precautions
> regarding synchronization between concurrent requests to
> the same table.
>
> I have not used MySQL in C++ yet, so I cannot help here
> (may be someone else can?).
>
> Best regards,
> Frank
>
> Dave Mason wrote:
>
>> Hi all,
>> I need to implement an alarm log, which will be a child of MibTable, 
>> with rows and columns that will correspond to similar rows and 
>> columns in a database.  The tables I have done before are entirely 
>> memory resident because they don't grow continuously, but the log 
>> table will keep growing.  I dont want to keep all the rows in memory, 
>> so does anybody have a suggestion as to how to have the table object 
>> read a row, update any new values (for a Set) or just return it (for 
>> a Get), then delete the row from memory before moving to the next 
>> row?  In a normal table, the table object creates a row, then the 
>> columnar objects are responsible for getting their values.  In this 
>> case, I'd like to operate on the whole row at once with a select or 
>> update statement.  Maybe you need to to have a MibTableRow method 
>> read the row into some temporary space, and let the columnar objects 
>> get their data from there?  Any tips about that would help a lot.
>>
>> Also, I'll probably use some public domain database like mysql, which 
>> I havent used before.  Questions about that are beyond the scope of 
>> this list, but any tips on how to integrate it with Agent++ would be 
>> very helpful too.
>>
>> Regards,
>> Dave
>>