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I've builded a .dll (C++ builder and MyDAC 40028) witch is acting as a communicationlayer between my software and the databaseserver.


I still have some strange issues:

- handling 2.550.800 rows

Handling 2.550.800 rows
As you see i have a lot of rows.... and there will be more, much more.

What do i want?
First i builded a Get function. This function is the external function for my software (not for the driver) to get information out of the MySQL databases and Tables. My driver is executing a select function and after this i want to return the results to my software.

The issue
I've tried to use MyTable for this, but when i set: "MyTable->Active->true" I have to wait a very long time for the results..... FetchAll doesn't matter if it is true or false and doing a select before with a limit also.

What is the best way to solve my issue? I thought about an internal table in the driver and fill this with the results of my query and pass this as result, but how can i pass a table??

Maybe i can return a bool which is saying if there are more then one results and then the program can get the next result by building a function NextRow... or something.

Does somebody have a nice idea about this?[/u]

> FetchAll doesn't matter if it is true or false and doing a select before with a limit also.
It may happen because you use ORDER BY clause or any other conditionals that need to process all the records in the table.

>What is the best way to solve my issue?
Try to change your query.

As Antaeus says, try to query only what's needed. If you really need to query that much, i would approach to a solution using the LIMIT clause to fetch for example from 10.000 records at a time, when finish processing get next 10.000... Also think that holding that much records in memory can make your computer get crazy swapping to disk.

( Reference for LIMIT clause is in http://dev.mysql.com/doc/refman/5.0/en/select.html )

Regards

About memory i think you are right... using Limit is the best solution in combination of a next command, i think

It's working now by putting everything in an internal table.......(memory gets almost full) and working with a next command.

so now i am going to try to work with limit command between the driver and the MySQL server. I have to test some things to know how it will react.

thank you for your help

ok, please share results at forum

ok this is what i builded now:

First i have a function in the DLL called GetSignals ( ........, int limitmin, limitmax)

this returns a stringlist with all the rowid's

then i builded a function where you can get a single signal
GetSignal ( int rowid )

this returns a stringslist with the single row and its columns.

now i started a new topic in the forum because the memory is getting ful....