Re: Memory management using Res and Row

Gary Anderson wrote:
> When the application exits, I seem to have a lot of
> un-released memory (leaks) that appear to be holding items read from the
> database during processing.

Whenever you think you have a leak, it's essential that you take the next step, which is to correlate memory use with some work unit. Does memory use go up as a function of time, or query count, or rows retrieved, or what? If it remains fixed, it's "overhead", not a "leak".

There is known overhead in the MySQL C API library, and a memory debugger is going to show it as a "leak" because it doesn't know better.   There's a way to release it -- see the C API docs -- but since most programs have to access the database for their entire run time, there's not much point in doing it; any platform MySQL runs on is going to have decent memory management, so it releases unfreed memory at exit. As a result, we don't bother to expose this as a feature in MySQL++.

> The manual indicates that a ResUse object
> contains a purge() method to release the resources held by the object,

This isn't generally needed. It's more an implementation detail than anything else. A quick glance at the source shows that ~ResUse() calls it, so if you have a leak due to not calling purge(), you really have a leak due to not destroying your ResUse objects.

> but I can't seem to find similar methods for Result,

Result derives from ResUse.

> ...Row or Query. Do such methods exist?

Do you need help?

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You mean other than the destructors?

> If not, how is this allocated memory freed?

The same way memory is freed in any C++ program.

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