presence: No autocommit+rollback if no active watchers

[Ozzyboshi]

Pre-Submission Checklist

• Commit message has the format required by CONTRIBUTING guide
• Commits are split per component (core, individual modules, libs, utils, ...)
• Each component has a single commit (if not, squash them into one commit)
• No commits to README files for modules (changes must be done to docbook files
  in doc/ subfolder, the README file is autogenerated)

Type Of Change

• Small bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds new functionality)
• Breaking change (fix or feature that would change existing functionality)

Checklist:

• PR should be backported to stable branches
• Tested changes locally
• Related to issue #XXXX (replace XXXX with an open issue number)

Description

This is a small performance improvement, the goal is to avoid issuing rollbacks if not necessary.
On my setup, Kamailio presence executes a lot of ROLLBACKS in MariaDB since function process_dialogs() runs repeatedly.
What see inside MariaDB logs is the following

SET autocommit=0
select `presentity_uri`,`callid`,`to_tag`,`from_tag`,`event` from `active_watchers` where `updated`=3 AND `event`<>'presence.winfo'\G
ROLLBACK

Maybe we can improve this behaviour telling presence to do autocommit to do not execute them if the select returns zero elements?

[miconda]

Maybe we can improve this behaviour telling presence to do autocommit to do not execute them if the select returns zero elements?

I am not sure I understand what you wanted to ask? Maybe you can elaborate more.

[linuxmaniac]

The thing here is to avoid using database transaction to select and just use it if there's going to be update commands later

[miconda]

@linuxmaniac: that's about the current patch of this PR, right? I wanted to clarify if @Ozzyboshi wants to propose another improvement that covers the case of current PR as well.

From my point of view, the PR can be merged, if no improvement/alternative is been planned in the near future.

[linuxmaniac]

yes, this is about this patch. No other improvements or alternatives were planned

[miconda]

It was the question at the end of @Ozzyboshi PR description that I wanted to clarify.