How to kill your Sitecore editor with one slash

 Is your page opening really slow in the Sitecore Content Editor?

I recently had an issue where one page (the homepage) of a site opened really slow in the Sitecore Content Editor. All other pages went very smooth, so it was clearly something particular to that page. And when I mean slow, I mean you click on the item and it takes one coffee for the editor to react. On the published site, there was no issue.

At first this was just annoying, but after a while you curious and annoyed and you want this fixed.

Debugging

The editor is pure Sitecore coding so how to start... one way is to enable the timing level for all events.

You will find this setting in the Sitecore.config file and if this is just for temporary debugging on a local instance you can alter it there. 

<!-- EVENT MAPS
      events.timingLevel =
        none   - No timing information is logged for any of the events (no matter what their local settings are)
        low    - Start/end timing is logged for events with handlers. Local settings override.
        medium - Start/end timing is logged for all events. Local settings override.
        high   - Start/end timing is logged for all events. Also, start/end for each handler is logged. Local settings override.
        custom - Only local settings apply. Events without settings are not logged.
    -->
  <events timingLevel="custom">

So we will change the timingLevel for all events to "high" instead of custom and restart the site.

Now let's keep an eye on the logs while we go back to the editor and open our homepage item. And bingo.. we get a lot of information in the logs but what was really interesting were the lines that said "Long running operation".

Long running operation

20204 11:29:46 DEBUG Long running operation: renderContentEditor pipeline[id={98E57B60-071A-44D1-A763-B6C1BCE0C630}]
20204 11:29:48 DEBUG Long running operation: getLookupSourceItems pipeline[item=/sitecore/templates/Feature/.../CtaRenderingParameters/__Standard Values, source=query:/$site/Data/.../*]
20204 11:29:50 DEBUG Long running operation: getLookupSourceItems pipeline[item=/sitecore/templates/Feature/.../CtaRenderingParameters/__Standard Values, source=query:/$site/Data/.../*]
20204 .....
20204 11:30:19 DEBUG Long running operation: getLookupSourceItems pipeline[item=/sitecore/templates/Feature/.../CtaRenderingParameters/__Standard Values, source=query:/$site/Data/.../*]
20204 11:30:19 DEBUG Long running operation: Running Validation Rules

Apparently we have a long running operation getLookupSourceItems and we are not doing this once, but a dozen times on the home page.  This is our cause - and ok, I exaggerated when I said a coffee but even a minute feels long to open an item.

So, we now now that the CtaRenderingParameters are doing something very slow and it is caused by the source for a field.

In that template I found (even two) droplist fields that use the same source: 

query:/$site/Data/Link Types/*

I am not writing Sitecore queries every day so I admit it took me a few minutes to figure out what was wrong with this thing. It looks like a normal query that fetches all items in a certain path. And it's just a small detail, but a significant one: the first slash should not be there 

query:$site/Data/Link Types/*

This works much smoother and the issue was fixed.

$site

We are using a resolveToken in the source. In the Sitecore docs you will find the list of available tokens and we are using $site here to get the path to the current site. 

But that path will already start with a slash. So although you (probably) want your query to start with a slash, you do not want it to start with two. As described in the query axes, one slash will give you the children (and will form one path) but two will give all descendants. And that is in most cases a very costly operation.

Conclusion

Be careful when putting sources - especially when using tokens. You might not notice anything bad or slow when just one component is added, but it can add up to a really slow item. Use the events timing level to get debugging information.