[overpass] runtime error: Query failed with the exception:

[Igor Brejc <>]

Hi,

I'm running some large queries on my private instance (v0.7.54). For a certain query, after about 20 minutes of waiting, I get this cryptic error in the <remark> tag of the resulting OSM file:

runtime error: Query failed with the exception: Query failed with the exception:

Two more questions: 

1. Is there a way to see what exactly the interpreter is doing during the execution of the query? I want to find out where the most of the time is spent.
2. Is there some kind of documentation about Overpass database? Or alternatively, which source code files should I study to figure out the structure of DB files?

Thanks, 

Igor