Experimenting with storing stacktraces differently

[simonswine]

With our given problems around retrieving esp. stacktraces in a reasonable amount of time. I have been experimenting a bit.

Two ideas:

• Rather than storing the full location ID list us a self referencing schema.
• Make use of parquet's nested object to keep track of the ids.

I will report back if any of the provide more tangible results.

This is the current size comparision between status quo and the self referencing model:

[cyriltovena]

That's interesting makes me wonder if we should explore a custom format for storing this.

[simonswine]

Superseeded by #767