DAX Co-work 2019-08-28 Meeting notes

• It would be possible & helpful to see info about queries in the monitoring dashboard
  • easy:
    • number of chunks
    • row count of merge table
    • row count of result table

We could put that information into the (what?) database.

There might be ways to do a similar thing to the above by caching the number of rows (overlap and non-overlap) and we could perform an optimized SELECT COUNT(*) on that.

Probably this is not high priority.

The only info we will ever get from TAP about failed queries in Qserv is what Qserv gives to TAP.

Discussed returning more query information to TAP in the error message. There is at least one issue with this; the TAP client may truncate the error message to as short ast 50 characters.

We discussed including the QueryID with each error message, and then logs could be searchable by Query ID. There is a problem with this; the Query ID gets generated somewhat late; after the query has been parsed (and chunked?). We could use the Message Table ID, which is generated when the query arrives from the lua plugin. We would then have to provide correlation between Message Table ID and Query ID, because workers do not have the Message Table ID.

This needs some architecture-level decision making. Christine wrote the ticket that captures this issue: DM-21115 "QServ error messages should contain enough info for QServ developers to diagnose QServ issues"