[Keyspace dashboard] Allow selecting multiple tables

[hopugop]

Describe the feature and the current behavior/state.
Table metrics are amazing. However, it only allows to choose from a single table at a time. It would be really useful to allow a view for all tables in a single view - think of it like a historical view of tables' operations, latency and dataset.

I recently used raw queries to achieve this, such as sum(scylla_column_family_total_disk_space{}) by(dc,ks,table) to aggregate disk utilization by table. There might be many others beneficial uses.

Who will benefit with this feature?
Anyone that is interested in historical metrics comparison for multiple tables.

[mykaul]

It makes sense to aggregate (sum? avg?) specific data from multiple tables - such as disk space. What else? Latency or ops make little sense to me.

[amnonh]

@mykaul @hopugop The title is confusing; in your graph, you do not aggregate; you show a line per table. So yes, technically, we can allow choosing multiple key spaces.

The table's drop-down menu will be more confusing when picking multiple keys paces.

[mykaul]

@mykaul @hopugop The title is confusing; in your graph, you do not aggregate; you show a line per table. So yes, technically, we can allow choosing multiple key spaces.

The table's drop-down menu will be more confusing when picking multiple keys paces.

I think aggregate is used in a confusing manner here - the intent is 'bring multiple data from multiple tables into a single view' - not an aggregate of 'sum the multiple data from multiple tables and display it' - but I may be wrong. I referred to the latter, but I think the original author referred to the former defintion.

[hopugop]

'bring multiple data from multiple tables into a single view' - not an aggregate of 'sum the multiple data from multiple tables and display it'

That's correct. I updated the issue title to match it.

[amnonh]

@hopugop We already support multiple tables, the limitation we have is allowing multiple keyspaces