Understanding how to choose between fields and tags in InfluxDB
I just read a tutorial that said fields are data and tags are metadata. That is a very intuitive definition. 

The example had pressure and temperature fields and a weather station tag. Again, crystal clear and perfectly matches the description. 

Unfortunately, they then said that if you are querying on pressure or temperature and not weather station, you should flip the field and tag designations around. In other words the definitions provided for field and tag are meaningless. 

The simple solution is to stipulate that fields can either be indexed or not indexed. Fields that are indexed are called tags. Use tag when you need to index a field (to dramatically improve query speed for example).