model  object  column   category  data_type  encoding  compression
table  table1  value    FIELD     INT64      PLAIN     UNCOMPRESSED
table  table2  site     TAG       STRING     PLAIN     UNCOMPRESSED
table  table2  rack     TAG       STRING     PLAIN     UNCOMPRESSED
table  table2  sensor   TAG       STRING     PLAIN     UNCOMPRESSED
table  table2  reading  FIELD     DOUBLE     PLAIN     UNCOMPRESSED
