So I just saw a post about how Kundera translates all JPQL to CQL.
On Mon, Oct 21, 2013 at 4:45 PM, Jon Haddad <j...@jonhaddad.com> wrote: > If you're working with CQL, you don't need to worry about the column > names, it's handled for you. > > If you specify multiple keys as part of the primary key, they become > clustering keys and are mapped to the column names. So if you have a > sensor_id / time_stamp, all your sensor readings will be in the same row in > the traditional cassandra sense, sorted by your time_stamp. > > On Oct 21, 2013, at 4:27 PM, Les Hartzman <lhartz...@gmail.com> wrote: > > So looking at Patrick McFadin's data modeling videos I now know about > using compound keys as a way of partitioning data on a by-day basis. > > My other questions probably go more to the storage engine itself. How do > you refer to the columns in the wide row? What kind of names are assigned > to the columns? > > Les > On Oct 20, 2013 9:34 PM, "Les Hartzman" <lhartz...@gmail.com> wrote: > >> Please correct me if I'm not describing this correctly. But if I am >> collecting sensor data and have a table defined as follows: >> >> create table sensor_data ( >> sensor_id int, >> time_stamp int, // time to the hour granularity >> voltage float, >> amp float, >> PRIMARY KEY (sensor_id, time_stamp) )); >> >> The partitioning value is the sensor_id and the rest of the PK components >> become part of the column name for the additional fields, in this case >> voltage and amp. >> >> What goes into determining what additional data is inserted into this >> row? The first time an insert takes place there will be one entry for all >> of the fields. Is there anything besides the sensor_id that is used to >> determine that the subsequent insertions for that sensor will go into the >> same row as opposed to starting a new row? >> >> Base on something I read (but can't currently find again), I thought that >> as long as all of the elements of the PK remain the same (same sensor_id >> and still within the same hour as the first reading), that the next >> insertion would be tacked onto the end of the first row. Is this correct? >> >> For subsequent entries into the same row for additional voltage/amp >> readings, what are the names of the columns for these readings? My >> understanding is that the column name becomes a concatenation of the >> non-row key field names plus the data field names.So if the first go-around >> you have <time_stamp>:<voltage> and <time_stamp>:<amp>, what do the >> subsequent column names become? >> >> Thanks. >> >> Les >> >> >
