nested map in cassandra data modelling

Question

I have following requirement of my dataset, need to unserstand what datatype should I use and how to save my data accordingly :-

CREATE TABLE events (
id text,
evntoverlap map<text, map<timestamp,int>>,
PRIMARY KEY (id)
) 

evntoverlap = {
               'Dig1': {{'2017-10-09 04:10:05', 0}}, 
               'Dig2': {{'2017-10-09 04:11:05', 0},{'2017-10-09 04:15:05', 0}},
               'Dig3': {{'2017-10-09 04:11:05', 0},{'2017-10-09 04:15:05', 0},{'2017-10-09 04:11:05', 0}}
              }

This gives an error :-

Error from server: code=2200 [Invalid query] message="Non-frozen collections are not allowed inside collections: map<text, map<timestamp, int>>"

How should I store this type of data in single column . Please suggest datatype and insert command for the same. Thanks,

Answer 1

There is limitation of Cassandra - you can't nest collection (or UDT) inside collection without making it frozen. So you need to "froze" one of the collections - either nested:

CREATE TABLE events (
id text,
evntoverlap map<text, frozen<map<timestamp,int>>>,
PRIMARY KEY (id)
);

or top-level:

CREATE TABLE events (
id text,
evntoverlap frozen<map<text, map<timestamp,int>>>,
PRIMARY KEY (id)
);

See documentation for more details.