Cassandra Data Modeling - Beginning Apache Cassandra Development - page 51

This generates an error because changing the comparator type is
not allowed (see Figure 2-19 ).

Figure 2-19 . Changing comparator type is not allowed

6. Although changing comparator type is not allowed, we can always

change the data type of the column and key validation class as fol-
lows:

update column family default with
key_validation_class=UTF8Type and
default_validation_class = UTF8Type;

Columns in a row are sorted by column names and that's where
comparator plays a vital role. Based on comparator type (i.e.,
UTF8Type , Int32Type , etc.) columns can be stored in a sorted
manner.

CQL3 Way

Cassandra CQL3 is the driving factor at present. Most of the high-level APIs are sup-
porting and extending further development around it.
Let's discuss a few tricks while dealing with data types in CQL3 way. We will ex-
plore with the default column family created in the Thrift way (see the preceding sec-
tion).

1. Let's try to fetch rows from the default column family (see Figure

2-20 ) .

Select * from default;

Figure 2-20 . Retrieving values using cql shell