word text PRIMARY KEY,
c1 int,
count int
)
-. index
1. 不指定partition， 普通查詢
select * from mytest1.wordstest where count = 40 ALLOW FILTERING
2. 個人理解： 二級索引很耗 性能：表太大，還是不要建立
Secondary indexes are tricky to use and can impact performance greatly. The index table is stored on each node in a cluster, so a query involving a secondary index can rapidly become a performance nightmare if multiple nodes are accessed
CREATE INDEX c1_index ON mytest1.wordstest (c1);
select * from mytest1.wordstest where c1 = 1;
二. materialized view 物化視圖
A materialized view is a table that is built from another table's data with a new primary key and new properties
https://docs.datastax.com/en/cql/3.3/cql/cql_using/useCreateMV.html
https://www.datastax.com/dev/blog/new-in-cassandra-3-0-materialized-views
CREATE MATERIALIZED VIEW wordstest_mv
AS SELECT count, word, c1
FROM mytest1.wordstest
WHERE count IS NOT NULL AND word IS NOT NULL
PRIMARY KEY (count, word);
Nee to know: The columns of the source table's primary key must be part of the materialized view's primary key.
select * from mytest1.wordstest_mv where c1 = 1;
Cassandra can only write data directly to source tables, not to materialized views. Cassandra updates a materialized view asynchronously after inserting data into the source table, so the update of materialized view is delayed. Cassandra performs a read repair to a materialized view only after updating the source table.
源表和物化視圖的數據更新不是同步的，數據插入源表後，不會同步更新物化視圖。通過執行repair 操作更新物化視圖的數據
https://docs.datastax.com/en/cql/3.3/cql/cql_using/useCreateMV.html