cassandra 中的 select 不同计数的方法是什么？

Question

I need to select distinct count in table in cassandra.

As I understand direct distinct count is not supported in cassandra not even nested queries like rdbms.

select count(*) from (select distinct key_part_one from stackoverflow_composite) as count;

SyntaxException: line 1:21 no viable alternative at input '(' (select count(*) from [(]...)

What are the ways to get it. whether I can get directly from cassandra or any addon tools/languages need to be used?

below is my create table statement.

CREATE TABLE nishant_ana.ais_profile_table (
    profile_key text,
    profile_id text,
    last_update_day date,
    last_transaction_timestamp timestamp,
    last_update_insertion_timestamp timeuuid,
    profile_data blob,
    PRIMARY KEY ((profile_key, profile_id), last_update_day)
) WITH CLUSTERING ORDER BY (last_update_day DESC)
    AND bloom_filter_fp_chance = 0.01
    AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}
    AND comment = ''
    AND compaction = {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 'max_threshold': '32', 'min_threshold': '4'}
    AND compression = {'chunk_length_in_kb': '64', 'class': 'org.apache.cassandra.io.compress.LZ4Compressor'}
    AND crc_check_chance = 1.0
    AND dclocal_read_repair_chance = 0.1
    AND default_time_to_live = 0
    AND gc_grace_seconds = 864000
    AND max_index_interval = 2048
    AND memtable_flush_period_in_ms = 0
    AND min_index_interval = 128
    AND read_repair_chance = 0.0
    AND speculative_retry = '99PERCENTILE';

I have just started using cassandra.

Answer 1

From Cassandra you can only do the select distinct partition_key from... .

If you need something like this, you can use Spark + Spark Cassandra Connector - it will work, but don't expect really real-time answers, as it needs to read necessary data from all nodes, and then calculate answer.