Cassandra删除查询,如果条件不起作用

时间:2019-03-15 20:50:14

标签: cassandra

我有一个cassandra表,想删除一行,但前提是只有一列具有一个特定值。

即使cassandra声称删除成功(它返回“ applied:true”),消息仍然存在。


让我们创建表并插入一些数据:

CREATE TABLE IF NOT EXISTS test
(
     id uuid PRIMARY KEY, 
     recipient text, 
     message text
);

INSERT INTO test (id, recipient, message) 
VALUES (7ee055ee-b5dd-4bfd-b184-614d51e268d5, 'felix', 'foo');

INSERT INTO test (id, recipient, message) 
VALUES (86c9d632-dc24-4635-8277-c987c78bd242, 'andrew', 'bar');

现在,我想删除一封邮件,但前提是请求删除的用户(在本例中为felix)是收件人,因此有权这样做:

cqlsh:service_message> DELETE FROM test WHERE id=7ee055ee-b5dd-4bfd-b184-614d51e268d5 IF recipient='felix';

 [applied]
-----------
      True

所以我现在认为查询确实成功了,但是如果我们看一下表,就会发现消息仍然存在。

cqlsh:service_message> SELECT * FROM test;

 id                                   | message | recipient
--------------------------------------+---------+-----------
 86c9d632-dc24-4635-8277-c987c78bd242 |     bar |    andrew
 7ee055ee-b5dd-4bfd-b184-614d51e268d5 |     foo |     felix

(2 rows)

一些其他信息:

cqlsh 5.0.1 | Cassandra 3.11.2 | CQL spec 3.4.4 | Native protocol v4

cqlsh> DESCRIBE KEYSPACE service_message 

CREATE KEYSPACE service_message WITH replication = {'class': 'SimpleStrategy', 'replication_factor': '3'}  AND durable_writes = true;

CREATE TABLE service_message.test (
    id uuid PRIMARY KEY,
    message text,
    recipient text
) WITH 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';

1 个答案:

答案 0 :(得分:0)

INSERT and UPDATE statements using the IF clause support lightweight transactions

来自CQL上的Datastax文档:https://docs.datastax.com/en/cql/3.3/cql/cql_using/useInsertLWT.html

我很确定不支持删除。如果要有效删除信息,可以考虑将UPDATE语句中单元格的值设置为null。通过删除或设置为空,您仍在创建逻辑删除。