CQL 版本 5.0.1
Cassandra 版本 3.11.9
root@3fdb49de030c:/# cqlsh
Connected to Test Cluster at 127.0.0.1:1234.
[cqlsh 5.0.1 | Cassandra 3.11.9 | CQL spec 3.4.4 | Native protocol v4]
Use HELP for help.
cqlsh>
在插入同一条记录时(如下图),
cqlsh> use mykeyspace;
cqlsh:mykeyspace>
cqlsh:mykeyspace>
cqlsh:mykeyspace>
cqlsh:mykeyspace>
cqlsh:mykeyspace> select * from mytable ;
column1 | column2 | column3 | column4 | column5 | column6
--------------------------------------+--------------------------------------+---------------------------------+-------------------+---------------------------------+--------------
54dc8b12-a934-4f2e-8a0d-e7eba3faa47e | 587df674-bc77-481b-b974-ddebd203e371 | 2021-04-02 13:29:37.841000+0000 | sample@abc.com | 2021-04-02 13:29:37.841000+0000 | [{"abc": "def"}]
(1 rows)
cqlsh:mykeyspace>
cqlsh:mykeyspace>
cqlsh:mykeyspace>
cqlsh:mykeyspace> // does not give error on changin non-primary key columns
cqlsh:mykeyspace> INSERT INTO mytable (column1, column2, column4, column6, column3, column5) VALUES (54dc8b12-a934-4f2e-8a0d-e7eba3faa47e, 587df674-bc77-481b-b974-ddebd203e371, 'sample@abc.com', 'xyz',toTimestamp(now()),toTimestamp(now()));
cqlsh:mykeyspace>
cqlsh:mykeyspace>
cqlsh:mykeyspace> select * from mytable ;
column1 | column2 | column3 | column4 | column5 | column6
--------------------------------------+--------------------------------------+---------------------------------+-------------------+---------------------------------+--------------
54dc8b12-a934-4f2e-8a0d-e7eba3faa47e | 587df674-bc77-481b-b974-ddebd203e371 | 2021-04-02 13:29:37.841000+0000 | sample@abc.com | 2021-04-02 13:29:37.841000+0000 | xyz
(1 rows)
cqlsh:mykeyspace>
cqlsh:mykeyspace>
cqlsh:mykeyspace>
cqlsh:mykeyspace>
cqlsh:mykeyspace>
cqlsh:mykeyspace> // does not give error on changing one of the primary key column
cqlsh:mykeyspace> INSERT INTO mytable (column1, column2, column4, column6, column3, column5) VALUES (54dc8b12-a934-4f2e-8a0d-e7eba3faa47e, 587df674-bc77-481b-b974-ddebd203e372, 'garbage', 'garbage',toTimestamp(now()),toTimestamp(now()));
cqlsh:mykeyspace>
cqlsh:mykeyspace>
cqlsh:mykeyspace>
cqlsh:mykeyspace> select * from mytable ; // PK(column1:column2)
column1 | column2 | column3 | column4 | column5 | column6
--------------------------------------+--------------------------------------+---------------------------------+---------------+---------------------------------+-----------------------
54dc8b12-a934-4f2e-8a0d-e7eba3faa47e | 587df674-bc77-481b-b974-ddebd203e371 | 2020-04-02 14:20:24.028000+0000 | sample@abc.com | 2020-04-02 14:20:24.028000+0000 | xyz
54dc8b12-a934-4f2e-8a0d-e7eba3faa47e | 587df674-bc77-481b-b974-ddebd203e372 | 2020-04-02 14:26:55.101000+0000 | garbage | 2020-04-02 14:26:55.101000+0000 | garbage
(2 rows)
cqlsh:mykeyspace>
cqlsh:mykeyspace>
cqlsh:mykeyspace>
cqlsh:mykeyspace> DESCRIBE TABLE mytable;
CREATE TABLE mykeyspace.mytable (
column1 uuid,
column2 uuid,
column3 timestamp,
column4 text,
column5 timestamp,
column6 text,
PRIMARY KEY (column1, column2)
)WITH CLUSTERING ORDER BY (column2 ASC)
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';
cqlsh:mykeyspace>
cqlsh:mykeyspace>
cqlsh:mykeyspace>
Cassandra 是否在插入重复记录(具有相同的主键)时不显示错误? 而是更新记录
如果不是,如何在使用 gocql 插入相同记录时错误处理重复记录?对于 http POST
请求...我们还没有使用幂等键
RDBMS SQL 服务器给出类似 Cannot insert duplicate key row
的错误
最佳答案
不幸的是,Cassandra 以其“锋利的边缘”而闻名,这就是其中之一。
Cassandra 看不出 INSERT
和 UPDATE
之间的区别。它们本质上是相同的。提供的键指示数据应该写在哪里,基于日志的存储引擎将它放在那里。这意味着您实际上可以使用 INSERT
执行更新,并使用 UPDATE
执行插入。
为了按照您描述的方式工作,Cassandra 必须知道所提供的键的值是否已经存在。唯一的方法是先读取这些键上的数据,然后写入。在并发、高吞吐量的分布式数据场景中,这样做是不安全的,因为在完成读取和执行写入之间可能会发生另一次写入。
如果您需要这种行为,您可以调用 lightweight transaction使用 IF [NOT] EXISTS
条件:
INSERT INTO mytable (column1, column2, column4, column6, column3, column5)
VALUES (54dc8b12-a934-4f2e-8a0d-e7eba3faa47e, 587df674-bc77-481b-b974-ddebd203e371, 'sample@abc.com', 'xyz',toTimestamp(now()),toTimestamp(now()))
IF NOT EXISTS;
这实际上是在后台写入之前执行读取,因此确实对性能有一些影响。
关于sql - 为什么 Cassandra 在插入重复记录时不会报错?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/66920348/