Cassandra墓碑计数多个查询与单个查询 [英] Cassandra tombstones count multiple queries vs single query

问题描述

我有一个cassandra表定义如下

I've a cassandra table definition as following

CREATE TABLE mytable
(
  colA text,
  colB text,
  timeCol timestamp,
  colC text,
  PRIMARY KEY ((colA, colB, timeCol), colC)
) WITH....

我想知道墓碑数是否会因以下类型的查询而异：

I want to know if number of tombstones would vary between following types of queries:

1. delete from mytable where colA = '...' AND colB = '...' and timeCol = 111

以上查询影响多个记录，（多个值colC）

Above query affect multiple records, (multiple values of colC)

2. delete from mytable where colA = '...' AND colB = '...' and timeCol = 111 AND colC = '...'

但是，对于最后一列 colC 的每个值都需要执行第二个查询，而第一个查询在一个执行中处理删除

However, 2nd query needs to be executed for each value of last column colC, while 1st query takes care of deletion in one execution

Cassandra会在这两种情况下创建相同数量的墓碑吗？

Will Cassandra create same number of tombstones in both the cases?

推荐答案

Cassandra将为每个delete语句创建一个单一的墓碑。但是，每个语句将创建一个不同类型的墓碑。

Cassandra will create a single tombstone for each delete statement. However, each statement will create a different type of tombstone.

1。从mytable中删除colA ='...'AND colB ='...'and timeCol = 111

墓碑：


{
key：00032e2e2e0000032e2e2e000008000000000000006f00，
metadata：{
deletionInfo：{
markedForDeleteAt：1427461335167000，localDeletionTime：1427461335
}
}，
columns：[]
}


行级别墓碑将确保所有列都被删除。

Row level tombstones will make sure all columns will be covered with the delete.

2。从mytable中删除colA ='...'AND colB ='...'and timeCol = 111 AND colC ='...'

创建列墓碑：


{
key：00032e2e2e0000032e2e2e000008000000000000006f00，
columns：[[...，...：！，1427461572135000，t，1427461572]]
}


这将只删除在此集群键下保存的值。

This will only delete values that have been saved under this clustering key.

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