cassandra中二级索引的范围查询 [英] Range query on secondary index in cassandra

问题描述

我使用的是 cassandra 2.1.10.所以首先我要清楚我知道二级索引是 cassandra 中的反模式.但是为了测试目的，我尝试了以下操作:

I am using cassandra 2.1.10. So First I will clear that I know secondary index are anti-pattern in cassandra.But for testing purpose I was trying following:

CREATE TABLE test_topology1.tt (
    a text PRIMARY KEY,
    b timestamp
) 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'}
    AND compression = {'sstable_compression': 'org.apache.cassandra.io.compress.LZ4Compressor'}
    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 = '99.0PERCENTILE';
CREATE INDEX idx_tt ON test_topology1.tt (b);

当我运行以下查询时，它给了我错误.

When I run following query it gives me error.

cqlsh:test_topology1> Select * from tt where b>='2016-04-29 18:00:00' ALLOW FILTERING;
InvalidRequest: code=2200 [Invalid query] message="No secondary indexes on the restricted columns support the provided operators: 'b >= <value>'"

虽然这个博客 表示允许过滤可用于查询二级索引.Cassandra 安装在 windows 机器上.

while this Blog says that allow filtering can be used to query secondary index. Cassandra is installed on windows machine.

推荐答案

在 Cassandra 2.2.x 及以下版本中不允许对二级索引列进行范围查询.但是，作为帖子深入查看 CQL WHERE 子句 指出，如果允许过滤，它们可以用于非索引列:

Range queries on secondary index columns are not allowed in Cassandra up to and including 2.2.x. However, as the post A deep look at the CQL WHERE clause points out, they are allowed on non-indexed columns, if filtering is allwed:

对二级索引的直接查询仅支持 =、CONTAINS 或包含 KEY 限制.

Direct queries on secondary indices support only =, CONTAINS or CONTAINS KEY restrictions.

[..]

二级索引查询允许你限制返回的结果使用 =, >, >=, <= 和 <, CONTAINS 和 CONTAINS KEY 限制在使用过滤的非索引列上.

Secondary index queries allow you to restrict the returned results using the =, >, >=, <= and <, CONTAINS and CONTAINS KEY restrictions on non-indexed columns using filtering.

所以，给定表结构和索引

So, given the table structure and index

CREATE TABLE test_secondary_index (
     a text PRIMARY KEY,
     b timestamp,
     c timestamp 
);
CREATE INDEX idx_inequality_test ON test_secondary_index (b);

以下查询失败，因为对索引列进行了不等式测试:

the following query fails because the inequality test is done on the indexed column:

SELECT * FROM  test_secondary_index WHERE b >= '2016-04-29 18:00:00' ALLOW FILTERING ;
InvalidRequest: code=2200 [Invalid query] message="No secondary indexes on the restricted columns support the provided operators: 'b >= <value>'"

但以下有效，因为不等式测试是在非索引列上完成的:

But the following works because the inequality test is done on a non-indexed column:

SELECT * FROM  test_secondary_index WHERE b = '2016-04-29 18:00:00' AND c >= '2016-04-29 18:00:00' ALLOW FILTERING ;

 a | b | c
---+---+---

(0 rows)

如果您在 c 列上添加另一个索引，这仍然有效，但仍然需要 ALLOW FILTERING 术语，这对我来说意味着 c 列上的索引不是在这个场景中使用.

This still works if you add another index on column c, but also still requires the ALLOW FILTERING term, which to me means that the index on column c is not used in this scenario.

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