Question

我有一个jsonb字段，其数据如下：

{"state": "initialize_done_state", ... }

此字段的GIN索引：

CREATE INDEX index_activities_on_data ON activities USING gin (data)

并执行查询：

select count(*)
from activities a
where a.created_at >= (date_trunc('month', current_date)::timestamp AT TIME ZONE 'MSK') and
      --a.data ->> 'state' = 'issued_success_state';
      a.data @>  '{ "state": "issued_success_state" }';

当我使用@＆gt; WHERE子句中的运算符，使用了gin索引：

Aggregate  (cost=406.91..406.92 rows=1 width=8)
->  Bitmap Heap Scan on activities a  (cost=32.75..406.67 rows=95 width=0)
Recheck Cond: (data @> '{"state": "issued_success_state"}'::jsonb)
Filter: (created_at >= timezone('MSK'::text, (date_trunc('month'::text, (('now'::cstring)::date)::timestamp with time zone))::timestamp without time zone))
->  Bitmap Index Scan on index_activities_on_data  (cost=0.00..32.73 rows=364 width=0)
Index Cond: (data @> '{"state": "issued_success_state"}'::jsonb)

并且在我使用时不使用 - ＆gt;＆gt;操作者：

Aggregate  (cost=59093.42..59093.43 rows=1 width=8)
->  Seq Scan on activities a  (cost=0.00..59092.23 rows=477 width=0)
Filter: (((data ->> 'state'::text) = 'issued_success_state'::text) AND (created_at >= timezone('MSK'::text, (date_trunc('month'::text, (('now'::cstring)::date)::timestamp with time zone))::timestamp without time zone)))

请解释原因？

Answer 1

来自the documentation:

jsonb的默认GIN运算符类支持使用顶级键存在运算符的查询？，？＆amp;和？|运算符和路径/值存在运算符@＆gt;。

您可以创建可与->>运算符一起使用的B树索引，例如

CREATE INDEX ON activities ((data->>'state'));

为什么不使用GIN索引？

1 个答案: