Sql 为什么不使用GIN索引？

我有一个jsonb字段，其中包含如下数据：

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

此字段上的索引：

CREATE INDEX index_activities_on_data ON activities USING gin (data)

以及执行查询：

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" }';

当我在WHERE子句中使用@>运算符时，会使用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)

当我使用->>运算符时，不使用：

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？

来自

jsonb的默认GIN运算符类支持具有顶级键exists运算符？、？&和？|运算符以及路径/值exists运算符@>的查询

您可以创建一个B树索引，该索引可与

->

运算符一起使用，例如

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

从

jsonb的默认GIN运算符类支持具有顶级键exists运算符？、？&和？|运算符以及路径/值exists运算符@>的查询

您可以创建一个B树索引，该索引可与

->

运算符一起使用，例如

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