检查Postgres JSON数组是否包含字符串

我有一张桌子来存储有关我的兔子的信息。看起来像这样:

create table rabbits (rabbit_id bigserial primary key, info json not null);

insert into rabbits (info) values

('{"name":"Henry", "food":["lettuce","carrots"]}'),

('{"name":"Herald","food":["carrots","zucchini"]}'),

('{"name":"Helen", "food":["lettuce","cheese"]}');

我该如何找到喜欢胡萝卜的兔子?我想出了这个:

select info->>'name' from rabbits where exists (

select 1 from json_array_elements(info->'food') as food

where food::text = '"carrots"'

);

我不喜欢那个查询。一团糟。

作为专职兔子管理员,我没有时间更改数据库架构。我只想适当地喂兔子。有没有更可读的方法来执行该查询?

回答:

从PostgreSQL

9.4开始,您可以使用?operator:

select info->>'name' from rabbits where (info->'food')::jsonb ? 'carrots';

如果改用 jsonb 类型,甚至可以?"food"键上为查询建立索引: __

alter table rabbits alter info type jsonb using info::jsonb;

create index on rabbits using gin ((info->'food'));

select info->>'name' from rabbits where info->'food' ? 'carrots';

当然,作为专职兔子饲养员,您可能没有时间这样做。

这是在一张1,000,000只兔子的桌子上性能改进的演示,其中每只兔子喜欢两种食物,其中10%像胡萝卜:

d=# -- Postgres 9.3 solution

d=# explain analyze select info->>'name' from rabbits where exists (

d(# select 1 from json_array_elements(info->'food') as food

d(# where food::text = '"carrots"'

d(# );

Execution time: 3084.927 ms

d=# -- Postgres 9.4+ solution

d=# explain analyze select info->'name' from rabbits where (info->'food')::jsonb ? 'carrots';

Execution time: 1255.501 ms

d=# alter table rabbits alter info type jsonb using info::jsonb;

d=# explain analyze select info->'name' from rabbits where info->'food' ? 'carrots';

Execution time: 465.919 ms

d=# create index on rabbits using gin ((info->'food'));

d=# explain analyze select info->'name' from rabbits where info->'food' ? 'carrots';

Execution time: 256.478 ms

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