查询不使用带有 jsonb 的索引 - Postgres

Question

出于某种原因，Postgres 似乎没有使用我们创建的索引。这是我正在测试的查询：

SELECT  "public"."influencers".* 
FROM "public"."influencers" 
WHERE (ig -> 'id' @> '"4878142508"') 
LIMIT 1

运行后EXPLAIN：

    ->  Seq Scan on influencers  (cost=0.00..32800.14 rows=216 width=1110)

这表明（如我所见）没有使用索引。

这是我们创建的数据库和索引：

CREATE TABLE public.influencers
(
    id integer NOT NULL DEFAULT nextval('influencers_id_seq'::regclass),
    location jsonb,
    gender text COLLATE pg_catalog."default",
    birthdate timestamp without time zone,
    ig jsonb,
    contact_info jsonb,
    created_at timestamp without time zone DEFAULT now(),
    updated_at timestamp without time zone DEFAULT now(),
    categories text[] COLLATE pg_catalog."default",
    search_field text COLLATE pg_catalog."default",
    search_vector tsvector,
    ig_updated_at timestamp without time zone,
    CONSTRAINT influencers_pkey PRIMARY KEY (id),
    CONSTRAINT ig_id_must_exist CHECK (ig ? 'id'::text),
    CONSTRAINT ig_username_must_exist CHECK (ig ? 'username'::text)
)

以及创建的索引（首先是相关索引 - 我认为应该使用的索引）：

CREATE INDEX idx_btree_ig_id
    ON public.influencers USING btree
    ((ig ->> 'id'::text) COLLATE pg_catalog."default")
    TABLESPACE pg_default;


CREATE INDEX ads_search_idx
    ON public.influencers USING gin
    (search_vector)
    TABLESPACE pg_default;


CREATE INDEX ig_last_post_location_aal1
    ON public.influencers USING btree
    (((ig -> 'last_post_location'::text) -> 'administrative_area_level_1_id'::text))
    TABLESPACE pg_default;

CREATE INDEX ig_last_post_location_aal2
    ON public.influencers USING btree
    (((ig -> 'last_post_location'::text) -> 'administrative_area_level_2_id'::text))
    TABLESPACE pg_default;

CREATE INDEX ig_last_post_location_aal3
    ON public.influencers USING btree
    (((ig -> 'last_post_location'::text) -> 'administrative_area_level_3_id'::text))
    TABLESPACE pg_default;

CREATE INDEX ig_last_post_location_country
    ON public.influencers USING btree
    (((ig -> 'last_post_location'::text) -> 'country_id'::text))
    TABLESPACE pg_default;

CREATE INDEX ig_last_post_location_locality
    ON public.influencers USING btree
    (((ig -> 'last_post_location'::text) -> 'locality_id'::text))
    TABLESPACE pg_default;

CREATE UNIQUE INDEX ig_unique_id
    ON public.influencers USING btree
    ((ig ->> 'id'::text) COLLATE pg_catalog."default")
    TABLESPACE pg_default;

CREATE TRIGGER influencers_search_vector_update
    BEFORE INSERT OR UPDATE 
    ON public.influencers
    FOR EACH ROW
    EXECUTE PROCEDURE tsvector_update_trigger(s, e, a, r, c, h, _, v, e, c, t, o, r, \, 0, 0, 0, p, g, _, c, a, t, a, l, o, g, ., s, i, m, p, l, e, \, 0, 0, 0, s, e, a, r, c, h, _, f, i, e, l, d, \, 0, 0, 0);

CREATE TRIGGER update_search_field_influencers_on_insert
    BEFORE INSERT
    ON public.influencers
    FOR EACH ROW
    EXECUTE PROCEDURE update_influencer_search_field();

CREATE TRIGGER update_search_field_influencers_on_update
    BEFORE UPDATE 
    ON public.influencers
    FOR EACH ROW
    EXECUTE PROCEDURE update_influencer_search_field();

怎么了？

Answer 1

指数idx_btree_ig_id会，如果你写的前提下使用WHERE状部分ig ->> 'id' = '"4878142508"'。（我假设ig具有类似的结构{"id": "4878142508", ...}）

如果要使用运算符@>，则需要在该列上创建gin 索引，然后可以像这样使用此索引：ig @> '{"id":"4878142508"}'

CREATE INDEX idx_gin_ig_id ON public.influencers USING gin (ig jsonb_path_ops);