删除在 Postgres 中运行缓慢

Question

我的删除查询在 Postgres 中运行缓慢

 delete  FROM Tab1  WHERE vdate =TO_DATE('20991231', 'yyyymmdd') 
AND DM =  'DK' AND T_CLASS_ID ='VK'and vk_id ='SM';

解释计划是

"Delete on Tab1  (cost=24181.99..172861.78 rows=0 width=0)"
"  ->  Bitmap Heap Scan on Tab1  (cost=24181.99..172861.78 rows=456808 width=6)"
"        Recheck Cond: ((T_class_id)::text = 'VK'::text)"
"        Filter: (((dm_id)::text = 'DK'::text) AND ((VK_id)::text = 'SM'::text) AND (vdate = to_date('20991231'::text, 'yyyymmdd'::text)))"
"        ->  Bitmap Index Scan on idx_T_class_id  (cost=0.00..24067.79 rows=1482581 width=0)"
"              Index Cond: ((T_class_id)::text = 'VK'::text)"

创建索引仍然很慢。请多多指教

表格的DDL脚本是

CREATE TABLE IF NOT EXISTS public.tab1
(
    ID  integer NOT NULL DEFAULT nextval('id_seq'::regcs),
    id_name character varying(255) COLLATE pg_catalog."default" NOT NULL,
    dm_id character varying(100) COLLATE pg_catalog."default" NOT NULL,
    vm_id character varying(255) COLLATE pg_catalog."default" NOT NULL,
    id_cs_id character varying(100) COLLATE pg_catalog."default" NOT NULL,
    st_id character varying(1) COLLATE pg_catalog."default",
    id_code character varying(100) COLLATE pg_catalog."default" NOT NULL,
    valid_start_date date NOT NULL,
    valid_end_date date NOT NULL,
    ir character varying(1) COLLATE pg_catalog."default",
    CONSTRAINT id_pkey PRIMARY KEY (id_id),
    CONSTRAINT fpk_id_cs FOREIGN KEY (id_cs_id)
        REFERENCES public.id_cs (id_cs_id) MATCH SIMPLE
        ON UPDATE NO ACTION
        ON DELETE NO ACTION,
    CONSTRAINT fpk_id_dm FOREIGN KEY (dm_id)
        REFERENCES public.dm (dm_id) MATCH SIMPLE
        ON UPDATE NO ACTION
        ON DELETE NO ACTION,
    CONSTRAINT fpk_id_vm FOREIGN KEY (vm_id)
        REFERENCES public.vm (vm_id) MATCH SIMPLE
        ON UPDATE NO ACTION
        ON DELETE NO ACTION
)

TABLESPACE pg_default;

ALTER TABLE IF EXISTS public.id
    OWNER to cdrdb;
-- Index: idx_id_cs_id

-- DROP INDEX IF EXISTS public.idx_id_cs_id;

CREATE INDEX IF NOT EXISTS idx_id_cs_id
    ON public.id USING btree
    (id_cs_id COLLATE pg_catalog."default" ASC NULLS LAST)
    TABLESPACE pg_default;
-- Index: idx_id_code

-- DROP INDEX IF EXISTS public.idx_id_code;

CREATE INDEX IF NOT EXISTS idx_id_code
    ON public.id USING btree
    (id_code COLLATE pg_catalog."default" ASC NULLS LAST)
    TABLESPACE pg_default;
-- Index: idx_id_dm_id

-- DROP INDEX IF EXISTS public.idx_id_dm_id;

CREATE INDEX IF NOT EXISTS idx_id_dm_id
    ON public.id USING btree
    (dm_id COLLATE pg_catalog."default" ASC NULLS LAST)
    TABLESPACE pg_default;
-- Index: idx_id_vm_id

-- DROP INDEX IF EXISTS public.idx_id_vm_id;

CREATE INDEX IF NOT EXISTS idx_id_vm_id
    ON public.id USING btree
    (vm_id COLLATE pg_catalog."default" ASC NULLS LAST)
    TABLESPACE pg_default;