Postgres SQL 查詢慢，大表（AWS RDS）

Question

目前該表最小行數為3000萬，並且還在增長，每當嘗試進行SELECT查詢時，都需要很長時間。 在提高數據庫性能之前需要優化查詢嗎？

POSTGRES 12 on AWS RDS db.t3.small, with 20GB storage

**Message Table**

id (bigint) -> pk
meta (jsonb)
snapshot_ts (integer) -> epoch timestamp
value (character varying 100)
type (character varying 50)
created (timestamp with timezone)
last_modified (timestamp with timezone)
attribute_id (bigint) -> Foreign Key
company_id (bigint) -> Foreign Key
project_id (bigint) -> Foreign Key
device_id (bigint) -> Foreign Key


EXPLAIN SELECT COUNT(*) FROM public.message
WHERE company_id=446 AND project_id=52 AND snapshot_ts>=1637568000.0 AND snapshot_ts<=1637654399.0 AND attribute_id=458

Aggregate  (cost=424254.13..424254.14 rows=1 width=8)
  ->  Index Scan using message_attribute_id_6578b282 on message  (cost=0.56..424253.07 rows=426 width=0)
        Index Cond: (attribute_id = 458)
        Filter: ((company_id = 446) AND (project_id = 52) AND ((snapshot_ts)::numeric >= 1637568000.0) AND ((snapshot_ts)::numeric <= 1637654399.0))


**Indexes**
indexname                       | indexdef
message_attribute_id_6578b282   | CREATE INDEX message_attribute_id_6578b282 ON public.message USING btree (attribute_id)
message_company_id_cef5ed5f     | CREATE INDEX message_company_id_cef5ed5f ON public.message USING btree (company_id)
message_device_id_b4da2571      | CREATE INDEX message_device_id_b4da2571 ON public.message USING btree (device_id)
message_pkey                    | CREATE UNIQUE INDEX message_pkey ON public.message USING btree (id)
message_project_id_7ba6787d     | CREATE INDEX message_project_id_7ba6787d ON public.message USING btree (project_id)

Answer 1

考慮到具體查詢：

SELECT COUNT(*)
FROM public.message
WHERE company_id=446 
  AND project_id=52 
  AND snapshot_ts>=1637568000.0 AND snapshot_ts<=1637654399.0 
  AND attribute_id=458

以下索引具有極大提高性能的潛力：

create index ix1 on public.message (
  company_id, project_id, attribute_id, snapshot_ts
);

但是，請記住，在 3000 萬行表上創建索引可能需要一些時間。