为什么 Postgres 只执行顺序扫描

如何解决为什么 Postgres 只执行顺序扫描

我正在 postgres 中对我的表运行一些查询。我的表包含从 2010 年到 2020 年大约 1.000.000 行的数据。无论我测试哪个查询，postgres 只执行顺序扫描。 例如： 我的数据如下所示：

CREATE TABLE public.timestamppsql
(
    id1 double precision,id6 double precision,id7 double precision,id8 double precision,id9 double precision,id10 double precision,id11 double precision,id12 double precision,id13 double precision,c14 text COLLATE pg_catalog."default",id15 double precision,id16 double precision,id17 double precision,id18 double precision,id19 double precision,id20 double precision,id21 double precision,id22 double precision,id23 double precision,timestamp1 timestamp without time zone,timestamp2 timestamp without time zone
)

explain (analyze,buffers,format text) select id13 from timestamppsql where timestamp1 >='2010-01-01 00:05:00' and timestamp1<='2010-01-02 00:05:00'

解释分析

    "Gather  (cost=1000.00..39459.55 rows=251 width=8) (actual time=0.171..166.399 rows=289 loops=1)"
"  Workers Planned: 1"
"  Workers Launched: 1"
"  Buffers: shared hit=28224"
"  ->  Parallel Seq Scan on timestamppsql  (cost=0.00..38434.45 rows=148 width=8) (actual time=78.040..157.282 rows=144 loops=2)"
"        Filter: ((timestamp1 >= '2010-01-01 00:05:00'::timestamp without time zone) AND (timestamp1 <= '2010-01-02 00:05:00'::timestamp without time zone))"
"        Rows Removed by Filter: 578448"
"        Buffers: shared hit=28224"
"Planning Time: 0.050 ms"
"Execution Time: 166.429 ms"

这个查询只影响 290 行，所以它应该使用索引扫描。我使用了很多查询，但每次 postgres 只执行顺序扫描。