即使查询使用索引扫描，需要40秒才能获得1000条记录

如何解决即使查询使用索引扫描，需要40秒才能获得1000条记录

我的表创建脚本如下，我的表根据销售时间按月进行分区。平均一天包含 300 万条记录。我的表总共包含 10 亿条记录

CREATE TABLE MyTable(
Id bigint not null,Col1 text,Col2 text,Col3 text,Col4 text,Col5 text,Col6 text,Col7 text,Col8 text,Col9 text,Saletime timestamp without timezone,CONSTRAINT pk_tbl_mytable PRIMARY KEY(id,saletime)
Usint INDEX TABLESPACE “MY_TS”
)PARTIOTION BY RANGE(Saletime)
TABLESPACE “MY_TS”;

我的查询在下面

with CTE AS(
SELECT Id,SaleTime from tbl_search_log
where saletime>’2019-11-01 00:00:00’ and saletime<’2019-12-30 00:00:00’
and siteid in(708,805,432,403)
order by saletime desc limit 1000 offset 0
)
Select S.Id,col1,col2,col3,col4,col5,col6,col7,col8
from mytable S
join CTE on S.id=CTE.Id
where S.saletime>’2019-11-01 00:00:00’ and S.saletime<’2019-12-30 00:00:00’
order by S.saletime desc
limit 1000;

当我使用上面的查询选择 1000 条记录时，几乎需要 35 到 40 秒 我的查询 Explain(Analyze,Buffers) 日志如下

Limit (cost=10924.12. 10926.62 rows=1000 width=209) (actual time=D40650.143..40650.302 rows=1000 loops=1) "

Buffers: shared hit-3034 read-2120"

Sort

(cost=10924.12. . 10926.62 rous-1000 width=209) (actual time=40650.142.40650.212 rows=1000 loops=1)"

Sort Key saletime DESOM

Sort Method: quicksort Memory: 290KB" Buffers: shared hit=3034 read=2120"

nested Loop (cost=8146.68.. 10874.29 rows=1000 width=209) actual time=D63.635..40643.680 rows=1000 loops=1)" Buffers shared hit=3034 read=2120

Limit (cost=8146.12..8262.79 rows=1000 width=16 actual time=13014 16.019 rows=1000 loops=1)

Buffers: shared hit=154"

-> Gather Merge (cost=8029.44.19796.80 rows=100856 width=16) actual time=12.954..15.511 rows=2000 loops=1)"

workers Planned: 2

Workers Launched: 2

Buffers: shared hit=168"

Sort (cost=7029.42..7155.49 rous=50428 width=16) (actual time-0.872..1.273 roMs=667 loops=3) "

Sort Keys Plc log 201911. saletime DESC Sort Method: top-N heapsort Memory: 190KB" Horker 0: Sort Method: quicksort Memory 25kB

Horker 1: Sort Method: quicksort Memory: 25KB"

Buffers: shared hit=168

Sort (cost=7029.42..7155.49 rous=50428 width=16) (actual time-0.872..1.273 roMs=667 loops=3) "

Sort Keys Plc log 201911. saletime DESC Sort Method: top-N heapsort Memory: 190KB" Horker 0: Sort Method: quicksort Memory 25kB

Horker 1: Sort Method: quicksort Memory: 25KB"

Buffers: shared hit=168

Parallel Index Only Scan using purlog 201911 p_rlog 201911 (cost=0.56..4012.37 rows=50428 width=16) (actual time=0.009..0.517 rows=2786 loops=3)" Index Cond: (siteid = ANY (4708,345,403 :: integer [])) AND (saletime 2019-11-01 00:00:00 : : timestamp without time zone) AND

(saletime < '2019-11-30 00:00:00 : timestamp without

time zone))"


Heap Fetches: 0"

Buffers: shared hit=154" ->

Index Scan using p_mytablelog201911 pkey on p_mytablelog201911 s cost=0.56..2.59 rows=1 width=153) (actyal time=40.599..40.602 row3=1 loops=1000) 
Index Cond: ((id = p rlog 201911.id) AND (saletime >= 2019-11-01 00:00:00 Btimestamp without time zone) AND
(saletime <= 2019-11-30 00:00:00 :: timestamp without time zone)) " 
Buffers:shared hit=2880 read=2120
planing time:0.800 ms
Execution Time: 40651.003 ms

请建议我解决这个性能问题。

tbl_search_log 和 MyTable 有近 10 亿条记录。 tbl_search_log 在 1 秒内给出结果。但 My Table 只需要更多时间。

注意： 我正在使用带有 Postgresql 12 的 Windows Server 操作系统 32 GB 内存工作内存 1GB 统计 10000 Random_Page_Cost 1.0 Shared_Buffers 8GB