这是我的函数的简化版本，其中包含查询(因此任何变量现在都无用)，并且该函数不会完成，但如果我单独运行相同的查询，它会在一秒钟内完成。
永远不会完成的函数
select * from test_function_difference(1);
CREATE OR REPLACE FUNCTION test_function_difference (
p_does_nothing int
)
RETURNS TABLE(
t_datum date,
t_capacity numeric,
t_used numeric,
t_category int,
t_category_name text,
t_used_p numeric,
t_unused_p numeric
)
VOLATILE
AS $dbvis$
declare
p_sql text := '';
p_execute text := '';
rec record;
begin
p_sql :=
'
with
vytizeni as (
select
date_trunc(''day'',mcz.datum)::date as datum ,
sum(zd.v_vytizeni)/3600.0 used
from v_ui_cdc_s5_misto_cas_zdroj_aggregace mcz
left join (select * , pul_den as den_noc from v_ui_cdc_s5_misto_cas_zdroj_aggregace_zdrobneni) zd on mcz.id = zd.id
where
datum between ''2018-12-31'' and ''2018-12-31''
and ( zahranicni = 0 or zahranicni is null )
and den_noc = -1
group by
date_trunc(''day'',mcz.datum)::date
)
,kapacita as (
select
date_trunc(''day'',datum)::date as datum ,
sum(obsazeni_g)/3600.0 capacity
from v_ui_cdc_s5_misto_cas_zdroj_aggregace
where
datum between ''2018-12-31'' and ''2018-12-31''
group by
date_trunc(''day'',datum)::date
)
,zdroj as (
select
k.datum,
k.capacity,
v.used,
-1 category
from kapacita k
join vytizeni v on k.datum = v.datum
)
select
c.* ,
kc.nazev::text categeroy_name,
case when sum(capacity)over(partition by datum) = 0 then 1 else used/sum(capacity)over(partition by datum) end as used_p,
greatest(1 - case when sum(capacity)over(partition by datum) = 0 then 1 else sum(used)over(partition by datum)/sum(capacity)over(partition by datum) end,0) as unused_p
from zdroj c
left join v_ui_cdc_s5_kategorie_cinnosti kc on kc.id = c.category
order by c.datum
';
raise notice '% ' , p_sql;
RETURN QUERY
execute p_sql;
END;
$dbvis$ LANGUAGE plpgsql
以及我单独运行的查询(在 533 毫秒内完成)
with
vytizeni as (
select
date_trunc('day',mcz.datum)::date as datum ,
sum(zd.v_vytizeni)/3600.0 used
from v_ui_cdc_s5_misto_cas_zdroj_aggregace mcz
left join (select * , pul_den as den_noc from v_ui_cdc_s5_misto_cas_zdroj_aggregace_zdrobneni) zd on mcz.id = zd.id
where
datum between '2018-12-31' and '2018-12-31'
and ( zahranicni = 0 or zahranicni is null )
and den_noc = -1
group by
date_trunc('day',mcz.datum)::date
)
,kapacita as (
select
date_trunc('day',datum)::date as datum ,
sum(obsazeni_g)/3600.0 capacity
from v_ui_cdc_s5_misto_cas_zdroj_aggregace
where
datum between '2018-12-31' and '2018-12-31'
group by
date_trunc('day',datum)::date
)
,zdroj as (
select
k.datum,
k.capacity,
v.used,
-1 category
from kapacita k
join vytizeni v on k.datum = v.datum
)
select
c.* ,
kc.nazev::text categeroy_name,
case when sum(capacity)over(partition by datum) = 0 then 1 else used/sum(capacity)over(partition by datum) end as used_p,
greatest(1 - case when sum(capacity)over(partition by datum) = 0 then 1 else sum(used)over(partition by datum)/sum(capacity)over(partition by datum) end,0) as unused_p
from zdroj c
left join v_ui_cdc_s5_kategorie_cinnosti kc on kc.id = c.category
order by c.datum
编辑:我能够在大约 28 分钟后从该函数中获得结果(我也在周日晚上尝试过，这意味着我拥有整个服务器的资源，因为在正常加载期间函数甚至在一小时后还没有完成)之后我独立运行查询并在 2.1 秒后得到结果以下是解释分析
功能:28分钟 https://explain.depesz.com/s/v9xJ
独立查询:2.1秒 https://explain.depesz.com/s/aBri
第二次独立运行 430ms https://explain.depesz.com/s/ENva
有趣的说明:如果我将间隔的开始日期编辑为“2018-12-30”或任何其他日期，该函数也会完成
这意味着
start date = '2018-12-31'
query => finishes under 1 second
function => won't finish
start date = '2018-12-30'
query => finishes under 1 second
function => finishes under 1 second
版本详细信息:x86_64-pc-linux-gnu 上的 PostgreSQL 10.7，由 gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-36) 编译，64 位
最佳答案
造成性能差异的原因是函数内部的执行没有使用并行查询，并行执行偶然选择了更好的执行计划。
该函数是否未标记为并行安全？这可能会带来很大的不同。
然而，核心问题是对 ui_cdc_s5_misto_cas_zdroj_aggregace 扫描结果行数的总体密斯估计，估计为 1 行，而不是 2243 行。
您应该分析该表以获得更好的估计。如果仅此无法改善估计值，请尝试在 ANALYZE 之前提高 default_statistics_target。
如果您需要提高 default_statistics_target 以获得更好的估计，请保留该更改
ALTER TABLE ui_cdc_s5_misto_cas_zdroj_aggregace
ALTER datum SET STATISTICS <whatever proved useful>
关于postgresql - Postgres 查询不会在函数中完成，但如果单独运行它可以工作，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/54945240/