[英]Speeding up SQL Server cross apply to get aggregated data
在SQL Server中,我试图将一个查询放在一起,该查询抓取一行并包含该行之前两小时窗口的聚合数据以及之后一小时窗口的聚合数据。 如何让这个运行得更快?
行具有毫秒精度的时间戳,并且间隔不均匀。 我在这个表中有超过5000万行,查询似乎没有完成。 许多地方都有索引,但它们似乎没有帮助。 我也在考虑使用窗口函数,但我不确定它是否可能有一个不均匀分布的行的滑动窗口。 此外,对于未来的一小时窗口,我不确定如何使用SQL窗口完成。
Box是一个字符串,有10个唯一值。 Process是一个字符串,有30个唯一值。 平均duration_ms是200毫秒。 错误占数据的比例不到0.1%。 5000万行描述了多年的数据。
select
c1.start_time,
c1.end_time,
c1.box,
c1.process,
datediff(ms,c1.start_time,c1.end_time) as duration_ms,
datepart(dw,c1.start_time) as day_of_week,
datepart(hour,c1.start_time) as hour_of_day,
c3.*,
c5.*
from metrics_table c1
cross apply
(select
avg(cast(datediff(ms,c2.start_time,c2.end_time) as numeric)) as avg_ms,
count(1) as num_process_total,
count(distinct process) as num_process_unique,
count(distinct box) as num_box_unique
from metrics_table c2
where datediff(minute,c2.start_time,c1.start_time) <= 120
and c1.start_time> c2.start_time
and c2.error_code = 0
) c3
cross apply
(select
avg(case when datediff(ms,c4.start_time,c4.end_time)>1000 then 1.0 else 0.0 end) as percent_over_thresh
from metrics_table c4
where datediff(hour,c1.start_time,c4.start_time) <= 1
and c4.start_time> c1.start_time
and c4.error_code= 0
) c5
where
c1.error_code= 0
编辑
版本:SQL Azure 12.0
以下应该是朝着正确方向迈出的一步......注意:c2.start_time&c4.start_time不再在DATEDIFF函数中包装,使它们成为SARGable ......
SELECT
c1.start_time,
c1.end_time,
c1.box,
c1.process,
DATEDIFF(ms, c1.start_time, c1.end_time) AS duration_ms,
DATEPART(dw, c1.start_time) AS day_of_week,
DATEPART(HOUR, c1.start_time) AS hour_of_day,
--c3.*,
avg_ms = CASE WHEN
c5.*
FROM
dbo.metrics_table c1
CROSS APPLY (
SELECT
AVG(CAST(DATEDIFF(ms, c2.start_time, c2.end_time) AS NUMERIC)) AS avg_ms,
COUNT(1) AS num_process_total,
COUNT(DISTINCT process) AS num_process_unique,
COUNT(DISTINCT box) AS num_box_unique
FROM
dbo.metrics_table c2
WHERE
--DATEDIFF(minute,c2.start_time,c1.start_time) <= 120
c2.start_time <= DATEADD(MINUTE, -120, c1.start_time)
--and c1.start_time> c2.start_time
AND c2.error_code = 0
) c3
CROSS APPLY (
SELECT
AVG(CASE WHEN DATEDIFF(ms, c4.start_time, c4.end_time) > 1000 THEN 1.0 ELSE 0.0 END
) AS percent_over_thresh
FROM
dbo.metrics_table c4
WHERE
--DATEDIFF(HOUR, c1.start_time, c4.start_time) <= 1
c4.start_time >= DATEADD(HOUR, 1, c1.start_time)
--and c4.start_time> c1.start_time
AND c4.error_code = 0
) c5
WHERE
c1.error_code = 0;
当然,除非有适当的索引,否则进行查询SARGable没有任何好处。 以下内容应该适用于所有3个metrics_table引用...(请参阅当前可用的索引,您可能不需要创建新索引)
CREATE NONCLUSTERED INDEX ixf_metricstable_errorcode_starttime ON dbo.metrics_table (
error_code,
start_time
)
INCLUDE (
end_time,
box,
process
)
WHERE
error_code = 0;
我使用Between
并在我的简单测试台中获得了良好的性能。 我还使用了columnstore,因为5000卷记录是DW卷:
CREATE TABLE dbo.metrics_table (
rowId INT IDENTITY,
start_time DATETIME NOT NULL,
end_time DATETIME NOT NULL,
box VARCHAR(10) NOT NULL,
process VARCHAR(10) NOT NULL,
error_code INT NOT NULL
);
-- Add records
;WITH cte AS (
SELECT TOP 3334 ROW_NUMBER() OVER ( ORDER BY ( SELECT 1 ) ) rn
FROM sys.columns c1
CROSS JOIN sys.columns c2
CROSS JOIN sys.columns c3
)
INSERT INTO dbo.metrics_table ( start_time, end_time, box, process, error_code )
SELECT
DATEADD( ms, rn, DATEADD( day, rn % 365, '1 Jan 2017' ) ) AS start_time,
DATEADD( ms, rn % 409, DATEADD( ms, rn, DATEADD( day, rn % 365, '1 Jan 2017' ) ) ) AS end_time,
'box' + CAST( boxes.box AS VARCHAR(10) ) box,
'process' + CAST( boxes.box AS VARCHAR(10) ) process,
ABS( CAST( rn % 3000 AS BIT ) -1 ) error_code
FROM cte c
CROSS JOIN ( SELECT TOP 10 rn FROM cte ) AS boxes(box)
CROSS JOIN ( SELECT TOP 30 rn FROM cte ) AS processes(process);
-- Create normal clustered index to order the data
CREATE CLUSTERED INDEX cci_metrics_table ON dbo.metrics_table ( start_time, end_time, box, process );
--CREATE CLUSTERED INDEX cci_metrics_table ON dbo.metrics_table ( box, process, start_time, end_time );
-- Convert to columnstore
CREATE CLUSTERED COLUMNSTORE INDEX cci_metrics_table ON dbo.metrics_table WITH ( MAXDOP = 1, DROP_EXISTING = ON );
IF OBJECT_ID('tempdb..#tmp1' ) IS NOT NULL DROP TABLE #tmp1
-- two hour window before, 1 hour window after
SELECT
c1.start_time,
c1.end_time,
c1.box,
c1.process,
DATEDIFF( ms, c1.start_time, c1.end_time ) AS duration_ms,
DATEPART( dw, c1.start_time ) AS day_of_week,
DATEPART( hour, c1.start_time ) AS hour_of_day,
c2.xavg,
c2.num_process_total,
c2.num_process_unique,
c2.num_box_unique,
c3.percent_over_thresh
INTO #tmp1
FROM dbo.metrics_table c1
CROSS APPLY
(
SELECT
COUNT(1) AS num_process_total,
AVG( CAST( DATEDIFF( ms, start_time, end_time ) AS NUMERIC ) ) xavg,
COUNT( DISTINCT process ) num_process_unique,
COUNT( DISTINCT box ) num_box_unique
FROM dbo.metrics_table c2
WHERE c2.error_code = 0
AND c2.start_time Between DATEADD( minute, -120, c1.start_time ) And c1.start_time
AND c1.start_time > c2.start_time
) c2
CROSS APPLY
(
SELECT
AVG( CASE WHEN DATEDIFF( ms, c4.start_time, c4.end_time ) > 1000 THEN 1.0 ELSE 0.0 END ) percent_over_thresh
FROM dbo.metrics_table c4
WHERE c4.error_code = 0
AND c4.start_time Between c1.start_time And DATEADD( minute, 60, c1.start_time )
AND c4.start_time > c1.start_time
) c3
WHERE error_code = 0
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