使用多个 OUTER APPLY 优化查询

Question

我有多个 OUTER APPLY 的查询，但所有 table 的连接列上都有主键（所以这里使用聚集索引）所以我不知道如何优化这个查询进一步。此外，在这里使用索引视图是不可能的，因为使用 ORDER BY 和 TOP 是被禁止的。

所以我有

Table Fields 带有 Id 主键和大量其他列。
WeatherHistory table 具有复杂的主键（FieldId 和 [Date]）和很多列，
NdviImageHistory table 与 FieldId、[Date]、[Base64] 列（复杂主键 FieldId 和 [Date]) 其中 [Base64] 存储图像 base64,
NaturalColorImageHistory table 与 FieldId、[Date]、[Base64] 列（复杂主键 FieldId 和 [Date]) 其中 [Base64] 存储图像 base64,
NdviHistory table with with with FieldId, [Date], MeanNdvi 列（复杂主键 FieldId 和[Date]),
FieldSeasonHistory table 与 Field、StartDate、EndDate 列（复杂主键 FieldId 和 [Date]).

我的查询

SELECT Fields.*,
    WeatherHistory.TempSumC AS CurrentTempSumC,
    TempSumF AS CurrentTempSumF,
    PrecipitationSumMm AS CurrentPrecipitationSumMm,
    nih.[Base64] AS CurrentNdviImageBase64,
    ncih.[Base64] AS CurrentNaturalColorImageBase64,
    MeanNdvi AS CurrentMeanNdvi,
    IsOpenSeason
FROM Fields
LEFT JOIN WeatherHistory ON FieldId = Id AND [Date] = CAST(GETUTCDATE() AS DATE)
OUTER APPLY
(
    SELECT TOP 1 [Base64]
    FROM NdviImageHistory
    WHERE FieldId = Id
    ORDER BY [Date] DESC
) nih
OUTER APPLY
(
    SELECT TOP 1 [Base64]
    FROM NaturalColorImageHistory
    WHERE FieldId = Id
    ORDER BY [Date] DESC
) ncih
OUTER APPLY
(
    SELECT TOP 1 MeanNdvi
    FROM NdviHistory
    WHERE FieldId = Id
    ORDER BY [Date] DESC
) nh
OUTER APPLY
(
    SELECT TOP 1 CASE WHEN EndDate IS NULL THEN 1 ELSE 0 END AS IsOpenSeason
    FROM FieldSeasonHistory
    WHERE FieldId = Id
    ORDER BY [StartDate] DESC
) fsh
WHERE UserId = (SELECT Id FROM Users WHERE Email = @email) AND IsArchived = 0

我没有创建任何索引，因为我认为自动生成的聚簇索引（基于主键）应该足够了（但我可能是错的）。此查询执行大约 15 秒，但我想减少查询时间。

编辑： 向 Fields table 的 UserId 和 IsArchived 列添加了索引。查询执行计划：

** 编辑 2：** 统计数据：

SQL Server parse and compile time: 
   CPU time = 0 ms, elapsed time = 0 ms.

 SQL Server Execution Times:
   CPU time = 0 ms,  elapsed time = 0 ms.
SQL Server parse and compile time: 
   CPU time = 0 ms, elapsed time = 0 ms.

 SQL Server Execution Times:
   CPU time = 0 ms,  elapsed time = 0 ms.

 SQL Server Execution Times:
   CPU time = 0 ms,  elapsed time = 0 ms.

 SQL Server Execution Times:
   CPU time = 0 ms,  elapsed time = 0 ms.

(13 row(s) affected)
Table 'FieldSeasonHistory'. Scan count 13, logical reads 26, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'NdviHistory'. Scan count 13, logical reads 26, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'NaturalColorImageHistory'. Scan count 13, logical reads 26, physical reads 0, read-ahead reads 0, lob logical reads 604, lob physical reads 0, lob read-ahead reads 0.
Table 'NdviImageHistory'. Scan count 13, logical reads 39, physical reads 0, read-ahead reads 0, lob logical reads 68, lob physical reads 0, lob read-ahead reads 0.
Table 'WeatherHistory'. Scan count 0, logical reads 39, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Users'. Scan count 0, logical reads 228, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Fields'. Scan count 1, logical reads 19, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

(1 row(s) affected)

 SQL Server Execution Times:
   CPU time = 15 ms,  elapsed time = 16 ms.
SQL Server parse and compile time: 
   CPU time = 0 ms, elapsed time = 0 ms.

 SQL Server Execution Times:
   CPU time = 0 ms,  elapsed time = 0 ms.

Answer 1

您需要为每个表创建多列索引。索引应该是 where 中的列，order by 中的列，然后是 select 中的列。例如：

NdviImageHistory(FieldId, [Date], [Base64])
NaturalColorImageHistory(FieldId, [Date], [Base64])
等等。

Answer 2

像这样更新您的查询。

SELECT Fields.*,
    WeatherHistory.TempSumC AS CurrentTempSumC,
    TempSumF AS CurrentTempSumF,
    PrecipitationSumMm AS CurrentPrecipitationSumMm,
    nih.[Base64] AS CurrentNdviImageBase64,
    ncih.[Base64] AS CurrentNaturalColorImageBase64,
    MeanNdvi AS CurrentMeanNdvi,
    IsOpenSeason
FROM Fields
LEFT JOIN WeatherHistory ON FieldId = Id AND [Date] = CAST(GETUTCDATE() AS DATE)
OUTER APPLY
(
    SELECT MAX(NdviImageHistory.ID) MAX_ID
    FROM NdviImageHistory
    WHERE FieldId = Id

) nih_ID
OUTER APPLY
(
    SELECT [Base64] FROM NdviImageHistory X WHERE X.ID = nih_ID.MAX_ID
)nih

用户更多外部申请所有这些表 {nih , ncih, nh, fsh } 试试这个。

我只为 [nih] 使用 1 个外层

从 OUTER APPLY Joins 中删除 TOP 1 和 Order by

使用多个 OUTER APPLY 优化查询

Optimize query with multiple OUTER APPLY

sql

sql-server

query-optimization

cross-apply

outer-apply