Sic*_*orf 6 sql-server index-tuning
有人可以指导我更好地理解具有多个不等式谓词的索引搜索吗?考虑下表:
CREATE TABLE [dbo].[table_1](
[DBINVHDID] [int] IDENTITY(1,1) NOT NULL,
[TYPE] [nvarchar](1) NULL,
[INV_NO] [nvarchar](13) NULL,
[ACCOUNT] [nvarchar](10) NULL,
[NAME] [nvarchar](40) NULL,
[ADDR1] [nvarchar](25) NULL,
[ADDR2] [nvarchar](25) NULL,
[ADDR3] [nvarchar](25) NULL,
[CONTACT] [nvarchar](25) NULL,
[GST_NO] [nvarchar](15) NULL,
[CR_TERMS] [nvarchar](10) NULL,
[OREF] [nvarchar](20) NULL,
[YREF] [nvarchar](20) NULL,
[SALESREP] [nvarchar](20) NULL,
[DISCOUNT] [decimal](18, 2) NULL,
[TRANSPORT] [decimal](18, 2) NULL,
[INS] [decimal](18, 2) NULL,
[GST] [decimal](18, 2) NULL,
[TOTAL] [decimal](18, 2) NULL,
[DATE] [smalldatetime] NULL,
[LINE] [smallint] NULL,
[PSLIP] [nvarchar](10) NULL,
[VAT] [nvarchar](1) NULL,
[STORE] [nvarchar](3) NULL,
[STKSTR] [nvarchar](3) NULL,
[POST] [smalldatetime] NULL,
[PAID] [decimal](18, 2) NULL,
[WEIGHT] [decimal](18, 4) NULL,
[INSURE] [nvarchar](15) NULL,
[HAND] [decimal](18, 2) NULL,
[CODC] [decimal](18, 2) NULL,
[TOPAY] [decimal](18, 2) NULL,
[IND1] [nvarchar](1) NULL,
[IND2] [nvarchar](1) NULL,
[IND3] [nvarchar](1) NULL,
[COST] [decimal](18, 2) NULL,
[REPC] [nvarchar](6) NULL,
[DISPATCH] [nvarchar](1) NULL,
[TILLNO] [nvarchar](2) NULL,
[USER] [nvarchar](6) NULL,
[RCOMM] [decimal](18, 2) NULL,
[DISP1] [nvarchar](1) NULL,
[DISP2] [nvarchar](7) NULL,
[PRNSEQ] [int] NULL,
[TIME] [nvarchar](20) NULL,
[ROUND] [decimal](18, 2) NULL,
[MESSAGE1] [nvarchar](50) NULL,
[MESSAGE2] [nvarchar](50) NULL,
[MESSAGE3] [nvarchar](50) NULL,
[PRINT] [nvarchar](1) NULL,
[PDATE] [smalldatetime] NULL,
[FILENO] [nvarchar](20) NULL,
[sched6] [nvarchar](1) NULL,
[BUYACC] [nvarchar](10) NULL,
[DBCLW] [nvarchar](20) NULL,
[PRINTCODE] [nvarchar](3) NULL,
[INV_HOLD] [nvarchar](1) NULL,
[CURRATE] [decimal](18, 4) NULL,
[CURCODE] [nvarchar](3) NULL,
[DEPOS] [smalldatetime] NULL,
[ROUTE] [nvarchar](5) NULL,
[DEL_METHOD] [nvarchar](1) NULL,
[DROPNO] [int] NULL,
[SEATNO] [int] NULL,
[DDATE] [smalldatetime] NULL,
[COMM] [nvarchar](20) NULL,
[ROT] [nvarchar](1) NULL,
[KNAPP] [nvarchar](1) NULL,
[OSEC] [nvarchar](1) NULL,
[OSECT] [nvarchar](3) NULL,
[UPDEXT] [nvarchar](1) NULL,
[EORDREFNO] [nvarchar](32) NULL,
[FSI] [nvarchar](1) NULL,
[MESSAGE_LINES] [nvarchar](500) NULL)
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这是索引:
CREATE INDEX [Index_1] ON table_1
([PRINT], [DEL_METHOD], [TYPE], [INV_NO], [DBINVHDID], [OSECT], [OSEC])
INCLUDE
( [BUYACC], [CR_TERMS], [DISP1], [NAME], [ROUTE], [SEATNO], [STORE])
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这是查询:
SELECT
[DBINVHDID],[STORE], [INV_NO], [DISP1],[SEATNO], [BUYACC],
[NAME],[ROUTE], [CR_TERMS], [DEL_METHOD]
FROM table_1
WHERE
[PRINT] = 'N'
AND ([TYPE] = '3' OR [TYPE]='5')
AND [DEL_METHOD] = 'C'
AND [OSECT] <> 'KNP'
AND [OSEC] <> '1'
ORDER BY [INV_NO] ASC
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查询计划:
我遇到的问题是,有一个 SEEK 谓词以及一个关于不等式的 PREDICATE:
如何重新创建该索引以便不存在剩余谓词?
最初,索引是使用定义中更左侧的 OSECT 和 OSEC 列创建的,这导致了残留 IO 警告和大量读取 - 然后我将这些列移到了等式列之后,从而清除了 IO 问题。
我想了解的是如何让这个索引完全满足查询而无需剩余谓词?
查询可以重写吗?
此外,还有过多的内存授予警告 - SQL 为该查询分配了过多的内存 - STATS 已通过 FULLSCAN 更新
过度授予是否与剩余谓词有关?
如何重新创建该索引以便不存在剩余谓词?
您似乎需要身份是唯一的。这需要强制执行:
CREATE UNIQUE CLUSTERED INDEX CX ON dbo.table_1 (DBINVHDID);
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然后创建过滤索引:
CREATE INDEX [Index_1]
ON table_1 ([PRINT], [DEL_METHOD], [TYPE], [INV_NO])
INCLUDE (
[DBINVHDID], [OSECT], [OSEC], [STORE], [DISP1], [SEATNO], [BUYACC],
[NAME], [ROUTE], [CR_TERMS])
WHERE
OSECT <> N'KNP'
AND OSEC <> N'1';
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将查询表达为:
SELECT
U.[DBINVHDID],
U.[STORE],
U.[INV_NO],
U.[DISP1],
U.[SEATNO],
U.[BUYACC],
U.[NAME],
U.[ROUTE],
U.[CR_TERMS],
U.[DEL_METHOD]
FROM
(
SELECT T1.*
FROM dbo.table_1 AS T1
WHERE
T1.[PRINT] = N'N'
AND T1.DEL_METHOD = N'C'
AND T1.[TYPE] = N'3'
UNION ALL
SELECT T2.*
FROM dbo.table_1 AS T2
WHERE
T2.[PRINT] = N'N'
AND T2.DEL_METHOD = N'C'
AND T2.[TYPE] = N'5'
) AS U
WHERE
U.OSECT <> N'KNP'
AND U.OSEC <> N'1'
ORDER BY
U.INV_NO ASC;
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这将给出一个没有剩余谓词且没有排序的执行计划:
如果这些条件在不同查询中可能有所不同,您可以省略索引的过滤部分。OSECT
然后,这两个不等式谓词OSEC
将作为残差谓词应用。
过度授予是否与剩余谓词有关?
内存授予是为了排序。据估计,它与需要排序的行的数量和大小成正比。谓词(可查找和残差)确实会影响基数估计。您的桌子似乎也是空的。在这种情况下,SQL Server 经常会发出毫无意义的“内存过多”警告,即使内存预留很小。
如果没有排序,就没有内存需求。
您不应在master数据库中创建表。
您的单个表是一堆无组织的数据。使用多个表来表示不同实体的关系设计可能会更容易查询。您应该考虑重新设计。
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