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Accepted
Marcello Miorelli
Asked: 2016-03-19 11:27:59 +0800 CST

Por que minha consulta EXISTS está fazendo uma varredura de índice em vez de uma busca de índice?

  • 772

Estou trabalhando na otimização de algumas consultas.

Para a consulta abaixo,

SET STATISTICS IO ON;
DECLARE @OrderStartDate DATETIME2 = '27 feb 2016';
DECLARE @OrderEndDate  DATETIME2 = '28 feb 2016';

SELECT  o.strBxOrderNo
        , o.sintOrderStatusID
        , o.sintOrderChannelID
        , o.sintOrderTypeID
        , o.sdtmOrdCreated
        , o.sintMarketID
        , o.strOrderKey
        , o.strOfferCode
        , o.strCurrencyCode
        , o.decBCShipFullPrice
        , o.decBCShipFinal
        , o.decBCShipTax
        , o.decBCTotalAmount
        , o.decWrittenTotalAmount
        , o.decBCWrittenTotalAmount
        , o.decBCShipOfferDisc
        , o.decBCShipOverride
        , o.decTotalAmount
        , o.decShipTax
        , o.decShipFinal
        , o.decShipOverride
        , o.decShipOfferDisc
        , o.decShipFullPrice
        , o.lngAccountParticipantID
        , CONVERT(DATE, o.sdtmOrdCreated, 120) as OrderCreatedDateConverted
FROM    tablebackups.dbo.tblBOrder o
WHERE   o.sdtmOrdCreated >= @OrderStartDate
        AND o.sdtmOrdCreated < @OrderEndDate
        AND EXISTS  (
            SELECT  *
            FROM    tablebackups.dbo.tblBOrderItem oi 
            WHERE   oi.strBxOrderNo = o.strBxOrderNo
            AND     oi.decCatItemPrice > 0
        )
OPTION (RECOMPILE);

Eu criei o seguinte índice FILTERED:

-- table dbo.tblBorderItem
CREATE NONCLUSTERED INDEX IX_tblBOrderItem_decCatItemPrice_INCL 
ON dbo.tblBorderItem 
( 
     strBxOrderNo ASC
    , sintOrderSeqNo ASC
    , decCatItemPrice   
)   
INCLUDE 
(
    blnChargeShipping
    , decBCCatItemPrice
    , decBCCostPrice
    , decBCFinalPrice
    , decBCOfferDiscount
    , decBCOverrideDiscount
    , decBCTaxAmount
    , decCostPrice
    , decFinalPrice
    , decOfferDiscount
    , decOverrideDiscount
    , decTaxAmount
    , decWasPrice
    , dtmOrdItemCreated
    , sintOrderItemStatusId
    , sintOrderItemType
    , sintQuantity
    , strItemNo
)  
WHERE decCatItemPrice > 0 
WITH (DROP_EXISTING = ON, FILLFACTOR = 95);

Este índice não é utilizado apenas para esta consulta em particular, existem outras consultas que utilizam este mesmo índice, por isso as colunas INCLUÍDAS.

Para esta consulta em particular, quero apenas verificar (EXISTS) se um pedido possui algum item onde decCatItemPrice > 0.

O SQL Server está fazendo uma varredura de índice, como você pode ver nas imagens abaixo.

  • As estatísticas acabaram de ser atualizadas.
  • A tabela de itens tem 41.208 linhas em teste.

Observe que não seleciono nenhuma coluna da tabela de itens.

Esta tabela de itens tem 164.309.397 ao vivo. Eu gostaria de evitar uma varredura lá.

perguntas:

Por que o SQL Server não está fazendo uma busca de índice?

Existem outros fatores/coisas que devo considerar para melhorar esta consulta?

(4537 row(s) affected) Table 'tblBorder'. Scan count 1, logical reads
116, physical reads 0, read-ahead reads 0, lob logical reads 0, lob
physical reads 0, lob read-ahead reads 0. Table 'tblBorderItem'. Scan
count 1, logical reads 689, physical reads 0, read-ahead reads 0, lob
logical reads 0, lob physical reads 0, lob read-ahead reads 0.

(1 row(s) affected)

insira a descrição da imagem aqui insira a descrição da imagem aqui

esta é a definição e índices na tabela tblBorderItem

    IF OBJECT_ID('[dbo].[tblBorderItem]') IS NOT NULL 
    DROP TABLE [dbo].[tblBorderItem] 
    GO
    CREATE TABLE [dbo].[tblBorderItem] ( 
    [strBxOrderNo]                VARCHAR(20)                      NOT NULL,
    [sintOrderSeqNo]              SMALLINT                         NOT NULL,
    [sintOrderItemStatusId]       SMALLINT                         NOT NULL,
    [sintNameStructureID]         SMALLINT                         NOT NULL,
    [strItemNo]                   VARCHAR(20)                      NOT NULL,
    [sintQuantity]                SMALLINT                         NOT NULL,
    [strCurrencyCode]             VARCHAR(3)                       NOT NULL,
    [decCostPrice]                DECIMAL(18,4)                    NOT NULL,
    [decCatItemPrice]             DECIMAL(18,2)                    NOT NULL,
    [decOfferDiscount]            DECIMAL(18,2)                    NOT NULL,
    [decOverrideDiscount]         DECIMAL(18,2)                    NOT NULL,
    [decFinalPrice]               DECIMAL(18,2)                    NOT NULL,
    [decTaxAmount]                DECIMAL(18,2)                    NOT NULL,
    [strBCCurrencyCode]           VARCHAR(3)                       NOT NULL,
    [decBCCostPrice]              DECIMAL(18,4)                    NOT NULL,
    [decBCCatItemPrice]           DECIMAL(18,4)                    NOT NULL,
    [decBCOfferDiscount]          DECIMAL(18,4)                    NOT NULL,
    [decBCOverrideDiscount]       DECIMAL(18,4)                    NOT NULL,
    [decBCFinalPrice]             DECIMAL(18,4)                    NOT NULL,
    [decBCTaxAmount]              DECIMAL(18,4)                    NOT NULL,
    [dtmOrdItemCreated]           DATETIME                         NOT NULL,
    [blnChargeShipping]           BIT                              NOT NULL,
    [lngTimeOfOrderQtyOnHand]     INT                                  NULL,
    [sdtmTimeOfOrderDueDate]      SMALLDATETIME                        NULL,
    [lngProdSetSeqNo]             INT                                  NULL,
    [lngProdRelationId]           INT                                  NULL,
    [lngProdRelationMemberId]     INT                                  NULL,
    [decWasPrice]                 DECIMAL(18,2)                        NULL,
    [sintOrderItemType]           SMALLINT                             NULL,
    [tsRowVersion]                TIMESTAMP                            NULL,
    [sdtmOrderItemStatusUpdated]  SMALLDATETIME                        NULL,
    CONSTRAINT   [PK_tblBOrderItem]  
PRIMARY KEY CLUSTERED    
([strBxOrderNo] asc, [sintOrderSeqNo] asc) 
WITH FILLFACTOR = 100)

    GO

    CREATE NONCLUSTERED INDEX 
    [IX_tblBOrderItem__dtmOrdItemCreated] 
       ON [dbo].[tblBorderItem] ([dtmOrdItemCreated] asc)
       WITH FILLFACTOR = 100


    CREATE NONCLUSTERED INDEX [IX_tblBOrderItem__sintOrderItemStatusId] 
       ON [dbo].[tblBorderItem] ([sintOrderItemStatusId] asc)
       INCLUDE ([sdtmOrderItemStatusUpdated], 
    [sintOrderSeqNo], [strBxOrderNo], [strItemNo])
       WITH FILLFACTOR = 100

CREATE NONCLUSTERED INDEX [IX_tblBOrderItem__
sintOrderItemStatusId_decFinalPrice_
sdtmOrderItemStatusUpdated_
include_strBxOrderNo] 
   ON [dbo].[tblBorderItem] 
([sintOrderItemStatusId] asc, 
 [decFinalPrice] asc, 
 [sdtmOrderItemStatusUpdated] asc)
   INCLUDE ([strBxOrderNo])
   WITH FILLFACTOR = 100

CREATE NONCLUSTERED INDEX [IX_tblBOrderItem__strBxOrderNo] 
   ON [dbo].[tblBorderItem] 
([strBxOrderNo] asc)
   WITH FILLFACTOR = 100


CREATE NONCLUSTERED INDEX [IX_tblBOrderItem__strItemNo] 
   ON [dbo].[tblBorderItem] ([strItemNo] asc)
   WITH FILLFACTOR = 100

CREATE NONCLUSTERED INDEX 
[IX_tblBOrderItem_decCatItemPrice_INCL] 
   ON [dbo].[tblBorderItem] 
([strBxOrderNo] asc, [sintOrderSeqNo] asc, [decCatItemPrice] asc)
   INCLUDE ([blnChargeShipping], 
[decBCCatItemPrice], [decBCCostPrice], [decBCFinalPrice], 
[decBCOfferDiscount], [decBCOverrideDiscount], 
[decBCTaxAmount], [decCostPrice], [decFinalPrice], 
[decOfferDiscount], [decOverrideDiscount], 
[decTaxAmount], [decWasPrice], [dtmOrdItemCreated], 
[sintOrderItemStatusId], [sintOrderItemType], 
[sintQuantity], [strItemNo])
   WHERE ([decCatItemPrice]>(0))
   WITH FILLFACTOR = 95

esta é a definição e índices na tabela tblBorder

IF OBJECT_ID('[dbo].[tblBorder]') IS NOT NULL 
DROP TABLE [dbo].[tblBorder] 
GO
CREATE TABLE [dbo].[tblBorder] ( 
[strBxOrderNo]                VARCHAR(20)                      NOT NULL,
[uidOrderUniqueID]            UNIQUEIDENTIFIER                 NOT NULL,
[sintOrderStatusID]           SMALLINT                         NOT NULL,
[sintOrderChannelID]          SMALLINT                         NOT NULL,
[sintOrderTypeID]             SMALLINT                         NOT NULL,
[blnIsBasket]                 BIT                              NOT NULL,
[sdtmOrdCreated]              SMALLDATETIME                    NOT NULL,
[sintMarketID]                SMALLINT                         NOT NULL,
[strOrderKey]                 VARCHAR(20)                      NOT NULL,
[strOfferCode]                VARCHAR(20)                      NOT NULL,
[lngShippedToParticipantID]   INT                              NOT NULL,
[lngOrderedByParticipantID]   INT                              NOT NULL,
[lngShipToAddressID]          INT                              NOT NULL,
[lngAccountAddressID]         INT                              NOT NULL,
[lngAccountParticipantID]     INT                              NOT NULL,
[lngOrderedByAddressID]       INT                              NOT NULL,
[lngOrderTakenBy]             INT                              NOT NULL,
[strCurrencyCode]             VARCHAR(3)                       NOT NULL,
[decShipFullPrice]            DECIMAL(18,2)                    NOT NULL,
[decShipOfferDisc]            DECIMAL(18,2)                    NOT NULL,
[decShipOverride]             DECIMAL(18,2)                    NOT NULL,
[decShipFinal]                DECIMAL(18,2)                    NOT NULL,
[decShipTax]                  DECIMAL(18,2)                    NOT NULL,
[strBCCurrencyCode]           VARCHAR(3)                       NOT NULL,
[decBCShipFullPrice]          DECIMAL(18,4)                    NOT NULL,
[decBCShipOfferDisc]          DECIMAL(18,4)                    NOT NULL,
[decBCShipOverride]           DECIMAL(18,4)                    NOT NULL,
[decBCShipFinal]              DECIMAL(18,4)                    NOT NULL,
[decBCShipTax]                DECIMAL(18,4)                    NOT NULL,
[decTotalAmount]              DECIMAL(18,2)                    NOT NULL,
[decBCTotalAmount]            DECIMAL(18,4)                    NOT NULL,
[decWrittenTotalAmount]       DECIMAL(18,2)                        NULL,
[decBCWrittenTotalAmount]     DECIMAL(18,4)                        NULL,
[blnProRataShipping]          BIT                              NOT NULL,
[blnChargeWithFirstShipment]  BIT                              NOT NULL,
[sintShippingServiceLevelID]  SMALLINT                         NOT NULL,
[sintShippingMethodID]        SMALLINT                         NOT NULL,
[sdtmDoNotShipUntil]          SMALLDATETIME                        NULL,
[blnHoldUntilComplete]        BIT                              NOT NULL,
[tsRowVersion]                TIMESTAMP                            NULL,
CONSTRAINT   [PK_tblBOrder]  
PRIMARY KEY CLUSTERED    
([strBxOrderNo] asc) WITH FILLFACTOR = 100)

GO

CREATE NONCLUSTERED INDEX 
[IX_tblBOrder__lngAccountAddressID] 
   ON [dbo].[tblBorder] 
   ([lngAccountAddressID] asc, [sintOrderStatusID] asc)
   WITH FILLFACTOR = 100

CREATE NONCLUSTERED INDEX 
[IX_tblBOrder__lngAccountParticipantID] 
   ON [dbo].[tblBorder] 
   ([lngAccountParticipantID] asc)
   WITH FILLFACTOR = 100

CREATE NONCLUSTERED INDEX 
[IX_tblBOrder__lngOrderedByAddressID] 
   ON [dbo].[tblBorder] 
   ([lngOrderedByAddressID] asc, [sintOrderStatusID] asc)
   WITH FILLFACTOR = 100

CREATE NONCLUSTERED INDEX 
[IX_tblBOrder__lngOrderedByParticipantID] 
   ON [dbo].[tblBorder] ([lngOrderedByParticipantID] asc)
   WITH FILLFACTOR = 100

CREATE NONCLUSTERED INDEX 
[IX_tblBOrder__lngShippedToParticipantID] 
   ON [dbo].[tblBorder] 
   ([lngShippedToParticipantID] asc)
   WITH FILLFACTOR = 100

CREATE NONCLUSTERED INDEX 
[IX_tblBOrder__lngShipToAddressID] 
   ON [dbo].[tblBorder] 
   ([lngShipToAddressID] asc, [sintOrderStatusID] asc)
   WITH FILLFACTOR = 100

CREATE NONCLUSTERED INDEX 
[IX_tblBOrder__sdtmOrdCreated_sintMarketID__include_strBxOrderNo] 
   ON [dbo].[tblBorder] 
   ([sdtmOrdCreated] asc, [sintMarketID] asc)
   INCLUDE ([strBxOrderNo])
   WITH FILLFACTOR = 100

CREATE NONCLUSTERED INDEX 
[IX_tblBOrder_sdtmOrdCreated_INCL] 
   ON [dbo].[tblBorder] 
   ([sdtmOrdCreated] asc)
   INCLUDE ([decBCShipFinal], [decBCShipFullPrice], 
            [decBCShipOfferDisc], [decBCShipOverride], 
            [decBCShipTax], [decBCTotalAmount], [decBCWrittenTotalAmount], 
            [decShipFinal], [decShipFullPrice], [decShipOfferDisc], 
            [decShipOverride], [decShipTax], [decTotalAmount], 
            [decWrittenTotalAmount], [lngAccountParticipantID], 
            [lngOrderedByParticipantID], [sintMarketID], 
            [sintOrderChannelID], [sintOrderStatusID], 
            [sintOrderTypeID], [strBxOrderNo], [strCurrencyCode], 
            [strOfferCode], [strOrderKey])
   WITH FILLFACTOR = 100

CREATE NONCLUSTERED 
INDEX [IX_tblBOrder_sintMarketID_sdtmOrdCreated] 
   ON [dbo].[tblBorder] 
   ([sintMarketID] asc, [sdtmOrdCreated] asc)
   INCLUDE ([sintOrderChannelID], [strBxOrderNo])
   WITH FILLFACTOR = 100

CREATE NONCLUSTERED 
INDEX [IX_tblBOrder__sintOrderChannelID_sdtmOrdCreated_INCL] 
   ON [dbo].[tblBorder] 
   ([sintOrderChannelID] asc, [sdtmOrdCreated] asc)
   INCLUDE ([decBCShipFinal], [decBCShipFullPrice], 
   [decBCShipTax], [decShipFinal], [decShipFullPrice], 
   [decShipTax], [lngAccountParticipantID], [sintMarketID], 
   [sintOrderTypeID], [strBxOrderNo], 
   [strCurrencyCode], [strOrderKey])
   WITH FILLFACTOR = 100

CREATE NONCLUSTERED INDEX [IX_tblBOrder_strBxOrderNo_sdtmOrdCreated_incl] 
   ON [dbo].[tblBorder] ([strBxOrderNo] asc, 
   [sdtmOrdCreated] asc)
   INCLUDE ([sintOrderChannelID], [sintOrderTypeID], [sintMarketID], 
   [strOrderKey], [lngAccountParticipantID], [strCurrencyCode], 
   [decShipFullPrice], [decShipFinal], [decShipTax], 
   [decBCShipFullPrice], [decBCShipFinal], 
   [decBCShipTax])

Conclusão

Apliquei meu índice no sistema LIVE e atualizei meu procedimento armazenado para usar SMALLDATETIME, a fim de corresponder os tipos de dados no banco de dados para as colunas envolvidas.

Após isso, ao olhar o plano de consulta vejo a imagem abaixo:

insira a descrição da imagem aqui

insira a descrição da imagem aqui

era exatamente como eu queria que fosse.

Acho que o otimizador de consulta, neste caso , fez um bom trabalho para obter o melhor plano de consulta em ambos os ambientes e estou feliz por não ter adicionado nenhuma dica de consulta.

Aprendi com as 3 respostas postadas. obrigado a Max Vernon , Paul White e Daniel Hutmacher por suas respostas.

sql-server performance

3 respostas

  1. Best Answer

    If you want good results from the query optimizer, it pays to be careful about data types.

    Your variables are typed as datetime2:

    DECLARE @OrderStartDate datetime2 = '27 feb 2016';
DECLARE @OrderEndDate  datetime2 = '28 feb 2016';

    But the column these are compared to is typed smalldatetime (as the sdtm prefix suggests!):

    [sdtmOrdCreated] SMALLDATETIME NOT NULL

    The type incompatibility makes it hard for the optimizer to work out the resulting cardinality estimate through a type conversion, as shown in the execution plan xml:

    <ScalarOperator ScalarString="GetRangeWithMismatchedTypes([@OrderStartDate],NULL,(22))">
<ScalarOperator ScalarString="GetRangeWithMismatchedTypes(NULL,[@OrderEndDate],(10))">

    The current estimate may or may not be accurate (probably not). Fixing the type incompatibility may or may not completely solve your plan selection problem, but it is the first (easy!) thing I would fix before looking deeper into the issue:

    DECLARE @OrderStartDate smalldatetime = CONVERT(smalldatetime, '20160227', 112);
DECLARE @OrderEndDate smalldatetime = CONVERT(smalldatetime, '20160228', 112);

    Always check the accuracy of cardinality estimates, and the reason for any discrepancy before deciding to rewrite the query or use hints.

    Consulte meu artigo do SQLblog.com, "buscas dinâmicas e conversões implícitas ocultas" para obter mais detalhes sobre a busca dinâmica.

    Atualização: Corrigir o tipo de dados deu a você o plano de busca que você queria. Os erros de estimativa de cardinalidade causados ​​pela conversão de tipo anterior deram a você o plano mais lento.

    • 16

  2. SQL Server is doing an index scan since it thinks that is cheaper than seeking to each required row. Most likely, SQL Server is correct, given the choices it has in your setup.

    Be aware SQL Server may actually be doing a range scan on the index, as opposed to scanning the entire index.

    If you provide the DDL for both tables, along with the other indexes you may have, we may be able to help you make this much less resource intensive.

    As a side note, never ever use date literals like that. Instead of:

    DECLARE @OrderStartDate DATETIME2 = '27 feb 2016';
DECLARE @OrderEndDate  DATETIME2 = '28 feb 2016';

    use this:

    DECLARE @OrderStartDate DATETIME2 = '2016-02-27T00:00:00.0000';
DECLARE @OrderEndDate  DATETIME2 = '2016-02-28T00:00:00.0000';

    Aaron's post may help clarify that.

    • 11

  3. To add to Max's answer, I would probably try to split your query into two parts:

    DECLARE @OrderStartDate DATETIME2 = {d '2016-02-27'};
DECLARE @OrderEndDate   DATETIME2 = {d '2016-02-28'};

--- Work variable declarations:
DECLARE @minOrderNo varchar(20), @maxOrderNo varchar(20);

--- Find the lowest and highest order number respectively for
--- your date range:
SELECT @minOrderNo=MIN(strBxOrderNo),
       @maxOrderNo=MAX(strBxOrderNo)
FROM    dbo.tblBOrder o
WHERE   o.sdtmOrdCreated >= @OrderStartDate AND
        o.sdtmOrdCreated <  @OrderEndDate;

--- Join orders and order items on their respective clustering keys.
SELECT    o.strBxOrderNo
        , o.sintOrderStatusID
        , o.sintOrderChannelID
        , o.sintOrderTypeID
        , o.sdtmOrdCreated
        , o.sintMarketID
        , o.strOrderKey
        , o.strOfferCode
        , o.strCurrencyCode
        , o.decBCShipFullPrice
        , o.decBCShipFinal
        , o.decBCShipTax
        , o.decBCTotalAmount
        , o.decWrittenTotalAmount
        , o.decBCWrittenTotalAmount
        , o.decBCShipOfferDisc
        , o.decBCShipOverride
        , o.decTotalAmount
        , o.decShipTax
        , o.decShipFinal
        , o.decShipOverride
        , o.decShipOfferDisc
        , o.decShipFullPrice
        , o.lngAccountParticipantID
        , CONVERT(DATE, o.sdtmOrdCreated, 120) as OrderCreatedDateConverted
FROM dbo.tblBOrder AS o
INNER /*MERGE*/ JOIN dbo.tblBOrderItem AS oi ON
    o.strBxOrderNo>=@minOrderNo AND      --- OrderNo filter on "orders"
    o.strBxOrderNo<=@maxOrderNo AND
    oi.strBxOrderNo=o.strBxOrderNo AND   --- Equijoin
    oi.strBxOrderNo>=@minOrderNo AND     --- OrderNo filter on "order items"
    oi.strBxOrderNo<=@maxOrderNo AND
    oi.decCatItemPrice > 0               --- Item price filter on "order items"
OPTION (RECOMPILE);

    This query will (a) eliminate the Sort operator (which is expensive because it is blocking and requires a memory grant), (b) create a Merge Join (which you could force with a join hint, but it should happen automatically with enough data). As a bonus, it'll also (c) eliminate the Index Scan.

    All in all, the MIN/MAX query uses a highly optimal index on the Orders table to identify a range of order numbers (included in the clustering key) from a non-clustered index on the date column:

    Plano de consulta MIN/MAX

    Then, you can Merge Join the two tables on their respective clustered indexes:

    Mesclar Junção de pedidos e itens de pedidos

    Obviously, I don't have your data to test with, but I imagine this should be a really well-performing solution.

    • 6

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