我正在开发一个系统,它定期(每天4-5次)运行一个选择语句,通常需要不到10秒,但定期需要40分钟.
该数据库位于Windows Server 2008 + SQL Server 2008 R2上; 都是64位.
运行数据库的计算机上有一个服务,它轮询数据库并为需要它的记录生成值.然后,使用MFC CRecordset类从使用CFC(VS 2010)编写的第二台计算机上的服务中使用多表连接选择来定期查询这些记录,以提取数据.导致问题的查询示例如下所示.
SELECT DISTINCT "JobKeysFrom"."Key" AS "KeyFrom","KeysFrom"."ID" AS "IDFrom",
"KeysFrom"."X" AS "XFrom","KeysFrom"."Y" AS "YFrom","JobKeysTo"."Key" AS "KeyTo",
"KeysTo"."ID" AS "IDTo","KeysTo"."X" AS "XTo","KeysTo"."Y" AS "YTo",
"Matrix"."TimeInSeconds","Matrix"."DistanceInMetres","Matrix"."Calculated"
FROM "JobKeys" AS "JobKeysFrom"
INNER JOIN "JobKeys" AS "JobKeysTo" ON
("JobKeysFrom"."Key"<>"JobKeysTo"."Key") AND
("JobKeysFrom"."JobID"=531) AND
("JobKeysTo"."JobID"=531)
INNER JOIN "Keys" AS "KeysFrom" ON
("JobKeysFrom"."Key"="KeysFrom"."Key") AND ("JobKeysFrom"."Status"=4)
INNER JOIN "Keys" AS "KeysTo" ON
("JobKeysTo"."Key"="KeysTo"."Key") AND ("JobKeysTo"."Status"=4)
INNER JOIN "Matrix" AS "Matrix" ON
("Matrix"."IDFrom"="KeysFrom"."ID") AND ("Matrix"."IDTo"="KeysTo"."ID")
ORDER BY "JobKeysFrom"."Key","JobKeysTo"."Key" …