sql server - Execute query command (dynamic sql) runs faster than ordinary query -

-

why second query execute command runs ~4 times faster first query without one? how can solve problem?

why additional table (workatable) created in second case?

variables:

declare @count int, @followerid bigint set @count=1024 set @followerid=10

first query (usual query):

select top (@count) photo.* photo  exists (select accountid follower follower.followerid=@followerid , follower.accountid = photo.accountid)  , photo.closed='false' order photo.createdate desc

log:

sql server parse , compile time: cpu time = 0 ms, elapsed time = 7 ms.

sql server execution times: cpu time = 0 ms, elapsed time = 0 ms.

table 'photo'. scan count 952, logical reads 542435, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

table 'follower'. scan count 1, logical reads 7, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

sql server execution times: cpu time = 1466 ms, elapsed time = 9620 ms.

execution plan:

first query execution plan

second query (the same query execute):

exec ('select top (' +@count + ') photo.* photo  exists ( select  accountid follower follower.followerid=' +@followerid + ' , follower.accountid = photo.accountid)  , photo.closed=''false'' order photo.createdate desc')

log:

sql server parse , 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 parse , compile time: cpu time = 25 ms, elapsed time = 25 ms.

table 'worktable'. scan count 0, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

table 'photo'. scan count 952, logical reads 542707, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

table 'follower'. scan count 6, logical reads 9, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

table 'worktable'. scan count 0, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

sql server execution times: cpu time = 1374 ms, elapsed time = 2140 ms.

sql server execution times: cpu time = 1405 ms, elapsed time = 2165 ms.

this because second query (depending on context of first query) more optimizable, since variables become inline constants. compare:

declare @count int, @followerid bigint set @count=1024 set @followerid=10  select top (@count) photo.* photo  exists (select accountid follower follower.followerid=@followerid , follower.accountid = photo.accountid)  , photo.closed='false' order photo.createdate desc

with:

select top (1024) photo.* photo  exists (select accountid follower follower.followerid=10 , follower.accountid = photo.accountid)  , photo.closed='false' order photo.createdate desc

this true if first query part of stored proc, variables arguments , particular query optimized different parameter values when stored proc compiled.


Comments

Post a Comment

Popular posts from this blog

ios - RestKit 0.20 — CoreData: error: Failed to call designated initializer on NSManagedObject class (again) -

-
this error has shown on many times, seems. prominent answer issue seems restkit 0.20 — coredata: error: failed call designated initializer on nsmanagedobject class however, solution posted doesn't work me. let's start beginning: i want upload file server. want parse response make sure uploaded. if not, try again later. model has boolean variable called nsnumber *senttoserver purpose (in coredata, bool saved nsnumber ) . because don't know whether sending going successful, save entity coredata model first before sending via restkit. when post request successful, server returns json string this: {"id":14,"created":true} notice that, of course, id not set on coredata model yet, both id , created new informations model. here's model: @interface recording : nsmanagedobject @property (nonatomic, retain) nsstring * audiofilepath; @property (nonatomic, retain) nsdate * createdat; @property (nonatomic, retain) nsstring * deviceid; @...
Read more

java - Digest auth with Spring Security using javaconfig -

-
so i'm trying create digest authentication spring following documentation trying translate xml "requirements" in java requirements. let's have xml in docs: <bean id="digestfilter" class= "org.springframework.security.web.authentication.www.digestauthenticationfilter"> <property name="userdetailsservice" ref="jdbcdaoimpl"/> <property name="authenticationentrypoint" ref="digestentrypoint"/> <property name="usercache" ref="usercache"/> </bean> <bean id="digestentrypoint" class= "org.springframework.security.web.authentication.www.digestauthenticationentrypoint"> <property name="realmname" value="contacts realm via digest authentication"/> <property name="key" value="acegi"/> <property name="noncevalidityseconds" value="10"/> </b...
Read more

laravel - PDOException in Connector.php line 55: SQLSTATE[HY000] [1045] Access denied for user 'root'@'localhost' (using password: YES) -

-
my .env: app_env=local app_debug=true app_key=myappkey app_url=http://localhost db_connection=mysql db_host=localhost db_port=3306 db_database=gestiontaller db_username=root db_password='root' cache_driver=file session_driver=file queue_driver=sync redis_host=127.0.0.1 redis_password=null redis_port=6379 mail_driver=smtp mail_host=mailtrap.io mail_port=2525 mail_username=null mail_password=null mail_encryption=null i've tried password ", ' , without, restarting server every time. i've tried changing localhost 172.0.0.1. yes, password correct, running mysql -u root -p introducing password root in prompt can go mysql. users table: +------------------+-----------+ | user | host | +------------------+-----------+ | debian-sys-maint | localhost | | mysql.sys | localhost | | root | localhost | | root1 | localhost | +------------------+-----------+ i've added homestead.yaml this: database_port: 3306 ...
Read more