RE: Simple SQL Query sometimes really Slow?
Brooke, Couple of points of inquiry. 1) 50k records can be a little OR a lot. How much actual data is returned. Is a lot of textual? Management studio might look really fast but the problem could be a lot of character data buffering to the web server. 2) have you looked at the activity monitor? Filter by your connection and watch for blocks or waits - taking note of the process blocking. 3) Indexing might be ok but maybe not. Take a look at the execution plan in Management Studio - it can tell you what the most expensive operations of the query are. 4) Double check parallelism on the server. This can bite you under certain conditions and will result in what look like randomly slow queries with no seeming blocks. See my blog post about it: http://www.coldfusionmuse.com/index.cfm/2011/11/18/cf.mssql.parallelism Hope this helps a little. Good luck! -mark -Original Message- From: Brook Davies [mailto:cft...@logiforms.com] Sent: Thursday, December 05, 2013 11:26 AM To: cf-talk Subject: Simple SQL Query sometimes really Slow? This may not be the right place to post this (man, CF-TALK has changed a lot in the last 5 or so years ;)). I have a simple SQL query that is showing up as running slow. When I run it via the Management Studio it is sometimes fast 0.1 seconds and sometimes, seemingly randomly slow 1.5 minutes!). Other queries on other tables are executing normally. This table only has 50k records and even a simple query is sometimes really slow. The query that runs slow is as simple as select commitDate,id from databaseChangeLog where usr_id = 62622 and form_id = 312468 and commitDate '2013-12-04 11:00:05.0' But is just as slow without the date part. The table has a clustered index on the primary key (id) and a non-clustered index on usr_id,form_id and commitDate. The index doesn't seem to make any difference. My guess is the table is locked. My question is: How can I determine if it is locked? What would be locking it. I checked all my code and there are no CFTRANSACTIONS or ISOLATED READS or anything like that. There are some inserts and the table has 2 TEXT columns which are being updated at times with fairly large values. But the only queries reported as slow are these simple SELECTS. The query execution plan uses the non-clustered index on (usr_id,form_id and commitDate). I'm just at a loss as to why this specific query is sometimes so slow.. where to look? Brook ~| Order the Adobe Coldfusion Anthology now! http://www.amazon.com/Adobe-Coldfusion-Anthology/dp/1430272155/?tag=houseoffusion Archive: http://www.houseoffusion.com/groups/cf-talk/message.cfm/messageid:357290 Subscription: http://www.houseoffusion.com/groups/cf-talk/subscribe.cfm Unsubscribe: http://www.houseoffusion.com/groups/cf-talk/unsubscribe.cfm
Re: Simple SQL Query sometimes really Slow?
Just for clarification, do you have a unique index with the three non-primary columns, or are those indexed individually? If individually, I would suggest a combined index, at least of the usr_id and form_id columns, as those are numeric values and then a separate index of the date column. Ive found mixing datatypes within an index usually doesnt gain much in query performance. Since 2008, SQL Server has the default Lock Escalation setting as Table, which means that the processing of large updates will lock to the table. You can see the specifics of whats happening under-the-hood with each of the escalation settings here: http://msdn.microsoft.com/en-us/library/ms190273.aspx You might try setting Lock Escallation to DISABLE and see if that resolves the issue. You can also turn on Snapshot Isolation to allow your reads to proceed, even when large updates are happening: http://msdn.microsoft.com/en-us/library/tcbchxcb%28VS.80%29.aspx HTH, Jon On Dec 5, 2013, at 12:26 PM, Brook Davies cft...@logiforms.com wrote: This may not be the right place to post this (man, CF-TALK has changed a lot in the last 5 or so years ;)). I have a simple SQL query that is showing up as running slow. When I run it via the Management Studio it is sometimes fast 0.1 seconds and sometimes, seemingly randomly slow 1.5 minutes!). Other queries on other tables are executing normally. This table only has 50k records and even a simple query is sometimes really slow. The query that runs slow is as simple as select commitDate,id from databaseChangeLog where usr_id = 62622 and form_id = 312468 and commitDate '2013-12-04 11:00:05.0' But is just as slow without the date part. The table has a clustered index on the primary key (id) and a non-clustered index on usr_id,form_id and commitDate. The index doesn't seem to make any difference. My guess is the table is locked. My question is: How can I determine if it is locked? What would be locking it. I checked all my code and there are no CFTRANSACTIONS or ISOLATED READS or anything like that. There are some inserts and the table has 2 TEXT columns which are being updated at times with fairly large values. But the only queries reported as slow are these simple SELECTS. The query execution plan uses the non-clustered index on (usr_id,form_id and commitDate). I'm just at a loss as to why this specific query is sometimes so slow.. where to look? Brook ~| Order the Adobe Coldfusion Anthology now! http://www.amazon.com/Adobe-Coldfusion-Anthology/dp/1430272155/?tag=houseoffusion Archive: http://www.houseoffusion.com/groups/cf-talk/message.cfm/messageid:357291 Subscription: http://www.houseoffusion.com/groups/cf-talk/subscribe.cfm Unsubscribe: http://www.houseoffusion.com/groups/cf-talk/unsubscribe.cfm
re: Simple SQL Query sometimes really Slow?
There are a couple of queries that you can run while your query is
executing to see if there is anything else running that is blocking the
execution. The first will show all running activities and identify if any
are blocking one another. The second is just a handy script to see what's
running currently.
/*** Find blocking SPIDS
***/ SELECT s.spid, BlockingSPID =
s.blocked, DatabaseName = DB_NAME(s.dbid), s.program_name,
s.loginame, ObjectName = OBJECT_NAME(objectid, s.dbid), Definition =
CAST(text AS VARCHAR(MAX)) FROM sys.sysprocesses sCROSS APPLY
sys.dm_exec_sql_text (sql_handle) WHERE s.spid 50
/*** Find all running queries
***/ SELECT sqltext.TEXT,
req.session_id, req.status, req.command, req.cpu_time,
req.total_elapsed_time FROM sys.dm_exec_requests req CROSS APPLY
sys.dm_exec_sql_text(sql_handle) AS sqltext
If these don't show anything blocking your query, you may want to look at
using query hints to force the use of a particular index. SQLServer will
somtimes choose a poor execution plan. You can give it hints on which
index to use at the table level using something like the following: SELECT
* FROM tablename WITH (INDEX({indexname})) WHERE . A good primer on
using index hints can be found here:
http://blog.sqlauthority.com/2009/02/08/sql-server-introduction-to-force-ind
ex-query-hints-index-hint-part2/
Hope this helps,
-- Jeff
Original Message
From: Brook Davies cft...@logiforms.com
Sent: Thursday, December 05, 2013 10:27 AM
To: cf-talk cf-talk@houseoffusion.com
Subject: Simple SQL Query sometimes really Slow?
This may not be the right place to post this (man, CF-TALK has changed a
lot
in the last 5 or so years ;)).
I have a simple SQL query that is showing up as running slow. When I run
it
via the Management Studio it is sometimes fast 0.1 seconds and
sometimes,
seemingly randomly slow 1.5 minutes!). Other queries on other tables are
executing normally. This table only has 50k records and even a simple
query
is sometimes really slow.
The query that runs slow is as simple as
select commitDate,id from databaseChangeLog
where usr_id = 62622 and form_id = 312468
and commitDate '2013-12-04 11:00:05.0'
But is just as slow without the date part. The table has a clustered
index
on the primary key (id) and a non-clustered index on usr_id,form_id and
commitDate. The index doesn't seem to make any difference.
My guess is the table is locked. My question is:
How can I determine if it is locked? What would be locking it. I checked
all
my code and there are no CFTRANSACTIONS or ISOLATED READS or anything
like
that. There are some inserts and the table has 2 TEXT columns which are
being updated at times with fairly large values. But the only queries
reported as slow are these simple SELECTS. The query execution plan uses
the
non-clustered index on (usr_id,form_id and commitDate).
I'm just at a loss as to why this specific query is sometimes so slow..
where to look?
Brook
~|
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Re: Simple SQL Query sometimes really Slow?
for analyzing the execution plan, check out SQL Sentry Plan Explorer. They have a free version, and it's a much better tool for execution plan analysis than Management Studio On Thu, Dec 5, 2013 at 10:03 AM, Mark A Kruger mkru...@cfwebtools.comwrote: Brooke, Couple of points of inquiry. 1) 50k records can be a little OR a lot. How much actual data is returned. Is a lot of textual? Management studio might look really fast but the problem could be a lot of character data buffering to the web server. 2) have you looked at the activity monitor? Filter by your connection and watch for blocks or waits - taking note of the process blocking. 3) Indexing might be ok but maybe not. Take a look at the execution plan in Management Studio - it can tell you what the most expensive operations of the query are. 4) Double check parallelism on the server. This can bite you under certain conditions and will result in what look like randomly slow queries with no seeming blocks. See my blog post about it: http://www.coldfusionmuse.com/index.cfm/2011/11/18/cf.mssql.parallelism Hope this helps a little. Good luck! -mark -Original Message- From: Brook Davies [mailto:cft...@logiforms.com] Sent: Thursday, December 05, 2013 11:26 AM To: cf-talk Subject: Simple SQL Query sometimes really Slow? This may not be the right place to post this (man, CF-TALK has changed a lot in the last 5 or so years ;)). I have a simple SQL query that is showing up as running slow. When I run it via the Management Studio it is sometimes fast 0.1 seconds and sometimes, seemingly randomly slow 1.5 minutes!). Other queries on other tables are executing normally. This table only has 50k records and even a simple query is sometimes really slow. The query that runs slow is as simple as select commitDate,id from databaseChangeLog where usr_id = 62622 and form_id = 312468 and commitDate '2013-12-04 11:00:05.0' But is just as slow without the date part. The table has a clustered index on the primary key (id) and a non-clustered index on usr_id,form_id and commitDate. The index doesn't seem to make any difference. My guess is the table is locked. My question is: How can I determine if it is locked? What would be locking it. I checked all my code and there are no CFTRANSACTIONS or ISOLATED READS or anything like that. There are some inserts and the table has 2 TEXT columns which are being updated at times with fairly large values. But the only queries reported as slow are these simple SELECTS. The query execution plan uses the non-clustered index on (usr_id,form_id and commitDate). I'm just at a loss as to why this specific query is sometimes so slow.. where to look? Brook ~| Order the Adobe Coldfusion Anthology now! http://www.amazon.com/Adobe-Coldfusion-Anthology/dp/1430272155/?tag=houseoffusion Archive: http://www.houseoffusion.com/groups/cf-talk/message.cfm/messageid:357293 Subscription: http://www.houseoffusion.com/groups/cf-talk/subscribe.cfm Unsubscribe: http://www.houseoffusion.com/groups/cf-talk/unsubscribe.cfm
Re: Simple SQL Query sometimes really Slow?
Could never figure this out, but we had a similar issue on 2005 with a date time column. I remember we changed from a cfquery to a stored procedure and it was resolved. Byron Mann Lead Engineer Architect HostMySite.com On Dec 5, 2013 12:27 PM, Brook Davies cft...@logiforms.com wrote: This may not be the right place to post this (man, CF-TALK has changed a lot in the last 5 or so years ;)). I have a simple SQL query that is showing up as running slow. When I run it via the Management Studio it is sometimes fast 0.1 seconds and sometimes, seemingly randomly slow 1.5 minutes!). Other queries on other tables are executing normally. This table only has 50k records and even a simple query is sometimes really slow. The query that runs slow is as simple as select commitDate,id from databaseChangeLog where usr_id = 62622 and form_id = 312468 and commitDate '2013-12-04 11:00:05.0' But is just as slow without the date part. The table has a clustered index on the primary key (id) and a non-clustered index on usr_id,form_id and commitDate. The index doesn't seem to make any difference. My guess is the table is locked. My question is: How can I determine if it is locked? What would be locking it. I checked all my code and there are no CFTRANSACTIONS or ISOLATED READS or anything like that. There are some inserts and the table has 2 TEXT columns which are being updated at times with fairly large values. But the only queries reported as slow are these simple SELECTS. The query execution plan uses the non-clustered index on (usr_id,form_id and commitDate). I'm just at a loss as to why this specific query is sometimes so slow.. where to look? Brook ~| Order the Adobe Coldfusion Anthology now! http://www.amazon.com/Adobe-Coldfusion-Anthology/dp/1430272155/?tag=houseoffusion Archive: http://www.houseoffusion.com/groups/cf-talk/message.cfm/messageid:357294 Subscription: http://www.houseoffusion.com/groups/cf-talk/subscribe.cfm Unsubscribe: http://www.houseoffusion.com/groups/cf-talk/unsubscribe.cfm
RE: Simple SQL Query sometimes really Slow?
Thank you everyone for all your suggestions. Gonna start testing them out. Byron: I have this issue when running the query via management studio and via cfquery so not sure if that is relevant.. Jon: I'm still running 2005 (if it ain't broke...), but was also thinking about trying READ UNCOMMITTED (maybe that would have the same effect as your suggestion?) Mark: The select is only returning a couple of columns (date/int) and no text.. I'll check the activity monitor.. the execution plan shows the index usage and doesn't appear to account for the delays... Jeff: Thanks for the Queries, I'll try them! Whohoo! Cftalk is alive!! Brook -Original Message- From: Byron Mann [mailto:byronos...@gmail.com] Sent: December-05-13 10:22 AM To: cf-talk Subject: Re: Simple SQL Query sometimes really Slow? Could never figure this out, but we had a similar issue on 2005 with a date time column. I remember we changed from a cfquery to a stored procedure and it was resolved. Byron Mann Lead Engineer Architect HostMySite.com On Dec 5, 2013 12:27 PM, Brook Davies cft...@logiforms.com wrote: This may not be the right place to post this (man, CF-TALK has changed a lot in the last 5 or so years ;)). I have a simple SQL query that is showing up as running slow. When I run it via the Management Studio it is sometimes fast 0.1 seconds and sometimes, seemingly randomly slow 1.5 minutes!). Other queries on other tables are executing normally. This table only has 50k records and even a simple query is sometimes really slow. The query that runs slow is as simple as select commitDate,id from databaseChangeLog where usr_id = 62622 and form_id = 312468 and commitDate '2013-12-04 11:00:05.0' But is just as slow without the date part. The table has a clustered index on the primary key (id) and a non-clustered index on usr_id,form_id and commitDate. The index doesn't seem to make any difference. My guess is the table is locked. My question is: How can I determine if it is locked? What would be locking it. I checked all my code and there are no CFTRANSACTIONS or ISOLATED READS or anything like that. There are some inserts and the table has 2 TEXT columns which are being updated at times with fairly large values. But the only queries reported as slow are these simple SELECTS. The query execution plan uses the non-clustered index on (usr_id,form_id and commitDate). I'm just at a loss as to why this specific query is sometimes so slow.. where to look? Brook ~| Order the Adobe Coldfusion Anthology now! http://www.amazon.com/Adobe-Coldfusion-Anthology/dp/1430272155/?tag=houseoffusion Archive: http://www.houseoffusion.com/groups/cf-talk/message.cfm/messageid:357295 Subscription: http://www.houseoffusion.com/groups/cf-talk/subscribe.cfm Unsubscribe: http://www.houseoffusion.com/groups/cf-talk/unsubscribe.cfm
