The strategy selected by the query optimiser to process a query.
6
votes
2answers
303 views
Code creates different plan when ran ad-hoc vs. in a stored procedure
I have a delete statement that is using a bad plan when run inside a stored procedure, but is choosing a much better plan when run ad-hoc.
I have rebuilt all the indexes for the tables used by the ...
2
votes
1answer
232 views
Postgres planer JOIN removal
I have two tables, one contains a lot of rarely update data, and one contains a little of frequently update data. Every record in second table has corresponding record in the first, like following:
...
2
votes
2answers
403 views
Clustered monotonically increased index insert performance
I have a table with field Id (bigint, IDENTITY) as primary key and clustered index on it.
I inserted 400 rows and saw execution plan. I got: the relative query cost for this insertion 36% and for this ...
1
vote
1answer
583 views
What I can do to speed up Key Lookup in my Query
I am using SQL2005 and against them I calling query simila to this
declare @art table (id int primary key, naziv varchar(35) null, sifra varchar(15) null, jm int null);
insert ...
2
votes
1answer
490 views
View SQL 2008 sp_cursorexecute Underlying Query and Execution Plan
I'm performance tuning a Dynamics AX application and see in a SQL trace a long-running, high-I/O query of the form exec sp_cursorexecute 1073742882 ... When I try and run that query in a new SQL ...
5
votes
1answer
312 views
The use of NOT logic in relation to indexes
According to MSFT's book on database development Exam 70-433: Microsoft SQL Server 2008 Database Development:
Neither leading wildcard characters not NOT logic allow the query optimizer to use ...
4
votes
1answer
293 views
how to improve performance by using or not using table variables
I have a table variable:
DECLARE @to_process TABLE
(
[Id] [bigint] NOT NULL,
[SequenceId] [bigint] NOT NULL,
...
)
INSERT INTO @to_process
( Id
, SequenceId
...
)
SELECT
...
14
votes
3answers
7k views
Execution Plan Basics — Hash Match Confusion
I am starting to learn execution plans and am confused about how exactly a hash match works and why it would be used in a simple join:
select Posts.Title, Users.DisplayName
From Posts JOIN Users on
...
2
votes
3answers
604 views
How does NHibernate handle execution plan?
I heard from a podcast that there are no ORMs that have a good solution for execution plan reuse. It will lead to increased execution plan cache which affects the performance.
How does NHibernate ...
4
votes
4answers
720 views
When is a full table scan better than index scan?
What are some scenarios (in SQL Server) in which a full table scan is better than an index scan?
16
votes
2answers
928 views
Guide to reading, comparing, and interpretting Execution Plans in SQL Server
I'm looking for a good, well-written and explained guide on reading and comparing execution plans in SQL Server. This is for more my own edification as well as for sharing with others.
If you want ...
