Questions tagged [optimizer-hints]
36 questions
36
votes
4 answers
Does GCC inline C++ functions without the 'inline' keyword?
Does GCC, when compiling C++ code, ever try to optimize for speed by choosing to inline functions that are not marked with the inline keyword?
Carl Seleborg
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13
votes
2 answers
What can happen as a result of using (nolock) on every SELECT in SQL Server?
I get that the (nolock) optimizer hint allows for "dirty reads", but under what very specific scenarios is this a bad idea? I've never seen such widespread use of (nolock) in an organization, and it makes me nervous. I'd like an explanation in terms…
Chris McCall
- 10,317
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4
votes
0 answers
How to use rowlock and readpast with NHibernate?
I have an application which currently reads data from a table using the following stored procedure:
CREATE PROCEDURE [dbo].[GetBatchOfEmails]
@BatchSize INT
AS
BEGIN
SET NOCOUNT ON;
WITH ResultSet AS
(
SELECT TOP(@BatchSize)…
Øyvind
- 1,600
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4
votes
2 answers
Oracle optimizer hints xmlagg function
I have a function which calls several tables / views etc. with a few xmlaggs of the data.
For some reason I am getting a performance increase when I am pulling in additional information even though this extra information isn't used for the rest of…
bob dylan
- 1,458
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3
votes
2 answers
How to compile and start VSC++ Projects Faster?
What techniques do you use to compile and start VSC++ projects fast?
For us, especially the loading of all the dlls take a long time. Is there a way to speed this up? The project loads a ton of .dlls and some of them are especially slow.
Now that we…
Tony
- 417
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- 11
3
votes
1 answer
Stored procedures and OPTIMIZE FOR UNKNOWN
I've read up on the SQL Server 2008 OPTIMIZE FOR UNKNOWN query hint. I understand how it works.
However, I have a question on where and when to use it. It cannot be specified inside a UDF. It can be specified inside a stored proc. However, this MSDN…
IamIC
- 17,747
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3
votes
0 answers
Indexes hints in a Subquery
I have a SQL statement that has performance issues.
Adding the following index and a SQL hint to use the index improves the performance 10 fold but I do not understand why.
BUS_ID is part of the primary key(T1.REF is the other part fo the key) and…
Medu
- 135
- 2
- 10
3
votes
2 answers
How do I force access by index rowid in Oracle?
I need help forcing Oracle to always use table access by index row id on table "r_rapport" (~60k rows) to subsequently avoid full table scans on "r_attributfeld" (~8m rows) . I have a query resulting in the following…
Thaylon
- 453
- 5
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3
votes
2 answers
Parallel Execution of Procedures in SQL Statement (Oracle 11g)
I have a SQL-Statement which uses a Check-Function which takes a quite long time for execution.
Now I want to Parallize the execution of the Check-Function, but it does not work.
Where is the mistake I made?
The sample below takes 5 Seconds to…
bernhard.weingartner
- 495
- 5
- 23
2
votes
2 answers
Optimizing simple search script in PowerShell
I need to create a script to search through just below a million files of text, code, etc. to find matches and then output all hits on a particular string pattern to a CSV file.
So far I made this;
$location = 'C:\Work*'
$arr = "foo", "bar" #Where…
cc0
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2
votes
3 answers
__builtin_expect from GCC with probability
__builtin_expect from GCC can be used by programmer to show which variants are expected to be very often and which are rare. But __builtin_expect have only "true" and "false" (0% or 100% probability)
For some big projects it is vary hard to get…
osgx
- 90,338
- 53
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2
votes
1 answer
Oracle 11g INDEX_SS Hint
Given a table with columns A, B, and C of type CHAR(15) and an unique index
If I have a query with a WHERE clause specifying A and C, oracle's optimizer chooses to do an index range scan. But if I know that the cardinality of B is low, should I…
Tony Meng
- 353
- 4
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2
votes
2 answers
Convincing the Oracle SQL optimizer that an indexed (though non-UNIQUE) column actually contains unique values in practice
I am writing a view that uses a column with a non-UNIQUE index on it. However, within the context of my view, I am confident that the column will only contain unique values (due to the conditions imposed in the WHERE clause).
The real problem…
Adam Paynter
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1
vote
1 answer
What is the best way to fix a Oracle Query performance in production? Changing application code? Using plan baseline?
Let's assume there is a C++ application executing a specific SQL query on Oracle database.
This query was working fine for last couple of years in production at a customer's environment, but suddenly one fine day the query started taking around 10x…
Jackie
- 11
- 1
1
vote
1 answer
Is there a way to monitor optimizer's step in Pytorch?
Consider that you are using a Pytorch optimizer such as torch.optim.Adam(model_parameters).
So in your training loop you will have something like:
optimizer = torch.optim.Adam(model_parameters)
# put the training loop…
White
- 305
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