473,605 Members | 2,455 Online
Bytes | Software Development & Data Engineering Community
+ Post

Home Posts Topics Members FAQ

Dynamic Cursor versus Forward Only Cursor gives Poor Performance

Hello,

I have a test database with table A containing 10,000 rows and a table
B containing 100,000 rows. Rows in B are "children" of rows in A -
each row in A has 10 related rows in B (ie. B has a foreign key to A).

Using ODBC I am executing the following loop 10,000 times, expressed
below in pseudo-code:

"select * from A order by a_pk option (fast 1)"
"fetch from A result set"
"select * from B where where fk_to_a = 'xxx' order by b_pk option
(fast 1)"
"fetch from B result set" repeated 10 times

In the above psueod-code 'xxx' is the primary key of the current A
row. NOTE: it is not a mistake that we are repeatedly doing the A
query and retrieving only the first row.

When the queries use fast-forward-only cursors this takes about 2.5
minutes. When the queries use dynamic cursors this takes about 1 hour.

Does anyone know why the dynamic cursor is killing performance?
Because of the SQL Server ODBC driver it is not possible to have
nested/multiple fast-forward-only cursors, hence I need to explore
other alternatives.

I can only assume that a different query plan is getting constructed
for the dynamic cursor case versus the fast forward only cursor, but I
have no way of finding out what that query plan is.

All help appreciated.

Kevin
Jul 20 '05 #1
1 7401
Please explain what you are trying to do here. Cursors are usually best
avoided and typically perform much less efficiently than set-based
solutions. If you describe the problem in more detail someone should be able
to suggest an alternative that doesn't use a cursor. Post DDL (CREATE TABLE
statements), some sample data (INSERT statements) and show your required
result.

--
David Portas
SQL Server MVP
--
Jul 20 '05 #2

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

1
7680
by: Jim | last post by:
I having a difficult time here trying to figure out what to do here. I need a way to scroll through a recordset and display the results with both forward and backward movement on a web page(PHP using ADO/COM).. I know that if I use a client side cursor all the records get shoved to the client everytime that stored procedure is executed..if this database grows big wont that be an issue?.. I know that I can set up a server side cursor...
2
1464
by: Richard | last post by:
Hi all, I had a stored procedure that i wanted to be able to pass parameters to so i used dynamic SQL. I am getting very strange errors though when i try to execute it. My code works just fine, but when i add the dynamic sql parts in, it gives the strangest errors. Here is the code that executes it... Declare @data_source varchar(50)
5
3815
by: Ralph | last post by:
Hi all, I'm a newbie to MS-SQL UDFs and seem to have a real big problem. I need to implement a logic to receive an adress build out of various user definable fields from various user defined tables. The function is already implemented in the Client software and as UDF-compliant in MySQL and Oracle. Now there's just MS-SQL left... The problem now is for sure, I'm in need of a scalar return value (a varchar) composed out of a dynamic...
0
1557
by: Shailesh | last post by:
If I'm not mistaken, C++ doesn't have support for dynamic class members. I'm considering if such a facility would be useful, and what method would make a good workaround. I have a generic buffer class, which can have one or more cursor classes attached to it. Right now, they are both separate classes, and I use them as follows: class Buffer { ...
5
6172
by: Todd Huish | last post by:
I have noticed something disturbing when retrieving datasets over a relatively slow line (multiple T1). I am looking at about 25 seconds to retrieve 500 rows via a php-odbc link. This same select from the cli is for all intents practicaly instantaneous. After much research I discovered that PHP by default uses a dynamic cursor type which can be quite a bit slower than a forward only cursor. BTW I have been searching forward only/read...
3
9625
by: JDPope | last post by:
I have a situation which I cannot get a good lead on how to resolve. One of the applications I support uses the Hibernate software to generate SQL. The app is JAVA with JDBC. In testing the users see no problems and think the app is running okay. I turned a database monitor on the app and see that the database is getting SQL return coes of -301 for a variety of database accesses (some times the same access works, okay other times -301)....
7
3382
by: serge | last post by:
How can I run a single SP by asking multiple sales question either by using the logical operator AND for all the questions; or using the logical operator OR for all the questions. So it's always either AND or OR but never mixed together. We can use Northwind database for my question, it is very similar to the structure of the problem on the database I am working on. IF(SELECT OBJECT_ID('REPORT')) IS NOT NULL DROP TABLE REPORT_SELECTION
13
5015
by: JayCallas | last post by:
I know this question has been asked. And the usual answer is don't use cursors or any other looping method. Instead, try to find a solution that uses set-based queries. But this brings up several questions / senarios: * I created several stored procedures that take parameters and inserts the data into the appropriate tables. This was done for easy access/use from client side apps (i.e. web-based).
7
6545
by: P. Adhia | last post by:
Sorry for quoting an old post and probably I am reading out of context so my concern is unfounded. But I would appreciate if I can get someone or Serge to confirm. Also unlike the question asked in the post below, my question involves non-partitioned table loads. I want to know if, in general, loading from cursor is slower than loading from a file? I was thinking cursor would normally be faster, because of DB2's superior buffer/prefetch...
0
8423
Oralloy
by: Oralloy | last post by:
Hello folks, I am unable to find appropriate documentation on the type promotion of bit-fields when using the generalised comparison operator "<=>". The problem is that using the GNU compilers, it seems that the internal comparison operator "<=>" tries to promote arguments from unsigned to signed. This is as boiled down as I can make it. Here is my compilation command: g++-12 -std=c++20 -Wnarrowing bit_field.cpp Here is the code in...
0
8411
jinu1996
by: jinu1996 | last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven tapestry of website design and digital marketing. It's not merely about having a website; it's about crafting an immersive digital experience that captivates audiences and drives business growth. The Art of Business Website Design Your website is...
1
8067
by: Hystou | last post by:
Overview: Windows 11 and 10 have less user interface control over operating system update behaviour than previous versions of Windows. In Windows 11 and 10, there is no way to turn off the Windows Update option using the Control Panel or Settings app; it automatically checks for updates and installs any it finds, whether you like it or not. For most users, this new feature is actually very convenient. If you want to control the update process,...
0
8281
tracyyun
by: tracyyun | last post by:
Dear forum friends, With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each protocol has its own unique characteristics and advantages, but as a user who is planning to build a smart home system, I am a bit confused by the choice of these technologies. I'm particularly interested in Zigbee because I've heard it does some...
0
6740
agi2029
by: agi2029 | last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing, and deployment—without human intervention. Imagine an AI that can take a project description, break it down, write the code, debug it, and then launch it, all on its own.... Now, this would greatly impact the work of software developers. The idea...
0
3956
by: adsilva | last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?
1
2437
by: 6302768590 | last post by:
Hai team i want code for transfer the data from one system to another through IP address by using C# our system has to for every 5mins then we have to update the data what the data is updated we have to send another system
1
1530
muto222
by: muto222 | last post by:
How can i add a mobile payment intergratation into php mysql website.
0
1270
bsmnconsultancy
by: bsmnconsultancy | last post by:
In today's digital era, a well-designed website is crucial for businesses looking to succeed. Whether you're a small business owner or a large corporation in Toronto, having a strong online presence can significantly impact your brand's success. BSMN Consultancy, a leader in Website Development in Toronto offers valuable insights into creating effective websites that not only look great but also perform exceptionally well. In this comprehensive...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.