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GauravBhabu
Advanced Member
4288 Posts |
 Posted - 17 August 2002 : 21:25:42
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quote:
Originally posted by ruirib
In fact I usually use client side cursors for paging, but I'm not sure what is best, speed wise: a client side forward only cursor, or a server side static cursor. Will have to test it later.
A client side forward only cursor will be processed as Client Side Static (or Keyset) Cursor.
You can determine how it was processed by writting
Response.write Recordset.CursorType
This will return a number value associated with the constant.
<Edit>Corrections |
Edited by - GauravBhabu on 17 August 2002 21:29:24 |
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RichardKinser
Snitz Forums Admin
USA
16655 Posts |
Posted - 17 August 2002 : 22:06:32
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| changed it back to adOpenStatic |
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ruirib
Snitz Forums Admin
Portugal
26364 Posts |
Posted - 17 August 2002 : 22:19:47
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quote:
Originally posted by RichardKinser
changed it back to adOpenStatic
Yes, I've just confirmed that whenever you use paging it's better to use server side cursors and use adOpenStatic. I've made some tests both with Access and SQL Server and the difference not being significative, server side cursors are obviously faster.
So I'd stick to adOpenStatic whenever paging is needed.
(Still puzzled as to why Wrox's book uses client side cursors for this. What a stupid thing to suggest...without clarifying why they do it, and the trade-offs involved)
(edited for clarity of meaning) |
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Edited by - ruirib on 17 August 2002 23:41:03 |
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RichardKinser
Snitz Forums Admin
USA
16655 Posts |
Posted - 17 August 2002 : 22:26:10
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| the files on this site have all been updated, so if there was going to be an error, we should see it. |
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ruirib
Snitz Forums Admin
Portugal
26364 Posts |
Posted - 17 August 2002 : 22:39:58
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| The difference will not be that relevant, since the page generation time for topic.asp is very small but the code for the Jump To Last Topic could also be changed to reflect these changes, that is, comment or remove the line that makes the cursor a client one and open the recordset as adOpenStatic. |
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RichardKinser
Snitz Forums Admin
USA
16655 Posts |
Posted - 17 August 2002 : 22:43:27
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| it's been changed. |
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GauravBhabu
Advanced Member
4288 Posts |
Posted - 17 August 2002 : 22:48:40
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[quote]
The Significance of Cursor Location
Every cursor uses temporary resources to hold its data. These resources can be memory, a disk paging file, temporary disk files, or even temporary storage in the database. The cursor is called a client-side cursor when these resources are located on the client computer. The cursor is called a server-side cursor when these resources are located on the server.
Client-Side Cursors
In ADO, call for a client-side cursor by using the adUseClient CursorLocationEnum. With a non-keyset client-side cursor, the server sends the entire result set across the network to the client computer. The client computer provides and manages the temporary resources needed by the cursor and result set. The client-side application can browse through the entire result set to determine which rows it requires.
Static and keyset-driven client-side cursors may place a significant load on your workstation if they include too many rows. While all of the cursor libraries are capable of building cursors with thousands of rows, applications designed to fetch such large rowsets may perform poorly. There are exceptions, of course. For some applications, a large client-side cursor might be perfectly appropriate and performance might not be an issue.
One obvious benefit of the client-side cursor is quick response. After the result set has been downloaded to the client computer, browsing through the rows is very fast. Your application is generally more scalable with client-side cursors because the cursor's resource requirements are placed on each separate client and not on the server.
Server-Side Cursors
In ADO, call for a server-side cursor by using the adUseServer CursorLocationEnum. With a server-side cursor, the server manages the result set using resources provided by the server computer. The server-side cursor returns only the requested data over the network. This type of cursor can sometimes provide better performance than the client-side cursor, especially in situations where excessive network traffic is a problem.
However, it is important to point out that a server-side cursor is—at least temporarily—consuming precious server resources for every active client. You must plan accordingly to ensure that your server hardware is capable of managing all of the server-side cursors requested by active clients. Also, a server-side cursor can be slow because it provides only single row access—there is no batch cursor available.
Server-side cursors are useful when inserting, updating, or deleting records. With server-side cursors, you can have multiple active statements on the same connection.
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GauravBhabu
Advanced Member
4288 Posts |
Posted - 17 August 2002 : 22:54:23
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| It is better to use, in most situations, a Client-Side Static cursor if no additions/changes to the database are required. |
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RichardKinser
Snitz Forums Admin
USA
16655 Posts |
Posted - 17 August 2002 : 23:01:46
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| so for displaying topics/replies it would be best to use a Client Side adOpenStatic cursor ? |
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ruirib
Snitz Forums Admin
Portugal
26364 Posts |
Posted - 17 August 2002 : 23:10:00
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quote:
Originally posted by GauravBhabu
Client-Side Cursors
In ADO, call for a client-side cursor by using the adUseClient CursorLocationEnum. With a non-keyset client-side cursor, the server sends the entire result set across the network to the client computer. The client computer provides and manages the temporary resources needed by the cursor and result set. The client-side application can browse through the entire result set to determine which rows it requires.
I don't know if they are referring to non-keyset cursors thinking about the future, because it seems now that there are only static client-side cursors. So, you'll get the entire recordset sent from the database to the Web Server.
quote:
One obvious benefit of the client-side cursor is quick response. After the result set has been downloaded to the client computer, browsing through the rows is very fast. Your application is generally more scalable with client-side cursors because the cursor's resource requirements are placed on each separate client and not on the server.
I suppose this depends on your page size, although I could not confirm this. The small tests I made (I used 15, 30 record and 100 records and paged through them), with a +-6000 record recordset, server-side cursors were always faster, both with Access and SQL Server. The difference to server side recordsets was more than a second (server side being faster), with Access and 100 page records.
Scalability? Well if you're using the same machine as Web server and database server I'd say scalability won't benefit from client side cursors as well. With different DB and Web servers maybe this improves, but then response time may be affected by network traffic, when using a client side cursor (as referred in the server side cursors text).
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GauravBhabu
Advanced Member
4288 Posts |
Posted - 17 August 2002 : 23:11:03
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| Yes, That will be a better option. |
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Gremlin
General Help Moderator
New Zealand
7528 Posts |
Posted - 17 August 2002 : 23:11:50
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| What are the bandwidth implications of that ? sending an entire recordset to the user could amount in some serious bandwidth increases for some forums couldnt it ? |
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ruirib
Snitz Forums Admin
Portugal
26364 Posts |
Posted - 17 August 2002 : 23:14:55
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quote:
Originally posted by GauravBhabu
Yes, That will be a better option.
Well as my previous post showed, it won't be faster (at least for my computer). Also with a Web Server / database server in the same machine how will scalability be better? So, if you have slower page generation times and no gain from scalability, how can it be better? |
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Edited by - ruirib on 17 August 2002 23:17:42 |
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RichardKinser
Snitz Forums Admin
USA
16655 Posts |
Posted - 17 August 2002 : 23:20:59
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| ok.. no client side cursors then. |
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ruirib
Snitz Forums Admin
Portugal
26364 Posts |
Posted - 17 August 2002 : 23:28:27
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Richard, maybe Gaurav has some info that I don't have. As I wrote, I was using client-side cursors whenever paging was needed until this very topic made me want to test it.
I did test it with Access and SQL Server and found server side cursors faster, specially with Access. However it is possible that further testing is needed.
Will these results be reproduced with a server with higher load? Well I guess I'm gonna stress test my server a bit and verify what happens. Will post about it a bit later... |
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