VFP9SP2 WestWind WebConnection App on WinServer 2012
I was looking at a notoriously slow query to see about optimizing it. Using SYS(3054,11,"cmemvar"), I was able to do so, but during my testing, I found that using MyDate BETWEEN Arg1 and Arg1 was the same optimization-wise as BETWEEN(MyDate,Arg1,Arg2). Somewhere in history, I thought that using VFP's native BETWEEN(field,d1,d2) was NOT Rushmore friendly. However, testing with SYS(3054) showed otherwise!
Just an interesting find this weekend for me whilst debugging.
Carry on! --Mike
I was working at a place that did ran batch processes at night using VFP. One of the managers came up to me and told me of a process that used to take 30 minutes now was taking 5 hours. Combined with the other processes, this meant we couldn't complete the processing overnight any longer and meet our deadlines.
I pulled the latest code into my test environment, and via logging I traced it down to one SELECT statement. It turns out one of our developers changed the code to read "WHERE B=A" where prior it was written "WHERE A=B". (Thanks source code control for allowing me to pinpoint when the change was made!) That small code change meant it no longer could take advantage of Rushmore and was basically doing a table scan. SYS(3054) is forever my friend. We were back to 30 minutes for that process and back on schedule without any major effort or rework.
I spoke to the developer who made the change and she didn't realize that a small change like that would affect performance in that way. It was logically the equivalent behavior. A great learning moment.
-----Original Message----- From: ProFox [mailto:profox-bounces@leafe.com] On Behalf Of mbsoftwaresolutions@mbsoftwaresolutions.com Sent: Sunday, March 18, 2018 2:34 PM To: ProFox profox@leafe.com Subject: Testing tells the tale (SYS 3054) -- "BETWEEN(a,b,c)" equivalent to "a BETWEEN b and c"
VFP9SP2 WestWind WebConnection App on WinServer 2012
I was looking at a notoriously slow query to see about optimizing it. Using SYS(3054,11,"cmemvar"), I was able to do so, but during my testing, I found that using MyDate BETWEEN Arg1 and Arg1 was the same optimization-wise as BETWEEN(MyDate,Arg1,Arg2). Somewhere in history, I thought that using VFP's native BETWEEN(field,d1,d2) was NOT Rushmore friendly. However, testing with SYS(3054) showed otherwise!
Just an interesting find this weekend for me whilst debugging.
Carry on! --Mike
[excessive quoting removed by server]
-----Original Message----- From: ProFox [mailto:profox-bounces@leafe.com] On Behalf Of mbsoftwaresolutions@mbsoftwaresolutions.com Sent: Sunday, March 18, 2018 2:34 PM To: ProFox profox@leafe.com Subject: Testing tells the tale (SYS 3054) -- "BETWEEN(a,b,c)" equivalent to "a BETWEEN b and c"
VFP9SP2 WestWind WebConnection App on WinServer 2012
I was looking at a notoriously slow query to see about optimizing it. Using SYS(3054,11,"cmemvar"), I was able to do so, but during my testing, I found that using MyDate BETWEEN Arg1 and Arg1 was the same optimization-wise as BETWEEN(MyDate,Arg1,Arg2). Somewhere in history, I thought that using VFP's native BETWEEN(field,d1,d2) was NOT Rushmore friendly. However, testing with SYS(3054) showed otherwise!
Just an interesting find this weekend for me whilst debugging.
Carry on! --Mike
Also found that the ALLTRIMs in some SQLs were defeating optimization as well. Just a tip for others here! I don't code that way but somebody in the history of this app did.
Mike,
I believe ALLTRIM()s in SQL doesn't "defeat" optimization, it's just that you can't have ragged (meaning, varying length) indexes in VFP.
A tag on ALLTRIM(field) is padded out to the full length of the field.
Bill Anderson
On Mon, Mar 19, 2018 at 12:55 PM, < mbsoftwaresolutions@mbsoftwaresolutions.com> wrote:
-----Original Message-----
From: ProFox [mailto:profox-bounces@leafe.com] On Behalf Of mbsoftwaresolutions@mbsoftwaresolutions.com Sent: Sunday, March 18, 2018 2:34 PM To: ProFox profox@leafe.com Subject: Testing tells the tale (SYS 3054) -- "BETWEEN(a,b,c)" equivalent to "a BETWEEN b and c"
VFP9SP2 WestWind WebConnection App on WinServer 2012
I was looking at a notoriously slow query to see about optimizing it. Using SYS(3054,11,"cmemvar"), I was able to do so, but during my testing, I found that using MyDate BETWEEN Arg1 and Arg1 was the same optimization-wise as BETWEEN(MyDate,Arg1,Arg2). Somewhere in history, I thought that using VFP's native BETWEEN(field,d1,d2) was NOT Rushmore friendly. However, testing with SYS(3054) showed otherwise!
Just an interesting find this weekend for me whilst debugging.
Carry on! --Mike
Also found that the ALLTRIMs in some SQLs were defeating optimization as well. Just a tip for others here! I don't code that way but somebody in the history of this app did.
[excessive quoting removed by server]
On 2018-03-19 18:29, Bill Anderson wrote:
Mike,
I believe ALLTRIM()s in SQL doesn't "defeat" optimization, it's just that you can't have ragged (meaning, varying length) indexes in VFP.
A tag on ALLTRIM(field) is padded out to the full length of the field.
Bill Anderson
Hi Bill!
But it really doesn't do anything for you, right? I mean, VFP works best when it's used for it's fixed-width strengths, right? (Keep in mind, I haven't chosen to use VFP backends since 2004!)
--Mike
Using ALLTRIM() on idexes is a bad idea, the full field is always better and faster, because VFP does not have to preprocess the value for searching, for adding a new value and for reindexing.
El lun., 19 de marzo de 2018 23:29, Bill Anderson billand88@gmail.com escribió:
Mike,
I believe ALLTRIM()s in SQL doesn't "defeat" optimization, it's just that you can't have ragged (meaning, varying length) indexes in VFP.
A tag on ALLTRIM(field) is padded out to the full length of the field.
Bill Anderson
On Mon, Mar 19, 2018 at 12:55 PM, < mbsoftwaresolutions@mbsoftwaresolutions.com> wrote:
-----Original Message-----
From: ProFox [mailto:profox-bounces@leafe.com] On Behalf Of mbsoftwaresolutions@mbsoftwaresolutions.com Sent: Sunday, March 18, 2018 2:34 PM To: ProFox profox@leafe.com Subject: Testing tells the tale (SYS 3054) -- "BETWEEN(a,b,c)" equivalent to "a BETWEEN b and c"
VFP9SP2 WestWind WebConnection App on WinServer 2012
I was looking at a notoriously slow query to see about optimizing it. Using SYS(3054,11,"cmemvar"), I was able to do so, but during my testing, I found that using MyDate BETWEEN Arg1 and Arg1 was the same optimization-wise as BETWEEN(MyDate,Arg1,Arg2). Somewhere in history, I thought that using VFP's native BETWEEN(field,d1,d2) was NOT Rushmore friendly. However, testing with SYS(3054) showed otherwise!
Just an interesting find this weekend for me whilst debugging.
Carry on! --Mike
Also found that the ALLTRIMs in some SQLs were defeating optimization as well. Just a tip for others here! I don't code that way but somebody in the history of this app did.
[excessive quoting removed by server]
I agree with your statement. Any function you toss into your index has to be run row by row to evaluate the correct value. This is not optimizable because the data is being tweaked. Using INTs as keys saves you from this nightmare.
On Tue, Mar 20, 2018 at 1:22 AM, Fernando D. Bozzo fdbozzo@gmail.com wrote:
Using ALLTRIM() on idexes is a bad idea, the full field is always better and faster, because VFP does not have to preprocess the value for searching, for adding a new value and for reindexing.
El lun., 19 de marzo de 2018 23:29, Bill Anderson billand88@gmail.com escribió:
Mike,
I believe ALLTRIM()s in SQL doesn't "defeat" optimization, it's just that you can't have ragged (meaning, varying length) indexes in VFP.
A tag on ALLTRIM(field) is padded out to the full length of the field.
Bill Anderson
On Mon, Mar 19, 2018 at 12:55 PM, < mbsoftwaresolutions@mbsoftwaresolutions.com> wrote:
-----Original Message-----
From: ProFox [mailto:profox-bounces@leafe.com] On Behalf Of mbsoftwaresolutions@mbsoftwaresolutions.com Sent: Sunday, March 18, 2018 2:34 PM To: ProFox profox@leafe.com Subject: Testing tells the tale (SYS 3054) -- "BETWEEN(a,b,c)" equivalent to "a BETWEEN b and c"
VFP9SP2 WestWind WebConnection App on WinServer 2012
I was looking at a notoriously slow query to see about optimizing it. Using SYS(3054,11,"cmemvar"), I was able to do so, but during my testing, I found that using MyDate BETWEEN Arg1 and Arg1 was the same optimization-wise as BETWEEN(MyDate,Arg1,Arg2). Somewhere in history, I thought that using VFP's native BETWEEN(field,d1,d2) was NOT Rushmore friendly. However, testing with SYS(3054) showed otherwise!
Just an interesting find this weekend for me whilst debugging.
Carry on! --Mike
Also found that the ALLTRIMs in some SQLs were defeating optimization
as
well. Just a tip for others here! I don't code that way but somebody
in
the history of this app did.
[excessive quoting removed by server]
-
Bill Anderson -
Fernando D. Bozzo -
Kevin J Cully -
mbsoftwaresolutions＠mbsoftwaresolutions.com -
Stephen Russell