Jennifer Gross
jengross at gte.net
Fri Feb 20 15:11:07 CST 2009
Wow, to sway the great John Colby. And in a "religious" argument no less. Now that made my day. Seriously smiling, Jennifer -----Original Message----- From: accessd-bounces at databaseadvisors.com [mailto:accessd-bounces at databaseadvisors.com] On Behalf Of jwcolby Sent: Friday, February 20, 2009 1:05 PM To: Access Developers discussion and problem solving Subject: Re: [AccessD] Find First in an Array? Now there is a reason that places the whole issue in a new light. Language data is indeed specific to a particular FE in a way that most other data is not. So perhaps for that specific task, a table in the FE makes perfect since. I would STILL cache it but that is another issue. Thanks Jennifer, John W. Colby www.ColbyConsulting.com Jennifer Gross wrote: > Hi Rocky, > > I have an application that uses a translation table is much the same > way yours does - from Michael Kaplan at Trigeminal. I keep the > translation table in the FE as well. One of the reasons for this is > that as I add objects to the FE I can get the captions translated and > add the records to the FE table. I don't need to append records to a > BE table during the dissemination of the FE to the individual users. > I've just found it easier of the years in terms of deployment - that I > don't have to make sure the live BE has been updated - it is all in > the FE which for the users just gets replaced when there is an update. > > Jennifer > > -----Original Message----- > From: accessd-bounces at databaseadvisors.com > [mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Rocky > Smolin at Beach Access Software > Sent: Friday, February 20, 2009 12:06 PM > To: 'Access Developers discussion and problem solving' > Subject: Re: [AccessD] Find First in an Array? > > > " I am not going to get into the "this is a local table so it goes in > the FE... oh damn, now I gotta go update the data in 5 different FEs". > BEs are for data (in my world)." > > In my case, where the 'data' is really static, and is needed by each > user, wouldn't the design be better with the language tables in the > FE? > > > Rocky Smolin > Beach Access Software > 858-259-4334 > www.e-z-mrp.com > www.bchacc.com > > > > -----Original Message----- > From: accessd-bounces at databaseadvisors.com > [mailto:accessd-bounces at databaseadvisors.com] On Behalf Of jwcolby > Sent: Friday, February 20, 2009 11:03 AM > To: Access Developers discussion and problem solving > Subject: Re: [AccessD] Find First in an Array? > > Jim, > > > So if your not comfortable with it then just ignore it? Humm. > > I was making a general observation, which I believe is true. People > tend to use the tools they know and are expert with, and only go > outside of their comfort zone when the tool fails them. I freely > acknowledge that this is true for me, and I am not accusing you of > anything. > > > No, that is not correct. A seek on an open table won't cache the > entire recordset in of > itself. What might be sitting in JET's cache is a few buffers worth of > index pages and a couple of buffers worth of data pages, but I'd highly > doubt you'd have the entire thing unless you just went through every > single record or used them a lot in comparison to everything else (JET's > cache is LRU based, so the pages could add up in the cache over time). > > By definition you have to have all of the data that is used for doing > any particular form. > > >Since a language table would be local to the FE, this would not be a > pull over the wire and it would be quite fast. > > It might be in your systems but it would not be in mine. I use a BE > because that is where data goes. I personally do not have ANY local > tables in the FE except for temp tables for processes. I have many > cases where there are different FEs for different purposes. I am not > going to get into the "this is a local table so it goes in the FE... > oh damn, now I gotta go update the data in 5 different FEs". BEs are > for data (in my world). > > >It's quite possible to that the disk drive would still have the data > in its own cache, so you might not even end up doing a hard hit to the > disk at all. > > Unlikely. The disk is also pulling forms, reports, running the > browser as the user goofs off, working on buffering music that the > user is listening to, and any of the other million things that go on > in a Windows environment. The probability that the data for a form > opened sometime previously would still be in the disk buffer is pretty > low I would guess. > > > But with the seek approach, you would not be tying up a chunk of > memory > to be used for only one > purpose. > > I have to say that with Windows XP requiring 256 megs just for it to > load, and Vista pushing twice that just for it to load, I am not > worrying about caching my "seldom changing / frequently used" data. > If I take even a few hundred K to cache the language strings for every > form in the system, I will not lose any sleep at all for doing that. I > would in fact just cache the form's opened... > > > It is when considering that point that I would not choose to do an > array based approach either, which would be really simple to write as > I could use > GetRows() to dump the set into an array. Since the array would already > be sorted, I could even do a B-tree search on it rather then a > sequential one. That might even beat out a class (hard to say with > VBA) in terms of speed. > > Even if I used a Getrows() to dump into an array I would promptly move > the data to a collection and get rid of the array. > > I think that a lot of stuff goes into determining when to use what > tools. I do not have a b-tree search algorithm for a generic array > but even if I did (and assuming that it was faster, doubtful), a > collection is USUALLY fast enough that it wouldn't be worth the > complexity of using such a tool, at least not on a routine basis. > > I use collections because: > > 1) They are DEAD simple. The syntax is simple, the usage is simple. > 2) It is easy code to read and maintain. > 3) They can hold a ton of stuff easily. > 4) They can hold just about anything, from simple variables to objects > and class instances (which are objects). > 5) They are very fast. > > If you think about it, Access uses collections EVERYWHERE, and I want > to emphasize the EVERYWHERE. Every single thing that you do with > Access from forms (a collection of) to controls on forms (a collection > of), to properties of controls and forms (a collection of), to fields > (a collection of), to querydefs (a collection of) etc etc ad nasium, > are all stored internally to Access (and when loaded into > memory) as collections. Notice that Microsoft doesn't store all these > items in tables. > If tables are so blazing fast, if all the things that you think are > true (jet cache / disk cache > etc) really are true, why does Access store everything in collections > instead of just leaving it in records on a disk? Can you say > programming / overhead nightmare? > > Microsoft has spent a lot of time and energy optimizing collections in > order to make Access itself fast. IMHO, why would I NOT use what > Microsoft uses and has spent so much effort to make fast and easy to > use? > > > John W. Colby > www.ColbyConsulting.com > > > Jim Dettman wrote: >> John, >> >> <<The bottom line is that to a large extent we all do what is >> comfortable to us as individual programmers and to heck with ....>> >> >> So if your not comfortable with it then just ignore it? Humm. >> >> <<Well... Hmmm... your way caches the entire recordset and all its >> associated junk - indexes etc. My way caches exactly and only the >> strings for one specific language.>> >> >> No, that is not correct. A seek on an open table won't cache the >> entire recordset in of itself. What might be sitting in JET's cache >> is a few buffers worth of index pages and a couple of buffers worth >> of > >> data pages, but I'd highly doubt you'd have the entire thing unless >> you just went through every single record or used them a lot in >> comparison to everything else (JET's cache is LRU based, so the pages >> could add up in the cache over time). >> >> But even if nothing is in the cache, a seek is based on an index >> and since JET indexes are B-tree based, you'd have your record within >> 2-3 disk hits at most, especially on a 2500 record table. Since a >> language table would be local to the FE, this would not be a pull >> over > >> the wire and it would be quite fast. It's quite possible to that the >> disk drive would still have the data in its own cache, so you might >> not even end up doing a hard hit to the disk at all. >> >> But if the data does happen to be in the JET cache, then I doubt >> there would be much of a difference between the two methods. I think >> the class approach would still be a tad faster, but not by much. And >> let me be clear; it's not the class approach that I don't agree with >> but the point that as an application developer do I cache things in > memory > on my own or not? >> It is when considering that point that I would not choose to do an >> array based approach either, which would be really simple to write as >> I could use >> GetRows() to dump the set into an array. Since the array would >> already > >> be sorted, I could even do a B-tree search on it rather then a > sequential > one. >> That might even beat out a class (hard to say with VBA) in terms of >> speed. >> >> But with the seek approach, you would not be tying up a chunk of >> memory to be used for only one purpose. >> >> From my viewpoint the seek approach is the best of both worlds, >> stuff gets cached if it is used a lot and if it is not, then it is >> not > >> cached. In that case, the memory gets used for something productive >> rather then sitting there. And I would be really surprised if > performance > wasn't acceptable. >> Jim. >> >> >> -----Original Message----- >> From: accessd-bounces at databaseadvisors.com >> [mailto:accessd-bounces at databaseadvisors.com] On Behalf Of jwcolby >> Sent: Friday, February 20, 2009 9:44 AM >> To: Access Developers discussion and problem solving >> Subject: Re: [AccessD] Find First in an Array? >> >> The bottom line is that to a large extent we all do what is >> comfortable to us as individual programmers and to heck with .... >> >> > You mentioned that JET always goes across the wire and that's not > true. >> If a page is in the >> local JET cache, then it won't. >> >> > But if every programmer were to approach application design with > the >> "load it into memory" >> approach because it's fast, then very quickly you can find that the >> OS > >> will start paging out to disk. So your really not in memory any >> more. >> >> Well... Hmmm... your way caches the entire recordset and all its >> associated junk - indexes etc. My way caches exactly and only the >> strings for one specific language. >> >> However your way (done on a form by form basis on demand) sounds like >> it could be flushing the jet cache as other processes run so that it >> may very well have to hit the disk again for the next form to load. >> At best it kind of sounds like "six of one, half a dozen of the >> other". >> >> > If I have an application that is a couple of hundred forms and >> user Jim D uses only one form, then that's a big waste. >> >> True, but if you cache the data as the form loads the first time then >> that goes away. I was proposing exactly that. Now you have the best >> of both worlds, you don't use time and resources until a form is >> actually loaded, but once it is loaded it can be loaded twice or a >> million times and always be fast. You should know from my JIT >> subforms I am all about doing stuff as / when needed. >> >> Notice that I am not caching constantly changing data, nor data that >> doesn't change but is rarely used, only data that rarely changes and >> is used constantly in the program. That "rarely changes / >> constantly used" is not a rare occasion in complex systems. To go to >> the disk dozens or hundreds or thousands of times a day to get the >> same data over and over IMHO is just silly, when I can just cache it >> and be done. It is even sillier when caching it is a trivial >> programming exercise. It is sillier yet when caching the data >> significantly speeds up the program. >> >> I learned a long time ago to organize my program into classes, each >> class performs a systemic task. >> I learned that when a set of data is in constant use in the program >> (and form translation fits that bill) then I would build a class >> system to cache it and the program always works faster. The "cache >> class system" looks very similar from data set to data set. It >> doesn't take me long to set it up because I have done it so often. >> >> So that is what I do. I do understand that it is only fast / >> efficient for me because I use classes all day every day, but so can >> any Access programmer as my lectures are intended to show. >> >> >> John W. Colby >> www.ColbyConsulting.com >> >> >> Jim Dettman wrote: >>> John, >>> >>> I posted a couple of comments yesterday to you and Drew, which >>> still haven't shown up on the list, but I'll answer the question you >>> just asked with "It depends on how big the collection is". >>> >>> What I wrote yesterday is that I would use a global recordset >>> variable, thus avoiding opening/closing the recordset repeatedly and > I'd > use seek. >>> You mentioned that JET always goes across the wire and that's not >>> true. If a page is in the local JET cache, then it won't. >>> >>> But here that is really not an issue because a language >>> translation >> table >>> is certainly going to be part of the front end, so the table will be >> local. >>> It's not going to change unless the app changes. >>> >>> Rocky has been talking about pulling 2500 records; if all that is >>> pulled into memory, that is a fair sized chunk. I'd much rather let >>> the system >> use >>> that memory as it sees fit rather then tying it up with one specific > task. >>> If I have an application that is a couple of hundred forms and user >>> Jim D uses only one form, then that's a big waste. Of course you >>> could mitigate that somewhat by only loading the translation when >>> the > >>> form loads and for the specific language as you mentioned. >>> >>> But if every programmer were to approach application design with >>> the >> "load >>> it into memory" approach because it's fast, then very quickly you >>> can find that the OS will start paging out to disk. So your really >>> not in memory >> any >>> more. >>> >>> That's why I think pulling something into memory like this is a >>> waste. >>> >>> FWIW, >>> Jim. > > -- > AccessD mailing list > AccessD at databaseadvisors.com > http://databaseadvisors.com/mailman/listinfo/accessd > Website: http://www.databaseadvisors.com > -- AccessD mailing list AccessD at databaseadvisors.com http://databaseadvisors.com/mailman/listinfo/accessd Website: http://www.databaseadvisors.com No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.0.237 / Virus Database: 270.11.1/1961 - Release Date: 02/19/09 18:45:00