ShaunR

Please read this and this. You'll be further along the way to a solution once you have.

SMS has been the greatest assault on the English language since, erm "American English"

The number of Thai people that think "before" is actually spelt "b4" is amazing.

I guess it depends on the XCode and OS version you are using. There is an option to tell XCode to build for all format (i386,x64 and PPC)

You may also links against various OS version. I usually do build for 10.5 SDK.

Yup. Still trying to get my head around all the compiler options (haven't even looked at linker stuff yet). Some compile, some don't.

Bitness? unless you have installed the SDK for 10.4 you should not have a bitness issue.

I've got them all installed I'm trying to compile against 10.4, 10.5, 10.6. Sometimes they won't compile at all depending on certain settings. I need to be able to figure out the minimum version since I won't have the luxury of just getting it to work on my system alone (looks like I'll have to install a few more Mac versions)

The wrapper was needed since I (ok the OS) dynamically call the built in OSX version of sqlite using the -lsqlite3 in the linker flag. I had to rename calls to avoid conflict.

This limit will go away if you compile the source for sqlite3.

Indeed. I'm in two minds about this. I would like to compile from source. But at the moment the debug is 5MB and a release is 2.4MB

There are many to play with. I'm far for mastering all of them....

I'm looking forward to see it

Chris

Xcode is not very intuitive and as soon as I figure out how and what it's doing..... will ditch it in favour of something else. In theory, we shouldn't need it at all since the Mac version of SQLite has all the scripts etc to build and install it.But I don't know what half the files are for (yet). It's a steep learning curve having never used a Mac before (just finding stuff takes me 1/2 an hour...lol). But getting there

I've used Inno Setup for a number of years now. Again its free. Very, very powerful and creates very compact intalls (typicaly 1/2 the size of msi).

In it raw form its almost unusable, but with this or this GUI its very sraight forward.

The order of writes to the hard drive is determined by what how the OSes elevator algorithm wants to sort the write requests in the write cache. The hard drive can also reorder things when they reach its cache. The application order determines when things are put into the cache. From the perspective of the programmer it appears that it happens in order, since the OS keeps the read cache directly in sync with the write cache.

Here's the best description I've found online of some of issues.

http://www.linux-mag...te_Barriers.pdf

That is an interesting article. But it is very Linux oriented (in particular XSF and changes between kernel versions). I don't know much about Linux file systems. But I do know NTFS does not suffer from this and the only currently supported OSs are windows.

My example code was an attempt at illustrating what happens at the hard drive level (it's not real code, but LabVIEW seemed an good choice for showing order of operation issues). Basically that the implicit order of the application doesn't apply at the hard drive level. But you can enforce an ordering with write barriers (fsync). I was mistaken about needing two files for there to be a problem, since a transaction in sqlite involves more than write request to the journal, and can easily take more than one the database file (so it's worse than I said). After looking more into it, I think that, with synchronous off, database corruption is quite likely if there's an OS/Hardware failure during a write.

"fsync" and "write barriers" are not the same thing. The latter is a firmware feature and the former is an OS function. Admittedly, on some OSs (read Linux) you can turn it on or off. But you cannot under Windows (I don't think).

Anyway if synchronous=off, on journaled filesystem was safe, you would think somewhere on the sqlite website (or mailing list) someone would mention the safe easy way to drastically improve speed on virtually all modern desktops, workstations and servers.

That depends. If the programmers are mainly non-windows programmers,then they may not mention it since they use a "cover-all" statements. After all. If they were wanted NTFS to be "utra-robust" and were worried about ll this. then they could have used "CreateFile" with the "FILE_FLAG_NO_BUFFERING" and "FILE_FLAG_WRITE_THROUGH" options. then they would not need "FlushFileBuffers" and not have the overhead associated with it..

Also if you really don't want to believe me about the reordering. NTFS only journals the metadata, not application data. In other words the file systems structure is safe from a crash but not files being written to it.

http://en.wikipedia....i/NTFS#NTFS_Log

As does EXT3 by default (ordered)

http://en.wikipedia....urnaling_levels

Although in EXT3 appened and making new files is as safe as the full data journal mode (I don't know if this also applies to ntfs). But SQLite often writes in the middle of the file.

In other words synchronous off is a very bad default setting.

Your making a bit of a meal out of this. There are better ways to ensure data-integrity if the data is that important. Don't forget. I'm not "removing" the functionality. If you really feel strongly about it then you can just turn it on. Although I suspect you will never use the API since it is natural to prefer your own in-house solution.

Fantastic.

Many, Many thanks. I really appreciate it.

You examples didn't work straight out of the box. But I re-compiled the framework with i386 rather than x64 and labVew now accepts it and I can run your dll verson vi.

I found another framework that Labview could load in the /development/frameworks. There are 3 examples located in there. 1 I can load. the others I cannot. After getting yours to work it it must be due to the bitness (although I'm not sure how to check).

Thanks to your example, I've compiled a framework with sqlite 3.7.3 successfully (lots of warnings though) and your re-hashes of my low-level VIs seem fine. I have a rough idea how things fit together now and I think I should be able to compile a framework without the intermediary LV_SQlite wrapper.

Looks like I'm going to be very unsociable tomorrow whilst I play with the Xcode settings

I'll let you know how I get on later in the week. Muchos Grassy Arse

I'm talking about the ordering between multiple files not a single file. The write cache handles single files just fine.

The order is pretty much dictated by the way the application is written and has little to do with the cache. A file is opened when you instruct the OS to open it. If you write an application as in your second example, then sure, you cannot guarantee the order because you cannot guarantee the order that Labview will execute those functions.

My point was I'm not sure if a lose of power with fsyncing will necessarily lead to a detectable corruption (I think it would catch some if not the majority of cases). Just because the structure is valid doesn't mean the data returned is correct.

Well. Assuming that corruption is going to happen (which I obviously don't agree with....at least on windows) then probably you are right. But it would be far worse to for the structure to be corrupted therefore not enabling retrieval of any information.

While browsing the sqlite source I found

**...Transactions still work if synchronous is off,

** and the database cannot be corrupted if this program

** crashes. But if the operating system crashes or there is

** an abrupt power failure when synchronous is off, the database

** could be left in an inconsistent and unrecoverable state.

** Synchronous is on by default so database corruption is not

** normally a worry.

Indeed. But as I said before. I believe the latter to only be relevant on non-journalled systems. Don't forget that SQLite is applicable for many OSs that do not have such a file system.

I was thinking that those three should be put in their own folder (being the only ones outside of the main api that I could see someone using).

I think there are very few instances (perhaps the savepoints or an in-memory database) where people will need/want to use them. Those that do would quickly see the way forward with an example or two. The "query by ref" is already in the "Query" polymorphic VI and I think fitting for that function.

One page is best, but an example of when this can be hard/impossible is with ActiveX/dotNET/Reference-y-type calls with wide nodes.

In this case, as long as you only have to scroll in one direction, thats ok IMO.

well. ActiveX and dotNET are banned in my applications

Without syncing there is no guarantee that sqlite's journal file is written to disk before it's database file. The write buffer isn't a FIFO, it reorders to optimize bandwidth (the harddrive cache may also reorder things).

(LAVAG keeps erroring when I try to link urls so I have to type them out) http://en.wikipedia.org/wiki/NCQ

The OSes journal is an exception since it can adjust the buffers order (or use some kind of IO write barrier).

http://en.wikipedia....i/Write_barrier

As far as the OS is concerned sqlite's journal is just a file like the database.

Indeed. The OS does see the journal file as just a file (it couldn't see it any other way). But I think we would all be in trouble if we couldn't rely on the OS to write files in a certain order. Imagine overwriting a value in a text file. I don't think it would be very useful if we couldn't guarantee that the second value we wrote wasn't the final value.

I just hex edited a string saved in sqlite database, it still passes the integrity check, a crc would catch this kind of corruption. The question is whether it's catches errors caused during crashes with sync turned off (my guess is it gets some but not all).

I think "integrity_check" is designed to detect database structure corruption. Have you tried to change a non-data byte?

Try it yourself.

Ahhh. You have to be careful here. You are using "stream" functions which are memory resident. SQLite (quite sensibly) uses "WriteFile". Additionally. It uses "WriteFile" in non-overlapped mode.

Try this instead.

#include <windows.h>#include <stdio.h>int main ( void ){  HANDLE out = CreateFile ( "test.txt", FILE_WRITE_DATA, 0, NULL,    CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL );  char s[50];  int i,n;DWORD l;  for (int i=0; i<10000; i++){  n=sprintf (s, "%d\n", i);  WriteFile ( out, s, n, &l, NULL );  }  int *nullptr = 0;   *nullptr=1; //crash before closing  CloseHandle ( out );  return 0;}

In the documentation for WriteFile it states:

If lpOverlapped is NULL, the write operation starts at the current file position and WriteFile does not return until the operation is complete, and the system updates the file pointer before WriteFile returns.

So it is a proper hand-off to the OS unlike the stream functions.

One way of doing my example without save points is to have the subvi's concatenate strings into a query that is run separately (this work around can't replace savepoints in all cases though).

Savepoints are easy for users to implement as long as there's an easy way to keep the database connection open between different calls. A midlevel api might work well in your case just something that handles preparing, stepping and column reading. The low level open and close vis and can be raised to the mid level api.

Indeed. As I said previously. "Query By Ref" is synonymous to "exec". So all you need is "Open", "Query By Ref" and "close". There is no need for an intermediate layer since the high level API is just a wrapper around the query functions. (In fact "Query Transaction" uses Query By Ref"). So. Nothing is precluded. Its just deciding what should be elevated to the higher levels.

The world is simply a better place when your vi fits on one screen.

Amen !

There is no excuse for it not to.

* If LabVIEW isn't open, Open Apllication Ref is returning an error. Is there a more elegant way of starting LabVIEW than using System Exec?

That's the only way as far as I know.

* How can I bring the LabVIEW.exe (or the opend vi's) to the front? Application.BringToFront didn't work (without error). Currently The opened vi's are behind my merge.exe and the hg repro browser.

You'll have to use OS specific calls such as "BringWindowToTop" if you are outside the LV environment.

I think the problem is that journal only maintains consistency (well not quite) on a single file while sqlite needs two files to be consistent with each other. Without syncing (which acts as a write barrier) the data may be written to the database before modifying sqlites journal. Now the OSes journal can be protected from that (since the OS can control the write buffer) but SQLite doesn't have such a protection. I'm curious how SQLite would perform if it used Transactional NTFS instead of syncs and an on disk journal.

The journal (either SQlites or the File systems) is always written to before any updates to the actual file(s) and the transaction is removed after the completion of that operation. In the event that something goes wrong. The journal is "replayed" on restart, therefore any transactions (or partial transactions) still persisting will be completed when the system recovers. The highest risk area is that a transaction is written to the DB but not removed from the journal (since if it exists in the journal it is assumed to be not actioned). In this case, when it is "replayed" it will either succeed (it never completed) or fail silently (it completed but never updated the journal). This is the whole point behind journalling. In this respect, the SQLite DB is only dependent on the SQLite journal for integrity. The OS will ensure the integrity of SQLites journal. And SQLite "should" ensure the integrity of the DB.

However. If the file system does not support journalling. then you are in a whole world of hurt if there is a power failure (you cannot guarantee the journal is not corrupt and if it is, this may also corrupt the DB when it is "replayed"). Then it is essential that SQLite ensures every transaction is written atomically.

That would be doable but the tricky part would be determining which is corrupt. The easy solution of storing the check sum of the database in another file suffers from the same out of ordering you can get without fsyncing (ie both databases are modified before the check sum is actually written to the disk). I'm unsure if pragma intergrity_check can catch all problems.

It ( intergrity_check) would be pretty useless if it didn't. I think it is fairly comprehensive (much more so than just a crc) since it will return the page, cell and reference that is corrupted. What you do with his info though is very unclear. I would quite happily use it.

I check that the number of input values is equal to the largest number of parameters used by a single statement. So all binding's must be overwritten in my API. The single question mark is confusing for multistatement queries. I could make an interface for named parameters (the low level part of my api exposes the functions if the user really wanted to use them). But I decided against it since I didn't think the lose in performance was worth the the extra dll calls and variable lookups. But named variable may be faster in some corner cases since my code will bind parameters that aren't used, but it's easy to minimize the impact of that (by optimizing the order of the parameters).

I could not detect any difference in performance between any of the varieties.There are no extra DLL calls (you just use the different syntax) or lookups (its all handled internally) and, as I said previously, it is persistent (like triggers). Therefore you don't need to ensure that you clear the bindings and you don't have to manage the number of bindings. It's really quite sweet In my high level API, I now link to variable name to the column name (since the column name(s) must be specified).

I just see composability to be a key feature of database interaction.

You'll probably want logging to be synced at least (a log of crash isn't useful use if the important piece never reaches the disk).

I think here you are talking about an application crash rather than a disk crash. If the disk crashes (or the power disappears), its fairly obvious what when and why it happened. For an application crash, the fsync (flushfilebuffers?) is irrelevant.

How about a bank example. Lets say you're writing a database for a bank. So we need a table for bank customers and how much money they have, and a second table for logging all the interactions on different accounts (so we can make bank statements). The following code is just hacked together for example so there likely are bugs in it.

We have three sub vis for our API, create customer, withdrawal and deposit. Now withdrawal subtracts money from the account and logs the withdrawal, and deposit does the same but increases the amount instead of decreasing. We want to make sure the logs match the amounts so we'll wrap all the changes in savepoints.

As for why this is useful consider what happens if I need to change the withdraw (maybe take cash from a credit account if it goes below 0 instead). Or I want the ability to lock an account (so no changes in balance). What happens if there are multiple connections to the database. If I wasn't in a transaction in the transfer the receipt account could be locked before the money is deposited which would error then I'd have to write code to undo my withdraw (now what do I do if that account get's locked before I can deposit it back). If I wanted to setup a automatic bill pay I could use the transfer vi in an automated billpay vi. In short savepoints allow for programmer to avoid code duplication by allowing composability of transactions.

Excellent example.

The more I think about this. The more I think it is really for power users. My API doesn't prevent you (the user) from using save-points with the low level functions, after all it's just a SQL statement before and after (like begin and end). However. It does require quite a bit of thought about the nesting since a "rollback To" in an inner statement will cancel intervening savepoints so you can go up, down and jump around the savepoint stack.

In terms of bringing this out into the high level APIs. I think it wouldn't be very intuitive and would essentially end up being like the "BEGIN..COMMIT" without the flexibility and true power of savepoints. Maybe a better way forward would be to provide an "Example" of savepoints using the low level functions.

Or you can use "vi.lib\Utility\config.llb\Escape String.vi" and "vi.lib\Utility\config.llb\Unescape String.vi" which are pretty good for dealing with these things (Although I believe I had to add something to deal with spave character '/20')

//Martin

Indeed. But if you know there are only a couple of escaped chars; then the above example is much faster.

I don't think it's *humanly* possible to have quite as good of a b-day as Penrod's was.

Oh I don't know. Depends on what they put in your drinks

I agree with Paul G. Sounds like it isn't really a text file (which is what the read spreadsheet is for).

Although.To answer your other question about getting rid if \## values.....

These are non-printable ascii values.

Use the "search and replace string" primitive and right-click on it to select "regular expression". Then create a "search" string. Right click on it to select "\" codes display.

Then you can use a string like [\04\12\14]+ to scan and remove the non-printable characters.

ok, i built this thing....

thanks a lot to the devil guy with the black eyebrows..

Sweet.

You could also make it a little more user friendly by causing the focus to go back to the input box so the user doesn't have to click on it after pressing a button and linking the "+" and "=" buttons to the keyboard

Can you dynamically register for the "Close Panel?" event on every VI in memory? Put up a poll for "all VIs in memory" that runs every 1/2 second or so and register for the "close panel?" event. I don't know how well that would work but it seems like something you haven't tried yet.

I think the target VI would have to be running to be able to hook that event.

Sorry, I meant, removed compiled code from VIs.

Darn..., to be clear the VIs posted at bitbucket should have the blockdiagrams present!

The world of SCC now gives me the power to get the latest version -1, remove the compiled code and recheck in.

EDIT:And if I really had removed the code, you could always get a version earlier.

Ton

Ooooh. Excited again

I'll be able to get my Twitter logger up and running once more

Nice work. Just need to remove the ogk stuff

> I too thought about using the pre-installed SQLite. But I'm not sure that I can guarantee that it will be 32 bit if the Mac starts in 64 bit mode. A wrapper is not a useful way forward as it requires upkeep of other code than Labview and > would require a lot of work re-implementing an interface which is already there. A windows wrapper went this route and its limited because of this.

> From my limited reading of the "framework" implementation its a bit like a fat arch. So does that mean I can compile a 32 bit and 64 bit and include both in the framework? Does the pre-installed SQLite have both 32 bit and 64 bit

> and switch transparently? Do I really have to type in each and every function rather than select it from the LV combo-box?

XCode will generate 32/64bit framework. I did not check it but I'm pretty sure the dylib is 32/64 bit. Anyway LV on the Mac is still 32 bit.....

And yes you will have to reselect the correct the lib and function name in you CLN. You could specify the lib name as a parameter of the CLN instead.

> (And does that mean I select the ". framework" instead of the dylib?) There seems to be little information on > the net for Mac developers.

Yes select "YourSQLite3.framework" in the CLN. Be carefull since LV does not unload it, you have to quit LV to load a new version!

> I will have a play with Xcode. I know its installed but not sure where to find it (doesn't show up under applications).

Its in /Developer/ or you may need to download the latest version from Apple.

> I've only just learnt to use CodeBlocks so naively though it would just be a case of re-compiling for the Mac (its also > available for the Mac)

It should work as long as it is able to generate frameworks.

ChS

OK. So I think you are saying that frameworks are the key and there's no such thing as a dylib in isolation (at least as far as Labview is concerned).

The problem I've come up against now is that I haven't been able to load ANY frameworks with Labview. Even those already installed with the Mac.

I managed to find the SQLite framework (its under TCL). Couldn't load that, maybe because its is compiled with the TCL interface (usual "not a valid library" error). I'm not familiar with TCL so don't know if that's the issue or just the fact that I cannot load frameworks full stop.

Bit of a newbies question. But.........

I can create a bare-bones framework structure using Xcode. And I can create a dylib with Codeblocks. I can also get it to copy the dylib to the framework. But under what do I add it to? Resources? Target? The framework seems geared towards distribution of applications and any tutorials I am able to find all talk about how to link the executable to the framework All I need is a wrapper for the dylib to get Labview to load it.

Like most things new to me. I tend to ask a lot of "silly" questions until I arrive at a "Eureka" moment when I am am able to visualise how everything fits together. At the moment I can see what I want. Have a some of the pieces needed to get to what I want, But don't know if I have all the pieces. Have the wrong pieces or Labvew is just being obstinate. Do you have an Xcode example of one that you made yourself using a dylib that Labview likes?

I've attached the dylib I've created. Perhaps you could wrap it so I can see how it all fits together?

Sorry for the late reply (I really want an up to date RSS-feed).

Here I have posted some VIs that are meant to calculate hashes and keyed hashes.

Ton

"removed source from VIs"

I was getting all excited until I read that

+1 for "couldn't give a monkeys" about twitter

I was using fysnc and FlushFileBuffers synonymously, since they perform the same job. There's probably some subtle difference between the two though.

Indeed. For windows there were "unconfirmed" reports of the OS ignoring (on occasion) the fushfilebuffers. And on "old" linux systems the fsync was a NO-OP.

I'm trying to minimize risk with the things I can control. For instance neither of us is using a memory journal since a crash in our programs in the middle of a writing transaction would very likely trash the database (even though it should be a little bit faster). I just like extending that safety to help mitigate hardware and os failures.

Well. thats not the reason I don't use it. There was little performance gain from purely having an in-memory journal alone (mainly because I open and close on every query). A WAL has a better impact, but at the expense of select queries.

There should be a flush cache command for the harddrive controller that the doesn't return until the cache has been written (this can be saftely ignored when the drive system has a battery backup, since it can guarantee that it will be written).

A good quality hard-disk will guarantee that data held in cache will be flushed on a power failure or brown-out condition (50 ms is required for CE approval). Which is probably longer than a couple of disk revs. From then on its up to the OS to re-construct using the journal. I think the real risk is if the file-system doesn't have journalling and therefore can exit in the middle of a write operation..

I work in an academic setting,so UPS and redundancy are often out of budget. I mainly using sqlite for settings, that if corrupted may cause serious problems. So backups don't help until there's been a problem. I would assume the extra durability would be good for embedded equipment in harsh environments.

I would be tempted to maintain 2 databases in this scenario (write to 2 one directly after the other). The probability that both would be corrupt (due to the reasons discussed previously) would be non-existent. And with the performance improvement of turning of Synch; you would still be in net profit.

If my transaction can't be written purely in one sqlite query (I put an example lower down in this post), then I need to keep the connection open. The low level stuff would work as well. Anyway in my library I need to keep the connection open to cache prepared statements.

If you don't "clear bindings". then the statements will be re-used. this is one of the good reasons for using named statements as opposed to the question mark or an integer.

The main use is to write composable transactions (in other words you can build a higher level api of subvi's that can be put together into a single transaction).

I my case I have a database of samples I'm keeping track off (this example is bit simplified). Now a sample has various properties, different classes of samples require different properties.

Now if the users wants to change a property a dialog vi pops up, this vi checks the type of property. For instance this says it's a ring it's so we call a subvi to update a list control of acceptable values that the user can select from. But the user wants to add a new possible value to ring. So the user clicks the insert new ring value button, types in a value and the new value is inserted in the database. So we recall the subvi to update the acceptable value list control. But the user changes his mind and clicks cancel, so we now need to remove the value(maybe multiple) he added. A very simple way to way to do this is to have the property editing dialog wrap every thing it does in a transaction, and just roll back if the user changes clicks cancel.

But what if the user wants to add a new sample. So the new sample dialog pops up, asks the users what class of sample to add. We look up which properties are required for that class, put that in a list of properties the users has to set (which might have default values). Now the user may cancel out of this new sample dialog so we're going to wrap this all up in a transaction as well. But we want to call our change property dialog to set each of the properties, but that was already wrapped in a transaction (and you can't begin a transaction within another transaction). Now an easy way to fix this is to switch from "begin transaction" to save points, since those can be put within each other, and they're functionally the same as begin transaction, when not within another transaction.

I think that's more of a case that you have coded to use a feature (I'm not saying that that's a bad thing!). There are many ways to skin this squirrel, even without using a database. I have thought about using SQlite for preferences (and also things like MRU lists). But for most applications I don't see much of a benefit (based on the fact that DBs are designed for mass storage and retrieval). Perhaps in your specific case this is appropriate. But I don't think most people think of preferences when they think of a DB. I see it being used more for logging, look-up tables and data that has to be viewed in a number of ways....all of which SQLite excels at.

Can you think of any other scenarios?

This may help (not that I've tried it)

Many thanks. I'll take a look.

Saved for 8.6

Hi, everybody…

I’m new… how are all of you???…

Anyway… I’m a student at ITV, in Mexico… and I was bla bla bla bla bla

Does someone know how to use the same “numeric” as an indicator and as a control… You know… like in a single display calculator…

Yes I know… it’s very basic… but I’m running in circles… I actually have to build a .Vi In which I have to use just two buttons (plus “+” & equals “=”) and a single numeric and do as much additions as I want like in a calculator… in fact it is kind of a calculator… ¬¬

I’ve been trying to use the flat sequence stuff … in a case that stays in truth state when a button is pushed… but that’s all my brain can do on my own… does some one know or has anyone ever done something like this???…

Thanks…

sincerely yours: a Child with troubles…

PD. i don't speak in english... so i'm sorry about it...

Something like this?

Don't have a definitive answer. But some things perhaps you could look at.

Under the App properties there is a "source Control" sub menu that look interesting. Looks like a hook into the LV source control stuff (read/write config looks interesting) . Maybe you could find a way to make Labview Mercurial aware!

A bit of a kludge. But you could monitor the revision number and action when it changes. As far as I'm aware, it is only up-issued after a save rather than a compile.

I posted an example using that approach somewhere on the Dark-side.

Ben

Theres one in the Examples Finder with LV2009 that uses the picture control. Wouldnt take much to mod it (there a "scale" vi )