Can I write to two tables in two parallel processes in SQLite?
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By Thang Nguyen
Currently, my vision software will do a compression (subtract to background image then count zero) and write to a table in SQLite file. Since we want to speed up the process, I write entire image in a temporary table. Then at the end, I read the table, do compression and write to the actual table, then drop the temporary table. This takes a lot of time too even I use the Journal mode = memory. I think the issue is I put the process code in 4 separated modules:
Select the temp table -> output array Compress the output array of step 1 Insert the compress data from step 2 to actual table Drop the temp table I am looking for an option to mix these steps together to speed up the speed for example select and delete the row in temp table at the same time then at the end I can drop the table faster. Currently, it takes significant time to drop the table. Our raw data can be up to 3GB. But I don't know how to combine the query. I also read that SQlite does not support this. So I also looking for an advice on how to make this process more efficient. I thought about using the queue too but I need input before I change it.
Thank you in advance.
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By kosist90
Dear Community,
let me present our new ANV Database Toolkit, which has been recently released at vipm.io.
Short introduction to the toolkit is posted by this link, and it also describes steps which should be done in order to use this toolkit.
ANV Database Toolkit helps developers design LabVIEW API for querying various databases (MS SQL, MySQL, SQLite, Access). It allows to create VIs which can be used as API with the help of graphical user interface. When using these VIs, toolkit handles connection with the database, thus relieving developers of this burden in their applications.
It has the following features:
Simplifies handling of databases in LabVIEW projects Allows to graphically create API VIs for Databases Supports Read, Write, Update and Delete queries Supports various database types (MS SQL, MySQL, SQLite, Access) Overall idea is that developer could create set of high-level API VIs for queries using graphical user interface, without actual writing of SQL queries. Those API VIs are used in the application, and handle database communication in the background. Moreover, SQL query could be applied to any of the supported database types, it is a matter of database type selection. Change of target database does not require changes in API VI which executes the query.
After installation of the toolkit, sample project is available, which shows possibilities of the toolkit in terms of execution different types of queries.
Note, that in order to install the toolkit, VI Package Manager must be launched with Administrator privileges.
This toolkit is paid, and price is disclosed based on price quotation. But anyway, there are 30 days of trial period during which you could tryout the toolkit, and decide whether it is helpful (and hope that it will be) for your needs.
In case of any feedback, ideas or issues please do not hesitate to contact me directly here, or at vipm.io, or at e-mail info@anv-tech.com.
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By drjdpowell
View File SQLite Library
Introductory video now available on YouTube: Intro to SQLite in LabVIEW
SQLite3 is a very light-weight, server-less, database-in-a-file library. See www.SQLite.org. This package is a wrapper of the SQLite3 C library and follows it closely.
There are basically two use modes: (1) calling "Execute SQL" on a Connection to run SQL scripts (and optionally return 2D arrays of strings from an SQL statement that returns results); and (2) "Preparing" a single SQL statement and executing it step-by-step explicitly. The advantage of the later is the ability to "Bind" parameters to the statement, and get the column data back in the desired datatype. The "Bind" and "Get Column" VIs are set as properties of the "SQL Statement" object, for convenience in working with large numbers of them.
See the original conversation on this here.
Hosted on the NI LabVIEW Tools Network.
JDP Science Tools group on NI.com.
***Requires VIPM 2017 or later for install.***
Submitter drjdpowell Submitted 06/19/2012 Category Database & File IO LabVIEW Version 2013 License Type BSD (Most common)
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By drjdpowell
Introductory video now available on YouTube: Intro to SQLite in LabVIEW
SQLite3 is a very light-weight, server-less, database-in-a-file library. See www.SQLite.org. This package is a wrapper of the SQLite3 C library and follows it closely.
There are basically two use modes: (1) calling "Execute SQL" on a Connection to run SQL scripts (and optionally return 2D arrays of strings from an SQL statement that returns results); and (2) "Preparing" a single SQL statement and executing it step-by-step explicitly. The advantage of the later is the ability to "Bind" parameters to the statement, and get the column data back in the desired datatype. The "Bind" and "Get Column" VIs are set as properties of the "SQL Statement" object, for convenience in working with large numbers of them.
See the original conversation on this here.
Hosted on the NI LabVIEW Tools Network.
JDP Science Tools group on NI.com.
***Requires VIPM 2017 or later for install.***
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By McQuillan
Hi Everyone,
I (re)watched James Powell's talk at GDevCon#2 about Application Design Around SQLite. I really like this idea as I have an application with lots of data (from serial devices and software configuration) that's all needed in several areas of the application (and external applications) and his talk was a 'light-bulb' moment where I thought I could have a centralized SQLite database that all the modules could access to select / update data.
He said the database could be the 'model' in the model-view-controller design pattern because the database is very fast. So you can collect data in one actor and publish it directly to the DB, and have another actor read the data directly from the DB, with a benefit of having another application being able to view the data.
Link to James' talk: https://www.youtube.com/watch?v=i4_l-UuWtPY&t=1241s)
I created a basic proof of concept which launches N-processes to generate-data (publish to database) and others to act as a UI (read data from database and update configuration settings in the DB (like set-point)). However after launching a couple of processes I ran into 'Database is locked (error 5) ', and I realized 2 things, SQLite databases aren't magically able to have n-concurrent readers/writers , and I'm not using them right...(I hope).
I've created a schematic (attached) to show what I did in the PoC (that was getting 'Database is locked (error 5)' errors).
I'm a solo-developer (and SQLite first-timer*) and would really appreciate it if someone could look over the schematic and give me guidance on how it should be done. There's a lot more to the actual application, but I think once I understand the limitations of the DB I'll be able to work with it.
*I've done SQL training courses.
In the actual application, the UI and business logic are on two completely separate branches (I only connected them to a single actor for the PoC)
Some general questions / thoughts I had:
Is the SQLite based application design something worth perusing / is it a sensible design choice? Instead of creating lots of tables (when I launch the actors) should I instead make separate databases? - to reduce the number of requests per DB? (I shouldn't think so... but worth asking) When generating data, I'm using UPDATE to change a single row in a table (current value), I'm then reading that single row in other areas of code. (Then if logging is needed, I create a trigger to copy the data to a separate table) Would it be better if I INSERT data and have the other modules read the max RowId for the current value and periodically delete rows? The more clones I had, the slower the UI seemed to update (should have been 10 times/second, but reduced to updating every 3 seconds). I was under the impression that you can do thousands of transactions per second, so I think I'm querying the DB inefficiently. The two main reasons why I like the database approach are:
External applications will need to 'tap-into' the data, if they could get to it via an SQL query - that would be ideal. Data-logging is a big part of the application. Any advice you can give would be much appreciated.
Cheers,
Tom
(I'm using quite a few reuse libraries so I can't easily share the code, however, if it would be beneficial, I could re-work the PoC to just use 'Core-LabVIEW' and James Powell's SQLite API)
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