Viewflow 1.6.0 introduces new fields ("data" is a JSON field, and "artifact" support for a generic foreign key). They are present on both Processes and Tasks.
Are these intended to be available to library users, or are they Viewflow internal-use-only? I did not see anything in the docs or the github issues list to clarify the matter, so a pointer would be appreciated if I missed it.
Yep, it's for library users, that allows using proxy models instead of real tables for keeping process-only data
Data field is the JSON. So it could be used with jsonstore field - https://github.com/viewflow/jsonstore that makes JSON data exposed as a real Django field. So it could be used with ModelForms as usual
Ex: https://github.com/viewflow/viewflow/blob/master/demo/helloworld/models.py#L6
Articact allow to link process and your data models, without creating a separate table for that.
All of those allow avoiding joins to build all tasks from different flows for a user.
Related
How would I allow my primary user to dynamically create forms they can issue to their end clients. Each of my primary users has their own unique information they would like to collect that I do not know before hand. I would like to avoid creating new models in code for their dynamic needs and then having to migrate the models.
I came across this which had an interesting response but it starts with disclaimer
The flexibility of Python and Django allow developers to dynamically create models to store and access data using Django’s ORM. But you need to be careful if you go down this road, especially if your models are set to change at runtime. This documentation will cover a number of things to consider when making use of runtime dynamic models.
Which leads me to believe a lot can go wrong.
However because I'm using wagtail I believe there is probably a way to use StructBlocks & StreamFields to accomplish it.
Any guidance would be helpful.
Wagtail provides a form builder module for this purpose.
I have two possible solutions for you, although it should be said that there is probably some library with Django that I don't know about that does this, but that being said.
Prompt your user for which fields they want and the field type.
Pass this as a dictionary to some function that would generate the HTML code for the form.
When this form is used, instead of worrying about storing the fields seperately, store a dictionary in the Models. There are two ways to do that here
Another way that you could do this, albeit more convoluted but more suited to your needs, is to use MongoDB for the database for Django instead. Because it is unstructured, it might be better suited for your use case. Instructions on using MongoDB for Django are here
I'm working on a Node.JS project with Mongodb as a database. I want to test how the api performs when the db collection has thousands of documents in it.
So I'm trying to fill the collection with test data but the problem here is, I've multiple associations for a single collections, i.e multiple reference fields in collection.
So is there any api available which allows me to generate data that supports reference fields too.
There is an old library for creating dummy data in mongoose: mongoose-dummy. But it doesn't look like it handles referenced documents.
You can also use faker to create eg. addresses, emails, names, numbers etc.
This is one of those things you really need to DIY (though you can use the above libraries to make it easier)
You created your application and models. Only you will be able to make realistic test data. For example, you will need to decide how many documents to create for a comment model on a blog post model based on what either historical data or your expectations if none exists.
So I have a rather large database where I want to show its metadata (schemas, tables, and columns) in a tree browser (I use Schemacrawler to fetch all the DB data, and JTree for the tree). However, because there are so many tables and columns, the TableColumnRetriever class takes ages to fetch the columns which causes a bottleneck in my implementation.
My idea is now to do lazy loading on the columns so they will only be fetched when a user clicks on a table. Is there a way in Schemacrawler to only fetch schemas and tables at the beginning (maybe set the SchemaInfoLevel to minimum?) and then later fetch the columns based on an input table/schema?
ps: I implement everything in Java.
SchemaCrawler does not have exactly the functionality you are looking for, to load do incremental loads of metadata. The reason is that SchemaCrawler builds an interconnected object model graph, where you can get from say a table to a foreign-key to another table using Java object references. However, there may be a couple of ways to address you issue that you can consider. One is that you can ask your end-users to provide you a description of what tables they are interested in, in the form of a regular expression. You can use SchemaCrawler’s powerful grep functionality to quickly retrieve that information. Another way is to take advantage of the fact that schemas do not change very often. You can cache the schema metadata when your application starts for the first time, using SchemaCrawler’s built-in functionality. If you end-user wants to refresh the schema at any time, they can do that with the understanding that it may take time. Otherwise, your application’s performance will be very good using cached data.
Sualeh Fatehi, SchemaCrawler
I evaluating CouchDB & I'm wondering whether it's possible to achieve the following functionality.
I'm planning to develop a web application and the app should allow a 'parent' table and derivatives of this table. The parent table will contains all the fields (master table) and the user will selectively choose fields, which should be saved as separate tables.
My queries are as follows:
Is it possible to save different versions of the same table using CouchDB?
Is there an alternative to creating child tables (and clutter the database)?
I'm new to NoSQL databases and am evaluating CouchDB because it supports JSON out of the box and this format seems to fit the application very well.
If there are alternatives to NOT save the derivatives as separate tables, the better will the application be. Any ideas how I could achieve this?
Thanks in advance.
CouchDB is a document oriented database which means you cannot talk in terms of tables. There are only documents. The _rev (or revision ID) describes a version of a document.
In CouchDB, there are 2 ways to achieve relationships.
Use separate documents
Use an embedded array
If you do not prefer to clutter your database, you can choose to use option (2) by using an embedded array.
This gives you the ability to have cascade delete functionality as well for free.
I'm developing a web application in Node.js with MongoDB as the back end. What I wanted to know is, what is the generally accepted procedure, if any exists, for creating initial collections and populating them with initial data such as a white list for names or lists of predefined constants.
From what I have seen, MongoDB creates collections implicitly any time data is inserted into the database and the collection being inserted into doesn't already exist. Is it standard to let these implicit insertions take care of collection creation, or do people using MongoDB have scripts setup which build the main structure and insert any required initial data? (For example, when using MySQL I'd have a .sql script which I can run to dump and rebuild /repopulate the database from scratch).
Thank you for any help.
MHY
If you have data, this post on SO might be interresting for you. But since Mongo understands JavaScript, you can easily write a script that prepares the data for you.
It's the nature of Mongo to create everything that does not exist. This allows a very flexible and agile development since you are not constrainted to types or need to check if table x already exists before working on it. If you need to create collections dynamically, just get it from the database and work it if (no matter if it exists or not).
If you are looking for a certain object, be sure to check it (not null or if a certain key exists) because it may affect your code if you work with null objects.
There's is absolutely no reason to use setup scripts merely to make collections and databases appear. Both DB and collection creation is done lazily.
Rember that MongoDB is a completely schema free document store so there's no way to even setup a specific schema in advance.
There are tools available to dump and restore database content supplied with mongo.
Now, if your application needs initial data (like configuration parameters or whitelists like you suggest) it's usually best practice to have your application components set up there own data as needed and offer data migration paths as well.