I'm planning to distribute load from my database making a copy on several servers (each server will have the same tables but with different company data).
In order to do this, I will need to programmatically change the Datastore associated to my Data Views. For other tables I'm using the "Before Connect" property.
It's possible to handle this in Genexus?
Thanks,
Yes, you can use dbConnection Data Type.
Just create a variable based on this data type, and use it's methods and properties to set it up when you need it to be changed...
Related
For a multi tenant application I need to create I want to evaluate how convenient is Slick for creating queries against Postgres different schemas (not to confuse with schema tables).
I'm having a hard time finding how to configure TableQuery to use dynamically the schema provided by the user. TableQuery[Users].resul should return different datasets depending on me querying tenant A or tenant B.
Is it possible with current Slick versions?
TableQuery itself will not need to be configured, as its methods only return queries and actions. Actions are run by a DatabaseDef instance, and that is what will need to be configured to access different schemas/databases/etc. Slick official documentation describes a simple way to create an instance of a DatabaseDef, which by default uses the Typesage Config library:
val db = Database.forConfig("mydb")
where "mydb" specifies a key in a property file Typesafe Config is looking at. You can create and manipulate Config instances programmatically as well, and create db instances from those. I suspect you will have to do something along the lines of creating a new Config instance (there is the convenient withValue() method to copy a Config and replace a config value at the specified key) and use that to create a new db instance for each new schema you are interested in querying.
I am looking for advice on how to use the QSYS2.DATA_AREA_INFO in a particular situation. So I have created a few views which selects data from multiple tables. I am trying to fetch data from a data area as well using the DATA_AREA_INFO function.
The views need to be installed in a number of data libraries. The create view SQL statement does not have any libraries hardcoded. The tables to pull data from will be based on the default library we set in iSeries navigator while creating the views. So once the view is created, it would permanently point to tables from the default data library set. (Hope this is correct?)
The issue is with fetching the data from the data area:
SELECT DATA_AREA_VALUE
FROM TABLE(QSYS2.DATA_AREA_INFO(
DATA_AREA_NAME => 'TESTDA1',
DATA_AREA_LIBRARY => '*LIBL'))
Writing the statement as above would result in the view selecting the data from the data area present in the library list.
But the jobs from which the views will be executed might not have a library list setup. Hence I cant rely on DATA_AREA_LIBRARY => '*LIBL'
Is there a way I can make the view point to the same data library always (same as how the tables work)?
You could wrap up the data area access in a (service)program which accesses the *dtaara via ILE. The advantage is, that your able to reuse the program in several ways, in and outside an sql context. You can find information about this technique here:
Scott Klement Powerpoint
In Meteor, I have a little confusion between Session and Local Collection.
I know that Session is a temporary reactive key-value store, client-side only, and is cleaned on page refresh.
Local collection seems to be the same: reactive, temporary client-side storage, cleaned on page refresh with more flexible function like insert, update & remove query like server-side Mongo collection.
So I guess I could manage everything in Local Collection without Session, or, everything in Session without Local Collection.
But what is the best and efficient way to use Session and/or Local collection?
Simply, when to use Session and not use it?
And when to use Local collection and when not use it?
As I read your question I told myself that this is a very easy question, but then I was scratching my head. I tried to figure out an example that you can just accomplish with session or collections. But I didn't found any use-case. So let's rollup things from begin. Basically you already answered the question on your own, because it is the little sugar that makes collections something special.
When to use a collection?
Basically a collection is a database artifact. Imagine you have a client-server-application. All the data is persisted in the server side storage. Now you can use a local collection to provide the user a small subset of the servers collection. So a client collection is a database with reduced amount of data. The advantage is that you can access the collection with queries. You can use the same queries on server and client. In additon a collection always contains multiple objects of the same type. Sometimes you produce data on client for the client. No server interaction needed. Than you can use a local collection. A local collection provides the same functionality as a normal collection without server communication. This should be used if you have multiple objects with the same structure and in special if you'd like to use query operators.
You can also save the data inside a session object. Session objects can contain multiple objects as well. But imaging you want to find an object in an objectarray indexed with a special id. Than you need to iterate throw the whole array in order to find this object. You have to write additional logic, that can be handled with collection like magic. Further, collections return cursors. A cursor is an reactive object that just changes if the selected data changes. That means if you use find with an id. Than this object just rerenders when the object to this id changes. With session you can't. When a session changes you need to rerender all depending objects.
When to use a session?
For everything else. Sessions are often just small objects that contain some configuration logic. It is basically just one object and not a multiple occurency of equal objects. Haven't time now to go in detail but if it does not fit the collection use-cases you can use sessions.
Have a look at this post that describes why sessions should not be overused.
I assume that by local collection you mean: new Mongo.Collection(null)
The difference is that local collections do not survive hot code pushes. A refresh will erase Session, but hot code push will not, there's special code in Meteor to persist the values of the Session variable in the case of a hot code push..
You would use Session whenever you're storing temporary values that do NOT need to be persisted to the database.
Trivial examples could include a users selection of filters or the item in an index vies that is currently selected.
manipulated data in minimongo (insert, update, delete etc) is intended to be sent back to the server and stored in the database. For example this could be updating a users profile information etc.
I want to store some user data in memory, like some in-memory noSQL database.
But later on I want to query that data with a dynamic query constructed from the user. That query is stored in a classic DB like a string, so when I need to query the data stored in memory I would like to parse that string and construct the desired query (by some known rules).
I looked at Redis and I figured out it isn't maintained for Windows anymore, I have also looked at RavenDB but it's main query language is LINQ, even though it can be created dynamic Lucene Query.
Can you suggest me another in memory DB that work with ASP.NET and can be queried with a dynamically created query? Maybe I haven't seen all the options.
I prefer name-value or JSON based noSQL so it's schema can be easyly modified without the constraints of the relation type of DBs
I would suggest to simply use sqlite. It can be easily used as an in-memory database (just open the database using ":memory:" instead of a file name).
You can use a simple 2 columns table with a primary key to emulate a key/value store.
Here are a few links you might find helpful:
http://www.sqlite.org/inmemorydb.html
How to create asp.net web application using sqlite
I've been using Core Data for about a week now, and really loving it, but one minor issue is that setting default values requires going through and setting up a temp interface to load the data, which I then do away with once I have the data seeded. Is there any way to edit values in a table, like how you can use phpMyAdmin to manipulate values in a MySQL database? Alternately, is there a way to write a function to import seed values from something like a Numbers spreadsheet if it doesn't detect the storedata XML file?
For your first question, you could edit the file directly but it's highly recommended you don't. How to edit it depends entirely on the store type you selected.
Regarding importing or setting up pre-generated data, of course: you can write code to manually insert entity instances into your Managed Object Context. There's a dedicated section on this very topic in the documentation. Further, if you have a lot of data to import, there's even a section on how to do this efficiently.
Is there any way to edit values in a
table, like how you can use phpMyAdmin
to manipulate values in a MySQL
database?
Xcode has a means of creating a quick and dirty interface for a data model. You just drag the data model file into a window in interface builder and it autogenerates an interface for you. This lets you view the data without having to have your entire app up and running.