I want a global variable which I can use in my different .xqy pages. Can I declare such a variable in xquery in Marklogic Server ?
You can declare a variable in any module. For instance, it is config.xqy.
declare variable $PRECISION as xs:integer := 4;
For using this variable you need to import this module in your work module.
import module namespace config = "http://your-namespace" at "config.xqy";
And refer to this variable:
$config:PRECISION
If your application is running on a single E-node, you can use server fields , which are sort of designed for this use case as well.
If you need values accessible across the server, there is a library in the Marklogic XQuery Commons for storing persistent key/value pairs:
https://github.com/marklogic/commons/blob/master/properties/properties.xqy
And you may have already considered this, but you could also just simply store the global data in a document on the database and access with doc() - or eval() if you need to get to it from a different database.
You have a few options. If you need a global constant variable, the config.xqy method mentions in #Andrew Orlov's answer is great because you avoid any locking from concurrent access to a properties.xml file.
If you need a variable that can be mutated across a cluster of nodes, the property.xqy example linked by #wst appears to use globally assigned namespaces to embed a retrievable key and value. Pretty clever. However, I'm not sure how much this is meant for heavy levels of change.
The E-node specific variable from #Eric Bloch is good, but please also be aware that it will not survive a system restart.
I'd be interested to know how these all compare performance-wise.
Related
During the recv subroutine I am currently changing my backend to another backend to handle the request, I need to declare a variable that will hold the value for the first/original backend that it was set to, so that when the request is restarted, I can then assign the backend back to this.
I can't just use the name for the backend and simply assign it back as I need it to be dynamic, storing it in a variable seems like the simplest solution but I can't seem to find any information on how this can be achieved through subroutines/ restarts.
If not possible are there any other solutions I could try to achieve this? Probably not possible from what I understand but even the ability to access an array of the backends defined and picking the first one would suffice, I just cant rely on naming the backend to assign it back.
Unfortunately it isn't possible to declare a variable as a BACKEND type (which is what req.backend returns).
See this 'Fastly Fiddle' example that demonstrates you'll get a compiler error of:
Expected variable type, one of: BOOL, INTEGER, FLOAT, TIME, RTIME, IP or STRING
There also isn't any way to get a list of available backends via VCL either.
Additionally you would need to hardcode the backend value (i.e. you need to explicitly know what backends are defined from the VCL perspective) as trying to store a backend into a header or variable will convert it to a STRING type representation (such as 6kLtu7NicmMs0DtKsuite9--F_origin_0).
This means even if you were able to parse the actual F_origin_0 backend from the string you wouldn't be able to assign it as a value to req.backend as that expects the value to be of type BACKEND (and VCL doesn't provide a way, AFAIK, to convert a string into that type).
In drools rule file how do I set the value of (or initialize) a global variable for optaplanner. My use case is following:
I want to declare a global java map that is constant and will not change during the execution. Every rule will access the map to check for a value, if value is in the map then rule will evaluate to false. The map is being generated before execution starts by accessing data in files/database.
This link https://issues.jboss.org/browse/PLANNER-94 is also requesting the access to global variable but this feature is rejected now.
How do i use the hack defined in this link: Setting global variables in working memory in Drools planner, from which object i should get CustomSolverPhaseCommand? [I am not able to comment on this post yet because i don't have enough reputation, sorry if it seems duplicate question].
I am creating SolverFactory from xml Resource and xml file contains the path to .drl file. Just like in .drl we can access object HardSoftScoreHolder scoreHolder, I want to access the map in the same way in 'then' part of rule.
can anyone please help?
Look at the examples that have a class that ends with Parameterization instead, such as ConferenceParametrization, this is probably a better alternative than globals.
Intro: I'm writing web interface with SQLAlchemy reflection that supports multiple databases. It turns out that authors of application defined postgresql with lowercase tables/columns, eg. job.jobstatus while sqlite has mixed case, eg Job.JobStatus. I'm using DeclarativeReflectedBase from examples to combine reflection and declarative style.
The issue: Configure SQLAlchemy to work with tables/columns case insensitive with reflection
I have done so far:
I have changed DeclarativeReflectedBase.prepare() method to pass quote=False into Table.__init__
What is left to be solved:
relationship definitions still has to obey case when configuring joins, like primaryjoin="Job.JobStatus==Status.JobStatus".
configure __tablename__ based on engine type
The question: Are my assumptions correct or is there more straightforward way? Maybe I could tell reflection to reflect everything lowercase and all problems are gone.
you'd probably want to look into defining a ".key" on each Column that's in lower case, that way you can refer to columns as lower case within application code. You should use the column_reflect event (See http://docs.sqlalchemy.org/en/latest/core/events.html#schema-events) to define this key as a lower case version of the .name.
then, when you reflect the table, I'd just do something like this:
def reflect_table(name, engine):
if engine.dialect.name == 'postgresql':
name = name.lower()
return Table(name, autoload=True, autoload_with=engine)
my_table = reflect_table("MyTable", engine)
I think that might cover it.
SqlMetal is creating object names such as...
The View:
Sales.ProductDescription
is created as:
Sales_ProductDescription
Ideally SqlMetal would create the ProductDescription class under a namespace .Sales. but thats probably too much to ask for. So is there anyways to get it to create the class without the sheme prefix such as "ProductDescription".
Thanks,
Justin
This would involve some modifications to the DBML file after it's been generated. However, in terms of maintainability that might restrict your ability to quickly regenerate when the schema changes.
If you have a volatile schema you could check out this collection of powershell scripts I wrote some time ago that will handle such changes to the DBML. It takes an XML file as input. Warning: the sample in the code repository may be out of date, but the scripts certainly work - I still use them.
SqlMetal has an optional parameter to include a namespace. The default value is no namespace. Check out this link on MSDN.
http://msdn.microsoft.com/en-us/library/bb386987.aspx
i'm building my web application to connect with db.
so far i have managed to deal with it, (although i didn't build BLL & DAL).
i have a table which has column "id". i know there is a way to declare it in the SQL Server to be incremented automatically. ( but i don't want it).
i want to declare a global application variable that will hold the value.
i have 2 questions:
how i declare it?
where i create it and initialize it ? (i have several login pages).
THANKS!
p.s
it would be helpful if someone will tell me how do i build the DAL with my stored procedures?
and for what i need yo use BLL which i cant do in the DAL?
You can use the Application object - it is part of the HttpContext and is directly accessible on any page.
If you don't want to use it, you may want to write a Globals class (or whatever name you like) that holds static members.
public class Globals
{
public static int Counter { get; set;}
}
// accessed from other classes:
Globals.Counter++;
Either approach will not work of you have a web farm or several web applications and will not survive restarts.
Regardless of these options, the right solution (even if you don't want to use it - can you explain why?), is to use the ID field with the IDENTITY clause.
Storing the variable is the easy part. Managing your own ID generation and the contention and concurrency issues is the hard part. Good luck.
There really is no such thing as a global variable in ASP.NET. Remember, HTTP is stateless.
The closest you can come is storing something in the Application object:
Application["myvar" ] = x;
x = Application["myvar"];
But even here, this variable is lost when the app needs to restart, which it can do from time to time.
A much better solution for what you describe is a database value.
Incrementing an integer and then throwing that incremented ID into the db is fraught with danger. Multithreading? What happens when the application bounces? Do dev and prod deployments share the same set of numbers?
It sounds like you need a globally unique identifier and can be created outside of the database. That sounds like a job for a GUID. Sure, it takes up more space in the db, but it probably isn't the worst thing you are going to do to the database.