I was wondering if it is possible to implement a custom index as a postgres extension? I tried to find an answer via Google, but was not very successful (mainly because of the ambiguity of the search query).
Maybe someone has already implemented a custom index and can point me to some literature or code.
According to the documentation:
The core system knows nothing about indexes beyond what is specified here, so it is possible to develop entirely new index types by writing add-on code.
To add a new index method, you create a new index access method.
An example of that is available as the “contrib” module bloom, which implements Bloom filters as a PostgreSQL index type. The source code of that module will server as guidance how to create your own index access method.
Related
I have asked this question on Github, issue #641, since it seems like a deficiency or an enhancement question.
Most databases (e.g. Oracle, SQL*Server, Sybase, ... ) send back a description of the resultset, even if there are zero rows. I cannot seem to find this in pqxx, nor can I find a way to describe SQL of any kind prior to execution. The only way I have been able to get the SQL metadata is by collection upon the first row retrieved, but this is limited to an actual row being retrieved. If there are zero rows, I have no way to determine the metadata.
Looking at the v15.x code base for libpq (standard C library), I see that psql has a "workaround" for this very problem. In the file src/bin/psql/common.c there is a function called static bool DescribeQuery(const char *query, double *elapsed_msec) (on or about line #1248).
This function has a rather ingenious solution for this very problem. They create an "unnamed" prepared statement, which they do not execute, instead they use the results of that call, which provides the field info, and subsequently query against the pg_catalog for the metadata descriptions (source below).
Unfortunately, the pqxx library doesn't provide enough (that I can tell) to duplicate this functionality. Does anyone have a solution for this problem?
Credit for resolution goes to Jeroen Vermeulen, on the Github issue #641. He suggested that the predicate AND false be added to the query to force a prototype result. By doing this an empty resultset is returned, with the fields available for metadata collection.
Just beginner for Spree Framework
I am trying to bring the whole code base to my local repository, so that I am make relevant changes as per my requirement like addition of different API calls to fill by Product tables.
Just like Devise, we can bring the code base to local code base for modification. In the same manner, I am willing to pull the code base and making changes as per requirement.
Please suggest something so that I can make changes as per my requirement.
I found Solidus as option to full fill my requirement.
Thanks
You can just override/add code as you want using class_eval. Here is example
#app/controllers/spree/admin/images_controller_decorator.rb
Spree::Admin::ImagesController.class_eval do
def index
#images = Spree::Image.all
end
end
I need help with creating UseCase template for Enterprise Architect (v 12.1). I have UseCase diagram like this one and I need to generate documentation from diagram named "Transaction" (as you can see on this picture):
The problem is, that one UseCase is located in another package. When generating documentation with my template (I need only " Transaction" package in my documentation not Transaction Validation or other packages), the UseCase of Transaction Validation is not generated (simply because of this element is from another package).
One more note - we don't write Structured Specification Scenario, but we write scenarions into "Description" tab. Like this one:
I tried to create template for generating elements located on diagram, but there is only option to generate Element.StructuredScenarioText for "foreign" element located on diagram when creating template (I need the red one values - ElemScenario.Scenario, ElemScenario.Type and ElemScenario.Notes):
Is there any option to generate Scenario (not structured) for "foreign" UseCase located on diagram?
Thanks for your help!
In order to include the description from an element's scenarios, select the RTF template section package / element / scenario and insert the Notes field.
Your other issue, how to include elements from other packages in a report, is a little trickier.
Normally you would base the template on the diagram and make sure you select Include all Diagram Elements in Report in the Generate Documentation dialog.
The problem in this case is that when you document elements in the context of a diagram, you only have access to a limited subset of the element fields. For scenarios, you're limited to the Element.StructuredScenarioText field, which in your case is empty. The same limited set of fields is available if you document elements in the context of a connector, ie elements connected to the element being documented, so you can't use that either.
The simplest option is to create a template fragment. With fragments you can implement your own selection using an SQL query or a custom script, and thus free your document from the package hierarchy.
Alternatively, you can run the generation from a higher package level which includes all your use cases (in your case, "Transactions in WO"), and add a filter in the Generate Documentation dialog to select only those use cases you want.
I am currently in the process of writing a custom DataProvider. Using the Intergrate External Data documentation.
I've managed to show the external data in the Sitecore back end. However whenever I try to view the data in the items I created, I am getting an error
Null ids are not allowed. <br> Parameter name: displayName
There seems to be precious little on the subject on how to create a custom DataProvider on the Sitecore Developer Network.
The example on their website seems to only show how to import a SINGLE item into a static database. However I am simply trying to merge some items into the hierarchy and I can't find any useful documentation.
It seems that one of your methods that should return an ID doesn't. It might be GetChildIds and/or GetParentId.
Nick Wesselman wrote a good article about it gathering all the information including an example on the Marketplace. I think that is your best start. You can read it here.
Turns out I needed to include at the very least, the Fields->Section->Template in the GetParent method. To be on the safe side I included the Fields/Sections/Templates into my implementations of
GetChildIDs
GetItemDefinition
GetParentID
It wasn't obvious that this was the case, since I had in fact implemented the GetTemplates method correctly, and I had expected that should be enough.
This should be a simple scenario - I have a data model with a parent/child relationship. For example's sake, let's say it's Orders and OrderDetails - 1 Order -> many OrderDetails.
I'd like to expose the model via oData using a standard DataService, but with a few limitations.
First, I should only see my Orders. That's simple enough using EntitySetRights.ReadSingle and a QueryInterceptor to make sure the order is in fact mine.
So far, so good! But how can the associated OrderDetail records be exposed in the oData feed in a way where I can read OrderDetails for a specific (read single) Order without giving access to the entire OrderDetails table?
In other words, I want to allow reading my details
myUrl.com/OrderService.svc/Orders(5)/OrderDetails <-- Good! My order is #5
but not everyone's details
myUrl.com/OrderService.svc/OrderDetails <-- Danger, Scarry, Keep Out!
Thanks for the help!
This is so called "containment" - your sample exactly described here: http://data.uservoice.com/forums/72027-wcf-data-services-feature-suggestions/suggestions/1012615-support-containment-hierarchical-models-in-odata?ref=title
WCF Data Services doesn't support this out of the box yet.
It is theoretically possible to implement such restriction with a custom LINQ provider. In your LINQ implementation you could detect the expansion (not that hard) and in that case allow it. But you could prevent queries to the entity set itself (also rather easy to recognize). For more details of how the LINQ expressions look plese refere to this series: http://blogs.msdn.com/b/vitek/archive/2010/02/25/data-services-expressions-part-1-intro.aspx
It depends on what provider you wanted to use originally. If you had a custom provider already this is not that hard. If you had a reflection based provider, it is possible to layer this on top. If you had EF, this might be rather tricky (not sure if it's even possible).