I am implementing data mapper in my zend framework 1.12 project and its working fine as expected. Now further more to enhance it i wants to optimize it in following way.
While fetching any data what id i wants to fetch any 3 field data out of 10 fields in my model table? - The current issue is if i fetches the only required values then other valus in domain object class remains blank and while saving that data i am saving while model object not a single field value.
Can any one suggest the efficient way of doing this so that i can fetch/update only required values and no need to fetch all field data to update the record.
If property is NULL ignore it when crafting the update? If NULLs are valid values, then I think you would need to track loaded/dirty states per property.
How do you go about white-listing the fields to retrieve when making the call to the mapper? If you can persist that information I think it would make sense to leverage that knowledge when going to craft the update.
I don't typically go down this path. I will lazy load certain fields on a model when it makes sense, but I don't allow loading parts of the object like this, rather I create an alternate object for use in rendering a list when loading the full object is too resource intensive. A generic dummy list object I just use with tabular data. It being populated from SQL or stored procedures result-sets, usually with my generic table mapper.
Related
We would like to create an OData REST API. Our data model is such that each customer has their own database. All database objects have the same definition across all customer databases, with the exception of a single table.
The customer specific table we will call Contact. When a customer adds a column the system creates a column with a standardised name with a definition translated from options selected by the user in the UI. The user only refers to the column data by a field name they have specified to enable the user to be able to generate friendly queries.
It seems to me that the following approaches could be used to enable OData for the model described:
1) Create an OData open type to cater for the dynamic properties. This has the disadvantage of user requests for a customer not providing an indication of the dynamic properties that can be queried against. Even though they will be known for the user (via token authentication). Also, because dynamic properties are a dictionary, some data pivoting and inefficient query writing would be required. Not sure how to implement the IQueryable handling of query options for the dynamic properties to enable our own custom field querying.
2) Create a POCO class with e.g. 50 properties; CustomField1, CustomField2... Then somehow control which fields are exposed for use in OData calls. We would then include a separate API call to expose the custom field mapping. E.g. custom field friendly name of MobileNumber = CustomField12.
3) At runtime, check to see if column definitions of table changed since last check. If have, generate class specific to customer using CodeDom and register it with OData. Aiming for a unique URL for each customer. E.g. http://domain.name/{customer guid}/odata
I think the ideal for us is option 2. However, the fact the CustomField1 could be an underlying SQL data type of nvarchar, int, decimal, datetime, etc, there are added complications.
Has anyone a working example of how to achieve what has been described, satisfactorily?
Thanks in advance for any help.
Rik
We have run into a similar situation but with our entire dataset being unknown until runtime. Using the ODataConventionModelBuilder and EdmModel classes, you can add properties dynamically to the model at runtime.
I'm not sure whether you will have to manually add all of the properties for this object type even though only some of them are unknown or whether you can add your main object and then add your dynamic ones afterwards, but I guess either would be workable.
If you can get hold of which type of user it is on the server, you could then add only the properties that you are interested in (like option 3 but not having to CodeDom).
There is an example of this kind of untyped OData server in the OData samples here that should get you started: https://github.com/OData/ODataSamples/tree/master/WebApi/v4/ODataUntypedSample
The research we carried out actually posed Option 1 as the most suitable approach for some operations. i.e. Create an SQL view that unpivots the data in a table to a key/value pair of column name/column value for each column in the table. This was suitable for queries returning small datasets. This was far less effort than Option 3 and less confusing for the user than Option 2. The unpivot query converted the field values to nvarchar (string) values and thus meant that filtering in the UI by column value data types was not simple to achieve. (If we decide to implement this ability, I believe this can be achieved by creating a custom attribute that derives from EnablQueryAttribute, marking the controller action with it and manipulate the IQueryable before execution).
However, we wanted to expose a /Contacts/Export endpoint that when called would output the columns from a table with a fixed schema joined on a table with a client specific schema and output to a CSV file. All the while utilising the OData supported filter syntax. One of our customer databases has more than 12 million rows of data and is made up of approximately 30 columns.
To achieve this it looks like our best bet would have been to work with the Microsoft.OData.Core.UriParser.UriQueryExpressionParser class, unfortunately Microsoft in their wisdom have declared this as internal, as well as many of it's dependants.
Walking an abstract syntax tree built from OData supported query options and applying our own visitor to each node to build some dynamic Linq query/SQL seems like a possible solution.
For the time-being we will simply implement a cut-down set of supported $filter criteria without the support for grouping parenthesis.
I am developing a SPA using Angular-Breeze-WebAPI-EntityFramework.
Now Breeze uses the Entity Framework metadata information to create it's own Breeze models. We use this in our application for Breeze validation.
So far, it's all been nice and easy. Now we are having to create a search page (say for querying customers). The search can be by Customer.Name or by Product.Id (which would return a list of customers who have bought that product). The result is a ng-repeater, which displays Customer.Name, Order.LastPlaced etc.
if you are getting confused by the tables and columns, forget that. What I am only trying to get to is that, both the search object and the result object are not 1:1 with Entity tables (or objects). So obviously I feel the need to create a custom object (one for the search and one for the results). My question primarily is where and how do I create that object?
If I create it at the data layer, Breeze would have no idea of the metadata for each of the properties (since it uses EF for that).
I obviously can't create just a JavaScript object, since I will have to query the database (using EF) to search and populate the object.
So where does one create such a custom object (traversing multiple tables) such that Breeze still can figure out the metadata and perform validation and such when the need arises?
Thank you all.
You can create metadata on the client for types that the server either doesn't know about or doesn't have the schema for. See http://www.breezejs.com/documentation/metadata-by-hand.
I'm building my EF (v4.0.30319) data model from my SQL Server database. Each table has Created and Updated fields populated via database triggers.
This database is the backend of a ASP.NET Web API application and I recently discovered a problem. The problem is, since the Created and Updated fields are not populated in the model passed into the api endpoint, they are written to the database as NULL. This overwrites any values already in the database for those properties.
I discovered I can edit the EF data model and just delete those two columns from the entity. It works and the datetimes are not overwritten with NULL. But this leads to another, less serious but more annoying, problem... my data model has a bunch of tables that contain these properties and all the tables need to be updated by removing these two columns.
Is there a way to tell EF to ignore certain columns in entities across the entire data model without manually deleting them?
As far as I know, no. Generating the model from the database is going to always create all of the fields from the database table. Well, as long as it has a primary key it will.
It is possible to only update the fields that you want i.e. don't include the "Created" and "Updated" fields in your create and update methods. I'd have to say though, that I'd think it'd be better if those fields didn't even exist on the model at that point. You may at one point see those fields on the model and not remember that they won't get persisted to the DB.
You may want to look into just inserting the datetimes into those fields when you call your create() and update() methods. Then you could just ditch the triggers. You'd obviously want to use a class library for all of your database operations so this functionality would be in one place. To keep it nice and neat, you know?
How can I change the type of a Core Data entity column programmatically? For example, form String to Int 16. The entity can be assumed empty (no data row).
Firstly, it's not an SQL column, it's the attribute of an entity. Attributes have behaviors, columns in SQL do not.
In answer to your question, once a data model model has been used to write data to a persistent store file (sqlite store or other formats) it cannot altered programatically. If you change an attribute, you need to perform a version migration.
See: Core Data Model Versioning and Data Migration Programming Guide for details.
A little general advice: Core Data is not SQL. Entities are not tables. Objects are not rows. Attributes are not columns. Relationships are not joins. Core Data is an object graph management system that may or may not persist the object graph and may or may not use SQL far behind the scenes to do so. Trying to think of Core Data in SQL terms will cause you to completely misunderstand Core Data and result in much grief and wasted time.
You can manipulate the attributes (including) type of an entity in an NSManagedObjectModel until it is used to initialize a persistent store coordinator. So, create the NSManagedObjectModel, mutate the attribute (not a column) type, then setup the Core Data stack as usual.
Of course, if you already have any data persisted using the original model, you'll have to perform a schema migration to update the data to the new type.
I'm implementing a new iPhone app and am relatively new to Cocoa development overall. I am at the stage of choosing how the persistence layer of this app will work, and it looks like I'm basically choosing between Core Data and sqlite3.
The persisted models in this app are intended to have a schema that is loaded at runtime (from some kind of defn file, probably XML). By which I mean, this app is intended to have objects that are user-definable to some extent, e.g. the Customer type (which has certain built-in fields like "name" and "email") can be modified to have extra fields based on the user's specific needs (e.g. a user might want to add a "favourite fruit" field to their Customer type).
Having said that, will Core Data work for an app with a non-baked-in data model like this? I've just started playing around with the Core Data object designer thing in XCode and it seems like this thing wants to work with objects that have fixed fields that are compiled in.
I'm definitely trying to take the path of least resistance here, and I can see the benefits of using an Apple-supplied data framework, but don't want to start down that path if it's going to lock me into a data model that's defined at compile time.
The Core Data data model needs to be defined at compile time, but that does not mean you can't allow for custom fields to be added and used by end users.
It just means that you would define an entity for custom fields and create the fields as objects.
It is best to design a data model that meets your needs rather than think of how you would solve the problem in SQL.