I am updating a function to seed a database with a RestKit version < 0.10.
There is a didSeedObject method to intersect the seeding. In my code it is used to map a relationship by primary / foreign key.
In RestKit > 0.20 the seeding code has changed.
There is now a RKManagedObjectImporter to do this.
My question is: How can I intersect the seeding so I can create the relationship in the same kind of way it was done with didSeedObject?
EDIT:
Since didSeedObject or a way to intersect the mapping seems to have disappeared in RestKit > 0.20 I am trying to do this differently by doing the mapping right away. Therefore I have created another question here.
Related
Context:
I have a data model in Power pivot with three tables, tTasks, tCaseworks and tCaseworkStatus. I am attempting to create two calculated columns in tCaseworks which from the two data tables. All three tables are linked through the common field casework_id (see illustration below).
The data model is regularly updated with new data. The way I am doing this is as follows:
All three tables are sourced from three corresponding tables in my Excel workbook.
A VBA script deletes all records in the three Excel tables and then refreshes the data model (sidenote: because the data model demands lookup tables to not be empty the VBA code adds one row per table before refreshing).
New data is then added to the excel tables and the data model is refreshed.
This process works perfectly.
Problem:
The problem arises when I am adding calculated columns to tCaseworks and then attempting to update the data as described above. I have added two calculated columns; has_task and status_now. I am using the following DAX code:
has_task:
has_task =
IF (
CONTAINS (
RELATEDTABLE ( tTasks );
tTasks[casework_id]; tCaseworks[casework_id]
);
"Yes";
"No"
)
status_now:
status_now =
VAR TableX = RELATEDTABLE(tCaseworkStatus)
VAR ResultX = IF(
CONTAINS(TableX;tCaseworkStatus[casework_status_code];"Completed");"Completed";
IF(CONTAINS(TableX;tCaseworkStatus[casework_status_code];"Dismissed");"Dismissed";
IF(CONTAINS(TableX;tCaseworkStatus[casework_status_code];"Begun");"Begun";
IF(CONTAINS(TableX;tCaseworkStatus[casework_status_code];"Created");"Created";
"Find no status"))))
RETURN
ResultX
Both of these calculated columns work as expected as long as I do not delete the data in the model (I do have one hickup with both columns as described in this separated problem, but I think that is unrelated).
When the data has been deleted and I refresh the model I get the following error message:
"We cannot get the data from the data model. This is the error message we got: A circular dependency was discovered: 'tCaseworks'[status_now],'tCaseworks'[status_now],'tCaseworks'[has_task],'tCaseworks'[has_task],'tCaseworks'[status_now]."
Question:
What is creating this dependency and how can I avoid it?
My attempted solutions:
The problem only arise when there are two of these calculated columns. Any one of these two works perfectly without the other upon refreshing. I know that calculated columns are prone to circular problems, but unfortunately I need to use columns and not measures. I suspect that perhaps my choice in formula is creating the problem, most likely the contains-function. However, I don't know about any alternative ways of building the formulas I need. Any suggestions?
Edit:
I originally only posted a portion of my data model as I wanted the question to be as concise as possible but I guess it might have been confusing. The whole model concerns five objects from a case handling system: Claims, Cases, Caseworks, Tasks and Action Points. These objects are hierarchical, one claim can have one or more cases, but one case can only have one claim. Similarly, a case can have several caseworks, a casework can have several tasks, a task can have several action points. Additionally, the latter four can have a status attribute which is changed regularly.
I attempted to organize my data model in such a way that I had a lookup table for each object with unique values. I have many attributes for each object in my data that I did not include in the example above, and my goal was to add useful attributes through calculated columns in these tables. The data tables with the changes were intented to provide insight to the lookup tables.
I think your relationship model is a bit unusual. DAX works best when using something like dimensional fact model
I would consider the tCaseworkStatus a fact table since its like a log of the changes to your data. tTasks is a dimension, since it just add an extra dimension to your data.
The tCaseworks is not necessary since it doesn't hold any actual data (only calculated data).
if you want your current model to work, it might fix your problem if you just delete the relationship between tTasks and tCaseworks, and add a new between tTasks and tCaseworksStatus
edit.
it just occurred to me that the reason you have it like this, is that you may have a many-to-many relationship between tTasks and tCaseworksStatus. if that is the case you might have to create a proper many-to-many table. which is kind of what your tCaseworks is, but you cant have a relationship to the same key like you currently have.
edit2.
the solution seemed to be that somehow the Relatedtable function in conjunction with the relationship model was causing the error. using Lookupvalue instead seems to to have fixed the issue.
I am new in laravel. In my tutorial video teacher use foreign in migration but,i can create my relationships without it and use just belongTo and hasMany.When i use foreign can not delete one post easily (error is you can not delete because parent foreign has child ......).
my question is my way is good or not? and why?
Thank you all
Your way is good but I think foreign keys are better. Had you not had that foreign key, you would have deleted the post but all that post's children (referred to as orphans because they no longer have a parent) would have stuck around. In order to get around the foreign key error, you would need to first delete all the children for that post, and then delete the post.
The good news is foreign keys can also do this for you so you don't need to worry about keeping track of all the children. When you setup the foreign key, if you add the on delete cascade clause, when deleting the post, the database would automatically remove all of the posts's children for you and deleting a post without first deleting the children would no longer result in an error.
If it's your preference to keep the children around even when the post is deleted, you can use on delete set null instead which would simply set the children's foreign key to null rather than delete the record.
This is all useful for enforcing data integrity (databases should contain only accurate and valid data).
The answer really is not 'is this good practice in Laravel' so much as 'is this good practice for database management'.
There are many articles on the topic as to the good and bad side of using foreign keys. Here is a good explanation on the DBA stack exchange
https://dba.stackexchange.com/questions/168590/not-using-foreign-key-constraints-in-real-practice-is-it-ok
My personal preference is to use them to maintain data integrity. The real power comes in adding cascading deletes to the relationship (if applicable to your design).
It really comes down to how good you want your database to be.The main reasons to use foreign keys in your database are
To prevent actions that would destroy links between your tables
This would prevent the invalid data from being inserted to the foreign key column as it has to point to a existing value
Also defining foreign keys makes your query faster depending on database I don't know the exact milliseconds but if I find it out I will post it.
Well from the laravel point of view the way you do is a better way as this is how one of the main teacher of the Laravel(Jeffrey Way) teaches in the getting started with laravel series.
Foreign Keys are the way to define relationship between tables in your database whereas Laravel belongsTo() or hasMany() is a way to define relationship between tables in Laravel
I have uploaded my MVC3 project , it's s simple blog , at first it works well but after couple hours! following error appears (I've made custom error to Off to see the error)
The model backing the 'SiteContext' context has changed since the database was created. Either manually delete/update the database, or call Database.SetInitializer with an IDatabaseInitializer instance. For example, the DropCreateDatabaseIfModelChanges strategy will automatically delete and recreate the database, and optionally seed it with new data.
to solve this I have to manually delete my database and create again and then restore to the backup that I have created. but after after 2 hours again I get the error!
I really don't have any idea , what caused that ??
When you create a model and ask EF to create a database from it, EF would hash the model and store the hash value with the database. Whenever the context is created, EF recomputes the hash and matches it against what is stored at the database. If the model changes in any way, the resulting hash will be different and EF will throw the exception you have just seen. This is done in order to keep the model in sync with the database.
Is there any way the model could have changed during runtime?
One thing you could do to figure out the difference is to
1.Re-create the database from the model as you are doing now and get it scripted (script1.sql).
2.Wait till the error happens and delete the db and re-create it again and script it (script2.sql)
3.Try to compare the two and see whether you can spot a difference in the schemas.
This should give you an idea of what has changed in the model.
Goodluck
I now writing automation program for system based on MSSQL Server, using Ruby 1.9.3 and ActiveRecord 3.1.6 without Rails.
Tables have nonstandard ids (stk_id, urb_id, instead of id), also some tables haven't primary keys.
Before I added column id and set it as primary key my program worked very slowly. I waited nearly 3 minutes while the program makes two operations of selection and some little processing in table with 9000 records. But when I added column id and set it as primary key, these operations were finished in less then 10 secs.
Yet another problem I found in deletion operation: it doesn't work at all without primary key in table. Error when trying to delete without primary key:
undefined method `to_sym' for nil:NilClass
I can't modify the table structure of the production database. Maybe someone knows how to solve this problem without adding id columns and setting primary keys?
Remark: A database without primary keys is BAD !
http://www.helium.com/items/1539899-why-a-relational-database-needs-a-primary-key
Using nonstandard keys is no problem, just use self.primary_key = "stk_id"
You may also use composite_primary_keys:
https://github.com/drnic/composite_primary_keys
Create indexed views on each of the tables with no primary key. A unique clustered index as well as other indexes as needed can be applied. Including a single table in the view should prevent you from violating the many conditions an indexed view requires/prohibits.
I suggest looking into using Sequel instead of ActiveRecord. It is not opinionated about the database schema like ActiveRecord is and may be easier to use with a database schema you can't modify.
I am wondering how to 'seed' an auto incrementing primary key value using Castle AR? For Example wanting the Orders table primary keys to start out as 10000. Is this something that is 1. possible 2. a good solution for creating order numbers?
Maybe there is a way to have consecutive auto incrementing field on the DB that is NOT the pk, seeded to 10000?
Castle ActiveRecord is built on top of NHibernate and features of AR heavily rely on features of NHibernate. NHibernate contains several primary key generators:
1. native - This is the default generator. If you specify this then NHibernate automatically chooses generator type based on underlying database. For example, if I would have used native instead of identity in the above mapping snippet you will still get the same SQL because NHibernate is smart enough to understand that the underlying database SQL Server and it supports identity columns. NHibernate converts the returned values using Convert.ChangeType method.
2. identity - This can be used with Identity columns provided with SQL Server, MySQL, Sybase etc.,
3. sequence - Firebird, DB2, PostgreSQL, Oracle, SAP DB supports sequences
4. increment - This generator does not uses any database feature like sequence or identity. NHibernate automatically increments 1 to last primary key value. This generator is helpful when dealing with single database system but it does not help in cluster based environment.
5. hilo - Hi/Lo algorithm is used to generate primary key values. This is very efficient when compared to other generator types. When used, NHibernate creates a separate table named hibernate_unique_key and creates a column named next_hi and then NHibernate uses this table as a reference when INSERT happens. We will talk elaborately on this later in this post.
6. uuid.hex - Uses System.Guid and its ToString method for generating string based primary key values.
7. guid - This can be used when the class property type is Guid.
8. guid.comb - This is similar as guid but uses a different algorithm to produce primary key values. Note that uuid.hex, guid, guid.comb uses UNIQUEIDENTIFIER as a column data type in SQL Server.
9. assigned - last but not least, this generator assumes that the primary key value is assigned by the user.
So you can see that there are no such build-in functionality. In order to create an order number you can use 2 ways:
1. select max order and manually set it
2. add some insert trigger to database
In my opinion you should use first way because in this way you will not rely on database. And you can reuse this functionality when you will need to move an object up or down. I'm usually using this way.