I keep receiving the error
"LINQ to Entities does not recognize the method 'System.String get_Item(Int32)' method, and this method cannot be translated into a store expression"
on the following line in my code
var Reviewer = repository.reviewers.FirstOrDefault(t => t.ReviewerName == formCollection[3]);
formCollection[3] is a string returned from a drop down I have contained within a form. The query seems to work O.K. until it returns the value from the database. What can I do to fix this?
OK, I was trying to do too much at once, when I finally thought about it and put formCollection[3] into a string variable and then used the string variable in the linq query everything worked out ok.
Related
I have the following code attempting to truncate a table. The Joomla documentation makes me believe this will work, but it does not. What am I missing?
$db = JFactory::getDbo();
truncate_query = $db->getQuery(true);
//$truncate_query = 'TRUNCATE ' . $db->quoteName('#__mytable');
$truncate_query->truncateTable($db->quoteName('#__mytable'));
$db->setQuery($truncate_query);
echo $truncate_query;
exit();
If I use the line that is commented out to manually generate the SQL, it does work. The reason I am still looking to use the truncateTable function is that I am trying to include the truncation in a transaction. When I use the manual statement, the table is still truncated even if another part of the transaction fails, which is annoying since the other statements rely on data that is truncated, so if the table is emptied when it shouldn't be there is no data left to run the transaction again. Very annoying!
Here's how you call/execute your truncation query:
JFactory::getDbo()->truncateTable('#__mytable');
And now some more details...
Here is the method's code block in the Joomla source code:
public function truncateTable($table)
{
$this->setQuery('TRUNCATE TABLE ' . $this->quoteName($table));
$this->execute();
}
As you can see the truncateTable() method expects a tablename as a string for its sole parameter; you are offering a backtick-wrapped string -- but the method already offers the backtick-wrapping service. (Even if you strip your backticks off, your approach will not be successful.)
The setQuery() and execute() calls are already inside the method, so you don't need to create a new query object nor execute anything manually.
There is no return in the method, so the default null is returned -- ergo, your $truncate_query becomes null. When you try to execute(null), you get nothing -- not even an error message.
If you want to know how many rows were removed, you will need to run a SELECT query before hand to count the rows.
If you want to be sure that there are no remaining rows of data, you'll need to call a SELECT and check for zero rows of data.
Here is my answer (with different wording) on your JSX question.
I'm trying to type cast the result from ActiveRecord::Base.connection.select_all, but type info seems to be empty. According to this Stackoverflow Post, the type info can be derived by result.column_types at least when using postgres adapter. But when I run the same code with mysql adapter, I get nothing returned.
result = ActiveRecord::Base.connection.select_all(User.all.to_sql)
result.column_types #=> returns {}
result.cast_value #=> returns uncasted values
I know there's something like this that casts the thing,
User.type_for_attribute('id').deserialize('100')
# => 100
But this won't work well when working with ActiveRecord::Result, because we don't know which column belongs to which ActiveRecord class (at least from the result).
**Question 1. Are there any easy ways to achieve type casting on ActiveRecord::Result?
I followed the source code a bit, and seems like mysql adapter isn't passing the type info when initialising the Result object. Below is how ActiveRecord::Result is initialised (gh code),
module ActiveRecord
class Result
def initialize(columns, rows, column_types = {})
#columns = columns
#rows = rows
#hash_rows = nil
#column_types = column_types
end
...
And here's ActiveRecord's mysql adapter code and you can see it doesn't pass anything as the third argument, whereas, postgres code does.
So I'm guessing type casting for mysql is done somewhere else.
Question 2. Anybody knows where the magic for mysql is happening along with the normal ActiveRecord usage like User.first.id?
I have been getting this annoying exception while trying to create a native query with my entity manager. The full error message is:
java.lang.IllegalStateException: During synchronization a new object was found through a relationship that was not marked cascade PERSIST: com.model.OneToManyEntity2#61f3b3b.
at org.eclipse.persistence.internal.sessions.RepeatableWriteUnitOfWork.discoverUnregisteredNewObjects(RepeatableWriteUnitOfWork.java:313)
at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.calculateChanges(UnitOfWorkImpl.java:723)
at org.eclipse.persistence.internal.sessions.RepeatableWriteUnitOfWork.writeChanges(RepeatableWriteUnitOfWork.java:441)
at org.eclipse.persistence.internal.jpa.EntityManagerImpl.flush(EntityManagerImpl.java:874)
at org.eclipse.persistence.internal.jpa.QueryImpl.performPreQueryFlush(QueryImpl.java:967)
at org.eclipse.persistence.internal.jpa.QueryImpl.executeReadQuery(QueryImpl.java:207)
at org.eclipse.persistence.internal.jpa.QueryImpl.getSingleResult(QueryImpl.java:521)
at org.eclipse.persistence.internal.jpa.EJBQueryImpl.getSingleResult(EJBQueryImpl.java:400)
The actual code that triggers the error is:
Query query;
query = entityManager.createNativeQuery(
"SELECT MAX(CAST(SUBSTRING_INDEX(RecordID,'-',-1) as Decimal)) FROM `QueriedEntityTable`");
String recordID = (query.getSingleResult() == null ?
null :
query.getSingleResult()
.toString());
This is being executed with an EntityTransaction in the doTransaction part. The part that is getting me with this though is that this is the first code to be executed within the doTransaction method, simplified below to:
updateOneToManyEntity1();
updateOneToManyEntity2();
entityManager.merge(parentEntity);
The entity it has a problem with "OneToManyEntity1" isn't even the table I'm trying to create the query on. I'm not doing any persist or merge up until this point either, so I'm also not sure what is supposedly causing it to be out of sync. The only database work that's being done up until this code is executed is just pulling in data, not changing anything. The foreign keys are properly set up in the database.
I'm able to get rid of this error by doing as it says and marking these relationships as Cascade.PERSIST, but then I get a MySQLContrainstraViolationException on the query.getSingleResult() line. My logs show that its doing some INSERT queries right before this, so it looks like its reaching the EntityManager.merge part of my doTransaction method, but the error and call stack point to a completely different part of the code.
Using EclipseLink (2.6.1), Glassfish 4, and MySQL. The entitymanager is using RESOURCE_LOCAL with all the necessary classes listed under the persistence-unit tag and exclude-unlisted-classes is set to false.
Edit: So some more info as I'm trying to work through this. If I put a breakpoint at the beginning of the transaction and then execute entityManager.clear() through IntelliJ's "Evaluate Expression" tool, everything works fine at least the first time through. Without it, I get an error as it tries to insert empty objects into the table.
Edit #2: I converted the nativeQuery part into using the Criteria API and this let me actually make it through my code so I could find where it was unintentionally adding in a null object to my entity list. I'm still just confused as to why the entity manager is caching these errors or something to the point that creating a native query is breaking because its still trying to insert bad data. Is this something I'd need to call EntityManager.clear() before doing each time? Or am I supposed to call this when there is an error in the doTransaction method?
So after reworking the code and setting this aside, I stumbled on at least part of the answer to my question. My issue was caused by the object being persisted prior to the transaction starting. So when I was entering my transaction, it first tried to insert/update data from my entity objects and threw an error since I hadn't set the values of most of the non-null columns. I believe this is the reason I was getting the cascade errors and I'm positive this is the source of the random insert queries I saw being fired off at the beginning of my transaction. Hope this helps someone else avoid a lot of trouble.
So, I am trying to execute a query using ArcGIS API, but it should match any Json queries. I am kind of new to this query format, so I am pretty sure I must be missing something, but I can't figure out what it is.
This page allows for testing queries on the database before I actually implement them in my code. Features in this database have several fields, including OBJECTID and Identificatie. I would like to, for example, select the feature where Identificatie = 1. If I enter this in the Where field though (Identificatie = 1) an error Failed to execute appears. This happens for every field, except for OBJECTID. Querying where OBJECTID = 1 returns the correct results. I am obviously doing something wrong, but I don't get it why OBJECTID does work here. A brief explanation (or a link to a page documenting queries for JSON, which I haven't found), would be appreciated!
Identificatie, along with most other fields in the service you're using, is a string field. Therefore, you need to use single quotes in your WHERE clause:
Identificatie = '1'
Or to get one that actually exists:
Identificatie = '1714100000729432'
OBJECTID = 1 works without quotes because it's a numeric field.
Here's a link to the correct query. And here's a link to the query with all output fields included.
I have a 'user' table with a field name 'process_salary?' which has a boolean datatype
#user = User.create(params[:user])
if #user.process_salary?
//some code here
else
//some code here
end
When I create a new object of user and check for process_salary it gives me following error
NoMethodError: undefined method `process_salary?' for #<User:0xb6ac2f68>
Why does this error occur? Can I avoid it without changing my column name?
When I check it with the debugger it crashes the first time, but after that it runs properly
The question-mark has a special meaning in ActiveRecord. It can be used to check whether a field is true. You are using it as part of your field name which wasn't such a good idea. You could try if #user.process_salary?? exists but I think ultimately it is easiest to change your database column to be called 'process_salary'.
Side note: The 'rails console' is really helpful for playing around with models.
As cellcortex posted, question marks at the end of column names are tricky in Rails. If you need to have it there for legacy reasons, you might be able access the attribute as follows:
#user['process_salary?']
or the more verbose:
#user.read_attribute['process_salary?']
You can of course test for nil using .nil?.