Is there a way to get the columns of a table in the order that they are defined within the database in activejdbc? I tried this:
User u = new User(); // User extends org.javalite.activejdbc.Model
Map<String, ColumnMetadata> columns = u.getMetaModel().getColumnMetadata();
However, the returned map has the columns in alphabetical order, not the order that is defined in the table.
I'm using MySQL if that matters.
It uses standard JDBC metadata calls, please see here: Registry#getColumns.
However this is returned from the JDBC driver, it is added to a Map in the code. As you know, maps are not ordered in any way. Not sure why you would need to get the columns in the same order as they are defined in the database, or if this is even possible.
If you really want this, you can drop to a DB level:
Connection con = Base.connection();
// get metadata from the connection any way you want
This way, you can get whatever driver can provide (your mileage is will be limited by the driver implementation)
Related
I have models:
class Reference(models.Model):
name = models.CharField(max_length=50)
class Search(models.Model):
reference = models.ForeignKey(Reference)
update_time = models.DateTimeField(auto_now_add=True)
I have an instance of Reference and i need to get all last searches for the reference. Now i am doing it in this way:
record = Search.objects.filter(reference=reference)\
.aggregate(max_date=Max('update_time'))
if record:
update_time = record['max_date']
searches = reference.search_set.filter(update_time=self.update_time)
It is not a big deal to use 2 queries except the one but what if i need to get last searches for each reference on a page? I would have got 2x(count of references) queries and it would not be good.
I was trying to use this solution https://stackoverflow.com/a/9838438/293962 but it didn't work with filter by reference
You probably want to use the latest method.
From the docs, "Returns the latest object in the table, by date, using the field_name provided as the date field."
https://docs.djangoproject.com/en/1.8/ref/models/querysets/#latest
so your query would be
Search.objects.filter(reference=reference).latest('update_time')
I implemented a snippet from someone in gist but I don't remember the user neither have the link.
A bit of context:
I have a model named Medicion that contains the register of mensuration of a machine, machines are created in a model instance of Equipo, Medicion instances have besides of a Foreign key to Equipo, a foreign key to Odometro, this model serves as a kind of clock or metre, that's why when I want to retrieve data (measurements aka instances of Medicion model) for a certain machine, I need to indicate the clock as well, otherwise it would retrieve me a lot of messy and unreadable data.
Here is my implementation:
First I retrieve the last dates:
ult_fechas_reg = Medicion.objects.values('odometro').annotate(max_fecha=Max('fecha')).order_by()
Then I instance an Q object:
mega_statement = Q() # This works as 'AND' Sql Statement
Then looping in every date retrieved in the queryset(annotation) and establishing the Q statement:
for r in ult_fechas_reg:
mega_statement |= (Q(odometro__exact=r['odometro']) & Q(fecha=r['max_fecha']))
Finally passed this mega statement to the queryset that pursues to retrieve the last record of a model filtered by two fields:
resultados = Medicion.objects.filter(mega_query).filter(
equipo=equipo,
odometro__in=lista_odometros).order_by('odometro', 'fecha') # lista_odometros is a python list containing pks of another model, don't worry about it.
I'm having a strange issue.
I created a model observer for my user model. The model observer is being run at 'saving'. when I dump the object at the very end of the user model to be displayed ( this is just before it saves.. according to laravel docs ) it displays all the attributes set correctly for the object, I've even seen an error that showed the correct attributes as set and being inserted into my database table. However, after the save has been completed and I query the database, two of the fields are not saved into the table.
There is no code written by myself sitting between the point where I dumped the attributes to check that they had been set and the save operation to the database. so I have no idea what could be causing this to happen. All the names are set correctly, and like I said, the attributes show as being inserted into the database, they just never end up being saved, I receive no error messages and only two out of ten attributes aren't being saved.
In my searches I have found many posts detailing that the $fillable property should be set, or issues relating to a problem with variables being misnamed or unset, however because I already have the specific attributes not being saved specified in the $fillable array, on top of the fact that they print out exactly as expected pre save, I don't believe those issues are related to the problem I am experiencing.
to save I'm calling:
User::create(Input::all());
and then the observer that handles the data looks like this:
class UserObserver {
# a common key between the city and state tables, helps to identify correct city
$statefp = State::where('id',$user->state_id)->pluck('statefp');
# trailing zeros is a function that takes the first parameter and adds zeros to make sure
# that in this case for example, the dates will be two characters with a trailing zero,
# based on the number specified in the second parameter
$user->birth_date = $user->year.'-'.$user->trailingZeros( $user->month, 2 ).'-'.$user->trailingZeros( $user->day, 2 );
if(empty($user->city)){
$user->city_id = $user->defaultCity;
}
$user->city_id = City::where( 'statefp', $statefp )->where('name', ucfirst($user->city_id))->pluck('id');
# if the user input zip code is different then suggested zip code then find location data
# on the input zip code input by the user from the geocodes table
if( $user->zip !== $user->defaultZip ){
$latlon = Geocode::where('zip', $user->zip)->first();
$user->latitude = $latlon['latitude'];
$user->longitude = $latlon['longitude'];
}
unset($user->day);
unset($user->month);
unset($user->year);
unset($user->defaultZip);
unset($user->defaultCity);
}
that is the code for the two values that aren't being set, when I run
dd($user);
all the variables are set correctly, and show up in the mysql insert attempt screen with correct values, but they do not persist past that point.. it seems to me that possibly mysql is rejecting the values for the city_id and the birth_date. However, I cannot understand why, or whether it is a problem with Laravel or mysql.
since I was calling
User::create();
I figured I'd try to have my observer listen to:
creating();
I'm not sure why it only effected the date and city variables, but changing the function to listen at creating() instead of saving() seems to have solved my problem.
I have been struggling with an issue for a couple of days. I am sharing a Content Provider with two different apps (app A and app B). All the stuff regarding DB creation and Content Provider management is done by app A. App B just accesses it using the corresponding Authorities and a Content Provider Client.
ContentProviderClient myCPClient = this.miContext.getContentResolver().acquireContentProviderClient(this.miUri);
The problem comes up when trying to query the database in a more complex way, i.e. using some key words like GROUP BY, HAVING, etc. I need to get unique references according to one specific column (I want to use GROUP BY), and I have found out that there is no rawQuery() method for a ContentProviderClient, but a simplified query() method (compared to the one available in the class SQLiteDatabase, which allows to formulate proper MySQL commands).
I have checked this answer, but since my ContentProvider is accessed from a different app, I do not have any class like MyContentProvider.
To sum up, is there any way to make a proper query (like rawQuery()) to a ContentProvider which was generated by a different app?
I have finally got to a solution which is rather simple and sensible. I got a very good explanation about Content Providers and Content Resolvers. The latter is used to access the former, which means that they can not control what is in the provider, but get data from them. This means that you can not make a Content Provider Client to use a rawQuery() if it is not implemented (override) in the query() method of the corresponding ContentProvider.
To work around my problem, I have used a flag in my provider client and modify my content provider to read it so I can make use of GROUP BY. I just wanted to get unique references from the database according to a particular column.
Here it is the solution, which is not a very clean one, but it works quite well.
For the ContentProviderClient,
ContentProviderClient myCPClient = this.miContext.getContentResolver().acquireContentProviderClient(this.miUri);
//I declare some variables for the query
//'selection' will get all the rows whose "_id" is greater than 0, i.e. all the rows
String selection = BaseDatosParam.Tabla._ID + ">?";
String[] selectionArgs = {"0"};
//'groupBy' is not formatted in any particular way. I just need it to contain the pattern "GROUP BY"
String groupBy = "GROUP BY" + BaseDatosParam.Tabla.REF;
//the last field of the query corresponds to 'sortOrder', but I
Cursor c = myCPClient.query(Uri.parse(miUri.toString()),
projection, selection, selectionArgs, groupBy);
In the ContentProvider,
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder)
{
String where = selection;
String groupBy = null;
SQLiteDatabase db = this.miBDManager.getWritableDatabase();
//We just check out whether 'sortOrder' includes the pattern "GROUP BY", otherwise that field will remain null
Pattern myPat = Pattern.compile("GROUP BY");
Matcher myMat = myPat.matcher(sortOrder);
if (myMat.find())
groupBy = myMat.replaceFirst("");
Cursor c = db.query(BaseDatosParam.Tabla.NOMBRE_TABLA, projection, where, selectionArgs, groupBy, null, null);
c.setNotificationUri(this.getContext().getContentResolver(), uri);
return c;
}
Regards,
OK, in good old fashioned PHP MVC, I might use a model to hit the DB, send info to my PHP controller that I pass on to the View. In the View, I might take that info (say i ajax'ed my controller for the info) and create a table or ul to display the data returned.
I've had trouble finding any modern (ver 6.1 is what i'm on) tutorial to show me how to preform this action in typo3.
Can anyone just "steer" me in the right direction? Perhaps provide an example via answer, or some links to further information that may compare it down to "old fashioned MVC"?
Extension has been suggested, but I'd like to know the very base process of what I'm asking before I try writing some extension, unless the extension is the only way. Although, my table is now on the SAME DB my typo3 is on, so shouldn't there be some command to just simply call my table and get the rows? Maybe send them to a ###sub-part###?
You can use a typoscript cObj content and the select option together with the function render_obj when your table name is like the typo3 nameing convention. The select pulls the record from the table and pass it to the render_obj function. It's a function that can apply to all cObj and iterate over the entire selection. stdWrap works only on the entire cObj. When you need to work through each record you need the render_obj function. For example:
10 = CONTENT
10 {
select {
pidInList = 1
where = colpos=1
orderBy = sorting
}
table = tt_content
renderObj.stdWrap.wrap = <li>|</li>
renderObj.stdWrap.required = 1
}
10.stdWrap.wrap = <ul>|</ul>
This gives you an unorderd list from the tt_content table with pid=1 and the content from the far left column.
I have some tables in a MySQL database to represent records from a sensor. One of the features of the system I'm developing is to display this records from the database to the web user, so I used ADO.NET Entity Data Model to create an ORM, used Linq to SQL to get the data from the database, and stored them in a ViewModel I designed, so I can display it using MVCContrib Grid Helper:
public IQueryable<TrendSignalRecord> GetTrends()
{
var dataContext = new SmgerEntities();
var trendSignalRecords = from e in dataContext.TrendSignalRecords
select e;
return trendSignalRecords;
}
public IQueryable<TrendRecordViewModel> GetTrendsProjected()
{
var projectedTrendRecords = from t in GetTrends()
select new TrendRecordViewModel
{
TrendID = t.ID,
TrendName = t.TrendSignalSetting.Name,
GeneratingUnitID = t.TrendSignalSetting.TrendSetting.GeneratingUnit_ID,
//{...}
Unit = t.TrendSignalSetting.Unit
};
return projectedTrendRecords;
}
I call the GetTrendsProjectedMethod and then I use Linq to SQL to select only the records I want. It is working fine in my developing scenario, but when I test it in a real scenario, where the number of records is way greater (something around a million records), it stops working.
I put some debug messages to test it, and everything works fine, but when it reaches the return View() statement, it simply stops, throwing me a MySQLException: Timeout expired. That let me wondering if the data I sent to the page is retrieved by the page itself (it only search for the displayed items in the database when the page itself needs it, or something like that).
All of my other pages use the same set of tools: MVCContrib Grid Helper, ADO.NET, Linq to SQL, MySQL, and everything else works alright.
You absolutely should paginate your data set before executing your query if you have millions of records. This could be done using the .Skip and .Take extension methods. And those should be called before running any query against your database.
Trying to fetch millions of records from a database without pagination would very likely cause a timeout at best.
Well, assuming information in this blog is correct, .AsPagination method requires you to sort your data by a particular column. It's possible that trying to do an OrderBy on a table with millions of records in it is just a time consuming operation and times out.