I am trying to do string replace on entries of a column inside a db table. So far, I have reached till here:
$misa = DB::table('mis')->pluck('name');
for($i=0;;$i++)
{
$misa[$i] = substr_replace("$misa[$i]","",-3);
}
The error I am getting is "Undefined offset:443".
P.S. I am not a full-fledged programmer. Only trying to develop a few simple programs for my business. Thank You.
Since it's a collection, use the transform() collection method transform it and avoid this kind of errors. Also, you can just use str_before() method to transform each string:
$misa = DB::table('mis')->pluck('name');
$misa->transform(function($i) {
return str_before($i, ':ut');
});
There are a few ways to make this query prettier and FASTER! The beauty of Laravel is that we have the use of both Eloquent for pretty queries and then Collections to manage the data in a user friendly way. So, first lets clean up the query. You can instead use a DB::Raw select and do all of the string replacing in the query itself like so:
$misa = DB::table('mis')->select(DB::raw("REPLACE(name, ':ut' , '') as name"));
Now, we have a collection containing only the name column, and you've removed ':ut' in your specific case and simply replaced it with an empty string all within the MySQL query itself.
Surprise! That's it. No further php manipulation is required making this process much faster (will be noticeable in large data sets - trust me).
Cheers!
Related
I am loading data from excel. In foreach I am checking for each record if it does exist in database:
$recordExists = $this->checkIfExists($record);
function checkIfExists($record) {
$foundRecord = $this->repository->newQuery()
->where(..., $record[...])
->where(..., $record[...])
...
->get();
}
When the excel contains up to 1000 values which is relatively small piece of data - the code runs around 2 minutes. I am guessing this is very inefficient way to do it.
I was thinking of passing the array of loaded data to the method checkIfExists but then I could not query on the data.
What would be a way to proceed?
You can use laravel queue if you want to do a lot of work within a very short time. Your code will run on backend. Client can not recognize the process. just show a message to client that this process is under queue. Thats it
You can check the Official Documentation From Below Url
https://laravel.com/docs/5.8/queues
If you passes all the data from the database to the function (so no more queries to the database), you can use laravel collections functions to filter.
On of them is where => https://laravel.com/docs/5.8/collections#method-where
function checkIfExists($record, Collection $fetchedDataFromDatabase) {
// laravel collectons 'where' function
$foundRecord = $fetchedDataFromDatabase
->where(..., $record[...])
->where(..., $record[...]);
}
other helpful functions.
filter
contains
Just trying to understand... if at the start of some method I eager load a record and its associated children like this:
#object = Object.include(:children).where(email:"test#example.com").first
Then does that mean that if later I have to look through that object's children this will not generate more database queries?
I.e.,
#found_child = #object.children.where(type_of_child:"this type").first
Unfortunately not - using ActiveRecord::Relation methods such as where will query the database again.
You could however filter the data without any further queries, using the standard Array / Enumerable methods:
#object.children.detect {|child| child.type_of_child == "this type"}
It will generate another database query in your case.
Eager loading is used to avoid N+1 queries. This is done by loading all associated objects. But this doesn't work when you want to filter that list with where later on, Rails will than build a new query and run that one.
That said: In your example the include makes your code actually slower, because it loads associated object, but cannot use them.
I would change your example to:
#object = Object.find_by(email: "test#example.com")
#found_child = #object.children.find_by(type_of_child: "this type")
(integer) cast must be done in Homestead for Controller parameter
I am having a hard time searching for the cause of a discrepancy between my local dev environment (Homestead) and the hosted one.
I define a route like this:
Route::get('group/{id}/data', 'GroupDataController#index');
And the code in the Controller looks like this:
public function index($id)
{
return Grouping::all()->where('group_id', $id);
}
Which works fine in production (hosted env), BUT when I execute it locally it throws and empty array [] unless I modify my Controller function to look like this:
public function index($id)
{
return Grouping::all()->where('group_id', (integer)$id);
}
I have no idea of what is going on in here, and I am tired of making changes all over my Controller to make it work on both environments.
I have searched in several place, but maybe I am using incorrect tokens for my search as I have found nothing.
Any help will be really appreciated.
The problem here is that you're not using the correct set of functions.
When you call Grouping::all(), this is actually returning an Eloquent Collection object with every record in your groupings table. You are then calling the where() method on this Collection. This causes two problems: one, it is horribly inefficient; two, the where() method on the Collection works differently than the where() method on the query builder.
The where() method on the Collection takes three parameters: the name of the field, the value in that field on which to filter, and finally a boolean value to tell it whether or not to do a strict comparison (===) or a loose comparison (==). The third parameter defaults to strict. This strict comparison is why you're having the issue you are having, but I cannot explain why one environment sees $id as an integer and the other doesn't.
The where() method on a query builder object will actually add a where clause to the SQL statement being executed, which is a much more efficient way of filtering the data. It also has more flexibility as it is not limited to just equals comparisons (the second parameter is the comparison operator for the where clause, but will default to "=" if it is left out).
You have two options to fix your issue. You can either pass in false as the third parameter to your where() method in the current code (bad), or you can update the code to actually filter using the query instead of filtering on the entire Collection (good).
I would suggest updating your code to this:
public function index($id) {
return Grouping::where('group_id', '=', $id)->get();
}
In the above code, Grouping::where('group_id', '=', $id) will generate a query builder object that has the given where clause, and then get() will execute the query and return the Collection of results.
I marked #patricus (thanks you, so much!) as the correct answer, for he really pointed me in the right direction to understand that there are some keywords that work differently under different contexts (like get()), but I will also point out, how my 2 confusing points were solved in my case:
The difference in my code between production and Homestead development environments was solved by pointing my Homestead to the production database. I am not sure what was the difference (maybe collation or table format), but it gave me a quick out.
I was trying to filter a list of elements in the database but I was constructing it with the wrong logic for Laravel.
To clear what I refer to in the second point, I was using this code:
Grouping::all(['id', 'name_id', 'product_id', 'ship_id'])->where('name_id', '=', $id);
I thought this could work, because it would be selecting all items, with the selected columns, and then filter those with a where clause. But I was wrong, since, as I found out later, the correct way of writing this is:
Grouping::where('name_id', $id)->select('id', 'name_id', 'product_id', 'ship_id')->get();
This is because I forgot completely that I was assembling the query, not writing the actions I expected the program to do.
This second syntax has more logic, since I specify the filter, then put the columns over what was filtered, and finally execute the query with the get() clause.
Of course, it can also be written the other side around for clearer fluent reading:
Grouping::select('id', 'name_id', 'product_id', 'ship_id')->where('name_id', $id)->get();
I have domain object named Roll and on the list page i want to show the user all the Roll objects iterating through a list, sorted by entry date.
Here is the code i am using
[rollList: Roll.findAll(sort:"rollDate"){userid==uid}]
rollDate is a field inside the Roll object with data type java.util.Date
Any suggestion on why the output is not sorted by rollDate. When i iterate through the rollList on the gsp page it is not sorted.
Also, on the Roll domain object i have even put this code, but it's still not sorting.
static mapping = {
sort "rollDate"
}
Thank you.
Why aren't you using the dynamic finders?
Roll.findAllByUserid( uid, [ sort:"rollDate", order: 'desc'] )
should work.
The findAll( Map, Closure ) method appeared not a long time ago, perhaps it was not tested well...
You might need to use order in your query as well, then add order to it
[rollList: Roll.findAll(sort:"rollDate", order: 'desc'){userid==uid}]
After trying both the solutions mentioned it still didn't work. So i thought something might be wrong on the front end.
While researching more i found that since i was using jquery data tables it used to re order the sorting. The solutions i found was here
jQuery DataTable rows order
So both the answers above are correct. The issue was actually with jquery data tables.
I have a course table which I need to search based on keywords typed in the search box.
Here is a sample query:
SELECT * FROM Courses WHERE
Title LIKE '%word%' OR Title LIKE '%excel%' OR
Contents LIKE '%word%' OR Contents LIKE '%excel%'
How can I convert this in LINQ where LINQ would dynamically generate WHERE statements based on each keywords.
I tried to user PredicateBuilder it works fine as long as the field is VARCHAR. For the "TEXT" fields the quotes are not generated thus causing compiler to give an error message. Here is the SQL generated by PredicateBuilder
SELECT [t0].[CoursesID], [t0].[Title], [t0].[Contents], [t0].[Active],
FROM [dbo].[Courses] AS [t0]
WHERE ([t0].[Title] LIKE '%word%') OR ([t0].[Contents] LIKE %word%) OR
([t0].Title] LIKE '%excel%') OR ([t0].[Contents] LIKE %excel%)
Notice there is no single Quote for the "Contents" field which is a Text field in the database.
Is there any easy way to build WHERE statement and attach it with query? Does anyone know how I can do this without PredicateBuilder?
Thanks in advance.
Since you are working w/ LINQ I suppose you are working against a LINQ-to-SQL data context right? I don't have a spare DataContext lying around to test this, but this should give you some ideas.
I don't know if it will work against data context though, but most of these are pretty basic stuff (chaining OR operator and Contains method call) so it shouldn't cause problem when the query translates to SQL.
First I create a custom function that would build my predicate:
Func<string, Func<DataItem, bool>> buildKeywordPredicate =
keyword =>
x => x.Title.Contains(keyword)
|| x.Contents.Contains(keyword);
This is a function which takes a single string keyword and then return another function which takes a DataItem and checks it against the keyword.
Basically, if you pass in "Stack", you'll get a predicate: x => x.Title.Contains("Stack") || x.Contents.Contains("Stack").
Next, since there are many possible keywords and you need to chain it with an OR operation, I create another helper function to chain 2 predicates together with an OR
Func<Func<DataItem,bool>, Func<DataItem, bool>, Func<DataItem, bool>> buildOrPredicate =
(pred1, pred2) =>
x => pred1(x) || pred2(x);
This function takes 2 predicates and then join them up with an OR operation.
Having those 2 functions, I can then build my where predicate like this:
foreach (var word in keywords) {
filter = filter == null
? buildKeywordPredicate(word)
: buildOrPredicate(filter, buildKeywordPredicate(word));
}
The first line inside the loop basically checks if the filter is null. If it is, then we want a simple keyword filter built for us.
Else if the filter is not null, we need to chain existing filters with an OR operation, so we pass the existing filter and a new keyword filter to buildOrPredicate to do just that.
And then we can now create the WHERE part of the query:
var result = data.Where(filter);
Passing in the complicated predicate we've just built.
I don't know if this will different from using PredicateBuilder but since we are deferring query translation to the LINQ-to-SQL engine, there should not be any problems.
But as I said, I havn't tested it against a real data context, so if there's any problems you can write in the comments.
Here's the console app that I built to test: http://pastebin.com/feb8cc1e
Hope this helps!
EDIT: For a more generic and reusable version which involves properly utilizing the Expression Trees in LINQ, check out Thomas Petricek's blog post: http://tomasp.net/articles/dynamic-linq-queries.aspx
As predicate builder doesn't know the DB type of the property the Contains method is called on, I guess this might be a problem inside linq to sql. Have you tried with a normal query (not with predicate builder) and a TEXT column with Contains?