I am trying to call the hint method on a MongoDB::Cursor object. However, it throwing an exception when it's trying to execute the query. See the code sample below:
sub some_method_which_returns_cursor {
my $cursor = $collection->find($filter);
if ($hint) {
$cursor->hint({‘some_index’ => 1}); #failing here.
}
if ($sort) {
$cursor->sort($sort);
}
return $cursor;
}
Any thoughts as to what's going on and how I can fix this?
Harish asked me via email and I'll repeat my answer here for posterity:
The hint method takes a string when given an index name, or an array reference when given keys/order pairs:
$cursor->hint("some_index"); # by name
$cursor->hint([field1 => 1, field2 => -1]); # by keys
It also takes a hash reference, but don't use that because modern Perls randomize key order when serializing, so your hint may not match an index.
Related
I need to be able to pluck specific values from data that I receive from different 3rd parties. The data can structured differently depending on the 3rd party. For example:
my $first =
{
email => "joe\#example.com",
firstname => "Joe",
lastname => "Regular",
};
my $second =
{
user => {
e-mail => "joe\#example.com",
firstName => "Joe",
lastName => "Regular",
}
};
I know what the data structure will be for each 3rd party, so I can define that as config. What I want to end up with is
my $email = _magic($first_config,$first);
my $other_email = _magic($second_config,$second);
Any ideas much appreciated.
Build a look-up table. And you can use a dispatch table, hash with values being code references, so that when a party-identification is used as the key the code for that party executes
my %get_value = ( first => \&fetch_first, second => \&fetch_second );
my $party = 'first'; # input via command-line options, STDIN ...
my $email = $get_value{$party}->();
where \&fetch_first is a reference to the subroutine fetch_first. You can also enter it directly, first => sub { ... }, suitable for simple code. See perlreftut, perlref, and perlsub.
There are many ways to carry data in your program, and so to implement the lookup itself.
Here is an illustration, built in steps. It uses the (confirmed) fact that the data is in valid Perl data structures, and for simplicity it specifies the data right in each sub.
sub fetch_first {
my $data = {
email => '...',
firstName => '...',
};
return $data->{email};
}
This only delivers the email address, but we can do better.
Once you dereference a code reference you can also pass arguments
my $first_name = $get_value{$party}->('firstName');
where the subs are now written to use this input to return the required field
sub fetch_first {
my ($query) = #_;
my $data = {
email => '...',
firstName => '...',
};
return $data->{$query};
}
A big weakness of the above is that the calling code must use valid names of keys, so it needs to know the details of implementation of what it is using.
This can be improved, for example by choosing an interface for the call which is then translated in the subs into key names (or via yet another look-up structure). Then you make calls such as
my $email = $get_value{$party}->('email'); # or: 'first', 'last'
and somewhere you have association first => 'firstName' (etc) which subs can look up.
The flexibility is greatly helped by data being set up in a consistent way. The whole thing can also be quite maintainable if the code is organized thoughtfully.
If this grows more complex the solution is to write a class. Then you can build a very nice system.
I'm working on super simple search across multiple fields in a document to see if any of them has a single value. (Note: some fields are using regex to search if value is contained in string). Using query builder I constructed the following.
public function search($value, $limit, $offset=0, $orderby = '', $order='' )
{
$regexVal = new \MongoRegex('/^.*(\b'.str_replace(' ', '\s', $value).'\b).*?$/i');
$query = $this->repository->createQueryBuilder();
$query->addOr($query->expr()->field('location')->equals($regexVal));
$query->addOr($query->expr()->field('mappedData.name')->equals($regexVal));
$query->addOr($query->expr()->field('mappedData.first_name')->equals($regexVal));
$query->addOr($query->expr()->field('mappedData.last_name')->equals($regexVal));
$query->addOr($query->expr()->field('mappedData.email')->equals($value));
$query->addOr($query->expr()->field('email')->equals($value));
$query->addOr($query->expr()->field('organization')->equals($value));
$query->limit($limit)
->skip($offset);
if( ! empty($orderby) && $order ){
$query->sort($orderby, $order);
}
return $query->getQuery()->execute();
}
If I dump out the constructed query values I get the following array in this gist. https://gist.github.com/jchamb/04a0400c989cd28b1841 The extra association field in there is being added by a Doctrine Filter.
Through Query builder I don't get any results, however if I construct the query myself and run it in an admin app like genghis, I get the expected single document result.
Actual written mongodb string looks like this. https://gist.github.com/jchamb/ce60829480576a88290d
This project is a zend2 app that was already using doctrine and mongo. I'm not much of an expert with mongo in general so I'm not sure what i'm doing wrong inside of Query Builder that i'm not getting the same result as executing the query directly. I can't find any info on stack or the query builder docs that gives any extra clues for the multiple addOrs syntax either.
Any help or direction would be really appreciated, in the most basic form I need query builder to get a document where association = x and ( field1 = val or field2 = value).
Thanks!
Really unsure what the exact issue was with the above, but after playing around, switching the order of query builder around fixes the problem.
public function search($value, $limit, $offset=0, $orderby = '', $order='' )
{
$regexVal = new \MongoRegex('/^.*(\b'.str_replace(' ', '\s', $value).'\b).*?$/i');
$query = $this->repository->createQueryBuilder()
->find()
->limit($limit)
->skip($offset);
$query->addOr($query->expr()->field('location')->equals($regexVal));
$query->addOr($query->expr()->field('mappedData.name')->equals($regexVal));
$query->addOr($query->expr()->field('mappedData.first_name')->equals($regexVal));
$query->addOr($query->expr()->field('mappedData.last_name')->equals($regexVal));
$query->addOr($query->expr()->field('mappedData.email')->equals($value));
$query->addOr($query->expr()->field('email')->equals($value));
$query->addOr($query->expr()->field('organization')->equals($value));
if( ! empty($orderby) && $order ){
$query->sort($orderby, $order);
}
return $query->getQuery()->execute();
}
Would love to still hear some feedback about why this works and the above didn't if anyone know more about the internals of query builder.
I have two tables in my database and one of the tables is associated with my Accounts table.
So in my Schema Result for Account.pm I added the following line.
__PACKAGE__->has_many('subjects', 'MyApp::DBIC::Schema::Subject', {'foreight.account_id' => 'self.account_id'});
Then in my controller I make a search like this.
$c->stash->{search_results} = $c->model('DB::Account')->search(
{ -or => [
firstname => {like => '%'.$search_term.'%'},
'subjects.subject_title' => {like => '%'.$search_term.'%'},
]
},
{
join => 'subjects',
rows => '3',
},
{
order_by => 'first name ASC',
page => 1,
rows => 10,
}
);
It does not output any errors, but I can't figure out how to output the results on my view file. Is this a correct method of making relations between two tables?
My goal: provided a search_term, search two tables and output the result in view file. My SQL would look something like this:
SELECT FROM Accounts,Subjects WHERE Accounts.firstname=$search_term OR Subjects.subject_title=$search_term LEFT JOIN Subjects ON Accounts.account_id=Subject.account_id
And would want to output the result in view file, as I stated above.
I am fairly new to Perl and some of the documentations don't make that much sense to me, still. So any help and tips are appreciated.
The join looks OK to me, but it would make sense to try a simplified version without the join to check that everything else is OK.
The behaviour of DBIx::Class::ResultSet::search differs depending on the context in which it's called. If it's called in list context then it executes the database query and returns an array of MyApp::DBIC::Schema::Account objects. For example:
my #accounts = $c->model('DB::Account')->search();
In your case you're calling search in scalar context, which means that rather than returning an array it will return a DBIx::Class::ResultSet object (or a subclass thereof), and crucially it won't actually execute a db query. For that to happen you need to call the all method on your resultset. So, assuming you're using the default template toolkit view you probably want something like this:
[% FOREACH search_result IN search_results.all %]
[% search_result.first_name %]
[% END %]
This 'lazy' behaviour of DBIx::Class is actually very useful, and in my opinion somewhat undersold in the documentation. It means you can keep a resultset in a variable and keep executing different search calls on it without actually hitting the DB, it can allow much nicer code in cases where you want to conditionally build up a complex query. See the DBIx::Class::Resultset documentation for further details.
You have error in your query:
Try:
$c->stash->{search_results} = $c->model('DB::Account')->search(
{ -or => [
firstname => {like => '%'.$search_term.'%'},
'subjects.subject_title' => {like => '%'.$search_term.'%'},
]
},
{
join => 'subjects',
order_by => 'firstname ASC',
page => 1,
rows => 10,
}
);
I've got an array like that
Word array (
{
translation = (
{
name = Roma;
lang = it;
},
{
name = Rome;
lang = en;
}
);
type = provenance;
value = RMU;
},
{
translation = (
{
name = "Milano";
lang = it;
},
{
name = "Milan";
lang = en;
}
);
type = destination;
value = MIL;
},)
The idea is to filter it using an NSPredicate and receive and an array of dictionaries based on the lang key, I'd like to get something like this made by filtering for lang == it,
Word array (
{
name = Roma;
lang = it;
type = provenance;
value = RMU;
},
{
name = "Milano";
lang = it;
type = destination;
value = MIL;
})
I can't simplify the data because it comes from a "JSON" service.
I've tried different predicates using SUBQUERY but none of them works, documentation about SUBQUERY is pretty poor, I'm missing something, probably the problem is that I'd like to receive an object that is really different from the source.
Of course I'm able to obtain that structure enumerating, I'm wondering if there is a shorter solution
This answer from Dave DeLong link to SUBQUERY explanation gave a me a lot of hints about SUBQUERY, but I'm not able to find a solution to my problem.
Can someone give me a hints about?
You can't do this with a predicate. (Well, you could, but it would be stupidly complex, difficult to understand and maintain, and in the end it would be easier to write the code yourself)
NSPredicate is for extracting a subset of data from an existing set. It only* does filtering, because a predicate is simply a statement that evaluates to true or false. If you have a collection and filter it with a predicate, then what happens is the collection starts iterating over its elements and asks the predicate: "does this pass your test?" "does this pass your test?" "does this pass your test?"... Every time that the predicate answers "yes this passes my test", the collection adds that object to a new collection. It is that new collection that is returned from the filter method.
THUS:
NSPredicate does not (easily) allow for merging two sets of data (which is what you're asking for). It is possible (because you can do pretty much anything with a FUNCTION() expression), but it makes for inherently unreadable predicates.
SO:
Don't use NSPredicate to merge your dataset. Do it yourself.
I have this query for example:
$dbAdapter = Zend_Db_Table::getDefaultAdapter();
$query_Group = $dbAdapter->select();
$query_Group->from(array('FI' => 'request_field'),
array('*'));
$resultRows = $dbAdapter->fetchAll($query_Group);
Ok, now how can I know if inside $resultRows there is the column "Label" for example?
I know I can do that:
foreach($resultRowsas $key => $Field)
{
if(isset($Field['Label'])
{ .... }
}
But if is possible I want it to know without loop it....
It is possible?
Thanks again....
$Field['Label'] will always be set. It may be empty, but will always be set!
if you want all records where the value is NULL, change your query appropriately
If I understood correctly, you want to know whether a given column exists in the table. In that case, you might call the describeTable() method for this.
You can see a description in the Zend_Db_Adapter documentation.
If the column is defined in the table schema, then you need to query for an appropriate value, like NULL, as #JellyBelly says. In this case, his answer is what you need.
Hope that helps,