Is there any way to find distinct value like using mongo command db.collection.distinct() using lokiJS
There is no in-built facility to get distinct values at the moment, so at the moment you would have to iterate a ResultSet or DynamicView to work that out, which should be pretty easy:
let dist = [];
view.forEach((elem) => {
if (dist.indexOf(elem) === -1) {
dist.push(elem);
}
});
return dist;
I can open an issue on github so the feature gets implemented if you want, as it sounds interesting.
Related
I have in my index a list of object, each of them has an objectID value.
On some search, i want to filter OUT a certain number of them, using there objectID.
For the moment it works with one value as a string, i would like to know how to do for multiple value.
filters = 'NOT objectID:' + objectIDToFilter;
This work for one object, what can i do to apply this for an array of ObjectID. because :
filters = 'NOT objectID:' + arrayObjectID;
does not work.
I was thinking of generating a huge string with an arrayId.map with all my 'NOT objectID:1 AND NOT objectID: 2 ...' but i wanted to know if there is a cleaner way to do it.
I unfortunately misunderstood the line in algolia doc :
Array Attributes: Any attribute set up as an array will match the filter as soon as one of the values in the array match.
This apparently refers to the value itself in Algolia and not the filter
So i did not found a solution on algolia doc, i went for the long string, hope there is no limits on how much filter we can add on a query (found nothing about that).
Here is what i did if someone need it :
let filters = `NOT objectID:${userID}`;
blockedByUsers.map((blockedByUser) => {
filters = filters + ` AND NOT objectID:${blockedByUser}`;
});
If you need to add multiple but don't have a starting point like i do, you can't start the query with an AND , a solution i found to bypass that:
let filters = `NOT objectID:${blockedByUsers[0]}`;
blockedByUsers.map((blockedByUser, i) => {
if (i > 0) filters = filters + ` AND NOT objectID:${blockedByUser}`;
});
There is probably a cleaner solution, but this work. If you have found other solution for that problems i'll be happy to see :)
I want to create query. I'm using FirestoreRecyclerAdapter. Initialising adapter I got error:
FAILED_PRECONDITION: The query requires an index.
How I can create index if eventId in my case is dynamic value?
I'm sure this is basic thing, cause I'm doing all according to manual. As I read in the documentation, sets of data should have crossing sets of keys ie {dataId, true} in both events and users in my case. Please help me where to go for solution.
Query query = mFirebaseFirestore.collection(EVENT_INFO).document(eventId)
.collection(USERS)
.whereEqualTo(FIELD_AGE, guestAge)
.whereEqualTo(EVENTS_ATTENDED + "."+ eventId, true)
.orderBy(FIELD_FAMILYNAME, Query.Direction.ASCENDING);
At that moment there is no such an options to do things beautifull with Firestore. So we should think of hiding items based on custom criteria inside onBindViewHolder method in our FirestoreRecyclerAdapter. Like follows:
protected void onBindViewHolder(GuestHolder holder, int position, GuestItem guest) {
Map<String, Boolean> map = guest.getEventsAttended();
if (map != null && map.containsKey(eventId)) {
holder.itemView.setVisibility(View.VISIBLE);
} else {
holder.itemView.setVisibility(View.GONE);
holder.itemView.setLayoutParams(new RecyclerView.LayoutParams(0, 0));
}}
Hope this helps someone.
UPDATE:
I understood that the solution to my problem is doing subqueries, which apply a different filter each time, and they have a reduced result set. But I can't find a way to do that in MyBatis logic. Here is my query code
List<IstanzaMetadato> res = null;
SqlSession sqlSession = ConnectionFactory.getSqlSessionFactory().openSession(true);
try {
IstanzaMetadatoMapper mapper = sqlSession.getMapper(IstanzaMetadatoMapper.class);
IstanzaMetadatoExample example = new IstanzaMetadatoExample();
Iterator<Map.Entry<Integer, String>> it = map.entrySet().iterator();
while (it.hasNext()) {
Map.Entry<Integer, String> entry = it.next();
example.createCriteria().andIdMetadatoEqualTo(entry.getKey()).andValoreEqualTo(entry.getValue());
}
example.setDistinct(true);
res = mapper.selectByExample(example);
I need to execute a new selectByExample but inside the while cycle, and it has to query the previus "SELECTED" results....
Is there a Solution ?
ORIGINAL QUESTION:
I have this table structure
I have to select rows from the table with different filters, specified by the final user.
Those filters are specified by a couple (id_metadato, valore), in example you can have id_metadato = 3 and valore = "pippo";
the user can specify 0-n filters from the web page typing 0-n values inside the search boxes which are based on id_metadato
Obviusly, the more filters the users specifies, the more restriction would have the final query.
In example if the user fills only the first search box, the query will have only a filter and would provide all the rows that will have the couple (id_metadato, valore) specified by the user.
If he uses two search boxes, than the query will have 2 filters, and it will provide all the rows that verify the first condition AND the second one, after the "first subquery" is done.
I need to do this dinamically, and in the best efficient way. I can't simply add AND clause to my query, they have to filter and reduce the result set every time.
I can't do 0-n subqueries (Select * from ... IN (select * from ....) ) efficiently.
Is there a more elegant way to do that ? I'm reading dynamic SQL queries tutorials with MyBatis, but I'm not sure that is the correct way. I'm still trying to figure out the logic of the resosultio, then I will try to implement with MyBatis.
Thanks for the answers
MyBatis simplified a lot this process of nesting subqueries, it was sufficient to concatenate the filter criterias and to add
the excerpt of the code is the following
try {
IstanzaMetadatoMapper mapper = sqlSession.getMapper(IstanzaMetadatoMapper.class);
IstanzaMetadatoExample example = new IstanzaMetadatoExample();
Iterator<Map.Entry<Integer, String>> it = map.entrySet().iterator();
while (it.hasNext()) {
Map.Entry<Integer, String> entry = it.next();
if (listaIdUd.isEmpty()) {
example.createCriteria().andIdMetadatoEqualTo(entry.getKey()).andValoreEqualTo(entry.getValue());
example.setDistinct(true);
listaIdUd = mapper.selectDynamicNested(example);
continue;
}
example.clear();
example.createCriteria().andIdMetadatoEqualTo(entry.getKey()).andValoreEqualTo(entry.getValue()).andIdUdIn(listaIdUd);
example.setDistinct(true);
listaIdUd = mapper.selectDynamicNested(example);
}
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'm trying to get a feel for how fast MongoDB is compared to traditional RDBMSs. To this end, I'm using Java to try and get the result of a traditional SQL join by defining a MongoDB function that will return an object after embedding another object into it:
s_with_user = function(rows){
var result=[]
db.subscriptions.find().limit(rows).forEach( function(s) {
s.user= db.users.find({id: s.user_id});
result.push( s );
});
return result;
}
Then, I use:
DB db = new Mongo("localhost", 27017).getDB("test");
Object result = db.eval("s_with_user(1000)");
Measuring the time taken for the last statement, I'm confident that MongoDB is running the command and evaluating the data I want. However, the result object is always null.
How can I do this in such a way that I can inspect the results?
First of all, Stennie is right about eval() not being the right way to do joins in MongoDB.
However, to try to answer your question, it would work this way:
String f = "function(rows) { ... }";
DB db = new Mongo("localhost", 27017).getDB("test");
Object result = db.eval( f, 1000 );
Also, your "join" function needs a small correction: it should use findOne instead of find:
s.user = db.users.findOne({id: s.user_id});