Develop Reference

How to efficiently query object with large field array?

So basically I have an object schema that has an array field that will hold ids for objects inside a different collection. This array field has the potential to have thousands of ids inside of it. I have been omitting this field using .select(["-fieldName"]); in my queries up till now but I need to include it in my query if I wanna add on to it.
I would assume querying an object with such a large field is costly in performance so therefore my question is how can I efficiently query such an object?
I would like to just omit this field in my query but then I can't add ids into it.

If you just want to add an item to the array field you can use the $push operator.
collection.updateOne(query, { $push: { arrayField: value } });

In MarkLogic, how do I search in JSON documents using only the key?

I have a bunch of JSON documents in my db. I need to perform delete operation on a few documents by searching the documents that have the particular field present in them {key only}. What query can I add to my code so that it finds all the documents with the field? I will be using them to get their values(integer), put them in an array and then use them one by one.

Expanding a bit on the link provided by George Bailey, you might want to use cts.uris() instead of cts.search() because xdmp.documentDelete() takes uri strings instead of documents:
const uris = cts.uris(
null,
['score-zero', 'unchecked'],
cts.jsonPropertyScopeQuery('theKey', cts.trueQuery())
);
xdmp.documentDelete(uris);
If it's a large number of documents, you might need to specify the start value and a limit on the call to cts.uris() to delete different slices of documents in multiple passes.
Hoping that helps,

underscore .find() multiples with same key value

I am currently trying to filter an object via POST from a form the form is made of checkboxes and as a result I need to be able to search an array of objects for multiple values on the same key.
My POST looks similar to this,
{
tax_year: ['2016/17', '2017/18'],
status : ['completed'],
user : [1,4,78]
}
How would I go about search an array of objects and returning all the objects that have a matching key and value? I know I can do a single find with underscore like so,
var result = _.where(historyData, {tax_year: "2016/17"});
but I have no clue as to how to search for multiple matching keys and values?

It seems that you're matching on both of the values in an array value (regardless of whether there are more array values or not). If that's true, you might have to use the _.filter() method, where you can provide whatever logic you need in the 'predicate'. Alternatively, you could add a unique identifier on the server side to each record and match on that.

How to do an 'AND' statement in Firebase or equivalent?

I need to do a query where I can show only specific data using an 'AND' statement or equivalent to it. I have taken the example which is displayed in the Firebase Documentation.
// Find all dinosaurs whose height is exactly 25 meters.
var ref = firebase.database().ref("dinosaurs");
ref.orderByChild("height").equalTo(25).on("child_added", function(snapshot) {
console.log(snapshot.key);
});
I understand this line is going to retrieve all the dinosaurs whose height is exactly 25, BUT, I need to show all dinosaurs whose height is '25' AND name is 'Dino'. Is there any way to retrieve this information?
Thanks in advance.

Actually firebase only supports filtering/ordering with one propery, but if you want to filter with more than one property like you said I want to filter with age and name, you have to use composite keys.
There is a third party library called querybase which gives you some capabilities of multy property filtering. See https://github.com/davideast/Querybase

You cannot query by multiple keys.
If you need to sort by two properties your options are:
Create a hybrid key. In reference to your example, if you wanted to get all 'Dino' and height '25' then you would create a hybrid name_age key which could look something like Dino_25. This will allow you to query and search for items with exactly the same value but you lose the ability for ordering (i.e. age less than x).
Perform one query on Firebase and the other client side. You can query by name on Firebase and then iterate through the results and keep the results that match age 25.
Without knowing much about your schema I would advise you to make sure you're flattening your data sufficiently. Often I have found that many multi-level queries can be solved by looking at how I'm storing the data. This is not always the case and sometimes you may just have to take one of the routes I have mentioned above.

Equal Precedence View Collation CouchDB?

According to the view collation documentation for CouchDB(
http://wiki.apache.org/couchdb/View_collation), member order does matter for collation. I was wondering if there is a way to disable this attribute such that collation order does not matter? I want to be able to "search" my views such that the documents that are emitted satisfy all the key ranges for the field.
here is some more on view collation for your reference: CouchDB sorting and filtering in the same view
Likewise, if it is possible to set CouchDB such that order does not matter for view collation, the following parameters used for the GET request should only emit docs where doc.phone_number == "ZZZZZZZ" , whereas right now it emits the documents that fall within the range of the first 3 keys and completely ignores the last key. This occurs because the last key has the least precedence in the current collation scheme.
startkey: [null,null,null,"ZZZZZZZ"],
endkey: ["\ufff0","\ufff0","\ufff0","ZZZZZZZZ"],
Sample Mapping Function
var map = function(doc) {
/*
//Keys emitted
1. name
2. address
3. age
3. phone_number
*/
emit([doc.name,doc.address,doc.num_age,doc.phone_number],doc._id)
}
Is this possible, or do I have to create multiple views to perform this? The use of multiple views seems very inefficent.
I've read that CouchDB-Lucene:( How to realize complex search filters in couchdb? Should I avoid temporary views? )would be helpful for complex searching, but that doesn't seem applicable in this case.

Use of multiple views is not inefficient, quite to the contrary : having four views (name, address, age and phone number) will not use significantly more time or memory than having a single view emit everything. It is the simple, straightforward, efficient way of performing "WHERE field = value" queries in CouchDB.
If you are in fact looking for "WHERE field = value AND field2 = value2" queries, then CouchDB will not help you, and you will need to use Lucene.
You need to understand that the collation merely describes how keys are ordered. Even if you could specify any arbitrary collation, you will still have to deal with the fact that CouchDB need you to define an order for the keys, and only lets you query contiguous ranges of keys. This is not compatible with multi-dimensional range queries.