Desired result
I am trying to query my collection and obtain every unique combination of a batch and entry code. I don't care about anything other than these fields, the parent objects do not matter to me.
What I have tried
I tried running:
db.accountant_ledgers.aggregate( [ {"$group": { "_id": { entryCode: "$actions.entry.entryCode", batchCode: "$actions.entry.batchCode" } } } ]);
Problem
I get unexpected results when I run that query. I'm looking for a list of every unique combination of batch and entry codes, but instead I get a list of arrays? Perhaps these are the results I'm looking for, but I have no idea how to read them if they are.
Theory
I think perhaps this could have to do with the fact that these fields are nested. Each object has several actions, each action has several entries. I believe that the result from that query is just the aggregated entry and batch codes found in each object. I don't know how long the list of results is, but I'd guess it's the same number as the total number of objects in my collection (~90 million).
EDIT: I found out that there are only 182 results from my query, which is clearly significantly smaller than 90 million. My new theory is that it has found all unique objects, with the criteria for "uniqueness" being the list of the batch and entry codes that appear in their actions, which makes sense. There should be a lot of repetition in the collection.
Question
How can I achieve the result I'm looking for? I'm expecting something like:
FEE, MG
EXN, WT
ACH, 9C
...etc
Notes
I apologize if this is a bad question, I'm not sure how else to frame it. Let me know if I can improve my question at all.
Picture below shows the results of the query.
EDIT FOR ADDITIONAL INFORMATION
I can't share any sample documents, but the general structure of the data is shown (crudely) in the below image. Each Entity has several Actions, each Action has one Entry and each Entry has one Batch code and one Entry code.
List item
You are getting a list of documents (each is a map or a hash), not a list of arrays.
The GUI you are using is trying to show you the contents of each document on the top level which is maybe what is confusing.
If you run the query in mongo shell you should see a list of documents.
It looks like your inputs are documents where entry code and batch code are arrays, if so:
Edit your question to include sample documents you are querying as text
You could use $unwind to flatten those arrays before using $group.
Related
Looking for a way to view the results of a query where the displayed fields in the doc are ordered (lexicographically in my case).
Example:
I'm getting back from a query one document, which is what I need. This document has 30 fields and I'm looking to see the value in one of them. My issue is that the order of the fields is, well, kinda random. Not sorted in any way I'm aware of.
I’m having trouble to use the text search and the autocomplete because I have a piece with +87k documents, some of them being big (~3.4MB of text).
I already:
Removed every field from the text index, except title , searchBoost and seoDescription ; these are the only fields copied to highSearchText and the field lowSearchText is always set to an empty string.
Modified the standard text index, including the fields type, published and trash in the beginning of it. I'm also modified the queries to have equality conditions on these fields. The result returned by the command db.aposDocs.stats() shows:
type_1_published_1_trash_1_highSearchText_text_lowSearchText_text_title_text_searchBoost_text: 12201984 (~11 MB, fits nicely in memory)
Verified that this index is being used, both in ‘toDistinc’ query as well in the final ‘toArray’ query.
What I think is the biggest problem
The documents have many repeated words in the title, so if the user types a word present in 5k document titles, the server suffers.
Idea I'm testing
The MongoDB docs says that to improve performance the entire collection must fit in RAM (https://docs.mongodb.com/manual/core/index-text/#storage-requirements-and-performance-costs, last bullet).
So, I created a separate collection named “search” with just the fields highSearchText (string, indexed as text) and highSearchWords (array, also indexed), which result in total size of ~ 19 MB.
By doing the same operations of the standard apostrophe autocomplete in this collection, I achieved much faster, but similar results.
I had to write events to automatically update the search collection when the piece changes, but it seems to work until now.
Issues
I'm testing this search collection with the autocomplete. For the simple text search, I’m just limiting the sorted response to 50 results. Maybe I'll have to use the search collection as well, because the search could still breaks.
Is there some easier approach I'm missing? Please, any ideas are welcome.
QUERYING MONGODB: RETREIVE SHOPS BY NAME AND BY LOCATION WITH ONE SINGLE QUERY
Hi folks!
I'm building a "search shops" application using MEAN Stack.
I store shops documents in MongoDB "location" collection like this:
{
_id: .....
name: ...//shop name
location : //...GEOJson
}
UI provides to the users one single input for shops searching. Basically, I would perform one single query to retrieve in the same results array:
All shops near the user (eventually limit to x)
All shops named "like" the input value
On logical side, I think this is a "$or like" query
Based on this answer
Using full text search with geospatial index on Mongodb
probably assign two special indexes (2dsphere and full text) to the collection is not the right manner to achieve this, anyway I think this is a different case just because I really don't want to apply sequential filter to results, "simply" want to retreive data with 2 distinct criteria.
If I should set indexes on my collection, of course the approach is to perform two distinct queries with two distinct mehtods ($near for locations and $text for name), and then merge the results with some server side logic to remove duplicate documents and sort them in some useful way for user experience, but I'm still wondering if exists a method to achieve this result with one single query.
So, the question is: is it possible or this kind of approach is out of MongoDB purpose?
Hope this is clear and hope that someone can teach something today!
Thanks
I am working on a database of Polish verbs and I'd like to find out how to display my results such that each verb conjugation appears in the following order: 1ps (1st person singular), 2ps, 3ps, 1ppl (1st person plural, etc.), 2ppl, 3ppl. It displays fine when I insert documents:
verb "żyć/przeżyć" conjugation as array and nested document
But when I go to perform queries it jumbles all the array elements up, in the first case (I want to see them in order of array indices), and sorts the nested document elements into alphabetical order (whereas I want to see them in the order in which they were inserted).
verb "żyć/przeżyć" conjugation array/document query
This should be an easy one to solve, I hope this comes across as a reasonable beginner's question. I have searched for answers but couldn't find much info on this topic. Any and all help is greatly appreciated!
Cheers,
LC.
Your screenshots highlight two different views in MongoDB Compass.
The Schema view is based on a sampling of multiple documents and the order of the fields displayed cannot be specified. The schema analysis (as at Compass 1.7) lists fields in case-insensitive alphabetical order with the _id field at the top. Since this is an aggregate schema view based on multiple documents, the ordering of fields is not expected to reflect individual document order.
If you want to work with individual documents and field ordering you need to use the Documents view, as per your second screenshot. In addition to displaying the actual documents, this view allows you to include sort and skip options for queries:
This seems like it should be very simple but I can't get it to work. I want to select all documents A where there are one or more B elements in a sub collection.
Like if a Store document had a collection of Employees. I just want to find Stores with 1 or more Employees in it.
I tried something like:
{Store.Employees:{$size:{$ne:0}}}
or
{Store.Employees:{$size:{$gt:0}}}
Just can't get it to work.
This isn't supported. You basically only can get documents in which array size is equal to the value. Range searches you can't do.
What people normally do is that they cache array length in a separate field in the same document. Then they index that field and make very efficient queries.
Of course, this requires a little bit more work from you (not forgetting to keep that length field current).