So I have a table which counts all the word that is searched in the website. and I have to view the result, order by the counts in the table for that word.
how to use the aggregate function in views(Drupal 8) for it?
If you open edit form for your view, in 3rd column "Advanced" you will see: "
Use aggregation: NO". You need to set "Yes". And after it you will see aggregation settings for all your fields in view.
It means that you can use aggregation functions in query. (eg. SUM)
PS: And I dont' fully undestand your question. You asked "how to use" or "should I use".
For 1st question I've answered below.
For 2nd question: it depends on how you're storing it in DB.
If you are storing word => total count, I think you don't need aggregation, if you create new row for every time when user search by some word, you will need aggregation in your view.
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 working on my app and I just ran into a dilemma regarding what's the best way to handle indexes for firestore.
I have a query that search for publication in a specify community that contains at least one of the tag and in a geohash range. The index for that query looks like this:
community Ascending tag Ascending location.geohash Ascending
Now if my user doesnt need to filter by tag, I run the query without the arrayContains(tag) which prompt me to create another index:
community Ascending location.geohash Ascending
My question is, is it better to create that second index or, to just use the first one and specifying all possible tags in arrayContains in the query if the user want no filters on tag ?
Neither is pertinently better, but it's a typical space vs time tradeoff.
Adding the extra tags in the query adds some overhead there, but it saves you the (storage) cost for the additional index. So you're trading some small amount of runtime performance for a small amount of space/cost savings.
One thing to check is whether the query with tags can actually run on just the second index, as Firestore may be able to do a zigzag merge join. In that case you could only keep the second, smaller index and save the runtime performance of adding additional clauses, but then get a (similarly small) performance difference on the query where you do specify one or more tags.
Background:
I am writing a mobile application which has lazy loading page. My backend is using go and mongodb with mongo-go driver. There are 10 elements on that page and i want to get next ten when i scroll to the bottom. I am planning to send ObjectID (_id) as request query parameter and get next ten elements starting from the index of id + 1.
I write what i want in mongo shell "language" so that more people understand what i want and can help in shell syntax.
Is there a way to get index of the document by it's _id or may be i can get skip until it in skip().
something like db.collection.find().skip(idOfDocument+1).limit(10)
I found the answer here.
nextDocuments = db.collection.find({'_id'> last_id}).limit(10)
Example:
{
shortName: "KITT",
longName: "Knight Industries Two Thousand",
fromZeroToSixty: 2,
year: 1982,
manufacturer: "Pontiac",
/* 25 more fields */
}
Ability to query by at least 20 fields which means that only 10 fields are left unindexed
There's 3 fields (all number) that could be used for sorting (both ways)
This leaves me wondering that how does sites with lots of searchable fields do it: e.g real estate or car sale sites where you can filter by every small detail and can choose between several sort options.
How could I pull this off with MongoDB? How should I index that kind of collection?
Im aware that there are dbs specifically made for searching but there must be general rules of thumb to do this (even if less performant) in every db. Im sure not everybody uses Elasticsearch or similar.
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Optional reading:
My reasoning is that index could be huge but the index order matters. You'll always make sure that fields that return the least results are first and most generic fields are last in index. However, what if user chooses only generic fields? Should I include non-generic fields to query anyway? How to solve ordering in both ways? Or index intersection saves the day and I should just add 20 different indexes?
text index is your friend.
Read up on it here: https://docs.mongodb.com/v3.2/core/index-text/
In short, it's a way to tell mongodb that you want full text search over a specific field, multiple fields, or all fields (yay!)
To allow text indexing of all fields, use the special symbol $**, and define it of type 'text':
db.collection.createIndex( { "$**": "text" } )
you can also configure it with Case Insensitivity or Diacritic Insensitivity, and more.
To perform text searches using the index, use the $text query helper, see: https://docs.mongodb.com/v3.2/reference/operator/query/text/#op._S_text
Update:
In order to allow user to select specific fields to search on, it's possible to use weights when creating the text-index: https://docs.mongodb.com/v3.2/core/index-text/#specify-weights
If you carefully select your fields' weights, for example using different prime numbers only, and then add the $meta text score to your results you may be able to figure out from the "textScore" which field was matched on this query, and so filter out the results that didn't get a hit from a selected search field.
Read more here: https://docs.mongodb.com/v3.2/tutorial/control-results-of-text-search/
We are developing a C++ application development tool that uses mongoDB as the underlying database. Say the user has developed a patient collection with fields _id (OID) & patient# with a unique ascending index on patient#. Say there are 10 patients with patient#s 1, 5, 7, 13, 14, 20, 21, 22, 23, 25. Patient# 20 is displayed fetched with limit(1). The user presses PageDown and patient# 21 is displayed -- easy with $gt with patient# = 20.
When the user presses PageUp, patient# 14 should be displayed. My (hopefully wrong) solution is to create a parallel descending index on patient# and $lt. That implies every collection a user creates requires both indexes on the primary key fields to get bidirectional movement. That would apply also to secondary indexes such as name.
Additionally, the user presses F5, is prompted "# of records to move", they enter 3, patient# 23 should be displayed. Or they enter -3, patient# 7 should be displayed. My idea: First use a covered query and return the following 3 patient#s from the index and then fetch the 3rd document. This isn't at all ideal when a less simplified application has hundreds of thousands of documents and the user wants to transverse by 10s of thousands of records. And, again, to achieve the backward movement, I believe I would need that second descending index.
Finally, I need a way to have the user navigate to the last index entry (patient #25). Going to the beginning is trivial. Again, second index?
My question: Is there a way to transverse the ascending index using (say) an iterator or pointer to the current index element and then use iterator/pointer arithmetic to achieve what I want? I.e., +1 will get me the "next" index element from which I could fetch the "next" document; -1 the "previous", +3 the third following, -3 the third previous; index size to the last. Or is there another solution without so much overhead (multiple indexes, large covered queries).
The way to achieve what you want is to have an index on the relevant fields and then do simple queries to get you the records you need when you need them.
It's important to not over-think the problem. Rather than trying to break down how the query optimizer would traverse the index and trying to "reduce" somehow the work it does, just use the queries you need to get the job done.
That means in your case querying for records you need and when the user wants to jump to a particular record querying for that record. If someone is looking at record 27 and they want to go to the next one you can query for smallest record greater than 27 via descending sort and limit(1) qualifier on your find.
I would encourage you to revisit your choice to have basically two primary keys - instead of separate patientID field which has a unique index, you can store patientId in the _id field and get to use the already existing unique index on _id that MongoDB requires in every collection.
A more concrete description of what I am trying to do can be found here:
How to get the previous mongoDB document from a compound index
The answer is: It can't be done in the current version. The 2nd jira ticket is a possible future fix.
See: SERVER-9540
and
SERVER-9547