I have a mongo collection which has documents with two fields "fieldA" and "fieldB", which are timestamps and I need to get all the documents which are "(fieldB-fieldA)/6000 > 2"... So I was looking for some function in order to do this...
I saw in some posts the function "$subtract" but that seems is in mongo 2.1.x and currently I'm using 2.0.x (it's the stable), any idea how to do this with 2.0.x? or Do I need to create a new field? or Can I only do it in the application side?
btw, I'm using the ruby mongo driver...
You can use the $where operator to specify query expressions as Javascript. In the shell:
db.myCollection.find( { $where: "(this.fieldB - this.fieldA)/6000 > 2" } );
You should note, however, that Javascript execution can be very slow. If this is a one time query, $where may be an ok solution. Otherwise, storing the result of the equation in a separate field is the best way to ensure that queries are timely.
Additional information on the $where operator:
http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-JavascriptExpressionsand%7B%7B%24where%7D%7D
Related
I have a springboot application that interacts with elastic search (or as it know now OpenSearch). It can perform basic operations such as search, index etc. I used this as my base (although I replaced high level client since it is deprecated) and to perform queries, I am using #Query annotation mostly (as described in section 2.2 here, although I also used QueryBuilders).
Now, I have an interesting use case - I would like to perform 2 queries at the same time. First query would find a file in elastic search that would contain 3 ids. These 3 ids are ids of other files in the same elastic search. The 2nd query would look for these 3 files and finally return them to me. Now, I can easily do it in 2 steps:
Have a query to find a file containing 3 ids and return it
Have a second query (multisearch query can do bulk search as I understand) to search
for 3 files using info from the first query.
However, I need them to happen within the same query - so within the same query I need to search for a file containing the 3 ids and then perform a search for these 3 files.
So currently my files in elastic search look like so:
{
"docId": "docId57",
"relatedDocs": [
{
"relatedId": "docId1",
"type": "apple"
},
{
"relatedId": "docId2",
"type": "orange"
},
{
"relatedId": "docId3",
"type": "banana"
}
]
}
and my goal is to have a query that will accept docId57 as an arg (so a method findFilesViaJoin(docId57) or something) and return a list of 3 files: file for docId1, file docId2 and file for docId3.
I know it is possible either via nested queries, child/parent queries or good old SQL queries (via jpa/hibarnate).
I attempted to use all of these and was unsuccessful for reasons described below.
Child/parent queries
So for child/parent queries, I attempted to use DSL with #Query but couldn't quite get it since I don't have a solid documentation to refer to (the one that actually helps with java not curls). After some time I found this and this articles - I maybe can figure out how to make it work with child/parent but neither explain how to do mapping. If this approach can do what I want, my question is: how to set up & map parent/child in springboot.
Using SQL queries
So for this one, I need to change my set up to use hibarnate. I used this as my base. It works, the only problem I have is that my SQL queries get ignored. Instead, the search is done based of a method's name, not the content of #Query. So it is as if I don't have an annotation used at all. So using the structure mentioned above, the following method in my app:
#Query("select t from MyModel t where t.docId = ?1")
findByRelatedDocsRelatedId(String id)
will return files that has a relatedId that matches the id passed via method ard id (as oppose to reading query from #Query that tells method to search all docs based on docId). Now, I don't mind using method name as a query to search for something. But then why would I use #Query for? (not to mention how do I create a name that does join). It might be possible that my hibernate is set up wrong (never used it before this week). So question here is, does anybody have a nice complete example of hibarnate being used with elastic search that does join query?
Nested queries
For these queries, I assume that I just need to figure out what to put inside the #Query but due to limited documentation about how to compose nested query I didn't manage to make it even remotely to work. Any concreate documentation on how to create DSL nested query would be appreciated.
Any of the ways I described will work for me. I think child/parent seems the best choice (seeing as they kind created for this purpose) but any will do.
I have found some information to accomplish this in mongoDB, but I need it with mongoid. So I can do something like:
User.last(7000).each do ....
I'm using:
MongoDB shell version: 2.4.3
Mongoid 2.6.0
Thanks!
Now I found a solution from mongoid origin:
User.all.desc('_id').limit(7000)
It sorts the users in descending order according to the id.
Aggregations can directly be chained to a Model in rails irrespective of the ORM used. We don't need to use all. You could just do the following
User.limit(3000).desc('_id')
This will only return the Mongoid criteria. To see the data you can chain .all to the criteria. You can directly do operations on the criteria also, without having to chain .all or to_a.
We're running Solr 3.6 and are trying to apply a conditional sort on the result set. To clarify, the data is a set of bids, and we want to add the option to sort by the current user's bid, so it can't function as a regular sort (as the bid will be different for each user that runs the query).
The documents in the result set include a "CurrentUserId" and "CurrentBid" field, so I think we need something like the following to sort:
sort=((CurrentUserId = 12345) ? CurrentBid : 0) desc
This is just pseudocode, but the idea is that if the currentUserId in Solr matches the user Id (12345 in this example), then sort by CurrentBid, otherwise, just use 0.
It seems like doing a sort by query might be the way to go with achieving this (or at least form part of the solution), using something like the following query:
http://localhost:8080/solr/select/?q=:&sort=query(CurrentUserId:10330 AND CurrentBid:[1 TO *])+desc
This doesn't seem to be working for me though, and results in the following error:
sort param could not be parsed as a query, and is not a field that exists in the index: ...
The Solr documentation indicates that the query function can be used as a sort parameter from Solr 1.4 onwards, so this seems like it should work.
Any advice on how to go about achieving this would be greatly appreciated.
According to the Solr Documentation link you provided,
Any type of subquery is supported through either parameter dereferencing $otherparam or direct specification of the query string in the LocalParams via "v".
So based on the examples and your query, I think one or both of the following should work:
http://localhost:8080/solr/select/?q=:&sort=query($qq)+desc&qq=(CurrentUserId:10330 AND CurrentBid:[1 TO *])
http://localhost:8080/solr/select/?q=:&sort=query({v='CurrentUserId:10330 AND CurrentBid:[1 TO *]'})+desc
Hi Experts
I have a special question About dynamic Linq to Sql.
Consider we want to search in a table according two fields*(LetterNo(string) and LetterDate(Datetime))*
.OK the problem is user can enter on of that fields or even both.
I searched in the internet and found "Linq.Dynamic" library in ScottGu weblog.but in that library if we want to use SqlParameter in exported command we should use #0 and param for that.problem is I don't know how many fields user entered.
I want use one query for that and no external tool like "Linq Kit PredicateBuilder".
If I create my query string Manually(and execute using ExecuteCommand) then I will abdicate SqlParameter and risk of Sql Injenction growing up.
How Can do that?
thanks
I suspect you are wanting to do something like the following:
IQueryable<Letter> query = context.Letters;
if (!string.IsNullOrEmpty(LetterNo))
query = query.Where(letter => letter.LetterNo == LetterNo);
If (LetterDate.HasValue)
query = query.Where(letter => letter.LetterDate == LetterDate);
When you execute query, it will combine the necessary expressions and issue a single query to the database based on the user's input.
I am quite sure that DQL will be the way to go, but I am wondering if Doctrine, i am using Doctrine 2, has someway to return the row count. I won't be using the rows itself, I just want the count.
I'm new to Doctrine2 but it looks like you can simply do this:
$query = $em->createQuery('SELECT COUNT(u.id) FROM Entities\User u');
$count = $query->getSingleScalarResult();
Source (Using Agregate Functions): http://www.doctrine-project.org/docs/orm/2.0/en/reference/dql-doctrine-query-language.html#dql-select-examples
Allowed aggregate functions: http://www.doctrine-project.org/docs/orm/2.0/en/reference/dql-doctrine-query-language.html#aggregate-functions
Here is another interesting point of view about using aggregated functions in DQL
http://doctrine-orm.readthedocs.org/en/latest/cookbook/aggregate-fields.html
Maybe you would avoid the creation of an specific query to obtain an aggregate value. In this case, aggregate fields are a good alternative.