We have following structure in MongoDB documents.
{
"id":"1111",
"keys":[
{
"name":"Country",
"value":"USA"
},
{
"name":"City",
"value":"LongIsland"
},
{
"name":"State",
"value":"NewYork"
}
]
}
Now using Springframework Query object, I figured out a way to pull the details using below syntax
query.addCriteria(
Criteria.where("keys.value").is(countryparam).
andOperator(
Criteria.where("keys.value").is(stateparam)
)
);
Two issue with this query model.
First issue is it is irrelevant if countryparam and stateparam are actually meant to match Country key name and State key name respectively. If just the values matches, the query returns the document. Means, if I have Country and City params, this just works if user passes Country and City values, even if they are swapped. So how can I exactly compare City to cityparam and State to Stateparam?
More complexity is if I have to extract the document basing on multiple key value pairs, I should be correspondingly able to match key name with respective value and query the document. How can I do this?
Thanks in advance!
Related
I want to put the query result from one collection in a variable and use it as input for query in another collection. The queries look like this as follows:
Query 1:
var ID=db.User.findOne({Name:"Ivan"}, {ID: 1});
db.Artists.find({"Listeners.ID":ID});
Query 2:
var Friends=db.Users.find({Friends:x});
//Users.Friends is an array of interger identifier for User
db. Artists.find({"Listeners.ID":{$in:Friends}});
But they all don't work. How to write the right one?
The query db.User.findOne({Name:"Ivan"}, {ID: 1}); does not return a single value, it returns the document, reduced to the field you requested. What you get is an object, with two fields: _id (because you didn't explicitly exclude it) and ID (when it exists in the document). Your var ID looks like this:
{
_id:ObjectId(<long hex string>),
ID:<value>
}
So when you want to query by the ID value, you need to specify it:
db.Artists.find({"Listeners.ID":ID.ID});
Regarding your second query: when you use find instead of findOne you get a cursor object which can then be used to retrieve the individual documents using cursor.next() or cursor.toArray().
If you only know the key name (say "nickname"), but not the exact path to that key in the object.
e.g. nickname may be at the first level like:
{"nickname":"Howie"}
or at the second level:
{"user":{"nickname":"Howie"}}
Is it possible to query for nickname equal "Howie" that would return both documents?
Unfortunately there is no wild card that allows you to search for a field at any level in the db. If the position is not relevant and you can modify the document structure you have 2 choices here. You can store your document as
{ fieldname:"nickname", value : "Howie" }
{ fieldname:"user/nickname", value: "Howie" }
You can then query using
db.so.find({fieldname:/nickname/, value:"Howie"})
Alternatively you can store as
db.so.insert({value:"Howie", fieldpath:["nickname"]})
db.so.insert({value:"Howie", fieldpath:["user", "nickname"]})
The advantage with the second approach is that you can now index {fieldpath:1, value:1} and a query on it such as
db.so.find({fieldpath:"nickname", value:"Howie"})
will be an indexed query.
I'm new to Couchbase and am struggling to get a composite index to do what I want it to. The use-case is this:
I have a set of "Enumerations" being stored as documents
Each has a "last_updated" field which -- as you may have guessed -- stores the last time that the field was updated
I want to be able to show only those enumerations which have been updated since some given date but still sort the list by the name of the enumeration
I've created a Couchbase View like this:
function (doc, meta) {
var time_array;
if (doc.doc_type === "enum") {
if (doc.last_updated) {
time_array = doc.last_updated.split(/[- :]/);
} else {
time_array = [0,0,0,0,0,0];
}
for(var i=0; i<time_array.length; i++) { time_array[i] = parseInt(time_array[i], 10); }
time_array.unshift(meta.id);
emit(time_array, null);
}
}
I have one record that doesn't have the last_updated field set and therefore has it's time fields are all set to zero. I thought as a first test I could filter out that result and I put in the following:
startkey = ["a",2012,0,0,0,0,0]
endkey = ["Z",2014,0,0,0,0,0]
While the list is sorted by the 'id' it isn't filtering anything! Can anyone tell me what I'm doing wrong? Is there a better composite view to achieve these results?
In couchbase when you query view by startkey - endkey you're unable to filter results by 2 or more properties. Couchbase has only one index, so it will filter your results only by first param. So your query will be identical to query with:
startkey = ["a"]
endkey = ["Z"]
Here is a link to complete answer by Filipe Manana why it can't be filtered by those dates.
Here is a quote from it:
For composite keys (arrays), elements are compared from left to right and comparison finishes as soon as a element is different from the corresponding element in the other key (same as what happens when comparing strings à la memcmp() or strcmp()).
So if you want to have a view that filters by date, date array should go first in composite key.
I'm trying to execute a query from java against a Map/Reduce view I have created on the CouchDB.
My map function looks like the following:
function(doc) {
if(doc.type == 'SPECIFIC_DOC_TYPE_NAME' && doc.userID){
for(var g in doc.groupList){
emit([doc.userID,doc.groupList[g].name],1);
}
}
}
and Reduce function:
function (key, values, rereduce) {
return sum(values);
}
The view seems to be working when executed from the Futon interface (without keys specified though).
What I'm trying to do is to count number of some doc types belonging to a single group. I want to query that view using 'userID' and name of the group as a keys.
I'm using Ektorp library for managing CouchDB data, if I execute this query without keys it returns the scalar value, otherwise it just prints an error saying that for reduce query group=true must be specified.
I have tried the following:
ViewQuery query = createQuery("some_doc_name");
List<String> keys = new ArrayList<String>();
keys.add(grupaName);
keys.add(uzytkownikID);
query.group(true);
query.groupLevel(2);
query.dbPath(db.path());
query.designDocId(stdDesignDocumentId);
query.keys(keys);
ViewResult r = db.queryView(query);
return r.getRows().get(0).getValueAsInt();
above example works without 'keys' specified.
I have other queries working with ComplexKey like eg:
ComplexKey key = ComplexKey.of(userID);
return queryView("list_by_userID",key);
but this returns only a list of type T (List) - using CouchDbRepositorySupport of course - and cannot be used with reduce type queries (from what I know).
Is there any way to execute the query with reduce function specified and a complex key with 2 or more values using Ektorp library? Any examples highly appreciated.
Ok, I've found the solution using trial and error approach:
public int getNumberOfDocsAssigned(String userID, String groupName) {
ViewQuery query = createQuery("list_by_userID")
.group(true)
.dbPath(db.path())
.designDocId(stdDesignDocumentId)
.key(new String[]{userID,groupName});
ViewResult r = db.queryView(query);
return r.getRows().get(0).getValueAsInt();
}
So, the point is to send the complex key (not keys) actually as a single (but complex) key containing the String array, for some reason method '.keys(...)' didn't work for me (it takes a Collection as an argument). (for explanation on difference between .key() and .keys() see Hendy's answer)
This method counts all documents assigned to the specific user (specified by 'userID') and specific group (specified by 'groupName').
Hope that helps anybody executing map/reduce queries for retrieving scalar values from CouchDB using Ektorp query.
Addition to Kris's answer:
Note that ViewQuery.keys() is used when you want to query for documents matching a set of keys, not for finding document(s) with a complex key.
Like Kris's answer, the following samples will get document(s) matching the specified key (not "keys")
viewQuery.key("hello"); // simple key
viewQuery.key(documentSlug); // simple key
viewQuery.key(new String[] { userID, groupName }); // complex key, using array
viewQuery.key(ComplexKey.of(userID, groupName)); // complex key, using ComplexKey
The following samples, on the other hand, will get document(s) matching the specified keys, where each key may be either a simple key or a complex key:
// simple key: in essence, same as using .key()
viewQuery.keys(ImmutableSet.of("hello"));
viewQuery.keys(ImmutableSet.of(documentSlug1));
// simple keys
viewQuery.keys(ImmutableSet.of("hello", "world"));
viewQuery.keys(ImmutableSet.of(documentSlug1, documentSlug2));
// complex key: in essence, same as using .key()
viewQuery.keys(ImmutableSet.of(
new String[] { "hello", "world" } ));
viewQuery.keys(ImmutableSet.of(
new String[] { userID1, groupName1 } ));
// complex keys
viewQuery.keys(ImmutableSet.of(
new String[] { "hello", "world" },
new String[] { "Mary", "Jane" } ));
viewQuery.keys(ImmutableSet.of(
new String[] { userID1, groupName1 },
new String[] { userID2, groupName2 } ));
// a simple key and a complex key. while technically possible,
// I don't think anybody actually does this
viewQuery.keys(ImmutableSet.of(
"hello",
new String[] { "Mary", "Jane" } ));
Note: ImmutableSet.of() is from guava library.
new Object[] { ... } seems to have same behavior as ComplexKey.of( ... )
Also, there are startKey() and endKey() for querying using partial key.
To send an empty object {}, use ComplexKey.emptyObject(). (only useful for partial key querying)
I have not clearly issue during query using two criterials like Id and Other. I use a Repository storing some data like id,iso,value. I have created an index("_id","Iso") to performs queries but queries are only returning my cursor if i use only one criterial like _id, but is returning nothing if a use two (_id, Iso) (commented code).
Are the index affecting the response or the query method are failing?
use :v1.6.5 and C# official.
Sample.
//Getting Data
public List<BsonObject> Get_object(string ID, string Iso)
{
using (var helper = BsonHelper.Create())
{
//helper.Db.Repository.EnsureIndex("_Id","Iso");
var query = Query.EQ("_Id", ID);
//if (!String.IsNullOrEmpty(Iso))
// query = Query.And(query, Query.EQ("Iso", Iso));
var cursor = helper.Db.Repository.FindAs<BsonObject>(query);
return cursor.ToList();
}
}
Data:
{
"_id": "2345019",
"Iso": "UK",
"Data": "Some data"
}
After that I have Updated my data using Update.Set() methods. I can see the changed data using MongoView. The new data are correct but the query is always returning the sames olds values. To see these values i use a page that can eventually cached, but if add a timestamp at end are not changing anything, page is always returning the same olds data. Your comments are welcome, thanks.
I do not recall offhand how the C# driver creates indexes, but the shell command for creating an index is like this:
db.things.ensureIndex({j:1});
Notice the '1' which is like saying 'true'.
In your code, you have:
helper.Db.Repository.EnsureIndex("_Id","Iso");
Perhaps it should be:
helper.Db.Repository.EnsureIndex("_Id", 1);
helper.Db.Repository.EnsureIndex("Iso", 1);
It could also be related to the fact that you are creating indexes on "_Id" and the actual id field is called "_id" ... MongoDB is case sensitive.
Have a quick look through the index documentation: http://www.mongodb.org/display/DOCS/Indexes