I have a need to get a Count of Documents in a particular collection :
There is an existing index Raven/DocumentCollections that stores the Count and Name of the collection paired with the actual documents belonging to the collection. I'd like to pick up the count from this index if possible.
Here is the Map-Reduce of the Raven/DocumentCollections index :
from doc in docs
let Name = doc["#metadata"]["Raven-Entity-Name"]
where Name != null
select new { Name , Count = 1}
from result in results
group result by result.Name into g
select new { Name = g.Key, Count = g.Sum(x=>x.Count) }
On a side note, var Count = DocumentSession.Query<Post>().Count(); always returns 0 as the result for me, even though clearly there are 500 odd documents in my DB atleast 50 of them have in their metadata "Raven-Entity-Name" as "Posts". I have absolutely no idea why this Count query keeps returning 0 as the answer - Raven logs show this when Count is done
Request # 106: GET - 0 ms - TestStore - 200 - /indexes/dynamic/Posts?query=&start=0&pageSize=1&aggregation=None
For anyone still looking for the answer (this question was posted in 2011), the appropriate way to do this now is:
var numPosts = session.Query<Post>().Count();
To get the results from the index, you can use:
session.Query<Collection>("Raven/DocumentCollections")
.Where(x=>x.Name == "Posts")
.FirstOrDefault();
That will give you the result you want.
Related
I have 2 tables contractPoint and contractPointHistory
ContractPointHistory
ContractPoint
I would like to get contractPoint where point will be subtracted by pointChange. For example: ContractPoint -> id: 3, point: 5
ContractPointHistory has contractPointId: 3 and pointChange: -5. So after manipulating point in contractPoint should be 0
I wrote this code, but it works just for getRawMany(), not for getMany()
const contractPoints = await getRepository(ContractPoint).createQueryBuilder('contractPoint')
.addSelect('"contractPoint".point + COALESCE((SELECT SUM(cpHistory.point_change) FROM contract_point_history AS cpHistory WHERE cpHistory.contract_point_id = contractPoint.id), 0) AS points')
.andWhere('EXTRACT(YEAR FROM contractPoint.validFrom) = :year', { year })
.andWhere('contractPoint.contractId = :contractId', { contractId })
.orderBy('contractPoint.grantedAt', OrderByDirection.Desc)
.getMany();
The method getMany can be used to select all attributes of an entity. However, if one wants to select some specific attributes of an entity then one needs to use getRawMany.
As per the documentation -
There are two types of results you can get using select query builder:
entities or raw results. Most of the time, you need to select real
entities from your database, for example, users. For this purpose, you
use getOne and getMany. But sometimes you need to select some specific
data, let's say the sum of all user photos. This data is not an
entity, it's called raw data. To get raw data, you use getRawOne and
getRawMany
From this, we can conclude that the query which you want to generate can not be made using getMany method.
I am using flask-sqlalchemy together with a sqlite database. I try to get all votes below date1
sub_query = models.VoteList.query.filter(models.VoteList.vote_datetime < date1)
sub_query = sub_query.filter(models.VoteList.group_id == selected_group.id)
sub_query = sub_query.filter(models.VoteList.user_id == g.user.id)
sub_query = sub_query.subquery()
old_votes = models.Papers.query.join(sub_query, sub_query.c.arxiv_id == models.Papers.arxiv_id).paginate(1, 4, False)
where the database model for VoteList looks like this
class VoteList(db.Model):
id = db.Column(db.Integer, primary_key=True)
user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
group_id = db.Column(db.Integer, db.ForeignKey('groups.id'))
arxiv_id = db.Column(db.String(1000), db.ForeignKey('papers.arxiv_id'))
vote_datetime = db.Column(db.DateTime)
group = db.relationship("Groups", backref=db.backref('vote_list', lazy='dynamic'))
user = db.relationship("User", backref=db.backref('votes', lazy='dynamic'), foreign_keys=[user_id])
def __repr__(self):
return '<VoteList %r>' % (self.id)
I made sure that the 'old_votes' selection above has 20 elements. If I use .all() instead of .paginate() I get the expected 20 result?
Since I used a max results value of 4 in the example above I would expect that old_votes.items has 4 elements. But it has only 2? If I increase the max results value the number of elements also increases, but it is always below the max result value? Paginate seems to mess up something here?
any ideas?
thanks
carl
EDIT
I noticed that it works fine if I apply the paginate() function on add_columns(). So if I add (for no good reason) a column with
old_votes = models.Papers.query.join(sub_query, sub_query.c.arxiv_id == models.Papers.arxiv_id)
old_votes = old_votes.add_columns(sub_query.c.vote_datetime).paginate(page, VOTES_PER_PAGE, False)
it works fine? But since I don't need that column it would still be interesting to know what goes wrong with my example above?
Looks to me that for the 4 rows returned (and filtered) by the query, there are 4 rows representing 4 different rows of the VoteList table, but they refer/link/belong to only 2 different Papers models. When model instances are created, duplicates are filtered out, and therefore you get less rows. When you add a column from a subquery, the results are tuples of (Papers, vote_datetime), and in this case no duplicates are removed.
I encountered the same issue and I applied van's answer but it did not work. However I agree with van's explanation so I added .distinct() to the query like this:
old_votes = models.Papers.query.distinct().join(sub_query, sub_query.c.arxiv_id == models.Papers.arxiv_id).paginate(1, 4, False)
It worked as I expected.
At a high level, I need a query that can pull a subset of records based on the sum of a column, just like Linq: How to query items from a collection until the sum reaches a certain value.
However, the key difference is that he's already got his records in an object, and I don't and can't. My table can have millions of records. If I build my query the way he did, I get this error:
"A lambda expression with a statement body
cannot be converted to an expression tree"
Which makes sense after researching it, LINQ can't turn the answer in the above referenced question into valid SQL.
I'm going to make a hypothetical table that represents my situation.
Order Id | Cookie Name | Qty
1 Sugar 5
2 Snickerdoodle 4
3 Chocolate chip 8
4 Snickerdoodle 10
5 Snickerdoodle 5
Given this sample, I need to write a query that grabs the first X orders of Snickerdoodle until the summed Qty exceedes an input from the parameter (i.e. If the user chooses 13, it would return records 2 & 4 ).
I'm using Nhibernate.Linq, because I'm more comfortable in LINQ. I'm completely open to ICreate if the need arises.
As a side note, I'm interested in this as a concept as well as a direct problem. Even though I need a Sum, there has to be a way to do something akin to a takewhile that executes until a condition is met.
pragmatic approach
int needed = ...;
int actual = 0;
int page = 0;
const int pagesize = 20; // set to some sensible value, eg. the pagesize of the grid shown to the user
var results = new List<CookieOrder>();
while (actual < needed)
{
var partialResults = session.Query<CookieOrder>()
.Where(c => c.Name == "Snickerdoodle")
.OrderBy(c => c.Id)
.Skip(page * pagesize)
.Take(pagesize)
.ToList();
for(int i = 0; i < partialResults.Length && actual < needed; i++)
{
results.Add(partialResults[i]);
actual = partialResults[i].Quantity;
}
page++;
}
return results;
I'm wondering what's the best approach for getting back the total number of records for a search, and at the same time, get back the Nth 128 record block segment of data which seems to be the cap imposed by RavenDb run-time.
For instance given this query, I also need to know the total number of records.
var bookmarks = session.Query<Bookmark>()
.OrderByDescending(i => i.DateCreated)
.Skip(pageCount * (pageNumber – 1))
.Take(pageCount)
.ToList();
Thank you,
Stephen
RavenQueryStatistics stats;
var bookmarks = session.Query<Bookmark>()
.OrderByDescending(i => i.DateCreated)
.Skip(pageCount * (pageNumber – 1))
.Take(pageCount)
.Statistics(out stats)
.ToList();
int bookmarksFound = stats.TotalResults;
I am trying to figure out how to do a Take and FetchMany Together.
var c = session.Query<Table1>().Take(5).FetchMany(x => x.Table2).ToList();
I expect this to return 5 rows from Table1 and unbound result from Table2. Instead I get one row back from Table1 and 5 rows from Table2.
var c = session.Query<Table1>().Take(1000).FetchMany(x => x.Table2).ToList();
I get 309 records from Table1(it has 6200 total records).
I don't get how nhibernate decided to return that many records.
well I am not sire but how this has a bearing on your code, but fetchmany will bring the whole result set to memory and then Take the specified subset.
use joinqueryover or joinalias to achieve the same..
var c = session.Query<Table1>().Take(5).FetchMany(x => x.Table2).ToList();
this becomes
Table2 table2Alias=null;
var c = session.QueryOver<Table1>().JoinAlias(x => x.Table2,()=>table2Alias).Take(5).ToList();
let me know if it works out for you.. or you can write an HQL query instead