Can you nest queries logically in ElasticSearch, so the output of one query is the input to another query.
Another, way to ask is how can I chain or pipe queries together?
This should be analogous to the IN operator or subqueries in SQL
i.e.:-
select au_lname, au_fname, title from
(select au_lname, au_fname, au_id from pubs.dbo.authors
where state = 'CA')
or
SELECT Name
FROM AdventureWorks2008R2.Production.Product
WHERE ListPrice =
(SELECT ListPrice
FROM AdventureWorks2008R2.Production.Product
WHERE Name = 'Chainring Bolts' );
Elasticsearch doesn't support subqueries; you would need to perform your first query, then construct a second query using the results of the first query as an input.
this is not supported in elastic-search you must normalize your data and have all field you need in one setting
That is totally correct, you must programm a subquery in your favorite programming language. An example can be found here:
https://sebastianviereck.de/elasticsearch-subquery-scoring-optimization/
Related
I have a requirement which is somewhat similar to this. My API supports a filter where there is more than 8 filter parameter. So, I want to create a query dynamically based on the filter parameter passed. I am using CriteriaBuilder to create a dynamic query.
Now, I am able to create dynamic queries successfully but the issue comes when the user wants to sort on an aggregate functions. In my query, I have 4 aggregate (count) function. So to support sorting on these columns, I just use the expression of this aggregate function but what I want is to use the alias of this expression
Repeating the expression in select and order by doesn't seem right to me. So, is there a solution/workaround to the problem. I want to declare the expression alias once and use it in both select and order by clause and if required in my group by clause in future
You probably need to build a custom projection class, you can find a decent and easy one, SQLProjectionWithAliasSupport in https://hibernate.atlassian.net/browse/HHH-2952 (from Sergey Pulyaev)
If then one wants to support also sub criteria, things get more complicate
I am using gorm to interact with a postgres database. I'm trying to ORDER BY a query that uses DISTINCT ON and this question documents how it's not that easy to do that. So I need to end up with a query in the form of
SELECT * FROM (<subquery>) ORDER BY column;
At first glance it looks like I need to use db.QueryExpr() to turn the query I have into an expression and build another query around it. However it doesn't seem gorm has an easy way to directly specify the FROM clause. I tried using db.Model(expr) or db.Table(fmt.Sprint(expr)) but Model seems to be completely ignored and fmt.Sprint(expr) doesn't return exactly what I thought. Expressions contain a few private variables. If I could turn the original query into a completely parsed string then I could use db.Table(query) but I'm not sure if I can generate the query as a string without running it.
If I have a fully built gorm query, how can I wrap it in another query to do the ORDER BY I'm trying to do?
If you want to write raw SQL (including one that has a SQL subquery) that will be executed and the results added to an object using gorm, you can use the .Raw() and .Scan() methods:
query := `
SELECT sub.*
FROM (<subquery>) sub
ORDER BY sub.column;`
db.Raw(query).Scan(&result)
You pass a pointer reference to an object to .Scan() that is structured like the resulting rows, very similarly to how you would use .First(). .Raw() can also have data added to the query using ? in the query and adding the values as comma separated inputs to the function:
query := `
SELECT sub.*
FROM (<subquery>) sub
WHERE
sub.column1 = ?
AND sub.column2 = ?
ORDER BY sub.column;`
db.Raw(query, val1, val2).Scan(&result)
For more information on how to use the SQL builder, .Raw(), and .Scan() take a look at the examples in the documentation: http://gorm.io/advanced.html#sql-builder
I have a few records in my elasticsearch collection and i want to use a GroupBy aggregation in elasticsearch querystring.
I want to know if it is possible, because i tried to google it always give result about this
i want to use this something like this in the query string , which can
give me records in the group.
For i.e.
http://localhost:9200/_all/tweets/_count?q=user:Pu*+user:Kim*
This will give me count of all the records which has name starts from Pu and Kim,
But i want to know that how many records are there has name starting with Pu
and Kim,
aggregations need to be specified in addition in the search request, you cannot specify them as part of a query string query.
You could also just execute two queries to find out this particular requirement...
I have to Pull all customers whose ids are in the list
I have a list of CustomerID`s
List custidlist=new List{1,2,3....etc.}();
i have to write a linq query to get all customers whose id`s are in the above list
custidlist.
var customers=db.Customers.Where(c=> custidlist.Contains(c.customerid));
Using Contains is not good in performance issue.
Can we use COMPARE OPERATOR LIKE THIS
var customers=db.Customers.Where(c=> custidlist.Compare(c.customerid)); ????
I Heard Compare is best for Performance
Since this is Linq to SQL / Entities your Linq Contains query will be translated to a SQL statement roughly like:
select * from Customers where customerId in (1,2,3)
Not only is your other suggestion not supported, but also you cannot do any better than this SQL performance wise.
When you write a Contains query in Linq to SQL it iwll be fired as an in query in SQL and running your query on the databse should be the fastest..
one caveats to this though is to remember in query might have a limit on the number of entities I think its around 2000+ in sql server and the way around this would be to batch your query.
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.