Errors in the use of Specification, returns one object out of 2 matching the search criteria, while builder returns the correct value.
springDatabaseItemRepository.findAll(builder.build(), pageable);
I'm looking for 3 conditions: 1 of which joins all queries and works. The other two are one simple query, the second is join connected using or. And after processing, only the results of join are returned to me.
I tried to change the processing and conditions, tried to read the documentation, but it didn't give me anything. Also, if you call join and a simple query separately, the results are returned correct.
Related
Lets say i have a graph:
A - follows -> B
A - follows -> C
Now, i have a query to get followers for both B and C (which should return me A 2 times).
MATCH (a)<-[:FOLLOWS]-(followers)
WHERE a.username IN ['B','C']
RETURN followers
If i make this query through Neo4J browser, i get 2 records: A node 2 times. This is correct.
If i make the same query through Spring Repository i get a list with only 1 object (A).
So, through Spring's repository any query for entities performs as if i add DISTINCT, so there is no difference between regular query and DISTINCT one.
If i query for some property of a node, i.e. A.username, i get a list with two duplicate strings (as intended).
Is this behaviour expected?
Why ?
Is there a way to query fo full entities with duplicates, the same
way that Cypher query works in Neo4J itself?
In general this behaviour is correct:
The A is always the same and gets mapped as one object. It won't make any sense to create the very same object twice.
I don't know from your question what the query should map to. But assuming it should create List<A> for this query it is correct.
Returning the a.username will not map to any entity but can only get collected in a projection / #QueryResult. This result has no concept of equality or similar and will always get created for any returned "row" from the response.
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 have the following ReQL Query which Identifies distinct addresses, but can't seem to add the not() method to get the opposite.
r.db('mydb').table('users').orderBy(r.desc('email')).without('id').distinct()
not operates on booleans. .distinct().not() doesn't modify the distinct operation. It just gets applied applies to its result, which doesn't make much sense.
You could instead do something like this
r.db('mydb').table('users')
.group('email').count().ungroup()
.filter(row => row('reduction').gt(1))('group')
eI need to select a particular single data element from first row ordered descending by date. Please specify the differences between the following keywords.
First
FirstOrDefault
singleOrDefault
Also need the precedence/order and usage rules of placing Orderby, where & select in Linq ORM Query. It would be much helpful if answer could be clear & descriptive.
Thanks in advance
A quick Google gives you the following Questions which address your question:
When to use .First and when to use .FirstOrDefault with LINQ?
LINQ: When to use SingleOrDefault vs. FirstOrDefault() with filtering criteria
You might also find the following article useful as it goes into each method:
http://www.technicaloverload.com/linq-single-vs-singleordefault-vs-first-vs-firstordefault/
As stated in the answers, the names do give it away (to those familiar), but here's a quick overview:
First
Will return the first entry in a collection (one or more results returned), will throw an exception if no records returned.
FirstOrDefault
Will return the first entry in a collection (one or more results returned), will return the appropriate default object if no records returned
SingleOrDefault
This one isn't really the same as the previously mentioned functions, it will return the result only if only one record is returned, otherwise will return the appropriate default object.
I tend to use First if I know that my results will always return "something", I use FirstOrDefault when I just want the first element but know that sometimes the query might return nothing. I've yet to personally use SingleOrDefault but it should only be used where your query is only ever going to return one row and that returned results should be ignored if more than one result exists.
I've got an Entity model (in Mongoid) that I'm trying to search on its keywords field which is an array. I want to do a query where I pass in an array of potential search terms, and any entity that matches any of the terms will pass.
I don't have this working well yet.
But, why I'm asking this question, is that it's more complex. I also DONT want to return any entities that have been marked as "do not return" which I do via a "ignore_project_ids" parameter.
So, when I query, I get 0 results. I was using Bonsai.io. But, I've moved this to my own EC2 instance to reduce complexity/variables on solving the problem.
So, what am I doing wrong? Here are the relevant bits of code.
https://gist.github.com/3405763
You want a terms query rather than a term query - a term query is only interested in equality, whereas a terms query requires that the field match any of the specified values.
Given that you don't seem to care about the query score (you're sorting by another attribute), you'll get faster queries by using a filtered query and expressing your conditions as filters