One way how to achieve this, could be to create as many subqueries joined by AND, as many attributes must be found/related to searched files
I searching for name / value
The first solution works with the name/value pairs, from upper layer. I.e user selected mode to be read-only... (the second will be a bit easier, expecting that we already have ID's of the searched Atttributes)
// Below I am using C# properties, which I guess are correct
// based on the mapping. Naming convention is more Java (camel)
// but this should work with above mapping
// (also - class name Contact, not File)
Files file = null; // this is an alias used below
// here the attributes collection represents search filter
// ... settings for which is user looking for
var attributes = new List<Attrs>
{
new Attrs{ name = "mode", value = "read-only" },
new Attrs{ name = "view", value = "visible" }
};
// Let's start with definition of the outer/top query
// which will return all files, which do meet all filter requirements
var query = session.QueryOver<Files>(() => file);
In the next step, we will iterate through attributes, i.e. filters collection
// here we will take each attribute and create a subquery
// all these subqueries, will be joined with AND
// so only these files, which do have all attributes, will be selected
foreach (var attr in attributes)
{
// create the subquery, returning the FileId
Attrs attribute = null;
var subQueryForAttribute = QueryOver.Of<Files_Attrs>()
.JoinQueryOver(fa => fa.attr, () => attribute)
.Select(x => x.file.id)
;
// now, take name and value
var name = attr.name;
var value = attr.value;
// and convert them into where condition
subQueryForAttribute.Where(() => attribute.name == name);
subQueryForAttribute.Where(() => attribute.value == value);
// finally, add this subquery as a restriction to the top level query
query.WithSubquery
.WhereProperty(() => file.id)
.In(subQueryForAttribute);
}
Now we have a query, which is ready to support paging - because we are working on a flat structure of files. So we can use Take and skip if needed and then get the list of searched files
// query.Take(25);
// query.Skip(100);
var list = query.List<Files>();
This is a query which will result in a SELECT like this
SELECT ...
FROM files
WHERE id IN (SELECT file_Id FROM files_attrs
INNER JOIN attrs ON attrs.id = file_attrs.attr_id
WHERE name = 'mode' AND value = 'read-only' )
AND id IN (SELECT file_Id FROM files_attrs
INNER JOIN attrs ON attrs.id = file_attrs.attr_id
WHERE name = 'view' AND value = 'visible' )
II searching by attributes ID
The second solution, has easier starting conditions, instead of attributes (name and value) we already have their Ids (cite from a question:)
Given a set of Attribute IDs, I'm hoping to run a query that gives me the files that have ALL of those matching Attributes.
// Below I am using C# properties, which I guess are correct
// based on the mapping. Naming convention is more Java (camel)
// but this should work with above mapping
// (also - class name Files, not File)
Files file = null; // this is an alias used below
// here the attributeIds collection represents attributes to be found
var attributeIds = new List<int> { 1, 4, 5 };
// Let's again start with definition of the outer/top query
// which will return all files, which do meet all filter requirements
var query = session.QueryOver<Files>(() => file);
Next is the iteration through the set of known IDs which must exist as relation (all of them)
// here we will take each attribute and create a subquery
// all these subqueries, will be joined with AND
// so only these files, which do have all attributes, will be selected
foreach (var attrId in attributeIds)
{
// create the subquery, returning the Files.id
var subQueryForAttribute = QueryOver.Of<Files_Attrs>()
// no need to join, all the stuff is in the pairing table
.Select(x => x.file.id)
;
var id = attrId; // local variable
// and convert them into where condition
subQueryForAttribute.Where(pair => pair.attr.id == id);
// finally, add this subquery as a restriction to the top level query
query.WithSubquery
.WhereProperty(() => file.id)
.In(subQueryForAttribute);
}
var list = query.List<Files>();
The solution with known IDS is a bit easier (less tables are needed in SQL statemenets)
NOTE: have to say: it is great to see, that you've introduced the many-to-one and one-to-many instead of many-to-many. I would, personally, say that exactly this example shows, how big profit it could bring... ability to search even with complex filters
Some links, to show the power of the QueryOver: Query on HasMany reference , and some good reason why not to use many-to-many mapping: many-to-many with extra columns nhibernate
