Hibernate Search allows to sort search results on relevance. Is it possible to obtain and display (e.g. in a jsp view) this information using Lucene query?
A Query in Hibernate Search can return Projections rather than the simple list of matching entities.
A projection result essentially means each result is an array containing the sequence of projections you asked for. Normally this is used to extract text from a specific field, so to not need loading the data from the database, but there are Projection constants to return also the Score value or the Explanation of the scoring.
query.setProjection( ProjectionConstants.SCORE, ProjectionConstants.EXPLANATION, ProjectionConstants.THIS );
See also the Reference documentation on projections explaining this and more.
Related
I am working on a database of Polish verbs and I'd like to find out how to display my results such that each verb conjugation appears in the following order: 1ps (1st person singular), 2ps, 3ps, 1ppl (1st person plural, etc.), 2ppl, 3ppl. It displays fine when I insert documents:
verb "żyć/przeżyć" conjugation as array and nested document
But when I go to perform queries it jumbles all the array elements up, in the first case (I want to see them in order of array indices), and sorts the nested document elements into alphabetical order (whereas I want to see them in the order in which they were inserted).
verb "żyć/przeżyć" conjugation array/document query
This should be an easy one to solve, I hope this comes across as a reasonable beginner's question. I have searched for answers but couldn't find much info on this topic. Any and all help is greatly appreciated!
Cheers,
LC.
Your screenshots highlight two different views in MongoDB Compass.
The Schema view is based on a sampling of multiple documents and the order of the fields displayed cannot be specified. The schema analysis (as at Compass 1.7) lists fields in case-insensitive alphabetical order with the _id field at the top. Since this is an aggregate schema view based on multiple documents, the ordering of fields is not expected to reflect individual document order.
If you want to work with individual documents and field ordering you need to use the Documents view, as per your second screenshot. In addition to displaying the actual documents, this view allows you to include sort and skip options for queries:
(MongoDB Full Text Search)
Hello,
I have put some fields in index and this is how I could search for a search_keyword.
BasicDBObject search = new BasicDBObject("$search", "search_keyword");
BasicDBObject textSearch = new BasicDBObject("$text", search);
DBCursor cursor = users.find(textSearch);
I don't want search_keyword to be searched in all the fields specified in the index. *Is there any method to specify search_keyword to be searched in specific fields from the index??*
If so, please give me some idea how to do it in Java.
Thank you.
If you want to index a single field and search for it then it is the way it works by default. Lets say you want to index the field companyName. When you perform $text search on this collection, only the data from the companyName field will be used because you only included that field in your index.
Now the second scenario, your $text index includes more than one field. In this case you cannot limit the search to only look for values indexed from a specific field. The $text index is constructed on the collection level and a collection can have at most one $text index. Your option to limit search on specific field in this case may be to use regex instead.
MongoDB has the flexibility to fulfil requirements of other scenarios, but you can also evaluate using other technologies if your application is heavily search-driven and you are primarily after a full-text search engine for locating documents by keyword with a rich query syntax. ElasticSearch might be an alternative here. It really depends on the type of the application and your needs.
I have a mongodb query, and I want to add a computed field. The computed field is based on where or not the item is in the results of another query. So my query returns the columns a,b,c,d, and then column e should be based on whether or not the current row would be matched by another query.
Is there an efficient way to do this in mongo? I'm not really sure how to do this one...
There is no way currently to execute a function as you describe within the database when returning a document via standard functions such as find. It's been requested by the community, but the general request is to operate only on a single document.
There are calculated fields using $project in the aggregation framework. But, they only operate on the current document in the pipeline. So, they can't summarize other queries.
You'll need to likely build your e value as part of your data access layer.
Obviously, changes in a database will not reflect what is in an index all the time. Is anyone using EF with Lucene and combining the results of a Lucene search with results form the same search in EF? I understand you would only want to pull back results from EF that are not in the Lucene results.
Update:
I guess the best way to handle this would be to first search the Lucene index and get a list of results, then you would do a search like this for EF:
Pseudo Code:
var result = (from ef in EntityFrameworkList
where !(from l in LuceneList
select l.documentId)
.Contains(ef.Id)
select ef);
LuceneList.AddRange(result);
For those who like method chains
var result = (EntityFrameworkList.Where(ef => !(LuceneList.Select(l => l.documentId))
.Contains(ef.Id)));
We indeed followed the approach I suggested in the update. One thing to note is we only used this for displaying small lists of results and not for every type of search. For Full Text Search on larger documents we only used the Lucene results since we are not storing FTS data in our database.
According to the documentation, Zend Lucene is supposed to sort lexicographically. I am finding this is not the case. If I have a query 'avg:[050 TO 300]', yes it will return all values in that range, but it will sort them according to the document id, not the value.
I have found that the find() function can accept additional parameters, allowing me to sort by a specific column (eg $hits = $index->find($query, 'avg', SORT_NUMERIC, SORT_ASC);). However, I am creating $query dynamically and do not want to sort every search by 'avg'.
How do I force Lucene to sort the results automatically, lexicographically, when I do a range search? And if that's not possible, how do I dynamically add a sort field to the find function?
Why don't you sort $hits by yourself after getting the result from $index->find(...)? Ok this looks like a workaround and will be time-consuming for very large resultsets, but I guess that this is the easiest way in most cases.