In my Lucene documents I have a field "company" where the company name is tokenized.
I need the tokenization for a certain part of my application.
But for this query, I need to be able to create a PrefixQuery over the whole company field.
Example:
My Brand
my
brand
brahmin farm
brahmin
farm
Regularly querying for "bra" would return both documents because they both have a term starting with bra.
The result I want though, would only return the last entry because the first term starts with bra.
Any suggestions?
Create another indexed field, where the company name is not tokenized. When necessary, search on that field rather than the tokenized company name field.
If you want fast searches, you need to have index entries that point directly at the records of interest. There might be something that you can to with the proximity data to filter records, but it will be slow. I see the problem as: how can a "contains" query over a complete field be performed efficiently?
You might be able to minimize the increase in index size by creating (for each current field) a "first term" field and "remaining terms" field. This would eliminate duplication of the first term in two fields. For "normal" queries, you look for query terms in either of these fields. For "startswith" queries, you search only the "first term" field. But this seems like more trouble than it's worth.
Use a SpanQuery to only search the first term position. A PrefixQuery wrapped by SpanMultiTermQueryWrapper wrapped by SpanPositionRangeQuery:
<SpanPositionRangeQuery: spanPosRange(SpanMultiTermQueryWrapper(company:bra*), 0, 1)>
Related
I'm creating a self-help FAQ type application and one of the requirements is that the end user has to be able to search for FAQ topics. I have three models of note, listed below with their relevant (i.e. searchable) columns:
Topic: Name, Description
Question: Name, Answer
Problem: Name, Solution
All three tables are linked to Topic via a TopicID column. The idea is to provide a single textbox where the user can enter a search query, something either as a sentence (e.g. "How do I perform X") or a phrase (e.g. "Performing X" or "Perform X"), and provide all Topics/Questions/Problems that have any of the words they entered in either the name or description/answer/solution fields; the model will only ever have those columns searchable and I don't have to worry about filtering out the common words like "How" and such (It would be nice but isn't a requirement as it's not an exact match but a fuzzy match).
For reasons outside of my control, I have to use a Stored Procedure. My question is what would be the most appropriate way to handle a search like this; I've seen similar questions regarding multiple columns but really there is not a variable number of columns, there are always two columns per table that are actually searchable. The issue is that the search query could, in theory, be nearly anything - a sentence, a phrase, a comma-separated list of terms (e.g. "x,y,z"), so I would have to split the search term into components (e.g. split on whitespace) and then search each pair of columns for every term? Is that reasonably easy to do in SQL Server? The alternative, a little messier, is to just pull all the data back and then split the query and filter the results in the server-side code as there shouldn't ever be that many items entered, but I would feel a little dirty doing something like that ;-)
Suggest creating a new Full Text Catalog, and assign the table and columns to that catalog. Ensure your catalog is being updated at the right frequency for your needs.
You can then query this catalog using the FREETEXT predicate. It sounds like you need to match on those suffixes like 'ing', so suggest FREETEXT over CONTAINS in this case.
You can use a variable in this search, so it'll be easy to fit into a stored proc.
declare #token varchar(256);
select #token = 'perform';
select * from Problem
where freetext(Name, #token)
or freetext(Solution, #token);
--this will match 'perform' and 'performing'
I was going thru all the existing questions posts but couldn't get something much relevant.
I have file with millions of records for person first name, last name, address1, address2, country code, date of birth - I would like to check my list of customers with above file on daily basis (my customer list also get updated daily and file also gets updated daily).
For first name and last name I would like fuzzy match (may be lucene fuzzyquery/levenshtein distance 90% match) and for remaining fields country and date of birth I wanted exact match.
I am new to Lucene, but by looking at number of posts, looks like its possible.
My questions are:
How should I index my input file? I need to build index on combination of FN, LN, country, DOB and use the index for search
How I can use Fuzzy query of Lucene here?
Is there any other way I can implement the same?
Rushik, here are a few ideas:
Consider using Solr. It is much easier to start using it, rather than bare Lucene.
Build a Lucene/Solr index of the file. It appears that a document per customer is enough, if you use a multi-valued field or two different fields for addresses.
Do you have a unique id per person? To use Solr, you need one. In Lucene, you can get away without using a unique id.
Store the country code as a "keyword". If you only require exact match for date of birth, you may do the same. For range queries, you will need another representation.
I assume your customer list is smaller than the file. A possible policy would be to daily index the changes in the file (Here a unique id is really handy - otherwise you need to delete by query, which may miss the mark). Then you can optimize the index, and after that run a search for your updated customer list.
What you describe is a BooleanQuery, Whose clauses are fuzzy queries for the first and last names and term queries for the other fields. You can create the query programmaticaly or using the query parser.
Consider using soundex for names as described here.
Some academic papers on this subject are well worth reading (google for the free PDFs):
A Comparison of Personal Name Matching: Techniques and Practical Issues (2006)
Overview of Record Linkage and Current Research Directions (2006)
A Parallel Open Source Data Linkage System (2004)
You should also consider the following libraries/frameworks:
Duke: https://github.com/larsga/Duke
Febrl: http://sourceforge.net/projects/febrl/
(Answered for future visitors.)
AJAX autocomplete is fairly simple to implement. However, I wonder how to handle smart tag suggestion like this on SO.
To clarify the difference between autocomplete and suggestion:
autocomplete: foo [foobar, foobaz]
suggestion: foo [barfoo, foobar, foobaz], or even better, with 'did you mean' feature: [barfoo, foobar, foobaz, fobar, fobaz]
I suppose I need some full text search in tags (all letters indexed, not just words). There would be no problem to do it witch regex or other patterns for limited number of tags (even client side).
But how to implement this feature for big number of tags?
Is there any particular reason (besides URL) the tags on SO are dash separated? What about Unicode characters in tags?
I store the tags in the table with the following columns: id, tagname.
My SQL query returns objects with following fields: id, tagname, count
(I use Doctrine ORM and pgsql as default db driver.)
I would go with SELECTING them from database by REGEXP at every keypress. I did this on my sites and the was no prefrormance problem (I do not have heavy loaded server thought). If you do not like this idea, I would cash all 1-5 letters combinations which will users enter and refresh them on daily basis in separate table. If this table is indexed than you have very fast implementation.
To elaborate more on the second appreach:
Briefly: 1. Make a table SEARCHTABLE representing 1-n relationship betwean keywords (limit it to 3-4 letters) and primary IDs of tags. 2. INDEX on both fields. 3. Everytime the user makes a search do look at the SEARCHTABLE and if the combination is there, use that - very fast, as everything is indexed. If not do the regexp search and put all results to SEARCHTABLE.
Notes:
You should invalidate the table if
you add tags, but this should much
less often than a search. When
invalidating table you do not
necesarilly TRUNCATE it, you can
easily rebuild it taking all
keywords into account.
If you want to speed it up, you can "pregenerate" all two or even three
letters searches.
If you care enough, you should be using information from n-1 letter kewords to generate
the n letter keyword. It speeds the things tremendously. Imagine that user has typed "mo"
and you have shown them appropriate result from SEARCHTABLE. Than when she types "n"
giving it "mon" you need only serach trough already selected items to generate new
response.
Hope it is more comprehensive now.
I want to do an AND query, say 'foo AND bar', in Lucene.NET. I have a WholeIndex field which has the whole document indexed, and I want Lucene to search in the whole document.
Up to here it's quite easy, but there's a constraint.
I want both terms 'foo' and 'bar' to be in the same field.
Is there an easy way to do this without querying the index for the full list of fields and searching in every field?
Edit: What I want to know is if there is a way to tell Lucene to perform a search in every field, without having to know all the fields in my index. An automated way to search the following:
"field1:(+foo +bar) field2:(+foo +bar) ... fieldN:(+foo +bar)"
You can use GetFieldNames to get all the field names, and then go programmatically over the list and generating a query like the one you wrote, using BooleanQuery.
I've had this long term issue in not quite understanding how to implement a decent Lucene sort or ranking. Say I have a list of cities and their populations. If someone searches "new" or "london" I want the list of prefix matches ordered by population, and I have that working with a prefix search and an sort by field reversed, where there is a population field, IE New Mexico, New York; or London, Londonderry.
However I also always want the exact matching name to be at the top. So in the case of "London" the list should show "London, London, Londonderry" where the first London is in the UK and the second London is in Connecticut, even if Londonderry has a higher population than London CT.
Does anyone have a single query solution?
dlamblin,let me see if I get this correctly: You want to make a prefix-based query, and then sort the results by population, and maybe combine the sort order with preference for exact matches.
I suggest you separate the search from the sort and use a CustomSorter for the sorting:
Here's a blog entry describing a custom sorter.
The classic Lucene book describes this well.
API for
Sortcomparator
says
There is a distinct Comparable for each unique term in the field - if
some documents have the same term in
the field, the cache array will have
entries which reference the same
Comparable
You can apply a
FieldSortedHitQueue
to the sortcomparator which has a Comparator field for which the api says ...
Stores a comparator corresponding to
each field being sorted by.
Thus the term can be sorted accordingly
My current solution is to create an exact searcher and a prefix searcher, both sorted by reverse population, and then copy out all my hits starting from the exact hits, moving to the prefix hits. It makes paging my results slightly more annoying than I think it should be.
Also I used a hash to eliminate duplicates but later changed the prefix searcher into a boolean query of a prefix search (MUST) with an exact search (MUST NOT), to have Lucene remove the duplicates. Though this seemed even more wasteful.
Edit: Moved to a comment (since the feature now exists): Yuval F Thank you for your blog post ... How would the sort comparator know that the name field "london" exactly matches the search term "london" if it cannot access the search term?