Source

whoosh / docs / source / recipes.rst

Whoosh recipes

General

Get the stored fields for a document from the document number

stored_fields = searcher.stored_fields(docnum)

Analysis

Eliminate words shorter/longer than N

Use a :class:`~whoosh.analysis.StopFilter` and the minsize and maxsize keyword arguments. If you just want to filter based on size and not common words, set the stoplist to None:

sf = analysis.StopFilter(stoplist=None, minsize=2, maxsize=40)

Allow optional case-sensitive searches

A quick and easy way to do this is to index both the original and lowercased versions of each word. If the user searches for an all-lowercase word, it acts as a case-insensitive search, but if they search for a word with any uppercase characters, it acts as a case-sensitive search:

class CaseSensitivizer(analysis.Filter):
    def __call__(self, tokens):
        for t in tokens:
            yield t
            if t.mode == "index":
               low = t.text.lower()
               if low != t.text:
                   t.text = low
                   yield t

ana = analysis.RegexTokenizer() | CaseSensitivizer()
[t.text for t in ana("The new SuperTurbo 5000", mode="index")]
# ["The", "the", "new", "SuperTurbo", "superturbo", "5000"]

Searching

Find every document

myquery = query.Every()

iTunes-style search-as-you-type

Use the :class:`whoosh.analysis.NgramWordAnalyzer` as the analyzer for the field you want to search as the user types. You can save space in the index by turning off positions in the field using phrase=False, since phrase searching on N-gram fields usually doesn't make much sense:

# For example, to search the "title" field as the user types
analyzer = analysis.NgramWordAnalyzer()
title_field = fields.TEXT(analyzer=analyzer, phrase=False)
schema = fields.Schema(title=title_field)

See the documentation for the :class:`~whoosh.analysis.NgramWordAnalyzer` class for information on the available options.

Shortcuts

Look up documents by a field value

# Single document (unique field value)
stored_fields = searcher.document(id="bacon")

# Multiple documents
for stored_fields in searcher.documents(tag="cake"):
    ...

Sorting and scoring

See :doc:`facets`.

Score results based on the position of the matched term

The following scoring function uses the position of the first occurance of a term in each document to calculate the score, so documents with the given term earlier in the document will score higher:

from whoosh import scoring

def pos_score_fn(searcher, fieldname, text, matcher):
    poses = matcher.value_as("positions")
    return 1.0 / (poses[0] + 1)

pos_weighting = scoring.FunctionWeighting(pos_score_fn)
with myindex.searcher(weighting=pos_weighting) as s:
    ...

Results

How many hits were there?

The number of scored hits:

found = results.scored_length()

Depending on the arguments to the search, the exact total number of hits may be known:

if results.has_exact_length():
    print("Scored", found, "of exactly", len(results), "documents")

Usually, however, the exact number of documents that match the query is not known, because the searcher can skip over blocks of documents it knows won't show up in the "top N" list. If you call len(results) on a query where the exact length is unknown, Whoosh will run an unscored version of the original query to get the exact number. This is faster than the scored search, but may still be noticeably slow on very large indexes or complex queries.

As an alternative, you might display the estimated total hits:

found = results.scored_length()
if results.has_exact_length():
    print("Scored", found, "of exactly", len(results), "documents")
else:
    low = results.estimated_min_length()
    high = results.estimated_length()

    print("Scored", found, "of between", low, "and", high, "documents")

Which terms matched in each hit?

# Use terms=True to record term matches for each hit
results = searcher.search(myquery, terms=True)

for hit in results:
    # Which terms matched in this hit?
    print("Matched:", hit.matched_terms())

    # Which terms from the query didn't match in this hit?
    print("Didn't match:", myquery.all_terms() - hit.matched_terms())

Global information

How many documents are in the index?

# Including documents that are deleted but not yet optimized away
numdocs = searcher.doc_count_all()

# Not including deleted documents
numdocs = searcher.doc_count()

What fields are in the index?

return myindex.schema.names()

Is term X in the index?

return ("content", "wobble") in searcher

How many times does term X occur in the index?

# Number of times content:wobble appears in all documents
freq = searcher.frequency("content", "wobble")

# Number of documents containing content:wobble
docfreq = searcher.doc_frequency("content", "wobble")

Is term X in document Y?

# Check if the "content" field of document 500 contains the term "wobble"

# Without term vectors, skipping through list...
postings = searcher.postings("content", "wobble")
postings.skip_to(500)
return postings.id() == 500

# ...or the slower but easier way
docset = set(searcher.postings("content", "wobble").all_ids())
return 500 in docset

# If field has term vectors, skipping through list...
vector = searcher.vector(500, "content")
vector.skip_to("wobble")
return vector.id() == "wobble"

# ...or the slower but easier way
wordset = set(searcher.vector(500, "content").all_ids())
return "wobble" in wordset