pocketsearch 0.5.0

A pure-Python full text indexing search engine based on sqlite and the FTS5 extension.

pocketsearch

pocketsearch is a pure-Python full text indexing search engine based on sqlite and the FTS5 extension. It provides

• Support for full text search
• A simple API for defining schemas and searching
• Support for text, numeric and date search

It does not have any external dependencies other than Python itself. pocketsearch has been tested on Python 3.8, Python 3.9, Python 3.10 and Python 3.11.

Status

The package is currently in Beta status.

Installation

Run

pip install pocketsearch

to install the package.

Getting started

By default, pocketsearch creates an in-memory database using a default search index schema containing only one field called 'text':

from pocketsearch import PocketSearch

pocket_search = PocketSearch()
pocket_search.insert(text="Hello World !")
print(pocket_search.search(text="hello")[0].text)
Hello World !

From a database perspective, the new document will be immediately available 
to the search index, as each insert is followed by a database commit.

Be ware that the search methods limits results to 10 by default. Results 
are ordered by the rank of the search result which is calculated by the 
FTS extension in sqlite and showing how relevant a document is to a 
given query. 

AND/OR queries

The FTS5 engines supports AND/OR queries. By default they are disabled in the API, if you want to make boolean queries, you have to use a lookup parameter in your query:

from pocketsearch import PocketSearch

pocket_search = PocketSearch()
pocket_search.insert(text="Hello World !")
print(pocket_search.search(text__allow_boolean="hello OR world")[0].text)
Hello World !

Please note, that AND as well as OR are case-sensitive in this context.

Counting results

By invoking the count method you get the number of search results:

print(pocket_search.search(text__allow_boolean="hello OR world").count())
1

Prefix queries

If you want to search for substrings, you can use prefix queries, by providing the allow_prefix lookup:

print(pocket_search.search(text__allow_prefix="hel*")[0].text)

Combining lookups

Lookups can also be combined:

print(pocket_search.search(text__allow_prefix__allow_boolean="hel* OR wor*")[0].text)
Hello World !

Ordering results

By invoking the order method you can influence how your results are sorted. By default search results are sorted by relevance to the query.

# Order by text in ascending order
pocket_search.search(text__allow_boolean="hello OR world").order_by("text")
# This is equivalent to the previous call:
pocket_search.search(text__allow_boolean="hello OR world").order_by("+text")
# Order by text in descending order
pocket_search.search(text__allow_boolean="hello OR world").order_by("-text")

Schemas

A search index may have an arbitrary list of fields that can be searched. Schemas are defined through Schema classes:

from pocketsearch import Schema, PocketSearch
from pocketsearch import Text, Int, Real, Numeric, Blob, Date, Datetime

class FileContents(Schema):

    text = Text(index=True)
    filename = Text(is_id_field=True)

# create pocketsearch instance and provide schema
pocket_search.PocketSearch(schema=FileContents)
pocket_search.insert(text="Hello world",filename="a.txt")

Following fields are available:

Field	SQLite data type
Text	TEXT
Int	INTEGER
Real	REAL
Numeric	Numeric
Blob	Blob
Date	Date
Datetime	Datetime

Following options are available for fields:

• index - if the field is a Text field, a full text search index is created, otherwise a standard sqlite3 index is created
• is_id_field - a schema can only have one IDField. It is used by the .insert_or_update method to decide if a document should be inserted or an existing document should be updated.

With respect to naming your fields following restrictions apply:

• Fields may not start with an underscore.
• Fields may not contain double underscores.

Once the schema is created, you can query multiple fields:

# Searches field text for "world"
pocket_search.search(text="world")
# Searches documents that contain "world" in text and have "a.txt" is a filename.
# Please note: as "filename" has not set its index option, only exact matches 
# will be considered.
pocket_search.search(text="world",filename="a.txt")

Please note that by default an AND query is performed, thus only documents are matched where text contains the word "world" and the filename is "a.txt"

Searching numeric data

You can also search for numeric data:

class Product(Schema):

    price = Int()
    description = Text(index=True) # Full text index
    category = Text()  # not part of FT index

pocket_search = PocketSearch(schema=Product)
# Create some sensible test data before proceeding ...
# Matches products with price=3
pocket_search.search(price=3)
# Matches products with price greater than 3
pocket_search.search(price__gt=3)
# Matches products with price lower than 3
pocket_search.search(price__lt=3)
# Matches products with price lower than equal 3
pocket_search.search(price__lte=3)
# Matches products with price greater than equal 3
pocket_search.search(price__gte=3)
# Matches products with price greater than equal 3 AND where the description contains "apple".
pocket_search.search(price__gte=3,description="apple")

Searching date fields

pocketsearch also provides some (experimental) support for searching dates:

class AllFields(Schema):

    published=Datetime()

pocket_search = PocketSearch(schema=self.Product)
# Search documents published in year 2023
pocket_search.search(published__year=2023)
# Search document published after 2020
pocket_search.search(published__year__gt=2023)
# Search documents published in month 6
pocket_search.search(published__month=6)
# Search documents published on 21/6/2023:
pocket_search.search(published__month=21,published__month=6,published_year=2023)

Making your database persistent

The previous examples use an in-memory sqlite database. If you want to actually store the database, you have to provide a name:

pocket_search = PocketSearch(db_name="my_db.db",writeable=True)
# now, all operations will be done on the my_db database that is stored in the 
# current working directory.

When working with search indices that are stored on disk, it is important to provide the writeable argument, as any PocketSearch instance that works with file sqlite databases, is in read-only mode be default (unlike their in-memory counterpart.).

Behind the scenes: how searching works

pocketsearch uses the FTS5 extension of sqlite. More information can be found here: https://www.sqlite.org/fts5.html

Internally, it:

• Creates two tables, one named "document" and one virtual table "document_idx" - the latter holds the full-text-search enabled files.
• The document_idx table is populated through triggers on the document table.
• It uses the unicode61 tokenizer as default.

If you want to change the tokenizer, you can do so by overriding the Meta class of a schema:

from pocketsearch import Schema, PocketSearch

class FileContents(Schema):

    class Meta:
        '''
        Additional options for setting up FTS5
        See https://www.sqlite.org/fts5.html for more information.
        If a value is set to None, we leave it up to sqlite to
        set proper defaults.
        '''
        sqlite_tokenize = "unicode61" # change to available tokenizer of your choice
        sqlite_remove_diacritics = None
        sqlite_categories = None
        sqlite_tokenchars = None
        sqlite_separators = None    

    text = Text(index=True)
    filename = Text(is_id_field=True)

Multiple indicies in one database

You can have multiple indicies in one database (only databases written to disk) by setting the "index_name" option:

pocket_search = PocketSearch(index_name="Product",schema=Product)

Contribute

Pull requests are welcome. If you come across any issues, please report them at https://github.com/kaykay-dv/pocketsearch/issues