Indexing and parsing dates/times¶
Indexing dates¶
Whoosh lets you index and search dates/times using the
whoosh.fields.DATETIME field type. Instead of passing text for the
field in
add_document(), you use a Python
datetime.datetime object:
from datetime import datetime, timedelta from whoosh import fields, index schema = fields.Schema(title=fields.TEXT, content=fields.TEXT, date=fields.DATETIME) ix = index.create_in("indexdir", schema) w = ix.writer() w.add_document(title="Document 1", content="Rendering images from the command line", date=datetime.utcnow()) w.add_document(title="Document 2", content="Creating shaders using a node network", date=datetime.utcnow() + timedelta(days=1)) w.commit()
Parsing date queries¶
Once you’ve have an indexed
DATETIME field, you can search it using a rich
date parser contained in the
whoosh.qparser.dateparse.DateParserPlugin:
from whoosh import index from whoosh.qparser import QueryParser from whoosh.qparser.dateparse import DateParserPlugin ix = index.open_dir("indexdir") # Instatiate a query parser qp = QueryParser("content", ix.schema) # Add the DateParserPlugin to the parser qp.add_plugin(DateParserPlugin())
With the
DateParserPlugin, users can use date queries such as:
20050912 2005 sept 12th june 23 1978 23 mar 2005 july 1985 sep 12 today yesterday tomorrow now next friday last tuesday 5am 10:25:54 23:12 8 PM 4:46 am oct 31 2010 last tuesday to today today to next friday jan 2005 to feb 2008 -1 week to now now to +2h -1y6mo to +2 yrs 23d
Normally, as with other types of queries containing spaces, the users need to quote date queries containing spaces using single quotes:
render date:'last tuesday' command date:['last tuesday' to 'next friday']
If you use the
free argument to the
DateParserPlugin, the plugin will
try to parse dates from unquoted text following a date field prefix:
qp.add_plugin(DateParserPlugin(free=True))
This allows the user to type a date query with spaces and special characters following the name of date field and a colon. The date query can be mixed with other types of queries without quotes:
date:last tuesday render date:oct 15th 2001 5:20am command
If you don’t use the
DateParserPlugin, users can still search DATETIME
fields using a simple numeric form
YYYY[MM[DD[hh[mm[ss]]]]] that is built
into the
DATETIME field:
from whoosh import index from whoosh.qparser import QueryParser ix = index.open_dir("indexdir") qp = QueryParser("content", schema=ix.schema) # Find all datetimes in 2005 q = qp.parse(u"date:2005") # Find all datetimes on June 24, 2005 q = qp.parse(u"date:20050624") # Find all datetimes from 1am-2am on June 24, 2005 q = qp.parse(u"date:2005062401") # Find all datetimes from Jan 1, 2005 to June 2, 2010 q = qp.parse(u"date:[20050101 to 20100602]")
About time zones and basetime¶
The best way to deal with time zones is to always index
datetimes in native
UTC form. Any
tzinfo attribute on the
datetime object is ignored
by the indexer. If you are working with local datetimes, you should convert them
to native UTC datetimes before indexing.
Date parser notes¶
Please note that the date parser is still somewhat experimental.
Setting the base datetime¶
When you create the
DateParserPlugin you can pass a
datetime object to
the
basedate argument to set the datetime against which relative queries
(such as
last tuesday and
-2 hours) are measured. By default, the
basedate is
datetime.utcnow() at the moment the plugin is instantiated:
qp.add_plugin(DateParserPlugin(basedate=my_datetime))
Registering an error callback¶
To avoid user queries causing exceptions in your application, the date parser attempts to fail silently when it can’t parse a date query. However, you can register a callback function to be notified of parsing failures so you can display feedback to the user. The argument to the callback function is the date text that could not be parsed (this is an experimental feature and may change in future versions):
errors = [] def add_error(msg): errors.append(msg) qp.add_plugin(DateParserPlug(callback=add_error)) q = qp.parse(u"date:blarg") # errors == [u"blarg"]
Using free parsing¶
While the
free option is easier for users, it may result in ambiguities.
As one example, if you want to find documents containing reference to a march
and the number 2 in documents from the year 2005, you might type:
date:2005 march 2
This query would be interpreted correctly as a date query and two term queries
when
free=False, but as a single date query when
free=True. In this
case the user could limit the scope of the date parser with single quotes:
date:'2005' march 2
Parsable formats¶
The date parser supports a wide array of date and time formats, however it is
not my intention to try to support all types of human-readable dates (for
example
ten to five the friday after next). The best idea might be to pick
a date format that works and try to train users on it, and if they use one of
the other formats that also works consider it a happy accident.
Limitations¶
- Since it’s based on Python’s
datetime.datetimeobject, the
DATETIMEfield shares all the limitations of that class, such as no support for dates before year 1 on the proleptic Gregorian calendar. The
DATETIMEfield supports practically unlimited dates, so if the
datetimeobject is every improved it could support it. An alternative possibility might be to add support for
mxDateTimeobjects someday.
- The
DateParserPlugincurrently only has support for English dates. The architecture supports creation of parsers for other languages, and I hope to add examples for other languages soon.
DATETIMEfields do not currently support open-ended ranges. You can simulate an open ended range by using an endpoint far in the past or future.