=== PQL
PQL stands for Python-Query-Language. PQL translates python expressions to MongoDB queries.
PQL uses the builtin python ast module for parsing and analysis of python expressions.
PQL is resilient to code injections as it doesn't evaluate the code.
Installation
pip install pql
Follow @alonhorev on twitter for updates. Source located at: http://github.com/alonho/pql
Find Queries
Schema-Free Example
The schema-free parser converts python expressions to mongodb queries with no schema enforcement:
>>> import pql
>>> pql.find("a > 1 and b == 'foo' or not c.d == False")
{'$or': [{'$and': [{'a': {'$gt': 1}}, {'b': 'foo'}]}, {'$not': {'c.d': False}}]}
Schema-Aware Example
The schema-aware parser validates fields exist:
>>> import pql
>>> pql.find('b == 1', schema={'a': pql.DateTimeField()})
Traceback (most recent call last):
...
pql.ParseError: Field not found: b. options: ['a']
Validates values are of the correct type:
>>> pql.find('a == 1', schema={'a': pql.DateTimeField()})
Traceback (most recent call last):
...
pql.ParseError: Unsupported syntax (Num).
Validates functions are called against the appropriate types:
>>> pql.find('a == regex("foo")', schema={'a': pql.DateTimeField()})
Traceback (most recent call last):
...
pql.ParseError: Unsupported function (regex). options: ['date', 'exists', 'type']
Referencing Fields
| pql | mongo |
|---|---|
| a | a |
| a.b.c | a.b.c |
| "a-b" | a-b |
Data Types
| pql | mongo |
|---|---|
| a == 1 | {'a': 1} |
| a == "foo" | {'a': 'foo'} |
| a == None | {'a': None} |
| a == True | {'a': True} |
| a == False | {'a': False} |
| a == [1, 2, 3] | {'a': [1, 2, 3]} |
| a == {"foo": 1} | {'a': {'foo': 1}} |
| a == date("2012-3-4") | {'a': datetime.datetime(2012, 3, 4, 0, 0)} |
| a == date("2012-3-4 12:34:56") | {'a': datetime.datetime(2012, 3, 4, 12, 34, 56)} |
| a == date("2012-3-4 12:34:56.123") | {'a': datetime.datetime(2012, 3, 4, 12, 34, 56, 123000)} |
| id == id("abcdeabcdeabcdeabcdeabcd") | {'id': bson.ObjectId("abcdeabcdeabcdeabcdeabcd")} |
Operators
| pql | mongo |
|---|---|
| a != 1 | {'a': {'$ne': 1}} |
| a > 1 | {'a': {'$gt': 1}} |
| a >= 1 | {'a': {'$gte': 1}} |
| a < 1 | {'a': {'$lt': 1}} |
| a <= 1 | {'a': {'$lte': 1}} |
| a in [1, 2, 3] | {'a': {'$in': [1, 2, 3]}} |
| a not in [1, 2, 3] | {'a': {'$nin': [1, 2, 3]}} |
Boolean Logic
| pql | mongo |
|---|---|
| not a == 1 | {'$not': {'a': 1}} |
| a == 1 or b == 2 | {'$or': [{'a': 1}, {'b': 2}]} |
| a == 1 and b == 2 | {'$and': [{'a': 1}, {'b': 2}]} |
Functions
| pql | mongo |
|---|---|
| a == all([1, 2, 3]) | {'a': {'$all': [1, 2, 3]}} |
| a == exists(True) | {'a': {'$exists': True}} |
| a == match({"foo": "bar"}) | {'a': {'$elemMatch': {'foo': 'bar'}}} |
| a == mod(10, 3) | {'a': {'$mod': [10, 3]}} |
| a == regex("foo") | {'a': {'$regex': 'foo'}} |
| a == regex("foo", "i") | {'a': {'$options': 'i', '$regex': 'foo'}} |
| a == size(4) | {'a': {'$size': 4}} |
| a == type(3) | {'a': {'$type': 3}} |
Geo Queries
| pql | mongo |
|---|---|
| location == geoWithin(center([1, 2], 3)) | {'location': {'$geoWithin': {'$center': [[1, 2], 3]}}} |
| location == geoWithin(centerSphere([1, 2], 3)) | {'location': {'$geoWithin': {'$centerSphere': [[1, 2], 3]}}} |
| location == geoIntersects(LineString([[1, 2], [3, 4]])) | {'location': {'$geoIntersects': {'$geometry': {'type': 'LineString', 'coordinates': [[1, 2], [3, 4]]}}}} |
| location == geoWithin(Polygon([[[1, 2], [3, 4], [5, 6]], [[1, 2], [3, 4], [5, 6]]])) | {'location': {'$geoWithin': {'$geometry': {'type': 'Polygon', 'coordinates': [[[1, 2], [3, 4], [5, 6]], [[1, 2], [3, 4], [5, 6]]]}}}} |
| location == near([1, 2], 10) | {'location': {'$maxDistance': 10, '$near': [1, 2]}} |
| location == near(Point(1, 2), 10) | {'location': {'$near': {'$geometry': {'type': 'Point', 'coordinates': [1, 2]}, '$maxDistance': 10}}} |
| location == nearSphere(Point(1, 2)) | {'location': {'$nearSphere': {'$geometry': {'type': 'Point', 'coordinates': [1, 2]}}}} |
| location == geoWithin(box([[1, 2], [3, 4], [5, 6]])) | {'location': {'$geoWithin': {'$box': [[1, 2], [3, 4], [5, 6]]}}} |
| location == geoWithin(polygon([[1, 2], [3, 4], [5, 6]])) | {'location': {'$geoWithin': {'$polygon': [[1, 2], [3, 4], [5, 6]]}}} |
Aggregation Queries
Example
Lets say you have a collection of car listings:
>>> list(db.cars.find())
[{'_id': ObjectId('51794ce58c998f1e2b654b50'),
'made_on': datetime.datetime(1971, 4, 7, 0, 0),
'model': 'fiat',
'price': 3},
{'_id': ObjectId('51794cea8c998f1e2b654b51'),
'made_on': datetime.datetime(1980, 10, 19, 0, 0),
'model': 'subaru',
'price': 5},
{'_id': ObjectId('51794cf08c998f1e2b654b52'),
'made_on': datetime.datetime(1983, 2, 27, 0, 0),
'model': 'kia',
'price': 4},
{'_id': ObjectId('51794d3c8c998f1e2b654b53'),
'made_on': datetime.datetime(1988, 1, 23, 0, 0),
'model': 'kia',
'price': 7}]
How do you get the number of cars and the sum of their prices per model per decade:
>>> collection.aggregate(project(model='model', made_on='year(made_on)', price='price * 3.7') |
match('made_on > 1975 and made_on < 1990') |
group(_id=project(model='model', decade='made_on - (made_on % 10)'),
count='sum(1)', total='sum(price)'))
{'ok': 1.0,
'result': [{'_id': {'decade': 1980, 'model': 'subaru'}, 'count': 1,'total': 18.5},
{'_id': {'decade': 1980, 'model': 'kia'}, 'count': 2, 'total': 40.7}]}
How would it look using the raw syntax:
[{'$project': {'made_on': {'$year': '$made_on'},
'model': '$model',
'price': {'$multiply': ['$price', 3.7]}}},
{'$match': {'$and': [{'made_on': {'$gt': 1975}},
{'made_on': {'$lt': 1990}}]}},
{'$group': {'_id': {'decade': {'$subtract': ['$made_on',
{'$mod': ['$made_on', 10]}]},
'model': '$model'},
'count': {'$sum': 1},
'total': {'$sum': '$price'}}}]
Referencing Fields
| pql | mongo |
|---|---|
| a | $a |
| a.b.c | $a.b.c |
Arithmetic Operators
| pql | mongo |
|---|---|
| a + 1 | {'$add': ['$a', 1]} |
| a / 1 | {'$divide': ['$a', 1]} |
| a % 1 | {'$mod': ['$a', 1]} |
| a * 1 | {'$multiply': ['$a', 1]} |
| a - 1 | {'$subtract': ['$a', 1]} |
| a > 0 | {'$gt': ['$a', 0]} |
| a >= 0 | {'$gte': ['$a', 0]} |
| a < 0 | {'$lt': ['$a', 0]} |
| a <= 0 | {'$lte': ['$a', 0]} |
Logical Operators
| pql | mongo |
|---|---|
| a == 0 | {'$eq': ['$a', 0]} |
| a != 0 | {'$ne': ['$a', 0]} |
| cmp(a, "bar") | {'$cmp': ['$a', 'bar']} |
| a and b | {'$and': ['$a', '$b']} |
| not a | {'$not': '$a'} |
| a or b | {'$or': ['$a', '$b']} |
| a if b > 3 else c | {'$cond': [{'$gt': ['$b', 3]}, '$a', '$c']} |
| ifnull(a + b, 100) | {'$ifnull': [{'$add': ['$a', '$b']}, 100]} |
Date Operators
| pql | mongo |
|---|---|
| dayOfYear(a) | {'$dayOfYear': '$a'} |
| dayOfMonth(a) | {'$dayOfMonth': '$a'} |
| dayOfWeek(a) | {'$dayOfWeek': '$a'} |
| year(a) | {'$year': '$a'} |
| month(a) | {'$month': '$a'} |
| week(a) | {'$week': '$a'} |
| hour(a) | {'$hour': '$a'} |
| minute(a) | {'$minute': '$a'} |
| second(a) | {'$second': '$a'} |
| millisecond(a) | {'$millisecond': '$a'} |
String Operators
| pql | mongo |
|---|---|
| concat("foo", "bar", b) | {'$concat': ['foo', 'bar', '$b']} |
| strcasecmp("foo", b) | {'$strcasecmp': ['foo', '$b']} |
| substr("foo", 1, 2) | {'$substr': ['foo', 1, 2]} |
| toLower(a) | {'$toLower': '$a'} |
| toUpper(a) | {'$toUpper': '$a'} |
TODO
- Generate a schema from a mongoengine or mongokit class.
- Add a declarative schema generation syntax.
- Add support for $where.
