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Access to database flexibly

Project description

Zugh

[WIP] Access to database in pythonic way

Zugh is a tool for generating SQL and accessing databases flexibly in pythonic way. It empower you to use complex SQL, but didn't need to write them directly.

Status

Work in progress.

Now we support MySQL only.

Required

  • Python >= 3.6
  • PyMySQL >= 0.9.3

Licence

MIT.

Install

Use pip:

pip install zugh

Usage

Note !
The time of writing each part of this document is out of order. So the results before and after the execution of SQL may not match. Nevertheless, I recommend that you start reading from scratch and try the code.

Connection

Config

>>> from zugh.db.connection import connect_config
>>> conn_config = connect_config('localhost', 'your_username', 'your_password')
# You can use conn_config dict to configure connection for DdataBase object
# or initial a connection pool

Pool

>>> from zugh.db.pool import ConnectionPool
>>> pool = ConnectionPool(conn_config)

Database

Create a database:

>>> from zugh.schema.db import DataBase
>>> db = DataBase('zugh', conn_config=conn_config)
# or db = DataBase('zugh', pool=pool)
>>> db.create()

Table

Create a table.

We haven't implemented those APIs to create a table yet, so just execute SQL with a connection:

>>> from zugh.db import connect
>>> sql = """
CREATE TABLE zugh.users (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `age` int(11) NOT NULL,
  `score` int(11) NOT NULL DEFAULT '0',
  PRIMARY KEY (`id`)
) Engine=InnoDB DEFAULT CHARSET=utf8mb4;
"""
>>> conn = connect(conn_config) # return a connection context
>>> with conn as cn:
        with cn.cursor() as cursor:
            cursor.execute(sql)

Initial a Table object:

>>> from zugh.schema.table import Table
>>> tb = Table('users', db)

Query Object

zugh.query.core.QueryBase provide a base class for Query class below:

  • zugh.query.core.SelectBase
  • zugh.query.core.Update
  • zugh.query.core.Insert
  • zugh.query.core.Delete
  • or subclass of above class

Query object is a instance of above class. If they were printed, a string of SQL statement would output.If configure properly, they can call .exe() method to execute. Usually, you don't use them directly.

Mostly, you would initial a zugh.schema.table.Table instance and call relative method, then will return a new Query object.

Dangerous queries, such as update, delete or similar mothed are expose after Table.where() method.

>>> q_1 = tb.where().select()
>>> type(q_1)
<class 'zugh.query.core.Select'>
>>> q_2 = tb.where().update(age=10)
>>> type(q_2)
<class 'zugh.query.core.Update'>
>>> q_3 = tb.where().delete()
>>> type(q_3)
<class 'zugh.query.core.Delete'>
>>> q_4 = tb.insert(dict(age=10, score=18))
>>> type(q_4)
<class 'zugh.query.core.Insert'>
>>> q_5 = q_1.order_by()
>> type(q_5)
<class 'zugh.query.core.OrderBy'>

Insert

Insert a Row

>>> q1 = tb.insert(age=16, score=7)
>>> print(q1)
INSERT INTO zugh.users (age, score) VALUES (16, 7)
>>> q2 = tb.where().select()
>>> print(q2)
SELECT * FROM zugh.users
>>> q2.exe() # execute q2
((), 0)
>>> q1.exe() # execute q1
1
>>> q2.exe() # execute q2 again
(((1, 16, 7),), 1)

Insert Ignore

>>> q3 = tb.insert_ignore(id=1, age=16, score=7)
>>> print(q3)
INSERT IGNORE INTO zugh.users (id, age, score) VALUES (1, 16, 7)
>>> q3.exe() # would show a duplicate key warning

Insert Or Update

You can use F object or values object to complete complex query.

from zugh.query.others import F, values
>>> row = dict(id=1, age=16, score=7)
>>> q4 = tb.upsert(row, dict(age=9))
>>> print(q4)
INSERT INTO zugh.users (id, age, score) VALUES (1, 16, 7) ON DUPLICATE KEY UPDATE age = 9
>>> update_fv = dict(age=F('age')-1, score=values('age')+1)
>>> q5 = tb.upsert(row, update_fv=update_fv)
>>> print(q5)
INSERT INTO zugh.users (id, age, score) VALUES (1, 16, 7) ON DUPLICATE KEY UPDATE age = age - 1, score = VALUES(age) + 1

Insert Multi Rows

>>> rows = [
    dict(age=9, score=8),
    dict(age=7, score=9),
    dict(age=17, score=7),
    dict(age=23, score=7),
  ]

>>> q6 = tb.insert_multi(rows)
>>> print(q6)
INSERT INTO zugh.users (age, score) VALUES (9, 8), (7, 9), (17, 7), (23, 7)
>>> q6.exe() # execute q6
4
>>> q2.exe()
(((1, 16, 7), (2, 9, 8), (3, 7, 9), (4, 17, 7), (5, 23, 7)), 5)

Select

>>> q7 = tb.where(id=3).select()
>>> print(q7)
SELECT * FROM zugh.users WHERE id = 3
>>> q7.exe()
(((3, 7, 9),), 1)
>>> q8 = tb.where().select('id', 'age')
>>> print(q8)
SELECT id, age FROM zugh.users
>>> q8.exe()
(((1, 16), (2, 9), (3, 7), (4, 17), (5, 23)), 5)

By default, when call .exe() of Select Query, it will return a tuple which contain queryset and number of rows. The format of queryset format is still tuple. If you prefer a dict-format queryset, you should pass a parameter cursorclass=pymysql.cursors.DictCursor to configure connection. For more infomation, please refer docs of PyMySQL.

Filter

the Table.where() method of Table instance act as a filter.

If don't need to filter table, You can call Table.select() directly. It is a shortup of Table.where().select().

Logic Express

>>> from zugh.query.logic import AND, OR, L
>>> q9 = tb.where('id>3', 'id<7').select()
>>> print(q9)
SELECT * FROM zugh.users WHERE id>3 AND id<7
>>> q9.exe()
(((4, 17, 7), (5, 23, 7)), 2)

>>> w1 = L('id<3')|L('id>7') # equal to OR('id<3', 'id>7')
>>> w2 = OR('id<3', 'id>7')
>>> w1
OR(L(id<3),L(id>7))
>>> w2
OR(L(id<3),L(id>7))
>>> print(w1)
id<3 OR id>7
>>> print(w2)
id<3 OR id>7

>>> q10 = tb.where(w2).select()
>>> print(q10)
SELECT * FROM zugh.users WHERE (id<3 OR id>7)
>>> q10.exe()
(((1, 16, 7), (2, 9, 8)), 2)

# you can combine complex Logic object use L, OR and AND

>>> w3 = L('id>3') & L('id<7') # equal to AND('id>3', 'id<7')
>>> print(w3)
id>3 AND id<7
>>> w4 = L('age>3') & L('age<20')
>>> print(w4)
age>3 AND age<20

>>> print(OR(w3, w4))
(id>3 AND id<7) OR (age>3 AND age<20)
>>> print(w3|w4)
(id>3 AND id<7) OR (age>3 AND age<20)

Compare

We use class or their instance to deal with compare express.You can find them in zugh.query.condition module.

SQL Operator Python Class/Instance/Operator example
= eq, = .where(name='lisa')
!= ne .where(name=ne('lisa'))
> gt .where(amount=gt(9))
>= ge .where(amount=ge(9))
< lt .where(amount=lt(6))
<= le .where(amount=le(5))
IN In .where(id=In(1,2,3,4))
NOT IN NIn .where(id=NIn(98,34,2))
LIKE like .where(name=like('lisa%'))
NOT LIKE unlike .where(name=unlike('john%'))
IS NULL NULL .where(age=NULL)
IS NOT NULL NOT_NULL .where(age=NOT_NULL)

Though works, eq is meaningless. For convenience, you would always use = .

>>> from zugh.query.condition import NOT_NULL, NULL, In, NIn, ge, gt, le, like, lt, ne, unlike
>>> q11 = tb.where(id=gt(3)).select()
>>> print(q11)
SELECT * FROM zugh.users WHERE id > 3

>>> q12 = tb.where(id=gt(3), age=lt(18)).select()
>>> print(q12)
SELECT * FROM zugh.users WHERE id > 3 AND age < 18
>>> q12.exe()
(((4, 17, 7),), 1)

>>> q13 = tb.where(id=In(1,3,5,7,9)).select('id', 'score')
>>> print(q13)
SELECT id, score FROM zugh.users WHERE id IN (1,3,5,7,9)
>>> q13.exe()
(((1, 7), (3, 9), (5, 7)), 3)

>>> q14 = tb.where(score=NULL).select()
>>> print(q14)
SELECT * FROM zugh.users WHERE score IS NULL

Alias

>>> from zugh.query.others import As
>>> from zugh.query.aggregate import Max
>>> qa = tb.where().select(max_age=Max('age'))
>>> print(qa)
SELECT max(age) AS max_age FROM zugh.users
>>> print(tb.where().select(As(Max('age'), 'max_age')))
SELECT max(age) AS max_age FROM zugh.users

We support alias, but the default cursorclass of PyMySQL will return query set in tuple. In this case, alias is useless. If you want to return dict, you need to configure connection parameter cursorclass=pymysql.cursors.DictCursor. For more information, please refer PyMySQL's documents.

Sort

>>> q15 = tb.where().select().order_by('age')
>>> print(q15)
SELECT * FROM zugh.users ORDER BY age
>>> q15.exe()
(((3, 7, 9), (2, 9, 8), (1, 16, 7), (4, 17, 7), (5, 23, 7)), 5)

# You can use prefix '-' to sort reverse.
>>> q16 = tb.where().select().order_by('-age', 'score')
>>> print(q16)
SELECT * FROM zugh.users ORDER BY age DESC, score
>>> q16.exe()
(((5, 23, 7), (4, 17, 7), (1, 16, 7), (2, 9, 8), (3, 7, 9)), 5)

Limit

We use a magical slice to act limit/offset, Select Query' slice will return a instance of zugh.query.core.Limit, which is a subclass of zugh.query.core.SelectBase.

>>> qm = tb.where().select()
>>> qm1 = qm[:3] # fetch frist three
>>> print(qm1)
SELECT * FROM zugh.users LIMIT 3
>>> qm2 = qm[2:4]
>>> print(qm2)
SELECT * FROM zugh.users LIMIT 2, 2
>>> qm3 = qm[2:]
>>> print(qm3)
SELECT * FROM zugh.users LIMIT 2, 18446744073709551614

Except for instances of Limit, all the others instance of SelectBase could use slice to return a instance of Limit.

The slice here don't accept negative numbers.

Aggregate

We provide some aggregation functions in zugh.query.aggregate moulde.

>>> from zugh.query.aggregate import Avg, Count, Max, Min, Sum
>>> q17 = tb.where().select(Avg('age'))
>>> print(q17)
SELECT avg(age) FROM zugh.users
>>> q17.exe()
(((Decimal('14.4000'),),), 1)

>>> q18 = tb.where().select('score', Count('id')).group_by('score')
>>> print(q18)
SELECT score, count(id) FROM zugh.users GROUP BY score
>>> q18.exe()
(((7, 3), (8, 1), (9, 1)), 3)

You can also use write 'raw' functions as long as you like it, such as:

q17 = tb.where().select('avg(age)')

Distinct

from zugh.query.others import distinct
>>> q19 = tb.where().select('distinct age', 'score')
>>> print(q15)
SELECT distinct age, score FROM zugh.users
>>> q19.exe()
(((16, 7), (9, 8), (7, 9), (17, 7), (23, 7)), 5)

>>> q20 = tb.where().select(distinct('age'), 'score')
>>> print(q20)
SELECT DISTINCT age, score FROM zugh.users

>>> q21 = tb.where().select(Count(distinct('age')))
>>> print(q21)
SELECT count(DISTINCT age) FROM zugh.users

Subquery

At present, In and NIn express support subquery, it could accept a instance of SelectBase as a parameter.But they can not accept instance of zugh.schema.table.TempTable as a parameter.

TempTable accept a Select Query as frist parameter and a alias string as second parameter. It would act like a normal read-only table, you could join it with others, or query data as a new instance TempTable.

>>> from zugh.schema.table import TempTable
>>> q22 = tb.where().select(Max('age'))
>>> print(q22)
SELECT max(age) FROM zugh.users

>>> q23 = tb.where(age=In(q22)).select()
>>> print(q23)
SELECT * FROM zugh.users WHERE age IN (SELECT max(age) FROM zugh.users)
>>> q23.exe()
(((5, 23, 7),), 1)

>>> q_t = tb.where(id=gt(2)).select()
>>> tb_t1 = q_t.as_table('ak') # equal to tb_t1 = TempTable(q_t, 'ak')
>>> tb_t1
TempTable(SELECT * FROM zugh.users WHERE id > 2)
>>>
>>> sql2  = """
CREATE TABLE zugh.account (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `user_id` int(11) NOT NULL,
  `amount` decimal(11,2) NOT NULL DEFAULT '0',
  PRIMARY KEY (`id`)
) Engine=InnoDB DEFAULT CHARSET=utf8mb4;
"""
>>> with conn as cn:
        with cn.cursor() as cursor:
            cursor.execute(sql2)
>>> tb2 = Table('account', db, alias='a') # If tend to join table, alias is necessary
>>> rows2 = (
  dict(user_id=1, amount='99.89'),
  dict(user_id=2, amount='292.2'),
  dict(user_id=3, amount='299.89'),
  dict(user_id=4, amount='192.1'),
  dict(user_id=5, amount='183.7'),
)
>>> tb2.insert_multi(rows2).exe()
>>>
>>> tb_t2 = tb_t1.inner_join(tb2, on='a.user_id = ak.id')
>>> q_t2 = tb_t2.select()
>>> print(q_t2)
SELECT * FROM (SELECT * FROM zugh.users WHERE id > 2) AS ak INNER JOIN zugh.account AS a ON a.user_id = ak.id
>>> q_t2.exe()
(((3, 7, 8, 3, 3, Decimal('299.89')), (4, 17, 8, 4, 4, Decimal('192.10'))), 2)

Join In

Let's add a new table and query from the join table:

>>> tb3 = Table('users', db, alias='b') # If tend to join table, alias is necessary
>>> tb_i = tb2.inner_join(tb3, on='a.user_id=b.id')
>>> q_i = tb_i.where(a__id=gt(2)).select('a.id', 'a.user_id', 'a.amount', 'b.score', 'b.age')
>>> print(q_i)
SELECT a.id, a.user_id, a.amount, b.score, b.age FROM zugh.account AS a INNER JOIN zugh.users AS b ON a.user_id=b.id WHERE a.id > 2
>>> q_i.exe()
(((3, 3, Decimal('299.89'), 8, 7), (4, 4, Decimal('192.10'), 8, 17)), 2)

If two underscores are used in the keyword of where method, the two underscores will be replaced by solid point. For example, a__id will be replaced with a.id. This idea was copied from the Django project.

We provide Table.inner_join(), Table.left_join() and Table.right_join() methods to support Table join.

Union

You can call union or union_all method from Select object. For example:

>>> from zugh.query.condition import gt, lt
>>> q_u1 = tb.where(id=lt(5)).select()
>>> q_u2 = tb.where(age=gt(20)).select()
>>> q_u = q_u1.union_all(q_u2)
>>> print(q_u)
SELECT * FROM zugh.users WHERE id < 5 UNION ALL SELECT * FROM zugh.users WHERE age > 20

Update

>>> tb.where(id=1).select().exe()
(((1, 16, 7),), 1)
>>> q24 = tb.where(id=1).update(age=28)
>>> print(q24)
UPDATE zugh.users SET age = 28 WHERE id = 1
>>> q24.exe()
1
>>> tb.where(id=1).select().exe()
(((1, 28, 7),), 1)

F Object

F object means that it is a field, not a string. It could be used in Table.where() or Where.update(). F class is a subclass of ArithmeticBase. So F objects can perform mathematical operations, and it will return a new ArithmeticBase instance.

See the following examples:

>>> from zugh.query.others import F
>>> tb.where(id=1).select().exe()
(((1, 28, 7),), 1)

>>> q25 = tb.where(id=1).update(age=F('age') - 2, score=F('score') + 6)
>>> print(q25)
UPDATE zugh.users SET age = age - 2, score = score + 6 WHERE id = 1
>>> q25.exe()
1
>>> tb.where(id=1).select().exe()
(((1, 26, 13),), 1)

# F object also use in filter
>>> q26 = tb.where(score=gt(F('age')*2)).select()
>>> print(q26)
SELECT * FROM zugh.users WHERE score > age * 2
>>> q26.exe()
((), 0)

Delete

>>> tb.where(id=5).select().exe()
(((5, 23, 7),), 1)
>>> q23 = tb.where(id=5).delete()
>>> print(q23)
DELETE FROM zugh.users WHERE id = 5
>>> q23.exe()
1
>>> tb.where(id=5).select().exe()
((), 0)

Decorator

db.query.query

query decorator wraps a function which return a Query object. When call the wrapped function, it would execute a Query object. For example:

>>> from zugh.query.aggregate import Max
>>> from zugh.db.query import query

>>> @query()
    def query_max_score():
      q1 = tb.where().select(Max('score'))
      q2 = tb.where(score=In(q1)).select()
      return q2

>>> query_max_score()
(((1, 26, 13),), 1)

query accept 2 parameters: conn_config and conn_pool. If the Query object returned don't configure connection, you can pass a conn_config dict or a connection pool to it.

db.query.transaction

transaction decorator wrap a function which return a list of Query ojbect. When call the wrapped function, it would execute the list of Query object as a transaction. If transaction succeed, return True, otherwise return False.

For example:

from zugh.db.query import transaction
from zugh.query.others import F

@transaction(conn_pool=pool)
def mv_score():
    q1 = tb.where(id=3).update(score=F('score') - 1)
    q2 = tb.where(id=4).update(score=F('score') + 1)
    return (q1, q2)

>>> mv_score()
True

String

Some string function awailable in zugh.query.string module.

concat 2 field:

from zugh.query.string import Concat, S, Substring
>>> q24 = tb.where().select(Concat('age', 'score'))
>>> print(q24)
SELECT concat(age, score) FROM zugh.users

S Object

In string functions, str meaning field name instead of string. You should use S object to represent string.

from zugh.query.string import Concat, S, Substring
>>> q25 = tb.where().select(Concat(S('PRI-'), 'age'))
>>> print(q25)
SELECT concat('PRI-', age) FROM zugh.users
>>> q25.exe()
((('PRI-26',), ('PRI-9',), ('PRI-7',), ('PRI-17',)), 4)

>>> print(tb.where().select(Substring('age', 2)))
SELECT substring(age, 2) FROM zugh.users

Math

Some math functions are awailable in zugh.query.math module.

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