link.dbrequest package

Submodules

link.dbrequest.manager module

class link.dbrequest.manager.QueryManager(user=None, pwd=None, hosts=None, path=None, fragment='', **kwargs)

Bases: link.middleware.core.Middleware

Manage storage backend and provide query system for it.

Parameters:backend (Driver) – Storage backend

all()

Get a query selecting all elements in store.

Return type:Query

create(*fields)

Put a new element into the store.

Parameters:fields (list of A) – List of assignments Returns:Created element Return type:Model

execute(ast, scope=None)

Send query to the storage driver.

Parameters:

• ast (dict or list) – AST describing the query
• scope (list of str or Query) – Query’s scope

Returns:

storage driver’s response

from_ast(ast)

Create a query from the provided AST.

Parameters:ast (list) – AST Return type:Query Raises:ASTError – if provided AST is not valid.

get(condition)

Get a single element matching the filter.

Parameters:condition (C or CombinedCondition) – Filter Returns:Matching element or None Return type:Model or None

prepare(f, *queries)

Get a lazy procedure.

Parameters:

• f (F) – Function to call
• queries (list of Query or str) – Function’s scope

Returns:

New lazy procedure

Return type:

Procedure

run(f, *queries)

Execute a procedure.

Parameters:

• f (F) – Function to call
• queries (list of Query or str) – Function’s scope

Returns:

Procedure’s result

Return type:

any

subset(scope)

Get a query selecting all scoped elements in store.

Parameters:scope (str, Query or list) – Query’s scope Return type:Query

static validate_ast(ast)

Validate AST semantics.

Raises:ASTError – if the AST semantics are not valid

link.dbrequest.driver module

class link.dbrequest.driver.Driver(obj, *args, **kwargs)

Bases: link.feature.core.Feature

Abstract storage driver feature.

QUERY_COUNT = 'count'

QUERY_CREATE = 'save'

QUERY_DELETE = 'delete'

QUERY_READ = 'find'

QUERY_RUN = 'run'

QUERY_UPDATE = 'update'

count_elements(ast)

Count number of elements matching the query described by the AST.

Parameters:ast (list or AST) – AST describing the query Returns:number of elements matching the query Return type:int

cursor_class

alias of Cursor

find_elements(ast)

Find elements matching the query described by the AST.

Parameters:ast (list or AST) – AST describing the query Returns:Cursor on matching elements Return type:Cursor

model_class

alias of Model

name = 'query'

process_query(query)

This method must be overriden, handles every query made to the storage.

Parameters:query (AST) – query to process Returns:driver’s response.

put_element(ast)

Put element into the store.

Parameters:ast (list) – AST describing the element to insert Returns:Inserted element Return type:Model

remove_elements(ast)

Delete elements matching the query described by the AST.

Parameters:ast (list or AST) – AST describing the query Returns:Number of elements deleted Return type:int

run_procedure(ast)

Run procedure on middleware.

Parameters:ast (AST) – AST describing the query Returns:Procedure’s result Return type:any

update_elements(filter_ast, update_ast)

Update elements matching the query described by the AST.

Parameters:

• filter_ast (list) – AST describing the query
• update_ast (list) – AST describing the update

Returns:

Number of elements modified

Return type:

int

link.dbrequest.model module

class link.dbrequest.model.Cursor(driver, cursor, *args, **kwargs)

Bases: six.Iterator

Cursor encapsulating storage driver’s cursor or result.

Parameters:

• driver (Driver) – storage driver
• cursor – storage’s cursor

cursor

driver

to_model(doc)

Convert raw element to Model.

Parameters:doc (dict) – raw element Returns:Element as Model Return type:Model

class link.dbrequest.model.Model(driver, data, *args, **kwargs)

Bases: object

Model class encapsulating elements in store.

Parameters:

• driver (Driver) – storage driver
• data (dict) – encapsulated data

data

delete()

Delete element from store.

driver

save()

Save element into store.

Returns:Inserted document Return type:Model

link.dbrequest.lazy module

class link.dbrequest.lazy.Dataset(manager, scope=None, *args, **kwargs)

Bases: link.dbrequest.lazy.Lazy

Lazy dataset, hold scoped set of data.

class link.dbrequest.lazy.Lazy(manager, scope=None, *args, **kwargs)

Bases: object

Object holding data that will be fetched by the manager when needed.

Parameters:

• manager (QueryManager) – Manager that will execute this query
• scope (str, Query or list) – Object’s scope (default: None)

execute()

Execute object

Returns:Data held by object Return type:any

class link.dbrequest.lazy.Procedure(f, *args, **kwargs)

Bases: link.dbrequest.lazy.Dataset

copy()

execute()

to_ast()

class link.dbrequest.lazy.Query(*args, **kwargs)

Bases: link.dbrequest.lazy.Dataset

Database agnostic query.

Parameters:manager (QueryManager) – Manager that will execute this query

copy()

Create a copy of this query.

Returns:Copy Return type:Query

count()

Count elements matched by this query.

Returns:Number of matching elements Return type:int

delete()

Delete elements matching the query.

Returns:Number of deleted elements. Return type:int

exclude(condition)

Returns a new query with a new (negated) filter added.

Parameters:condition (C or CombinedCondition) – Filter Returns:Query Return type:Query

execute()

filter(condition)

Returns a new query with a new filter added.

Parameters:condition (C or CombinedCondition) – Filter Returns:Query Return type:Query

get(condition)

Add filter to the query, and get a single element matching the query.

Parameters:condition (C or CombinedCondition) – Filter Returns:Matching element or None Return type:Model or None

group(key, *expressions)

Group elements by key matching the query using the expressions.

Parameters:

• key (str) – Key used to group elements
• expressions (list of CombinableExpression) – Expressions

Returns:

Grouped elements.

to_ast()

Returns a copy of query’s AST

Returns:AST Return type:list

update(*fields)

Update elements matching the query.

Parameters:fields (list of A) – Assignments Returns:Number of modified elements. Return type:int

link.dbrequest.ast module

class link.dbrequest.ast.AST(name, val, *args, **kwargs)

Bases: dict

Helper for create AST nodes.

Parameters:

• name (str) – AST node name
• val – AST node value

name

val

exception link.dbrequest.ast.ASTError

Bases: exceptions.Exception

Basic AST semantic error.

exception link.dbrequest.ast.ASTInvalidFormatError

Bases: link.dbrequest.ast.ASTError

Error raised when supplied AST is not a valid expected type.

exception link.dbrequest.ast.ASTInvalidStatementError(stmt)

Bases: link.dbrequest.ast.ASTError

Error raised when trying to execute an unknown statement.

exception link.dbrequest.ast.ASTLastStatementError(stmt, pos)

Bases: link.dbrequest.ast.ASTError

Error raised when trying to execute a statement that must be in the end of the sequence.

exception link.dbrequest.ast.ASTSingleStatementError(stmt)

Bases: link.dbrequest.ast.ASTError

Error raised when trying to execute statements that must be in a sequence.

class link.dbrequest.ast.ModelBuilder(*args, **kwargs)

Bases: object

Class used to link nodes in AST together.

parse(node, parent=None)

Parse AST to resolve link between nodes.

Parameters:

• node (AST or list or value) – node to parse
• parent (AST or None) – parent node (default: None)

Returns:

Node

Return type:

same as param node

class link.dbrequest.ast.NodeWalker

Bases: object

Walk through AST.

find_walker(node)

Find method used to walk through specific node.

Parameters:node (AST) – node to walk through Returns:Method used to walk through the node Return type:callable or None

walk(node, *args, **kwargs)

Walk through AST (depth first).

Parameters:

• node (any) – Root node to start walking through
• args (iterable) – Positional arguments for walker method
• kwargs (dict) – Keyword arguments for walker method

Returns:

Walker method’s result

link.dbrequest.tree module

class link.dbrequest.tree.Node(name, *args, **kwargs)

Bases: object

Base class for AST nodes.

Parameters:name – Node’s value.

get_ast()

Returns simplified AST.

Returns:AST node as dict Return type:dict

class link.dbrequest.tree.Value(name, *args, **kwargs)

Bases: link.dbrequest.tree.Node

Node representing a value.

get_ast()

link.dbrequest.comparison module

class link.dbrequest.comparison.C(name, *args, **kwargs)

Bases: link.dbrequest.tree.Node, link.dbrequest.comparison.Comparable, link.dbrequest.comparison.CombinableCondition

Condition on a property.

get_ast()

class link.dbrequest.comparison.CombinableCondition

Bases: object

Combine conditions with boolean operators.

AND = 'and'

OR = 'or'

XOR = 'xor'

class link.dbrequest.comparison.CombinedCondition(left, operator, right, inverted=False, *args, **kwargs)

Bases: link.dbrequest.tree.Node, link.dbrequest.comparison.CombinableCondition

Combination of two conditions.

Parameters:

• left (CombinableCondition) – left condition
• operator (str) – combination condition
• right (CombinableCondition) – right condition
• inverted (bool) – Equivalent of not (<condition>) (default: False)

get_ast()

class link.dbrequest.comparison.Comparable(*args, **kwargs)

Bases: object

Base class for conditions, overriding logical operators. Check if property exists by default.

EQ = 'eq'

EXISTS = 'exists'

GT = 'gt'

GTE = 'gte'

LIKE = 'like'

LT = 'lt'

LTE = 'lte'

NE = 'ne'

link.dbrequest.assignment module

class link.dbrequest.assignment.A(propname, val=None, unset=False, *args, **kwargs)

Bases: link.dbrequest.tree.Node

Node representing an assignment.

Parameters:

• propname (str) – Name of assigned property
• val (Node, or Python type) – Value to assign to property (ignored if unset is True)
• unset (bool) – Unset the property (default: False)

get_ast()

link.dbrequest.expression module

class link.dbrequest.expression.CombinableExpression

Bases: object

Base class for expressions, overriding mathematical expressions.

ADD = 'add'

BITAND = 'and'

BITLSHIFT = 'lshift'

BITOR = 'or'

BITRSHIFT = 'rshift'

BITXOR = 'xor'

DIV = 'div'

MOD = 'mod'

MUL = 'mul'

POW = 'pow'

SUB = 'sub'

class link.dbrequest.expression.CombinedExpression(left, operator, right, *args, **kwargs)

Bases: link.dbrequest.tree.Node, link.dbrequest.expression.CombinableExpression

Combination of two expressions.

Parameters:

• left (CombinableExpression) – left expression
• operator (str) – combination expression
• right (CombinableExpression) – right expression

get_ast()

class link.dbrequest.expression.E(name, *args, **kwargs)

Bases: link.dbrequest.tree.Node, link.dbrequest.expression.CombinableExpression

Expression referencing a property, usable in mathematical expressions to represent a formula applied on the referenced property.

get_ast()

class link.dbrequest.expression.F(funcname, *arguments)

Bases: link.dbrequest.expression.E

Function, representing a mathematical function.

Parameters:

• funcname (str) – Mathematical function
• arguments (list) – List of expressions/values to use as function arguments

get_ast()

Module contents