ConfDB Query Language¶
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ConfDB offers flexible query language based on predicate logic. ConfDB queries may be used for config processing, including fetching, classification and validation.
Common Concepts¶
Contexts¶
Query context is the couple of variables and their values. It is a simple key-value structure implemented over python’s dict. Context represents a possible state of pipeline. Contexts are grouped together representing possibilities on each stage of pipeline. Within the possibilities, each context is independent on each other.
Variables can be either bound (known values) or unbound (superposition of possible values).
Predicates¶
Predicate is the logic function, defined by its arguments and accepting possibilities on input, evaluating them and passing outcomes as output. Predicates evaluate input context independently. Each input context may be evaluated to one or more output context.
Pipelining¶
Predicates may be combined together into sequential (and) and parallel (or) chains. Chains can be grouped together by bracket operator. Resulting chains build pipeline which is valid predicate too.
Query¶
Query is the pipeline, which can be applied to exact ConfDB state and input context to produce output contexts with possible outcomes
Syntax¶
Query is the Python expression
Variable¶
Variable is coded as plain python variables
Predicate¶
Predicate is coded as python function call
Match('interface', X, 'description', Y)
See Built-in predicates for possible predicates and examples
Sequential chain¶
Sequential chain is the combination of two predicates when output of first predicate serves as input to the second one
Sequential chain is coded by boolean and operator
P1() and P2()
Sequential chain can contain more than two operators like
P1() and P2() and P3() and P4()
Parallel chain¶
Parallel chain consists of two or more predicates independently accepting same input and combining and deduplicating resulting outputs
Parallel chains are coded by or operator
P1() or P2()
Built-in predicates¶
Simple Logic¶
-
True
()¶ Always True, pass context unmodified
-
False
()¶ Always False, breaks predicate chain
Context Manipulation¶
-
Set
(**kwargs)¶ Add or modify variables of context. If variable value is a list, expand the list and apply production
Set(X=2)
Set(X=[1, 2, 3])
-
Del
(*args)¶ Delete variables from context. Deduplicate contexts when necessary
Del(X)
ConfDB Matching¶
-
Match
(*args)¶ Match *args against ConfDB. Bind unbound variables on match
- Parameters
*args –
ConfDB path
Match('interface', X, 'description', Y)
-
NotMatch
(self, _input, *args)¶ Pass only if *args is not matched against ConfDB. Bind unbound variables when possible
- Parameters
*args –
ConfDB path
NotMatch('interface', X, 'description')
ConfDB Manipulation¶
-
Fact
(*args)¶ Set Fact to database
- Parameters
*args –
ConfDB path of fact, eigther constants or bound variables
Fact('interface', X, 'hints', 'test')
Filtering and Checking¶
-
Filter
(expr)¶ Pass context only if expr is evaluated as True
- Parameters
expr – Python expression
Filter(X % 2 == 0)
-
Re(pattern, name, ignore_case=None):
Match variable name against regular expression pattern. Pass context further if matched. If regular expression contains named groups, i.e. (?P<group_name>….), apply them as context variables
- Parameters
pattern – Regular expression pattern
name – Variable name
ignore_case – Ignore case during match
Re("a+", X)
Re("a+", X, ignore_case=True)
Re("-(?P<abs>\d+)", X)
-
HasVLAN(vlan_filter, vlan_id):
Check vlan_id is within vlan_filter expression
- Parameters
vlan_filter – VC Filter expression
vlan_id – Vlan Id or bound variable
HasVlan("1-99,200-299", X)
Aggregation¶
-
Group(stack=None, *args, **kwargs):
Group input context on given variables
(
Match("interfaces", name)
or Match("interfaces", name, "type", type)
or Match("interfaces", name, "description", description)
or Match("interfaces", name, "admin-status", admin_status)
) and Group("name")
-
Collapse(*args, **kwargs):
Collapse multiple keys to a single one following rules
- Parameters
kwargs – One of collapse operation should be specified * join=<sep> – join lines with separator sep * joinrange=<sep> – join lines with separator sep and apply range optimization
Collapse("interfaces", X, "tagged-vlans", join=",")
Collapse("interfaces", X, "tagged-vlans", joinrange=",")
Debugging¶
-
Dump(message=None):
-
Dump current context to stdout and pass unmodified
- Parameters
message – Optional message
Dump()
Dump("Point1")
-
Sprintf(name, fmt, *args):
Perform string formatting and apply result to context variable
- Parameters
name – Target variable name
fmt – String format
args – Values or bound variables
Sprintf(y, 'x = %s, y = %s', x, '2')