query

Overview ¶

Package query provides the means the filter a collection of arbitrary data structures according to user provided query.

Here's an example for a query over docker containers:

matcher, err := query.Parse("!running & (exit!=0 | name~junk", ...)
if matcher.Match(container) {
  :
  :
}

The queries supported by this library are parsed from a string represetnation according to the following rules:

Boolean fields ¶

The simplest form a query is a simple boolean field:

running

String fields ¶

Fields of type string are supported and can be used with the following operators:

• "=" : Exact equality name=library/container

• "!=" : Not equal to: name!=value

• "~" : Like, i.e. the field value must contain the provided value: name~value

• "!~" : Not like: name!~value

String slice fields ¶

bateau/query also supports multi-valued fields. The same operators as for string fields (=, !=, ~, !~) are available for multi-valued fields.

• "=" : Matches if any value of the slice is exactly equal to the provided value cmd=/bin/sh

• "!=" : Fails if any value of the slice is exactly equal to the provided value cmd!=/bin/sh

• "~" : Matches if any value of the slice contains the provided value cmd~sh

• "!~" : Fails if any value of the slice contains the provided value cmd!~sh

Negation ¶

A condition can be negated using the "!" operator, e.g.:

!running

or

!name=server

And ¶

Two or more conditions can be combined using the boolean and operator "&"

running & name=server

or

running & image=mongo & cmd~sh

Or ¶

Two or more conditions can be combined using the boolean or operator "|"

running | name=server

or

running | image=mongo | cmd~sh

Parenthesis ¶

To control the evaluation precedence, conditions can be wrapped between "(" and ")":

running & !(name=server | image~mongo)

Grammar ¶

The query langauge is described below using the EBNF notation:

expr     -> or
or       -> and ('|' and)*
and      -> atom ('&' atom)*
atom     -> cond | '(' expr ')' | '!' atom
cond     -> LITERAL (OPERATOR LITERAL)?
LITERAL  -> "[^|&!=~]+"
OPERATOR -> '=' | '!=' | '~' | '!~' | '<' | '<=' | '>' | '>='