Comment on page
Post-Filters
Filters applied on a query result AFTER grouping, sorting and slicing.
Once a query returns some results, a post-filter can be applied on them to further restrict the number of matching results that are returned.
Post-filter expressions are processed in the V8 engine and NOT the query engine, using a jsep expression parser that has been augmented with a few extensions.
The filter expression is applied individually to each item in the result array (these items may be entire groups). Only those items for which the expression evaluates to a truthy value are passed through.
Important: jsep does not support object literals, only array literals. This may be fixed in a fork, maintained by RecallGraph, in the future.
Most of the following (non-mutating) standard operators are understood by jsep out of the box. A few are implemented using extensions. Regardless, they are all processed exactly as they would be processed in a normal JavaScript runtime
- Property accessors (including method calls)
- Implicit (using implicit
thiscontext per item in a result array; method calls on thethisobject not accessible with this style)
- Literals
Some of the core JS operators listed above are actually implemented using extensions in jsep. Additionally, some useful operators that are not part of JS syntax are also supported for convenience.
- 1.
=~- Regex Match. Filters on a regex pattern. The left operand must match the regex pattern given in the right operand for the filter to pass. - 2.
=*- Glob Match. Filters on a glob pattern. The left operand must match the glob pattern given in the right operand for the filter to pass.
Apart from the regular operators and member functions that the built-in data types support, it is often handy to be able to invoke
Math functions or methods from the lodash utility. jsep has been extended to provide access to these functions and some more, using named object literals that represent these modules. The available namespaces are listed below, along with special shortcuts, if any, to access them.All methods and properties of the
Math global object are available under this namespace. An example usage may be:$Math.sin(this['x']) < $Math.cos($Math.PI) * this.y + z
//this['x']: Bracket notation for accessing property 'x' of 'this'.
//this.y: Dot notation for accessing property 'y' of 'this'.
//z: Implicit notation for accessing property 'z' of 'this'.
All methods and properties of the
lodash utility module are available under this namespace. In addition to being referred to by the $_ namespace handle, this is also the default namespace under which methods are searched when they are invoked as standalone functions, without a property dereference. For example:$_.difference(this.x, y).length < 2
some(x, partialRight($_.lte, 2))
//partialRight is used in place of an anonymous function
// defintion, since such function defs are not supported by
// jsep.
Note that the default namespace is searched only when a function call is made, and not when just referencing the function as a member. In that case, the member will be searched for under the
this context of the current object under iteration of the result array.This namespace is reserved for some special functions defined by RecallGraph. The supported methods are:
typeof(<operand>)
glob(str, pattern)
regex(str, pattern)
This method returns the type of the parameter passed to it. Its behavior is identical to the JavaScript
typeof operator. For example:$RG.typeof(x)
$RG.typeof(this.y)
$RG.typeof(this[z])
//this[z] (without quotes) is shorthand for this[this.z],
// i.e. an indirect property reference.
$RG.glob('aaabbbccc', '*b*')
//jsep supports string literals.
$RG.regex('aaabbbccc', 'a+b{3}c*')
//jsep supports string literals.
Last modified 3yr ago