queryBuilder (version 0.1.0)

query-rules: Define filtering query

Description

Query is configuration consisting of rules and group. Rule defines a single filtering expression whereas group is combining multiple rules (or nested groups) with the provided condition.

Usage

queryGroup(..., condition = "AND")
queryRule(field, operator, value = NULL, ...)

Value

Nested lists structure.

Arguments

...

Rules defined with queryRule function.

condition

Group condition. By default 'AND' and 'OR' are available. To set custom one use setQueryConditions.

field

Field of the filter applied to the rule. To set custom one use setQueryOperators.

operator

Name of the operator to be applied to the rule.

value

(optional) Values that should be applied to the rule. Some operators, such as 'is_null', don't require any value provided.

Details

Having the example expression `a == 1 | (vs == 0 & qsec > 10)` we can distinct the following rules and groups:

Rules: - `am == 1` - related to `am` field, applies `==` operator with `1` value, - `vs == 0` - related to `vs` field, applies `==` operator with `1` value, - `qsec > 10` - related to `qsec` field, applies `>` operator with `10` value.

Groups: - `(vs == 0 & qsec > 10)` - combines two rules (`vs == 0` and `qsec > 10`) with `&` condition, - `a == 1 | (vs == 0 & qsec > 10)` - combines rule `a == 1` and group `(vs == 0 & qsec > 10)` with `|` condition.

Such query can be defined by 'queryBuilder' the following way:

queryGroup( condition = "OR", queryRule("am", "equal", 1) queryGroup( condition = "AND", queryRule("vs", "equal", 0), queryRule("qsec", "greater", 10) ) )

Connection between conditions and operators names and their R-based counterparts are defined with queryBuilderConfig class.

The defined query can be then converted to filtering expression with queryToExpr function.

Examples

queryGroup(
  condition = "OR",
  queryRule("am", "equal", 1),
  queryGroup(
    condition = "AND",
    queryRule("vs", "equal", 0),
    queryRule("qsec", "greater", 10)
  )
)