new_relexpr: Relational expressions

In duckdblabs/duckplyr: A 'DuckDB'-Backed Version of 'dplyr'

Relational expressions

Description

These functions provide a backend-agnostic way to construct expression trees built of column references, constants, and functions. All subexpressions in an expression tree can have an alias.

new_relexpr() constructs an object of class "relational_relexpr". It is used by the higher-level constructors, users should rarely need to call it directly.

relexpr_reference() constructs a reference to a column.

relexpr_constant() wraps a constant value.

relexpr_function() applies a function. The arguments to this function are a list of other expression objects.

relexpr_window() applies a function over a window, similarly to the SQL OVER clause.

relexpr_set_alias() assigns an alias to an expression.

Usage

new_relexpr(x, class = NULL)

relexpr_reference(name, rel = NULL, alias = NULL)

relexpr_constant(val, alias = NULL)

relexpr_function(name, args, alias = NULL)

relexpr_window(
  expr,
  partitions,
  order_bys = list(),
  offset_expr = NULL,
  default_expr = NULL,
  alias = NULL
)

relexpr_set_alias(expr, alias = NULL)

Arguments

x	An object.
class	Classes added in front of the "relational_relexpr" base class.
name	The name of the column or function to reference.
rel	The name of the relation to reference.
alias	An alias for the new expression.
val	The value to use in the constant expression.
args	Function arguments, a list of expr objects.
expr	An expr object.
partitions	Partitions, a list of expr objects.
order_bys	which variables to order results by (list).
offset_expr	offset relational expression.
default_expr	default relational expression.

Value

an object of class "relational_relexpr"

an object of class "relational_relexpr"

an object of class "relational_relexpr"

an object of class "relational_relexpr"

an object of class "relational_relexpr"

Examples

relexpr_set_alias(
  alias = "my_predicate",
  relexpr_function(
    "<",
    list(
      relexpr_reference("my_number"),
      relexpr_constant(42)
    )
  )
)

duckdblabs/duckplyr documentation built on Nov. 6, 2024, 10 p.m.