Clone a LazyFrame

Description

This makes a very cheap deep copy/clone of an existing LazyFrame. Rarely useful as LazyFrames are nearly 100% immutable. Any modification of a LazyFrame should lead to a clone anyways, but this can be useful when dealing with attributes (see examples).

Usage

<LazyFrame>$clone()

Value

A polars LazyFrame

Examples

library("polars")

df1 <- as_polars_lf(iris)

# Make a function to take a LazyFrame, add an attribute, and return a LazyFrame
give_attr <- function(data) {
  attr(data, "created_on") <- "2024-01-29"
  data
}
df2 <- give_attr(df1)

# Problem: the original LazyFrame also gets the attribute while it shouldn't!
attributes(df1)

#> $class
#> [1] "polars_lazy_frame" "polars_object"    
#> 
#> $created_on
#> [1] "2024-01-29"

# Use $clone() inside the function to avoid that
give_attr <- function(data) {
  data <- data$clone()
  attr(data, "created_on") <- "2024-01-29"
  data
}
df1 <- as_polars_lf(iris)
df2 <- give_attr(df1)

# now, the original LazyFrame doesn't get this attribute
attributes(df1)

#> $class
#> [1] "polars_lazy_frame" "polars_object"