{polarssql} is an experimental DBI-compliant interface to
Polars.
Polars is not an actual database, so does not support full {DBI}
functionality. Please check the Polars User
Guide for
supported SQL features.
The polars R package and {polarssql}
can be installed from R-universe:
Sys.setenv(NOT_CRAN = "true") # for installing the polars package with pre-built binary
install.packages("polarssql", repos = c("https://rpolars.r-universe.dev", getOption("repos")))library(DBI)
con <- dbConnect(polarssql::polarssql())
dbWriteTable(con, "mtcars", mtcars)
# We can fetch all results:
res <- dbSendQuery(con, "SELECT * FROM mtcars WHERE cyl = 4")
dbFetch(res)
#> mpg cyl disp hp drat wt qsec vs am gear carb
#> 1 22.8 4 108.0 93 3.85 2.320 18.61 1 1 4 1
#> 2 24.4 4 146.7 62 3.69 3.190 20.00 1 0 4 2
#> 3 22.8 4 140.8 95 3.92 3.150 22.90 1 0 4 2
#> 4 32.4 4 78.7 66 4.08 2.200 19.47 1 1 4 1
#> 5 30.4 4 75.7 52 4.93 1.615 18.52 1 1 4 2
#> 6 33.9 4 71.1 65 4.22 1.835 19.90 1 1 4 1
#> 7 21.5 4 120.1 97 3.70 2.465 20.01 1 0 3 1
#> 8 27.3 4 79.0 66 4.08 1.935 18.90 1 1 4 1
#> 9 26.0 4 120.3 91 4.43 2.140 16.70 0 1 5 2
#> 10 30.4 4 95.1 113 3.77 1.513 16.90 1 1 5 2
#> 11 21.4 4 121.0 109 4.11 2.780 18.60 1 1 4 2
# Clear the result
dbClearResult(res)
# Or a chunk at a time
res <- dbSendQuery(con, "SELECT * FROM mtcars WHERE cyl = 4")
while (!dbHasCompleted(res)) {
chunk <- dbFetch(res, n = 5)
print(nrow(chunk))
}
#> [1] 5
#> [1] 5
#> [1] 1
# Clear the result
dbClearResult(res)
# We can use table functions to read files directly:
tf <- tempfile(fileext = ".parquet")
on.exit(unlink(tf))
polars::as_polars_lf(mtcars)$sink_parquet(tf)
dbGetQuery(con, paste0("SELECT * FROM read_parquet('", tf, "') ORDER BY mpg DESC LIMIT 3"))
#> mpg cyl disp hp drat wt qsec vs am gear carb
#> 1 33.9 4 71.1 65 4.22 1.835 19.90 1 1 4 1
#> 2 32.4 4 78.7 66 4.08 2.200 19.47 1 1 4 1
#> 3 30.4 4 95.1 113 3.77 1.513 16.90 1 1 5 2{polarssql} also provides functions that are simpler to use, inspired
by the {duckdb} package,
library(polarssql)
# These functions use the built-in connection by default, so we don't need to specify connection
# Resgister a data.frame to the built-in connection
polarssql_register(df = mtcars)
# Get the query result as a polars LazyFrame
polarssql_query("SELECT * FROM df WHERE cyl = 4")
#> polars LazyFrame
#> $describe_optimized_plan() : Show the optimized query plan.
#>
#> Naive plan:
#> SELECT [col("mpg"), col("cyl"), col("disp"), col("hp"), col("drat"), col("wt"), col("qsec"), col("vs"), col("am"), col("gear"), col("carb")] FROM
#> FILTER [(col("cyl")) == (4)] FROM
#>
#> DF ["mpg", "cyl", "disp", "hp"]; PROJECT */11 COLUMNS; SELECTION: "None"
# Unregister the table
polarssql_unregister("df")And, basic supports for {dbplyr} is also implemented.
library(dplyr, warn.conflicts = FALSE)
# Resgister a data.frame to the built-in connection, and query it via dbplyr
tbl_polarssql(mtcars) |>
filter(cyl == 4) |>
arrange(desc(mpg)) |>
head(3) |>
compute()
#> shape: (3, 11)
#> ┌──────┬─────┬──────┬───────┬───┬─────┬─────┬──────┬──────┐
#> │ mpg ┆ cyl ┆ disp ┆ hp ┆ … ┆ vs ┆ am ┆ gear ┆ carb │
#> │ --- ┆ --- ┆ --- ┆ --- ┆ ┆ --- ┆ --- ┆ --- ┆ --- │
#> │ f64 ┆ f64 ┆ f64 ┆ f64 ┆ ┆ f64 ┆ f64 ┆ f64 ┆ f64 │
#> ╞══════╪═════╪══════╪═══════╪═══╪═════╪═════╪══════╪══════╡
#> │ 33.9 ┆ 4.0 ┆ 71.1 ┆ 65.0 ┆ … ┆ 1.0 ┆ 1.0 ┆ 4.0 ┆ 1.0 │
#> │ 32.4 ┆ 4.0 ┆ 78.7 ┆ 66.0 ┆ … ┆ 1.0 ┆ 1.0 ┆ 4.0 ┆ 1.0 │
#> │ 30.4 ┆ 4.0 ┆ 95.1 ┆ 113.0 ┆ … ┆ 1.0 ┆ 1.0 ┆ 5.0 ┆ 2.0 │
#> └──────┴─────┴──────┴───────┴───┴─────┴─────┴──────┴──────┘