Reads a CSV file into DuckDB

Directly reads a CSV file into DuckDB, tries to detect and create the correct schema for it. This usually is much faster than reading the data into R and writing it to DuckDB.

duckdb_read_csv(
  conn,
  name,
  files,
  ...,
  header = TRUE,
  na.strings = "",
  nrow.check = 500,
  delim = ",",
  quote = "\"",
  col.names = NULL,
  col.types = NULL,
  lower.case.names = FALSE,
  sep = delim,
  transaction = TRUE,
  temporary = FALSE
)

Arguments

conn

A DuckDB connection, created by dbConnect().

name

The name for the virtual table that is registered or unregistered

files

One or more CSV file names, should all have the same structure though

...

Reserved for future extensions, must be empty.

header

Whether or not the CSV files have a separate header in the first line

na.strings

Which strings in the CSV files should be considered to be NULL

nrow.check

How many rows should be read from the CSV file to figure out data types

delim

Which field separator should be used

quote

Which quote character is used for columns in the CSV file

col.names

Override the detected or generated column names

col.types

Character vector of column types in the same order as col.names, or a named character vector where names are column names and types pairs. Valid types are DuckDB data types, e.g. VARCHAR, DOUBLE, DATE, BIGINT, BOOLEAN, etc.

lower.case.names

Transform column names to lower case

sep

Alias for delim for compatibility

transaction

Should a transaction be used for the entire operation

temporary

Set to TRUE to create a temporary table

Value

The number of rows in the resulted table, invisibly.

Details

If the table already exists in the database, the csv is appended to it. Otherwise the table is created.

Examples

if (FALSE) { # duckdb:::TEST_RE2
con <- dbConnect(duckdb())

data <- data.frame(a = 1:3, b = letters[1:3])
path <- tempfile(fileext = ".csv")

write.csv(data, path, row.names = FALSE)

duckdb_read_csv(con, "data", path)
dbReadTable(con, "data")

dbDisconnect(con)


# Providing data types for columns
path <- tempfile(fileext = ".csv")
write.csv(iris, path, row.names = FALSE)

con <- dbConnect(duckdb())
duckdb_read_csv(con, "iris", path,
  col.types = c(
    Sepal.Length = "DOUBLE",
    Sepal.Width = "DOUBLE",
    Petal.Length = "DOUBLE",
    Petal.Width = "DOUBLE",
    Species = "VARCHAR"
  )
)
dbReadTable(con, "iris")
dbDisconnect(con)
}