duckdb_read_csv function

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

Returns

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

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)