Skip to contents

Read database tables as Arrow objects

Source: R/dbReadTableArrow.R
dbReadTableArrow.Rd

[Experimental]

Reads a database table as an Arrow object. Use dbReadTable() instead to obtain a data frame.

Methods in other packages

This documentation page describes the generics. Refer to the documentation pages linked below for the documentation for the methods that are implemented in various backend packages.

Usage

dbReadTableArrow(conn, name, ...)

Arguments

conn

A DBIConnection object, as returned by dbConnect().

name

The table name, passed on to dbQuoteIdentifier(). Options are:

  • a character string with the unquoted DBMS table name, e.g. "table_name",

  • a call to Id() with components to the fully qualified table name, e.g. Id(schema = "my_schema", table = "table_name")

  • a call to SQL() with the quoted and fully qualified table name given verbatim, e.g. SQL('"my_schema"."table_name"')

...

Other parameters passed on to methods.

Value

dbReadTableArrow() returns an Arrow object that contains the complete data from the remote table, effectively the result of calling DBI::dbGetQueryArrow() with SELECT * FROM <name>.

An empty table is returned as an Arrow object with zero rows.

Details

This function returns an Arrow object. Convert it to a data frame with as.data.frame() or use dbReadTable() to obtain a data frame.

Failure modes

An error is raised if the table does not exist.

An error is raised when calling this method for a closed or invalid connection. An error is raised if name cannot be processed with DBI::dbQuoteIdentifier() or if this results in a non-scalar.

Specification

The name argument is processed as follows, to support databases that allow non-syntactic names for their objects:

  • If an unquoted table name as string: dbReadTableArrow() will do the quoting, perhaps by calling dbQuoteIdentifier(conn, x = name)

  • If the result of a call to DBI::dbQuoteIdentifier(): no more quoting is done

See also

Other DBIConnection generics: DBIConnection-class, dbAppendTable(), dbAppendTableArrow(), dbCreateTable(), dbCreateTableArrow(), dbDataType(), dbDisconnect(), dbExecute(), dbExistsTable(), dbGetException(), dbGetInfo(), dbGetQuery(), dbGetQueryArrow(), dbIsReadOnly(), dbIsValid(), dbListFields(), dbListObjects(), dbListResults(), dbListTables(), dbQuoteIdentifier(), dbReadTable(), dbRemoveTable(), dbSendQuery(), dbSendQueryArrow(), dbSendStatement(), dbUnquoteIdentifier(), dbWriteTable(), dbWriteTableArrow()

Examples

# Read data as Arrow table
con <- dbConnect(RSQLite::SQLite(), ":memory:")

dbWriteTable(con, "mtcars", mtcars[1:10, ])
dbReadTableArrow(con, "mtcars")
#> <nanoarrow_array_stream struct<mpg: double, cyl: double, disp: double, hp: double, drat: double, wt: double, qsec: double, vs: double, am: double, gear: double, carb: double>>
#>  $ get_schema:function ()  
#>  $ get_next  :function (schema = x$get_schema(), validate = TRUE)  
#>  $ release   :function ()  

dbDisconnect(con)