Add a column to a DuckLake table

Adds a column in place with ALTER TABLE ... ADD COLUMN. This is a metadata-only change: no data files are rewritten, history is preserved, and earlier snapshots still show the old schema. Compare replace_table(), which rewrites the whole table.

Usage

add_table_column(table_name, column_name, type, default = NULL)

Arguments

table_name

The table to change.

column_name

Name of the new column.

type

SQL type for the new column, e.g. "INTEGER", "DECIMAL(10,2)", or "TIMESTAMP WITH TIME ZONE".

default

Optional default value (an R scalar: character, numeric, logical, Date, or POSIXct, the last rendered in UTC). In DuckLake the default applies to existing rows as well as future inserts, so the new column appears filled everywhere. Without a default, the column reads NA for existing rows. DuckLake accepts constant defaults only; an expression such as now() is not supported.

Value

Invisibly returns NULL.

See also

drop_table_column(), rename_table_column(), set_column_type(), rename_ducklake_table()

Other schema evolution: drop_table_column(), rename_ducklake_table(), rename_table_column(), set_column_not_null(), set_column_type()

Examples

lake_dir <- tempfile("addcol_lake_")
dir.create(lake_dir)
attach_ducklake("addcol_lake", lake_path = lake_dir)
create_table(mtcars, "cars")

add_table_column("cars", "grade", "VARCHAR")
#> Added column "grade" (VARCHAR) to "cars".
#> ℹ Metadata-only change; no data files were rewritten.
add_table_column("cars", "discount", "DECIMAL(5,2)", default = 0)
#> Added column "discount" (DECIMAL(5,2)) to "cars".
#> ℹ Metadata-only change; no data files were rewritten.

detach_ducklake("addcol_lake", shutdown = TRUE)
unlink(lake_dir, recursive = TRUE)