Change the type of a DuckLake table column

Changes a column's type in place with ALTER TABLE ... ALTER COLUMN ... SET TYPE. DuckLake permits widening promotions only (for example INTEGER to BIGINT, or FLOAT to DOUBLE): every existing value must be representable in the new type, so no data can be lost and no data files need rewriting.

Usage

set_column_type(table_name, column_name, type)

Arguments

table_name

The table to change.

column_name

Name of the column.

type

The new (wider) SQL type.

Value

Invisibly returns NULL.

Details

To narrow a type, which DuckLake refuses, take the explicit route: add_table_column() with the smaller type, copy the values over (after checking they fit), drop_table_column() the original, and rename_table_column() the new column into place.

See also

add_table_column(), drop_table_column(), rename_table_column()

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

Examples

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

# Widening promotions only: INTEGER -> BIGINT is fine
add_table_column("cars", "order_id", "INTEGER")
#> Added column "order_id" (INTEGER) to "cars".
#> ℹ Metadata-only change; no data files were rewritten.
set_column_type("cars", "order_id", "BIGINT")
#> Column "order_id" in "cars" is now BIGINT.

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