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ducklake_column

This table describes the columns that are part of a table, including their types, default values, etc.

Column name Column type  
column_id BIGINT  
begin_snapshot BIGINT  
end_snapshot BIGINT  
table_id BIGINT  
column_order BIGINT  
column_name VARCHAR  
column_type VARCHAR  
initial_default VARCHAR  
default_value VARCHAR  
nulls_allowed BOOLEAN  
parent_column BIGINT  
  • column_id is the numeric identifier of the column. If the Parquet file includes a field identifier, it corresponds to the file's field_id. This identifier should remain consistent throughout all versions of the column, until it's dropped. The column_id must be unique per table.
  • begin_snapshot refers to a snapshot_id from the ducklake_snapshot table. This version of the column exists starting with this snapshot id.
  • end_snapshot refers to a snapshot_id from the ducklake_snapshot table. This version of the column exists up to but not including this snapshot id. If end_snapshot is NULL, this version of the column is currently valid.
  • table_id refers to a table_id from the ducklake_table table.
  • column_order is a number that defines the position of the column in the list of columns. It needs to be unique within a snapshot but does not have to be contiguous (gaps are ok).
  • column_name is the name of this version of the column, e.g., my_column.
  • column_type is the type of this version of the column as defined in the list of data types.
  • initial_default is the initial default value as the column is being created, e.g., in ALTER TABLE, encoded as a string. Can be NULL.
  • default_value is the operational default value as data is being inserted and updated, e.g., in INSERT, encoded as a string. Can be NULL.
  • nulls_allowed defines whether NULL values are allowed in this version of the column. Note that default values have to be set if this is set to false.
  • parent_column is the column_id of the parent column. This is NULL for top-level and non-nested columns. For example, for STRUCT types, this would refer to the "parent" struct column.

Every ALTER of the column creates a new version of the column, which will use the same column_id.