A Delta table feature that separates the logical names of columns from their physical names, so columns can be renamed or dropped as a metadata-only change and names may contain characters like spaces.
Read more: Microsoft Learn
In the Ultra Transcenders books
Each book explains Column mapping in context, with comparison tables and the common traps.
Terms in this definition
- Delta table
The default kind of table on Databricks, kept in Delta Lake format. Streams can read from it using
spark.readStream.table(...)and can also write to it. - Logical
Independent of any implementation. Each logical design is made real through a physical counterpart.
- Physical
Describes the concrete, real-world parts that put a logical architecture into effect.
- LIKE
Compares strings with a pattern that can contain the % and _ wildcards. Because it only understands character patterns, searching big volumes of text this way is much slower than using full-text search.
Related terms
- DROP COLUMN
Deletes a column through
ALTER TABLE. On a Delta table this, likeRENAME COLUMN, relies on column mapping modename, since data files stay as they are. - RENAME
The DDL clause for giving a table or column a new name, through
ALTER TABLE ... RENAME TOorRENAME COLUMN. Delta tables need column mapping modenamebefore a column can be renamed.