join package

The join package provides functions that join two table streams together. Import the join package:

import "join"

Outer joins

The join transformation supports left, right, and full outer joins.

• Left outer joins generate at least one output row for each record in the left input stream. If a record in the left input stream does not have a match in the right input stream, r is substituted with a default record in the as function.
• Right outer joins generate at least one output row for each record in the right input stream. If a record in the right input stream does not have a match in the left input stream, l is substituted with a default record in the as function.
• Full outer joins generate at least one output row for each record in both input streams. If a record in either input stream doesn’t have a match in the other input stream, one of the arguments to the as function is substituted with a default record (either l or r, depending on which one is missing the matching record)

A default record has the same columns as the records in the corresponding input table, but only group key columns are populated with a value. All other columns are null.

Inner joins

Inner joins drop any records that don’t have a match in the other input stream. There is no need to account for default or unmatched records when performing an inner join.

Functions