This works the same as the "#filter_columns" method in the pg_query Ruby gem, and returns the table name (if present) and column name for every column that's referenced in a JOIN or WHERE clause.
To support this functionality, the nodes() and nodes_mut() functions gain a 4th value for each result item, indicating whether the current node can be considered a filter column. This is intended to be used when matching a ColumnRef node, to determine whether it is part of a WHERE/JOIN clause, or part of something else (e.g. target list, or ORDER BY, etc).
This works the same as the "#filter_columns" method in the pg_query Ruby gem, and returns the table name (if present) and column name for every column that's referenced in a JOIN or WHERE clause.
To support this functionality, the nodes() and nodes_mut() functions gain a 4th value for each result item, indicating whether the current node can be considered a filter column. This is intended to be used when matching a ColumnRef node, to determine whether it is part of a WHERE/JOIN clause, or part of something else (e.g. target list, or ORDER BY, etc).