Function generate_schema_search_terms

datafusion/sql/src/expr/identifier.rs:354–369

Possibilities we search with, in order from top to bottom for each len: len = 2: 1. (table.column) 2. (column).nested len = 3: 1. (schema.table.column) 2. (table.column).nested 3. (column).nested1.nested2 len = 4: 1. (catalog.schema.table.column) 2. (schema.table.column).nested1 3. (table.column).nested1.nested2 4. (column).nested1.nested2.nested3 len = 5: 1. (catalog.schema.table.column).nest

(
    ids: &[String],
)

// 3. (table.column).nested1.nested2.nested3[.nestedN]+
// 4. (column).nested1.nested2.nested3.nested4[.nestedN]+
fn generate_schema_search_terms(
    ids: &[String],
) -> impl Iterator<Item = (Option<TableReference>, &String, &[String])> {
    // Take at most 4 identifiers to form a Column to search with
    // - 1 for the column name
    // - 0 to 3 for the TableReference
    let bound = ids.len().min(4);
    // Search terms from most specific to least specific
    (0..bound).rev().map(|i| {
        let nested_names_index = i + 1;
        let qualifier_and_column = &ids[0..nested_names_index];
        // Safe unwrap as qualifier_and_column can never be empty or exceed the bounds
        let (relation, column_name) = form_identifier(qualifier_and_column).unwrap();
        (relation, column_name, &ids[nested_names_index..])
    })
}

#[cfg(test)]
mod test {