Function create_index_mapping

crates/paimon/src/arrow/schema_evolution.rs:42–72

Create index mapping from table fields to underlying data fields using field IDs. For example, the table and data fields are as follows: - table fields: `1->c, 6->b, 3->a` - data fields: `1->a, 3->c` We get the index mapping `[0, -1, 1]`, where: - `0` is the index of table field `1->c` in data fields - `-1` means field `6->b` does not exist in data fields - `1` is the index of table field `3->a`

(
    table_fields: &[DataField],
    data_fields: &[DataField],
)

///
/// Reference: [SchemaEvolutionUtil.createIndexMapping](https://github.com/apache/paimon/blob/release-1.3/paimon-core/src/main/java/org/apache/paimon/schema/SchemaEvolutionUtil.java)
pub fn create_index_mapping(
    table_fields: &[DataField],
    data_fields: &[DataField],
) -> Option<Vec<i32>> {
    let mut field_id_to_index: HashMap<i32, i32> = HashMap::with_capacity(data_fields.len());
    for (i, field) in data_fields.iter().enumerate() {
        field_id_to_index.insert(field.id(), i as i32);
    }

    let mut index_mapping = Vec::with_capacity(table_fields.len());
    for field in table_fields {
        let data_index = field_id_to_index
            .get(&field.id())
            .copied()
            .unwrap_or(NULL_FIELD_INDEX);
        index_mapping.push(data_index);
    }

    // Check if mapping is identity (no evolution needed).
    let is_identity = index_mapping.len() == data_fields.len()
        && index_mapping
            .iter()
            .enumerate()
            .all(|(i, &idx)| idx == i as i32);

    if is_identity {
        None
    } else {
        Some(index_mapping)
    }
}

#[cfg(test)]
mod tests {