Method extract_value_versioned

nodedb-strict/src/decode.rs:271–292

Decode a tuple written with an older schema version. Columns present in the old schema are extracted normally. Columns added in newer schema versions return their declared default value, or `Value::Null` for nullable columns without a default. `old_col_count` is the number of columns in the schema version that wrote this tuple. Correctness invariant: a non-nullable column added via `ALTER ADD C

(
        &self,
        tuple: &[u8],
        col_idx: usize,
        old_col_count: usize,
    )

    /// `NOT NULL` without a `DEFAULT`, so every non-nullable column in the
    /// schema must have `col.default` populated.
    pub fn extract_value_versioned(
        &self,
        tuple: &[u8],
        col_idx: usize,
        old_col_count: usize,
    ) -> Result<Value, StrictError> {
        self.check_bounds(col_idx)?;

        if col_idx >= old_col_count {
            // Column was added after this tuple was written: materialize the
            // declared default, or null for nullable columns without a default.
            let col = &self.schema.columns[col_idx];
            let value = col
                .default
                .as_deref()
                .map(nodedb_types::columnar::StrictSchema::parse_default_literal)
                .unwrap_or(Value::Null);
            return Ok(value);
        }

        self.extract_value(tuple, col_idx)
    }

    /// Access the schema this decoder was built for.
    pub fn schema(&self) -> &StrictSchema {