databendlabs/databend · error

internal error: entered unreachable code

Error message

internal error: entered unreachable code

What it means

VirtualColumnMeta::physical_type maps a stored physical-type tag constant to a VirtualColumnPhysicalType, and panics with unreachable! on an unknown tag (or expect-fails when the extended type payload is missing). Indicates virtual column metadata on disk uses a tag this binary does not understand, or extended-type metadata is incomplete.

Solutions

1. Upgrade to a Databend version that supports the virtual column physical type in the metadata
2. Inspect the segment's virtual column meta to identify the unknown tag value
3. Rebuild virtual column metadata (re-run virtual column computation) for the affected table
4. For developers: replace unreachable! with an error carrying the tag, and validate extended_physical_type at write time

Example fix

// before
_ => unreachable!(),
// after
unknown => Err(ErrorCode::StorageOther(format!(
    "unknown virtual column physical type tag {unknown:#x}; upgrade Databend"
))),

// rust: check the virtual column tag is recognized before use
const KNOWN_TAGS: &[u8] = &[VIRTUAL_COLUMN_NULLABLE_TYPE, VIRTUAL_COLUMN_TIMESTAMP_TZ_TYPE,
    VIRTUAL_COLUMN_INTERVAL_TYPE, VIRTUAL_COLUMN_EXTENDED_TYPE];
assert!(KNOWN_TAGS.contains(&tag), "unknown virtual column tag");

fn is_known_virtual_tag(tag: u8) -> bool {
    matches!(tag, VIRTUAL_COLUMN_NULLABLE_TYPE | VIRTUAL_COLUMN_TIMESTAMP_TZ_TYPE
        | VIRTUAL_COLUMN_INTERVAL_TYPE | VIRTUAL_COLUMN_EXTENDED_TYPE)
}

let pty = std::panic::catch_unwind(|| meta.physical_type())
    .map_err(|_| "unsupported virtual column physical type; upgrade Databend")?;

When it happens

Trigger: Reading a segment containing virtual column metadata whose type tag is none of the known VIRTUAL_COLUMN_*_TYPE constants, or a VIRTUAL_COLUMN_EXTENDED_TYPE entry whose extended_physical_type field is None.

Common situations: Version skew: newer Databend wrote new virtual column physical types (e.g. new extended types) and an older binary reads the segment; partially written/corrupted segment metadata.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• expect tuple type
• internal error: entered unreachable code
• internal error: entered unreachable code
• internal error: entered unreachable code
• {}

AI-assisted analysis of databendlabs/databend@288d84d76e (2026-09-11). Data as JSON: /api/errors/e89ee3a7204ffcbf. Report an issue: GitHub.

Appendix: source

Thrown at src/query/storages/common/table_meta/src/meta/v2/segment.rs:260

            VIRTUAL_COLUMN_INT16_TYPE => VirtualColumnPhysicalType::Number(NumberDataType::Int16),
            VIRTUAL_COLUMN_INT32_TYPE => VirtualColumnPhysicalType::Number(NumberDataType::Int32),
            VIRTUAL_COLUMN_FLOAT64_TYPE => {
                VirtualColumnPhysicalType::Number(NumberDataType::Float64)
            }
            VIRTUAL_COLUMN_FLOAT32_TYPE => {
                VirtualColumnPhysicalType::Number(NumberDataType::Float32)
            }
            VIRTUAL_COLUMN_STRING_TYPE => VirtualColumnPhysicalType::String,
            VIRTUAL_COLUMN_BINARY_TYPE => VirtualColumnPhysicalType::Binary,
            VIRTUAL_COLUMN_DATE_TYPE => VirtualColumnPhysicalType::Date,
            VIRTUAL_COLUMN_TIMESTAMP_TYPE => VirtualColumnPhysicalType::Timestamp,
            VIRTUAL_COLUMN_TIMESTAMP_TZ_TYPE => VirtualColumnPhysicalType::TimestampTz,
            VIRTUAL_COLUMN_INTERVAL_TYPE => VirtualColumnPhysicalType::Interval,
            VIRTUAL_COLUMN_EXTENDED_TYPE => self
                .extended_physical_type
                .clone()
                .expect("extended virtual column type is missing"),
            _ => unreachable!(),
        }
    }
}

/// Retained path frequencies for one source variant column in a block.
#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq, FrozenAPI)]
pub struct VirtualColumnPathStatistics {
    /// `(segment-local virtual path id, saturated value_count)` pairs.
    pub path_counts: Vec<(ColumnId, u32)>,
    /// Whether every observed non-direct path for this source is represented in
    /// `path_counts`. Direct paths are intentionally represented only by
    /// `VirtualBlockMeta.virtual_column_metas`; false means producer-side
    /// truncation omitted some non-direct paths.
    pub path_statistics_complete: bool,
}

/// Path frequencies for one source variant column before segment-local path ids
/// are assigned. Each pair is `(canonical_path, saturated value_count)`.

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