Struct Column 

pub struct Column {
    pub logical_type: LogicalTypeID,
    pub physical_type: PhysicalTypeID,
    pub table_id: u64,
    pub col_idx: u32,
    pub file_name: String,
    pub file_handle: FileHandle,
    pub buffer_manager: Arc<Mutex<BufferManager>>,
    pub compression_type: CompressionType,
    pub value_size: usize,
    pub num_values: u64,
    pub num_pages: u64,
    pub page_row_offsets: Vec<u64>,
}

A column stores values of a single type across multiple pages.

The column owns a dedicated file (named col_{table_id}_{col_idx}) and uses the BufferManager for all page-level I/O with automatic caching.

Fields

logical_type: LogicalTypeID

The logical type of values stored in this column.

physical_type: PhysicalTypeID

Physical type derived from logical_type.

table_id: u64

The owning table ID (used to construct the file name).

col_idx: u32

The column index within the table.

file_name: String

File name used in the BufferManager’s file registry.

file_handle: FileHandle

File handle for low-level page I/O.

buffer_manager: Arc<Mutex<BufferManager>>

Shared buffer manager for page caching and eviction.

compression_type: CompressionType

Compression algorithm applied to serialized values.

value_size: usize

Byte size of the serialized primitive value (0 for variable-length types).

num_values: u64

Total number of values stored.

num_pages: u64

Number of pages allocated.

page_row_offsets: Vec<u64>

Cumulative value count per page (for binary-search lookup). page_row_offsets[i] = the global row index of the first value in page i.

Implementations

impl Column

pub fn new( logical_type: LogicalTypeID, table_id: u64, col_idx: u32, db_path: &Path, buffer_manager: Arc<Mutex<BufferManager>>, page_size: usize, ) -> Self

Create a new column backed by a file in db_path.

The file is named col_{table_id}_{col_idx} and registered with the BufferManager automatically.

compression_type determines the compression algorithm applied to serialized values. Use CompressionType::Uncompressed for no compression.

pub fn with_compression( logical_type: LogicalTypeID, table_id: u64, col_idx: u32, db_path: &Path, buffer_manager: Arc<Mutex<BufferManager>>, page_size: usize, compression_type: CompressionType, ) -> Self

Create a new column with a specific compression algorithm.

pub fn append_value(&mut self, value: &Value) -> Result<()>

Append a single value to the column.

Append a single value to the column.

Automatically allocates a new page when the current one is full or when the current page has reached the maximum values per page (256).

Serialized values are compressed according to self.compression_type.

pub fn get_value(&self, row_idx: u64) -> Result<Value>

Get a single value by row index.

pub fn scan_values(&self, start: u64, count: u64) -> Result<Vec<Value>>

Scan a range of values (inclusive of start, exclusive of start + count).

pub fn read_value_bytes(&self, row_idx: u64) -> Result<Vec<u8>>

Read the raw serialised bytes of a single value (useful for compression).

pub fn flush(&self) -> Result<()>

Flush the column’s dirty pages to disk.

pub fn save_metadata(&self) -> Result<()>

Save column metadata to a .meta sidecar file so it can be reconstructed after a crash or restart without scanning every page.

Layout (all little-endian): magic: 4 bytes b“CMET“ version: u32 logical_type: u32 table_id: u64 col_idx: u32 num_values: u64 num_pages: u64 page_row_offsets: [u64; num_pages]

pub fn load_metadata(&mut self) -> Result<bool>

Load column metadata from a .meta sidecar file.

Returns Ok(true) if metadata was loaded successfully, Ok(false) if no metadata file exists (fresh column).

Trait Implementations

impl Debug for Column

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.