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Columns API

Classes for storing per-document values (column-oriented storage) used for fast sorting, faceting, and filtering. Columns are the mechanism by which Whoosh stores field values alongside the inverted index, in a column-oriented layout for efficient range access.

The default column type for most fields is VarBytesColumn, although numeric and date fields use NumericColumn. Expert users may use other column types that may be faster or more storage-efficient based on the field contents.

A Column object stores configuration information and provides two important methods: writer() to return a ColumnWriter and reader() to return a ColumnReader.

Module Functions​

bytes_column​

whoosh.columns.bytes_column

A default VarBytesColumn instance used as the column type for string fields.

numeric_column​

whoosh.columns.numeric_column

A default NumericColumn instance used as the column type for numeric fields.

Base Classes​

Column​

class whoosh.columns.Column

Base class for all column types.

Class Attributes:

  • reversible (bool): Whether values can be reversed for descending sort. Default False.

Methods:

  • writer(dbfile): Returns a ColumnWriter for this column type.
  • reader(dbfile, basepos, length, doccount): Returns a ColumnReader for this column type.
  • default_value(reverse=False): Returns the default value for documents without a column value at index time.
  • stores_lists(): Returns True if the column stores a list of values per document instead of a single value.

ColumnWriter​

class whoosh.columns.ColumnWriter(dbfile)

Base class for writing column values to disk.

Constructor:

  • dbfile: The StructFile to write to.

Methods:

  • fill(docnum): Fills any gap in docnums up to docnum with default values.
  • add(docnum, value): Adds a value for the given docnum.
  • finish(docnum): Called when done writing. Default does nothing.

ColumnReader​

class whoosh.columns.ColumnReader(dbfile, basepos, length, doccount)

Base class for reading column values from disk.

Constructor:

  • dbfile: The StructFile to read from.
  • basepos: The offset within the file at which the column starts.
  • length: The length in bytes the column occupies in the file.
  • doccount: The number of rows (documents) in the column.

Methods:

  • __getitem__(docnum): Returns the value for the given docnum.
  • sort_key(docnum): Returns the value for sorting (defaults to __getitem__).
  • __iter__(): Yields values for all documents.
  • load(): Returns a list of all values.
  • set_reverse(): Prepares the reader for reverse iteration.

Concrete Column Types​

VarBytesColumn​

class whoosh.columns.VarBytesColumn(
    allow_offsets=True,
    write_offsets_cutoff=2**15
)

Stores variable-length byte strings. The default value for documents without a value is b'' (empty bytes).

Constructor:

  • allow_offsets: Whether to write offsets for faster lookup when there are many rows. Default True.
  • write_offsets_cutoff: Write offsets when there are more than this many rows (default 2**15).

FixedBytesColumn​

class whoosh.columns.FixedBytesColumn(blocksize, default=emptybytes)

Stores fixed-length byte strings, saving space by not storing the length of each value.

Constructor:

  • blocksize: Fixed size of each value in bytes.
  • default: Default value for documents without a value.

RefBytesColumn​

class whoosh.columns.RefBytesColumn(
    cachesize=1000,
    stable=True,
    default=emptybytes
)

Stores references to unique values rather than the values themselves, saving space when the field has few unique values. Uses a DocIdSet to track which documents contain each value.

Constructor:

  • cachesize: Size of the LRU cache for value lookups (default 1000).
  • stable: Whether to use a stable sort of references (default True).
  • default: Default value for missing documents.

NumericColumn​

class whoosh.columns.NumericColumn(
    typecode,
    default=None,
    nullable=False
)

Stores numbers (int, float, datetime) encoded as binary values. Extends FixedBytesColumn.

Constructor:

  • typecode: A struct typecode string (e.g., "I" for unsigned int, "q" for long, "d" for float).
  • default: Default numeric value (None for the type's zero value).
  • nullable: Whether None values are allowed.

BitColumn​

class whoosh.columns.BitColumn

Stores boolean values as a bitmap. Each value is either True (1) or False (0). Uses a BitSet internally.

CompressedBytesColumn​

class whoosh.columns.CompressedBytesColumn(default=emptybytes)

Wraps a VarBytesColumn with zlib compression for the value bytes.

CompressedBlockColumn​

class whoosh.columns.CompressedBlockColumn

Stores values with block-level zlib compression. More efficient for large columns.

StructColumn​

class whoosh.columns.StructColumn(struct, name)

Wraps a FixedBytesColumn to store structured binary data (e.g., tuples encoded with struct).

Constructor:

  • struct: A struct.Struct object defining the format.
  • name: Field name for error messages.

EmptyColumnReader​

class whoosh.columns.EmptyColumnReader(default, doccount)

A ColumnReader that returns a constant default value for every document. Used when a field has no column.

MultiColumnReader​

class whoosh.columns.MultiColumnReader(readers)

Combines multiple ColumnReader instances into one for multi-segment indices.

Constructor:

  • readers: List of ColumnReader instances (one per segment).

TranslatingColumnReader​

class whoosh.columns.TranslatingColumnReader(child, translator)

Wraps a ColumnReader to apply a translation function to the values.

Constructor:

  • child: The underlying ColumnReader.
  • translator: Function that maps sort keys to human-readable values.

WrappedColumn​

class whoosh.columns.WrappedColumn(child)

Base class for column wrappers that adapt another column type.

WrappedColumnWriter​

class whoosh.columns.WrappedColumnWriter(child)

Base class for column writer wrappers.

WrappedColumnReader​

class whoosh.columns.WrappedColumnReader(child)

Base class for column reader wrappers.

ClampedNumericColumn​

class whoosh.columns.ClampedNumericColumn(child, clampfn)

Wraps a NumericColumn to clamp values to a valid range before sorting.

Constructor:

  • child: The wrapped NumericColumn.
  • clampfn: Function that clamps a value to the valid range.

PickleColumn​

class whoosh.columns.PickleColumn(child, ...)

Wraps another column to store pickled Python objects.

ListColumn​

class whoosh.columns.ListColumn(child)

Base class for columns that store multiple values per document.

ListColumnReader​

class whoosh.columns.ListColumnReader(child)

Reader for list-valued columns.

VarBytesListColumn​

class whoosh.columns.VarBytesListColumn

A ListColumn variant of VarBytesColumn that stores lists of byte strings.

FixedBytesListColumn​

class whoosh.columns.FixedBytesListColumn(blocksize)

A ListColumn variant of FixedBytesColumn that stores lists of fixed-size byte strings.