GovernorDimension

class lsst.daf.butler.GovernorDimension(name: str, *, metadata_columns: NamedValueAbstractSet[IntColumnSpec | StringColumnSpec | FloatColumnSpec | HashColumnSpec | BoolColumnSpec], unique_keys: NamedValueAbstractSet[IntColumnSpec | StringColumnSpec | HashColumnSpec], doc: str)

Bases: Dimension

Governor dimension.

A special Dimension with no dependencies and a small number of rows, used to group the dimensions that depend on it.

Parameters:

namestr

Name of the dimension.

metadata_columnsNamedValueAbstractSet [ MetadataColumnSpec ]

Field specifications for all non-key fields in this dimension’s table.

unique_keysNamedValueAbstractSet [ KeyColumnSpec ]

Fields that can each be used to uniquely identify this dimension (given values for all required dimensions). The first of these is used as (part of) this dimension’s table’s primary key, while others are used to define unique constraints.

docstr

Extended description of this element.

Notes

Most dimensions have exactly one governor dimension as a required dependency, and queries that involve those dimensions are always expected to explicitly identify the governor dimension value(s), rather than retrieve all matches from the database. Because governor values are thus almost always known at query-generation time, they can be used there to simplify queries, provide sensible defaults, or check in advance for common mistakes that might otherwise yield confusing (albeit formally correct) results instead of straightforward error messages.

Governor dimensions may not be associated with any kind of topological extent.

Governor dimension rows are often affiliated with a Python class or instance (e.g. lsst.obs.base.Instrument) that is capable of generating the rows of at least some dependent dimensions or providing other related functionality. In the future, we hope to attach these instances to governor dimension records (instantiating them from information in the database row when it is fetched), and use those objects to add additional functionality to governor dimensions, but a number of (code) dependency relationships would need to be reordered first.

Attributes Summary

MAX_KEY_LENGTH
documentation	Extended description of this dimension element.
implied	Return the implied dimensions.
is_cached	Whether this element's records should be aggressively cached, because they are small in number and rarely inserted.
metadata_columns	Additional metadata fields included in this element's table.
name	Return unique string identifier for this endpoint (str).
required	Return the required dimensions.
topology	Return the relationship families to which this endpoint belongs.
unique_keys	Descriptions of unique identifiers for this dimension.

Attributes Documentation

MAX_KEY_LENGTH = 128

documentation

implied

is_cached

metadata_columns

name

required

topology

unique_keys