Dimension¶
-
class
lsst.daf.butler.
Dimension
¶ Bases:
lsst.daf.butler.DimensionElement
A named data-organization concept that can be used as a key in a data ID.
Attributes Summary
RecordClass
The DimensionRecord
subclass used to hold records for this element (type
).alternateKeys
Additional unique key fields for this dimension that are not the primary key ( NamedValueAbstractSet
ofFieldSpec
).alwaysJoin
If True
, always include this element in any query or data ID in which itsrequired
dimensions appear, because it defines a relationship between those dimensions that must always be satisfied.dimensions
The union of required
andimplied
, with all elements inrequired
before any elements inimplied
.governor
The GovernorDimension
that is a required dependency of this element, orNone
if there is no such dimension (GovernorDimension
orNone
).graph
Minimal graph that includes this element ( DimensionGraph
).implied
Other dimensions that are uniquely identified directly by a record of this dimension element. metadata
Additional metadata fields included in this element’s table ( NamedValueSet
ofFieldSpec
).name
Unique string identifier for this endpoint ( str
).primaryKey
The primary key field for this dimension ( FieldSpec
).required
Dimensions that are necessary to uniquely identify a record of this dimension element. spatial
This endpoint’s SPATIAL
family.temporal
This endpoint’s TEMPORAL
family.topology
The relationship families to which this endpoint belongs, keyed by the category for that family. uniqueKeys
All fields that can individually be used to identify records of this element, given the primary keys of all required dependencies ( NamedValueAbstractSet
ofFieldSpec
).viewOf
Name of another table this element’s records are drawn from ( str
orNone
).Methods Summary
hasTable
()Return True
if this element is associated with a table (even if that table “belongs” to another element).Attributes Documentation
-
RecordClass
¶ The
DimensionRecord
subclass used to hold records for this element (type
).Because
DimensionRecord
subclasses are generated dynamically, this type cannot be imported directly and hence can only be obtained from this attribute.
-
alternateKeys
¶ Additional unique key fields for this dimension that are not the primary key (
NamedValueAbstractSet
ofFieldSpec
).If this dimension has required dependencies, the keys of those dimensions are also included in the unique constraints defined for these alternate keys.
-
alwaysJoin
¶ If
True
, always include this element in any query or data ID in which itsrequired
dimensions appear, because it defines a relationship between those dimensions that must always be satisfied.
-
dimensions
¶ The union of
required
andimplied
, with all elements inrequired
before any elements inimplied
.This differs from
self.graph.dimensions
both in order and in content:- as in
self.implied
, implied dimensions are not expanded recursively here; - implied dimensions appear after required dimensions here, instead of being topologically ordered.
As a result, this set is ordered consistently with
self.RecordClass.fields
.- as in
-
governor
¶ The
GovernorDimension
that is a required dependency of this element, orNone
if there is no such dimension (GovernorDimension
orNone
).
-
graph
¶ Minimal graph that includes this element (
DimensionGraph
).self.graph.required
includes all dimensions whose primary key values are sufficient (often necessary) to uniquely identifyself
(includingself
ifisinstance(self, Dimension)
.self.graph.implied
includes all dimensions also identified (possibly recursively) by this set.
-
implied
¶ Other dimensions that are uniquely identified directly by a record of this dimension element.
For elements with a database representation, these are exactly the dimensions used to form foreign key constraints whose fields are not (wholly) also part of the primary key.
Unlike
self.graph.implied
, this set is not expanded recursively.
-
metadata
¶ Additional metadata fields included in this element’s table (
NamedValueSet
ofFieldSpec
).
-
primaryKey
¶ The primary key field for this dimension (
FieldSpec
).Note that the database primary keys for dimension tables are in general compound; this field is the only field in the database primary key that is not also a foreign key (to a required dependency dimension table).
-
required
¶ Dimensions that are necessary to uniquely identify a record of this dimension element.
For elements with a database representation, these dimension are exactly those used to form the (possibly compound) primary key, and all dimensions here that are not
self
are also used to form foreign keys.For
Dimension
instances, this should be exactly the same asgraph.required
, but that may not be true forDimensionElement
instances in general. When they differ, there are multiple combinations of dimensions that uniquely identify this element, but this one is more direct.
-
topology
¶ The relationship families to which this endpoint belongs, keyed by the category for that family.
-
uniqueKeys
¶ All fields that can individually be used to identify records of this element, given the primary keys of all required dependencies (
NamedValueAbstractSet
ofFieldSpec
).
Methods Documentation
-