QueryBuilder¶
- class lsst.daf.butler.registry.queries.QueryBuilder(summary: QuerySummary, backend: QueryBackend, context: QueryContext | None = None, relation: Relation | None = None)¶
Bases:
object
A builder for potentially complex queries that join tables based on dimension relationships.
- Parameters:
- summary
QuerySummary
Struct organizing the dimensions involved in the query.
- backend
QueryBackend
Backend object that represents the
Registry
implementation.- context
QueryContext
, optional Object that manages relation engines and database-side state (e.g. temporary tables) for the query. Must have been created by
backend.context()
, which is used ifcontext
is not provided.- relation
Relation
, optional Initial relation for the query.
- summary
Methods Summary
finish
([joinMissing])Finish query constructing, returning a new
Query
instance.joinDataset
(datasetType, collections, *[, ...])Add a dataset search or constraint to the query.
Methods Documentation
- finish(joinMissing: bool = True) Query ¶
Finish query constructing, returning a new
Query
instance.- Parameters:
- joinMissing
bool
, optional If
True
(default), automatically join any missing dimension element tables (according to the categorization of theQuerySummary
the builder was constructed with).False
should only be passed if the caller can independently guarantee that all dimension relationships are already captured in non-dimension tables that have been manually included in the query.
- joinMissing
- Returns:
- query
Query
A
Query
object that can be executed and used to interpret result rows.
- query
- joinDataset(datasetType: DatasetType, collections: Any, *, isResult: bool = True, findFirst: bool = False) bool ¶
Add a dataset search or constraint to the query.
Unlike other
QueryBuilder
join methods, this must be called directly to search for datasets of a particular type or constrain the query results based on the exists of datasets. However, all dimensions used to identify the dataset type must have already been included inQuerySummary.requested
when initializing theQueryBuilder
.- Parameters:
- datasetType
DatasetType
The type of datasets to search for.
- collections
Any
An expression that fully or partially identifies the collections to search for datasets, such as a
str
,re.Pattern
, or iterable thereof.can be used to return all collections. See Collection expressions for more information.
- isResult
bool
, optional If
True
(default), include the dataset ID column in the result columns of the query, allowing completeDatasetRef
instances to be produced from the query results for this dataset type. IfFalse
, the existence of datasets of this type is used only to constrain the data IDs returned by the query.joinDataset
may be called withisResult=True
at most one time on a particularQueryBuilder
instance.- findFirst
bool
, optional If
True
(False
is default), only include the first match for each data ID, searching the given collections in order. Requires that all entries incollections
be regular strings, so there is a clear search order. Ignored ifisResult
isFalse
.
- datasetType
- Returns:
- anyRecords
bool
If
True
, joining the dataset table was successful and the query should proceed. IfFalse
, we were able to determine (from the combination ofdatasetType
andcollections
) that there would be no results joined in from this dataset, and hence (due to the inner join that would normally be present), the full query will return no results.
- anyRecords