QueryBuilder¶
- class lsst.daf.butler.registry.queries.QueryBuilder(summary: QuerySummary, managers: RegistryManagers, doomed_by: Iterable[str] = ())¶
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.
- managers
RegistryManagers
A struct containing the registry manager instances used by the query system.
- doomed_by
Iterable
[str
], optional A list of messages (appropriate for e.g. logging or exceptions) that explain why the query is known to return no results even before it is executed. Queries with a non-empty list will never be executed.
- summary
Methods Summary
finish
([joinMissing])Finish query constructing, returning a new
Query
instance.finishJoin
(table, joinOn)Complete a join on dimensions.
hasDimensionKey
(dimension)Return
True
if the given dimension's primary key column has been included in the query (possibly via a foreign key column on some other table).joinDataset
(datasetType, collections, *[, ...])Add a dataset search or constraint to the query.
joinDimensionElement
(element)Add the table for a
DimensionElement
to the query.joinTable
(table, dimensions, *[, datasets])Join an arbitrary table to the query via dimension relationships.
startJoin
(table, dimensions, columnNames)Begin a join on dimensions.
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:
- finishJoin(table: FromClause, joinOn: List[ColumnElement]) None ¶
Complete a join on dimensions.
Must be preceded by call to
startJoin
.- Parameters:
- table
sqlalchemy.sql.FromClause
SQLAlchemy object representing the logical table (which may be a join or subquery expression) to be joined. Must be the same object passed to
startJoin
.- joinOn
list
ofsqlalchemy.sql.ColumnElement
Sequence of boolean expressions that should be combined with AND to form (part of) the ON expression for this JOIN. Should include at least the elements of the list returned by
startJoin
.
- table
- hasDimensionKey(dimension: Dimension) bool ¶
Return
True
if the given dimension’s primary key column has been included in the query (possibly via a foreign key column on some other table).
- 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
- joinDimensionElement(element: DimensionElement) None ¶
Add the table for a
DimensionElement
to the query.This automatically joins the element table to all other tables in the query with which it is related, via both dimension keys and spatial and temporal relationships.
External calls to this method should rarely be necessary;
finish
will automatically call it if theDimensionElement
has been identified as one that must be included.- Parameters:
- element
DimensionElement
Element for which a table should be added. The element must be associated with a database table (see
DimensionElement.hasTable
).
- element
- joinTable(table: FromClause, dimensions: NamedValueAbstractSet[Dimension], *, datasets: DatasetQueryColumns | None = None) None ¶
Join an arbitrary table to the query via dimension relationships.
External calls to this method should only be necessary for tables whose records represent neither datasets nor dimension elements.
- Parameters:
- table
sqlalchemy.sql.FromClause
SQLAlchemy object representing the logical table (which may be a join or subquery expression) to be joined.
- dimensionsiterable of
Dimension
The dimensions that relate this table to others that may be in the query. The table must have columns with the names of the dimensions.
- datasets
DatasetQueryColumns
, optional Columns that identify a dataset that is part of the query results.
- table
- startJoin(table: FromClause, dimensions: Iterable[Dimension], columnNames: Iterable[str]) List[ColumnElement] ¶
Begin a join on dimensions.
Must be followed by call to
finishJoin
.- Parameters:
- table
sqlalchemy.sql.FromClause
SQLAlchemy object representing the logical table (which may be a join or subquery expression) to be joined.
- dimensionsiterable of
Dimension
The dimensions that relate this table to others that may be in the query. The table must have columns with the names of the dimensions.
- columnNamesiterable of
str
Names of the columns that correspond to dimension key values; must be
zip
iterable withdimensions
.
- table
- Returns:
- joinOn
list
ofsqlalchemy.sql.ColumnElement
Sequence of boolean expressions that should be combined with AND to form (part of) the ON expression for this JOIN.
- joinOn