DataCoordinateQueryResults¶

class lsst.daf.butler.registry.queries.DataCoordinateQueryResults(db: lsst.daf.butler.registry.interfaces._database.Database, query: lsst.daf.butler.registry.queries._query.Query, *, records: Optional[Mapping[str, Mapping[tuple, lsst.daf.butler.core.dimensions._records.DimensionRecord]]] = None)¶

Bases: lsst.daf.butler.DataCoordinateIterable

An enhanced implementation of DataCoordinateIterable that represents data IDs retrieved from a database query.

Parameters:

db : Database: Database engine used to execute queries.
query : Query: Low-level representation of the query that backs this result object.
records : Mapping, optional: A nested mapping containing DimensionRecord objects for all dimensions and all data IDs this query will yield. If None (default), DataCoordinateIterable.hasRecords will return False. The outer mapping has str keys (the names of dimension elements). The inner mapping has tuple keys representing data IDs (tuple conversions of DataCoordinate.values()) and DimensionRecord values.

Notes

Constructing an instance of this does nothing; the query is not executed until it is iterated over (or some other operation is performed that involves iteration).

Instances should generally only be constructed by Registry methods or the methods of other query result objects.

Attributes Summary

`graph`	Dimensions identified by these data IDs (`DimensionGraph`).
`universe`	Universe that defines all known compatible dimensions.

Methods Summary

`any`(*, execute, exact)	Test whether this query returns any results.
`constrain`(query, columns, …)	Constrain a SQL query to include or relate to only known data IDs.
`count`(*, exact)	Count the number of rows this query would return.
`expanded`()	Return a results object for which `hasRecords` returns `True`.
`explain_no_results`()	Return human-readable messages that may help explain why the query yields no results.
`findDatasets`(datasetType, str], collections, …)	Find datasets using the data IDs identified by this query.
`fromScalar`(dataId)	Return a `DataCoordinateIterable` containing the single data ID.
`hasFull`()	Indicate if all data IDs in this iterable identify all dimensions.
`hasRecords`()	Return whether all data IDs in this iterable contain records.
`materialize`()	Insert this query’s results into a temporary table.
`subset`(graph, *, unique)	Return a results object containing a subset of the dimensions of this one, and/or a unique near-subset of its rows.
`toSequence`()	Transform this iterable into a `DataCoordinateSequence`.
`toSet`()	Transform this iterable into a `DataCoordinateSet`.

Attributes Documentation

graph¶: Dimensions identified by these data IDs (DimensionGraph).

universe¶

Universe that defines all known compatible dimensions.

(DimensionUniverse).

Methods Documentation

any(*, execute: bool = True, exact: bool = True) → bool¶

Test whether this query returns any results.

Parameters:

execute : bool, optional: If True, execute at least a LIMIT 1 query if it cannot be determined prior to execution that the query would return no rows.
exact : bool, optional: If True, run the full query and perform post-query filtering if needed, until at least one result row is found. If False, the returned result does not account for post-query filtering, and hence may be True even when all result rows would be filtered out.

Returns:

any : bool: True if the query would (or might, depending on arguments) yield result rows. False if it definitely would not.

constrain(query: lsst.daf.butler.core.simpleQuery.SimpleQuery, columns: Callable[[str], sqlalchemy.sql.elements.ColumnElement]) → None¶

Constrain a SQL query to include or relate to only known data IDs.

Parameters:	query : `SimpleQuery` Struct that represents the SQL query to constrain, either by appending to its WHERE clause, joining a new table or subquery, or both. columns : `Callable` A callable that accepts `str` dimension names and returns SQLAlchemy objects representing a column for that dimension’s primary key value in the query.

count(*, exact: bool = True) → int¶

Count the number of rows this query would return.

Parameters:	exact : `bool`, optional If `True`, run the full query and perform post-query filtering if needed to account for that filtering in the count. If `False`, the result may be an upper bound.
Returns:	count : `int` The number of rows the query would return, or an upper bound if `exact=False`.

Notes

This counts the number of rows returned, not the number of unique rows returned, so even with exact=True it may provide only an upper bound on the number of deduplicated result rows.

expanded() → lsst.daf.butler.registry.queries._results.DataCoordinateQueryResults¶

Return a results object for which hasRecords returns True.

This method may involve actually executing database queries to fetch DimensionRecord objects.

Returns:	results : `DataCoordinateQueryResults` A results object for which `hasRecords` returns `True`. May be `self` if that is already the case.

Notes

For very result sets, it may be much more efficient to call materialize before calling expanded, to avoid performing the original query multiple times (as a subquery) in the follow-up queries that fetch dimension records. For example:

with registry.queryDataIds(...).materialize() as tempDataIds:
    dataIdsWithRecords = tempDataIds.expanded()
    for dataId in dataIdsWithRecords:
        ...

explain_no_results() → Iterator[str]¶

Return human-readable messages that may help explain why the query yields no results.

Returns:	messages : `Iterator` [ `str` ] String messages that describe reasons the query might not yield any results.

Notes

Messages related to post-query filtering are only available if the iterator has been exhausted, or if any or count was already called (with exact=True for the latter two).

At present, this method only returns messages that are generated while the query is being built or filtered. In the future, it may perform its own new follow-up queries, which users may wish to short-circuit simply by not continuing to iterate over its results.

findDatasets(datasetType: Union[lsst.daf.butler.core.datasets.type.DatasetType, str], collections: Any, *, findFirst: bool = True) → lsst.daf.butler.registry.queries._results.ParentDatasetQueryResults¶

Find datasets using the data IDs identified by this query.

Parameters:	datasetType : `DatasetType` or `str` Dataset type or the name of one to search for. Must have dimensions that are a subset of `self.graph`. collections : `Any` An expression that fully or partially identifies the collections to search for the dataset, such as a `str`, `re.Pattern`, or iterable thereof. `...` can be used to return all collections. See Collection expressions for more information. findFirst : `bool`, optional If `True` (default), for each result data ID, only yield one `DatasetRef`, from the first collection in which a dataset of that dataset type appears (according to the order of `collections` passed in). If `True`, `collections` must not contain regular expressions and may not be `...`.
Returns:	datasets : `ParentDatasetQueryResults` A lazy-evaluation object representing dataset query results, iterable over `DatasetRef` objects. If `self.hasRecords()`, all nested data IDs in those dataset references will have records as well.
Raises:	ValueError Raised if `datasetType.dimensions.issubset(self.graph) is False`.

static fromScalar(dataId: lsst.daf.butler.core.dimensions._coordinate.DataCoordinate) → lsst.daf.butler.core.dimensions._dataCoordinateIterable._ScalarDataCoordinateIterable¶

Return a DataCoordinateIterable containing the single data ID.

Parameters:	dataId : `DataCoordinate` Data ID to adapt. Must be a true `DataCoordinate` instance, not an arbitrary mapping. No runtime checking is performed.
Returns:	iterable : `DataCoordinateIterable` A `DataCoordinateIterable` instance of unspecified (i.e. implementation-detail) subclass. Guaranteed to implement the `collections.abc.Sized` (i.e. `__len__`) and `collections.abc.Container` (i.e. `__contains__`) interfaces as well as that of `DataCoordinateIterable`.

hasFull() → bool¶

Indicate if all data IDs in this iterable identify all dimensions.

Not just required dimensions.

Returns:	state : `bool` If `True`, `all(d.hasFull() for d in iterable)` is guaranteed. If `False`, no guarantees are made.

hasRecords() → bool¶

Return whether all data IDs in this iterable contain records.

Returns:	state : `bool` If `True`, `all(d.hasRecords() for d in iterable)` is guaranteed. If `False`, no guarantees are made.

materialize() → Iterator[lsst.daf.butler.registry.queries._results.DataCoordinateQueryResults]¶

Insert this query’s results into a temporary table.

Returns:

context : typing.ContextManager [ DataCoordinateQueryResults ]: A context manager that ensures the temporary table is created and populated in __enter__ (returning a results object backed by that table), and dropped in __exit__. If self is already materialized, the context manager may do nothing (reflecting the fact that an outer context manager should already take care of everything else).

Notes

When using a very large result set to perform multiple queries (e.g. multiple calls to subset with different arguments, or even a single call to expanded), it may be much more efficient to start by materializing the query and only then performing the follow up queries. It may also be less efficient, depending on how well database engine’s query optimizer can simplify those particular follow-up queries and how efficiently it caches query results even when the are not explicitly inserted into a temporary table. See expanded and subset for examples.

subset(graph: Optional[lsst.daf.butler.core.dimensions._graph.DimensionGraph] = None, *, unique: bool = False) → lsst.daf.butler.registry.queries._results.DataCoordinateQueryResults¶

Return a results object containing a subset of the dimensions of this one, and/or a unique near-subset of its rows.

This method may involve actually executing database queries to fetch DimensionRecord objects.

Parameters:

graph : DimensionGraph, optional: Dimensions to include in the new results object. If None, self.graph is used.
unique : bool, optional: If True (False is default), the query should only return unique data IDs. This is implemented in the database; to obtain unique results via Python-side processing (which may be more efficient in some cases), use toSet to construct a DataCoordinateSet from this results object instead.

Returns:

results : DataCoordinateQueryResults: A results object corresponding to the given criteria. May be self if it already qualifies.

Notes

This method can only return a “near-subset” of the original result rows in general because of subtleties in how spatial overlaps are implemented; see Query.subset for more information.

When calling subset multiple times on the same very large result set, it may be much more efficient to call materialize first. For example:

dimensions1 = DimensionGraph(...)
dimensions2 = DimensionGraph(...)
with registry.queryDataIds(...).materialize() as tempDataIds:
    for dataId1 in tempDataIds.subset(
            graph=dimensions1,
            unique=True):
        ...
    for dataId2 in tempDataIds.subset(
            graph=dimensions2,
            unique=True):
        ...

toSequence() → lsst.daf.butler.core.dimensions._dataCoordinateIterable.DataCoordinateSequence¶

Transform this iterable into a DataCoordinateSequence.

Returns:	seq : `DataCoordinateSequence` A new `DatasetCoordinateSequence` with the same elements as `self`, in the same order. May be `self` if it is already a `DataCoordinateSequence`.

toSet() → lsst.daf.butler.core.dimensions._dataCoordinateIterable.DataCoordinateSet¶

Transform this iterable into a DataCoordinateSet.

Returns:	set : `DataCoordinateSet` A `DatasetCoordinateSet` instance with the same elements as `self`, after removing any duplicates. May be `self` if it is already a `DataCoordinateSet`.

Navigation

DataCoordinateQueryResults¶