DimensionRecordQueryResults¶
- class lsst.daf.butler.registry.queries.DimensionRecordQueryResults¶
Bases:
Iterable
[DimensionRecord
]An interface for objects that represent the results of queries for dimension records.
Methods Summary
any
(*[, execute, exact])Test whether this query returns any results.
count
(*[, exact])Count the number of rows this query would return.
Return human-readable messages that may help explain why the query yields no results.
limit
(limit[, offset])Make the iterator return limited number of records.
order_by
(*args)Make the iterator return ordered result.
Methods Documentation
- abstract any(*, execute: bool = True, exact: bool = True) bool ¶
Test whether this query returns any results.
- Parameters:
- execute
bool
, optional If
True
, execute at least aLIMIT 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. IfFalse
, the returned result does not account for post-query filtering, and hence may beTrue
even when all result rows would be filtered out.
- execute
- Returns:
- abstract count(*, exact: bool = True) int ¶
Count the number of rows this query would return.
- Parameters:
- Returns:
- count
int
The number of rows the query would return, or an upper bound if
exact=False
.
- count
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.
- abstract 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.
- messages
Notes
Messages related to post-query filtering are only available if the iterator has been exhausted, or if
any
orcount
was already called (withexact=True
for the latter two).This method first yields messages that are generated while the query is being built or filtered, but may then proceed to diagnostics generated by performing what should be inexpensive follow-up queries. Callers can short-circuit this at any time by simply not iterating further.
- abstract limit(limit: int, offset: int | None = None) DimensionRecordQueryResults ¶
Make the iterator return limited number of records.
- Parameters:
- Returns:
- result
DimensionRecordQueryResults
Returns
self
instance which is updated to return limited set of records.
- result
Notes
This method can modify the iterator in place and return the same instance. Normally this method is used together with
order_by
method.
- abstract order_by(*args: str) DimensionRecordQueryResults ¶
Make the iterator return ordered result.
- Parameters:
- *args
str
Names of the columns/dimensions to use for ordering. Column name can be prefixed with minus (
-
) to use descending ordering.
- *args
- Returns:
- result
DimensionRecordQueryResults
Returns
self
instance which is updated to return ordered result.
- result
Notes
This method can modify the iterator in place and return the same instance.