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DM-29737: Perform a brute-force search if binary search fails #580

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Apr 15, 2021
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DM-29737: Perform a brute-force search if binary search fails #580

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24 changes: 19 additions & 5 deletions include/lsst/afw/table/Catalog.h
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Original file line number Diff line number Diff line change
Expand Up @@ -608,7 +608,9 @@ class CatalogT {
* In Python, this method returns a Record, not an iterator.
*
* @note The catalog must be sorted in ascending order according to the given key
* before calling find (i.e. isSorted(key) must be true).
* before calling find (i.e. isSorted(key) must be true) for maximal efficiency.
* If the value searched for is not found, it assumes that the catalog is unsorted
* and performs a brute-force search instead of failing immediately.
*
* Returns end() if the Record cannot be found.
*/
Expand Down Expand Up @@ -758,9 +760,15 @@ typename CatalogT<RecordT>::iterator CatalogT<RecordT>::find(typename Field<T>::
detail::KeyExtractionFunctor<RecordT, T> f = {key};
// Iterator adaptor that makes a CatalogT iterator work like an iterator over field values.
typedef boost::transform_iterator<detail::KeyExtractionFunctor<RecordT, T>, iterator> SearchIter;
// Use binary search for log n search; requires sorted table.
// Try binary search for log n search assuming the table is sorted.
// If the search is unsuccessful, try a brute-force search before quitting.
SearchIter i = std::lower_bound(SearchIter(begin(), f), SearchIter(end(), f), value);
if (i.base() == end() || *i != value) return end();
if (i.base() == end() || *i != value)
{
i = std::find(SearchIter(begin(), f), SearchIter(end(), f), value);
if (i.base() == end() || *i != value)
return end();
}
return i.base();
}

Expand All @@ -771,9 +779,15 @@ typename CatalogT<RecordT>::const_iterator CatalogT<RecordT>::find(typename Fiel
detail::KeyExtractionFunctor<RecordT, T> f = {key};
// Iterator adaptor that makes a CatalogT iterator work like an iterator over field values.
typedef boost::transform_iterator<detail::KeyExtractionFunctor<RecordT, T>, const_iterator> SearchIter;
// Use binary search for log n search; requires sorted table.
// Try binary search for log n search assuming the table is sorted.
// If the search is unsuccessful, try a brute-force search before quitting.
SearchIter i = std::lower_bound(SearchIter(begin(), f), SearchIter(end(), f), value);
if (i.base() == end() || *i != value) return end();
if (i.base() == end() || *i != value)
{
i = std::find(SearchIter(begin(), f), SearchIter(end(), f), value);
if (i.base() == end() || *i != value)
return end();
}
return i.base();
}

Expand Down