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This paper proposes a category- and selection-enabled nearest neighbor join (NNJ) between relation r and relation s , with similarity on T and support for category attributes C and selection predicate θ . Our solution does not suffer from redundant fetches and index false hits , which are the main performance bottlenecks of current nearest neighbor join techniques. A category-enabled NNJ leverages the category attributes C for query evaluation. For example, the categories of relation r can be used to limit relation s accessed at most once. Solutions that are not category-enabled must process each category independently and end up fetching, either from disk or memory, the blocks of the input relations multiple times. A selection-enabled NNJ performs well independent of whether the DBMS optimizer pushes the selection down or evaluates it on the fly. In contrast, index-based solutions suffer from many index false hits or end up in an expensive nested loop. Our solution does not constrain the physical design, and is efficient for row- as well as column-stores. Current solutions for column-stores use late materialization, which is only efficient if the data is clustered on the category attributes C . Our evaluation algorithm finds, for each outer tuple r , the inner tuples that satisfy the equality on the category and have the smallest distance to r with only one scan of both inputs. We experimentally evaluate our solution using a data warehouse that manages analyses of animal feeds.

In this chapter, we present a series of country case studies, addressing specific challenges of reducing ammonia emissions and managing nitrogen on farm and field scale. Section 8.1 introduces nitrogen management activities in an intensively farmed region of Italy, while Sect. 8.2 addresses aspects of animal feed in Swiss pig farming. The following Sect. (8.3) illustrates N management in cattle and poultry operations in Switzerland. The assessment of ammonia abatement cost in dairy farming in the Russian Federation is covered in Sect. 8.4, with Sect. 8.5 discussing the costs of adoption of low ammonia emission slurry application methods on grassland in Ireland. A further case study on slurry application addresses the costs incurred by the trailing hose technique and by slurry dilution with water under Swiss frame conditions (Sect. 8.6). Section 8.7 highlights the estimated cost of abating volatilized ammonia from urea by urease inhibitors in the EU, and finally Sect. 8.8 discusses potential N2O reduction associated with the use of urease inhibitors in Spain (Authors of this section: Stefan Reis1,2, Mark A. Sutton1, Clare Howard1,3 (1) NERC Centre for Ecology & Hydrology, Bush Estate, Penicuik, EH26 0QB, UK; (2) Knowledge Spa, University of Exeter Medical School, Truro, TR1 3HD, UK; (3) School of Geosciences, University of Edinburgh, Institute of Geography, Drummond Street, Edinburgh, EH8 9XP, UK).