45 lines
1.8 KiB
Elixir
45 lines
1.8 KiB
Elixir
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defmodule RDF.Query.BGP.BlankNodeHandler do
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@moduledoc false
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alias RDF.BlankNode
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@blank_node_prefix "_:"
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@default_remove_bnode_query_variables Application.get_env(:rdf, :default_remove_bnode_query_variables, true)
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def preprocess(triple_patterns) do
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Enum.reduce(triple_patterns, {false, []}, fn
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original_triple_pattern, {had_blank_nodes, triple_patterns} ->
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{is_converted, triple_pattern} = convert_blank_nodes(original_triple_pattern)
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{had_blank_nodes || is_converted, [triple_pattern | triple_patterns]}
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end)
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end
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defp convert_blank_nodes({%BlankNode{} = s, %BlankNode{} = p, %BlankNode{} = o}), do: {true, {to_string(s), to_string(p), to_string(o)}}
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defp convert_blank_nodes({s, %BlankNode{} = p, %BlankNode{} = o}), do: {true, {s, to_string(p), to_string(o)}}
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defp convert_blank_nodes({%BlankNode{} = s, p, %BlankNode{} = o}), do: {true, {to_string(s), p, to_string(o)}}
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defp convert_blank_nodes({%BlankNode{} = s, %BlankNode{} = p, o}), do: {true, {to_string(s), to_string(p), o}}
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defp convert_blank_nodes({%BlankNode{} = s, p, o}), do: {true, {to_string(s), p, o}}
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defp convert_blank_nodes({s, %BlankNode{} = p, o}), do: {true, {s, to_string(p), o}}
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defp convert_blank_nodes({s, p, %BlankNode{} = o}), do: {true, {s, p, to_string(o)}}
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defp convert_blank_nodes(triple_pattern), do: {false, triple_pattern}
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def postprocess(solutions, has_blank_nodes, opts) do
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if has_blank_nodes and
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Keyword.get(opts, :remove_bnode_query_variables, @default_remove_bnode_query_variables) do
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Enum.map(solutions, &remove_blank_nodes/1)
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else
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solutions
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end
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end
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defp remove_blank_nodes(solution) do
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solution
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|> Enum.filter(fn
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{@blank_node_prefix <> _, _} -> false
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_ -> true
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end)
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|> Map.new
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end
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end
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