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# frozen_string_literal: true
class NextTraversalIdsSiblingFunction < Gitlab::Database::Migration[1.0]
include Gitlab::Database::SchemaHelpers
FUNCTION_NAME = 'next_traversal_ids_sibling'
def up
# Given array [1,2,3,4,5], concatenate the first part of the array [1,2,3,4]
# with the last element in the array (5) after being incremented ([6]).
#
# [1,2,3,4,5] => [1,2,3,4,6]
execute(<<~SQL)
CREATE OR REPLACE FUNCTION #{FUNCTION_NAME}(traversal_ids INT[]) RETURNS INT[]
AS $$
BEGIN
return traversal_ids[1:array_length(traversal_ids, 1)-1] ||
ARRAY[traversal_ids[array_length(traversal_ids, 1)]+1];
END;
$$
LANGUAGE plpgsql
IMMUTABLE
RETURNS NULL ON NULL INPUT;
SQL
end
def down
execute("DROP FUNCTION #{FUNCTION_NAME}(traversal_ids INT[])")
end
end
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