Genre Database Optimization

Book Inventroy Database

# For databases that each item might have more than one tags like genres. 
# It is not an optimal solution to append appropriate genres to each items seperately. For example; when we search for adventure novels,
# the database nelow will firts loop through each book and then each genre it contains which will give a O(N^2).

{
  "novels" : {
      "The Lord of The Rings" : {
        "author" : "JRR Tolkien",
        "genre" : ["Fantasy", "Adventure"]
      },
      "The Godfather" : {
        "author" : "Marco Puzo",
        "genre" : ["Crime", "Thriller"]
      }
      "Corleone Family" : {
        "author" : "Ed Falco",
        "genre" : ["Crime", "Thriller"]
      }
      "Childhood's End" : {
        "author" : "Arthur C. Clarke",
        "genres" : "Science Fiction", "Adventure"
      }
    }
}

# The optimal approach for this situation is assigning a seperate parent "genre" 
# property that contains genres as keys and books as values like below format. 
# This will give a much faster search result with O(N).

{
	"novels" : {
		"The Lord of The Rings" : {
			"author" : "JRR Tolkien",
		},
		"The Godfather" : {
			"author" : "Marco Puzo",
		}
		"Corleone Family" : {
			"author" : "Ed Falco",
		}
		"Childhood's End" : {
			"author" : "Arthur C. Clarke",
		}
	}
	
	"genres" : {
		"Fantasy" : ["The Lord of The Rings"],
		"Adventure" : ["The Lord of The Rings", "Childhood's End"],
		"Crime" : ["The Godfather", "Corleone Family"],
		"Thriller" : ["The Godfather","Corleone Family"],
		"Science Fiction" : ["Childhood's End"]
	} 
}