Hi all - I'd like some advice on how to write a rather complicated (for me, anyway) query and if there's any nifty Postgres features I can take advantage of in this situation. Imagine a database, if you will, used to store recipes. I have a recipes table:
RecipeId RecipeTitle RecipeRating
And an ingredients table:
RecipeId IngredientId Amount
When the user searches for a new pasta dish, the UI would generate a query something like this:
SELECT * FROM Recipes where RecipeTitle ilike '%pasta%';
I only need the data from the recipes table since I display a summary of the search results and don't load the full recipe until the user clicks on the link. This works great. However, I'm now in the process of implementing an ingredient blacklist. This means NEVER show me any recipes which have one of my blacklisted ingredients, as if I ingest any I will die a painful death. Or maybe my god will smite me or something. This table would look like:
UserId IngredientId
Ok, now the question. What's the best way to query for my pasta dish above while excluding any recipe that contains one or more of my blacklisted ingredients? I don't want to join in Ingredients because I'd then have a row for each ingredient of each recipe (which would cause me massive headache and redesign).. I thought about some weird nested query, but I'm concerned it might be slow (searching for recipes is the central feature of my site and must be fast, fast and fast). This basically boils down to some weird Cartesian product thing.
I am, however, willing to redesign the mechanism I store blacklisted ingredients with. I could store this as an array on the Users table, or anything else that might make things easier. Any advice on this?
