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I need to store a list of items and that list belongs to a single user. The lists are going to be huge, so this has to be done as efficiently as possible. The lists also have to be modifiable to a small degree (able to add new items).

This is my (possible) solution:
Have a table items, where we store the data of our items. Table lists contains info about our lists (name, user_id etc). Table lists_lengths contains our lists lengths, e.g:

list_id | item_id_start | item_id_end
------------------------------------
1       | 1             | 200
2       | 201           | 220
1       | 221           | 300

If the lists get a lot of modifications, this might end up being a poor design though. Is this good or is the blatant list_id in the items table just the way to go?

  • List 1 contains 1-200 and 221-300, correct? And no item shows up in two lists, correct? – Rick James Apr 7 '15 at 21:57
  • How big is "huge?" Thousands, millions, billions? – Michael Green Apr 8 '15 at 1:51
  • How's about you do it the standard way, test its performance, then tweak if necessary? – Neil McGuigan Apr 8 '15 at 7:41
  • Correct. Each list can contain up to 500,000 items. Each user is going to have 5-20 of them. There's enough users that optimization is something that I'm worried about. – Oskar Apr 8 '15 at 7:46
  • What would the "standard" way be? list_id in items table? I might just go with that and restructure if issues arise. – Oskar Apr 8 '15 at 8:06
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Once the table gets really big, you will find that looking up an item to find out what list it is in becomes painfully slow.

I discuss that, plus provide efficient code, in my blog on ip-ranges. Your use case (non-overlapping ranges of items "owned" by various "lists") seems to be the same problem.

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