Sometimes, you want to restrict which items are returned by a query. For example, you only want the items written before 2024, that have “manifesto” in the title, or that were authored by the “John von Neumann.”

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What is a “wishlist”

Metadata filters are easy if the data that you’re working with is very homogenous, i.e., everything has the same metadata fields. Sadly, few real-world datasets are. The wishlist is a way to specify metadata filters that get applied on a best-effort basis. For example, if you want documents authored by John von Neumann. You can just set the author filter to “John von Neumann”. Amazingly, this will work even if no items have the author field, but instead have a creator, created_by, authored_by, or author_ fields. This doesn’t just make it easier for humans to write metadata filters, it is easier for LLMs too. You can let an LLM hallucinate any parameters, and we match it to metadata that actually exists. No knowledge about the data is required.

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Writing a wishlist

{
    "$and": [
        'lang': {'$eq': 'en'},
        'topic': {'$in': ['thermodynamics', 'radiation']},
        'time_added': {'$gte': '2023-01-01T00:00:00Z', '$lt': '2024-01-01T00:00:00Z'}
    ]
}
Here, only objects in that fulfill all three conditions will be returned. You have the following logic operators:
  • $and: all conditions must be true
  • $or: at least one condition must be true
  • $not: the condition must be false
You can also use the following comparison operators:
  • $eq: equal to
  • $ne: not equal to
  • $gt: greater than
  • $gte: greater than or equal to
  • $lt: less than
  • $lte: less than or equal to
  • $in: in a list
  • $nin: not in a list
  • $exists: either “true” or “false”
If there are multiple conflicting conditions, the first one will be used.

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Enforcing metadata filters

In some cases, for example when using metadata distinguish between users, it makes sense to enforce a filter. To do that, you can set $strict to true in the metadata filter. 
{
    "$and": [
        'lang': {'$eq': 'en', '$strict': true},
        'topic': {'$in': ['thermodynamics', 'radiation']},
        'time_added': {'$gte': '2023-01-01T00:00:00Z', '$lt': '2024-01-01T00:00:00Z'}
    ],

}