PGVECTOR-ELIXIR extension: example with the classification of data using OpenAI

# 1. An example of a usage of `pgvector`.

We want to classify a dataset using "a certain distance" among the rows. The idea is to send the data to the (rate limited) [OpenAI api endpoint](https://platform.openai.com/docs/api-reference/introduction), get in return tokens for each row, store as a vector, and then apply a distance sorting query between rows based on this vector field.

Note: the distance operator `<=>` is also used with `PostGIS`.

[](https://www.crunchydata.com/blog/whats-postgres-got-to-do-with-ai)

# 2. `pgvector` and indexes

[](https://www.crunchydata.com/blog/pgvector-performance-for-developers)

A summary of the post above, as found in the post!:
`pgvector `provides a comprehensive, performant, and 100% open source database for vector data. As a developer, the key to getting performance from `pgvector` are:

- Ensure your query is using the indexes
- Ensure your indexes have the optimal list size
- Ensure you have enough memory for the index