Add Chromadb methods to your Rails Models. This is a model concern.

chromable.rb

# Add to model:
#  include Chromable
#  chroma do
#    hnsw_space :cosine
#    embedding :name
#    document :label
#    metadata :name
#  end
# Usage:
# Hint.upsert Hint.all
#       @hints = Hint.chroma_query "dogs", where: {name: {"$ne": "dogs"}}
# Implement own embedding service:       embeddings = EmbeddingsService.call texts
# I used https://github.com/michaelfeil/infinity

module Chromable
  extend ActiveSupport::Concern

  included do
    class_attribute :chroma_configuration
  end

  class_methods do
    def chroma(&block)
      self.chroma_configuration = ChromaConfiguration.new
      self.chroma_configuration.instance_eval(&block) if block_given?
    end

    def chroma_query query, results: 10, where: {}, where_document: {}, include: %w[documents]
      embedding = EmbeddingsService.call query

      col = chroma_collection

      col.query query_embeddings: [embedding[0]], results: results, where: where, where_document: where_document, include: include
    end

    def chroma_collection
      @@col ||= Chroma::Resources::Collection.get_or_create self.chroma_collection_name, {
        "hnsw:space": self.chroma_configuration.hnsw_space_param.to_s
      }
    end

    def chroma_delete
      Chroma::Resources::Collection.delete chroma_collection_name
    end

    def chroma_collection_name
      if Rails.env.test?
        "#{self.table_name}_test"
      else
        self.table_name
      end
    end

    def chroma_count
      chroma_collection.count
    end

    def chroma_delete ids: nil, where: {}, where_document: {}
      if ids.present?
        ids = ids.map {|i| i.to_s }
      end

      chroma_collection.delete ids: ids, where: where, where_document: where_document
    end

    def chroma_get(ids: nil, where: {}, sort: nil, limit: nil, offset: nil, page: nil, page_size: nil, where_document: {}, include: %w[documents])
      if ids.present?
        ids = ids.map {|i| i.to_s }
      end

      chroma_collection.get ids: ids, where: where, sort: sort, limit: limit, offset: offset, page: page, page_size: page_size, where_document: where_document, include: include
    end

    def chroma_upsert items
      texts = items.pluck self.chroma_configuration.embedding_name.to_sym

      embeddings = EmbeddingsService.call texts

      objs = items.map.with_index do |h, i|
        h.to_embedding embeddings[i]
      end

      chroma_collection.upsert objs
    end
  end

  def to_embedding embedding=nil
    embedding_hash = {id: id.to_s, embedding: embedding}

    if self.class.chroma_configuration
      embedding_hash.merge!(self.class.chroma_configuration.to_embedding_hash(self))
    end

    Chroma::Resources::Embedding.new **embedding_hash
  end

  class ChromaConfiguration
    attr_accessor :embedding_name, :document_name, :metadata_names, :hnsw_space_param

    def initialize
      self.hnsw_space_param = :l2
    end

    def embedding(name)
      self.embedding_name = name
    end

    def document(name)
      self.document_name = name
    end

    def hnsw_space(name)
      self.hnsw_space_param = name
    end

    def metadata(*names)
      self.metadata_names = names
    end

    def to_embedding_hash(model_instance)
      embedding_hash = {}

      if document_name
        embedding_hash[:document] = model_instance.send(document_name)
      end

      if metadata_names
        metadata_hash = {}
        metadata_names.each do |metadata_name|
          metadata_hash[metadata_name.to_s] = model_instance.send(metadata_name)
        end
        embedding_hash[:metadata] = metadata_hash
      end

      embedding_hash
    end
  end
end

I'm using the default chromadb settings, and my embedding size is 1024.

Ok I'll test it again.

I'm using the default chromadb settings, and my embedding size is 1024.

I've found the issue. Searching takes a lot of cpu resources, so if the server is constrained for cpu time searching will slow to a crawl (postgres and other services don't have this issue). There must be some optimization on Chroma's side to fix this.