-- Restore the legacy 1536-dimensional column. Embeddings with any other
-- dimension cannot be represented and are cleared during rollback.
ALTER TABLE article_embeddings
  ALTER COLUMN vector_embedding TYPE vector(1536)
  USING CASE
    WHEN vector_embedding IS NULL THEN NULL
    WHEN vector_dims(vector_embedding) = 1536 THEN vector_embedding::vector(1536)
    ELSE NULL
  END;

CREATE INDEX IF NOT EXISTS idx_article_embeddings_vector
  ON article_embeddings USING ivfflat (vector_embedding vector_cosine_ops)
  WITH (lists = 100);