pgvectorscale is easy to add onto pgvector

Wed, 28 May 2025 17:12:53 -0000

I was surprised how easy it was to include pgvectorscale to your instance.

In order to add to my multi-collection AI app. It was three lines.

CREATE EXTENSION IF NOT EXISTS vectorscale CASCADE;
CREATE INDEX document_embedding_idx ON document_embedding
USING diskann (embedding vector_cosine_ops);

That is unless you do what I did and didn't hard specify your embedding limit in your vector data type.

My original setup

-- CREATE EXTENSION IF NOT EXISTS vector;
CREATE TABLE QuoteEmbeddings (
    id SERIAL PRIMARY KEY,
    content_item_id INTEGER NOT NULL,
    content_snippet TEXT NOT NULL,
    embedding vector NOT NULL,
    CONSTRAINT fk_content_item
      FOREIGN KEY(content_item_id)
   REFERENCES ContentItem(id)
      ON DELETE CASCADE
);

This would produce Too many dimensions to index (max is 16000) regardless of the size of the dimensions.

My fix was to be explicit.

-- Table 2: QuoteEmbeddings
 CREATE TABLE QuoteEmbeddings (
     id SERIAL PRIMARY KEY,
     content_item_id INTEGER NOT NULL,
     content_snippet TEXT NOT NULL,
     embedding vector(768) NOT NULL, -- NOTE the (768)
     CONSTRAINT fk_content_item
       FOREIGN KEY(content_item_id)
       REFERENCES ContentItem(id)
       ON DELETE CASCADE
 );

Too bad i realized that after I dropped all my tables and will need to reindex them.