What data types does pgvector provide and how do you define vector columns?

pgvector introduces several new data types to PostgreSQL for storing vector data. The primary type is vector, with additional types for half-precision and binary vectors added in later releases.

-- Basic vector column (fixed dimensions)
CREATE TABLE documents (
    id         BIGSERIAL PRIMARY KEY,
    content    TEXT,
    embedding  VECTOR(1536)    -- 1536-dim for text-embedding-3-small
);

-- Half-precision to save storage (2x space reduction)
CREATE TABLE documents_small (
    id         BIGSERIAL PRIMARY KEY,
    embedding  HALFVEC(1536)
);

-- Binary vectors (very compact; special distance operators)
CREATE TABLE binary_items (
    id         BIGSERIAL PRIMARY KEY,
    embedding  BIT(1536)
);

-- Variable dimensions (no dimension constraint)
CREATE TABLE flexible (
    id         BIGSERIAL PRIMARY KEY,
    embedding  VECTOR         -- accepts any dimension
);
-- NOTE: indexes on variable-dim columns require expression/partial indexes

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