app/models.py

"""ORM model for the chunks table.

The `ts` column is a STORED generated tsvector (English config) derived from
`content`, so it stays in sync automatically and can back a GIN index.
"""
from __future__ import annotations

import uuid

from pgvector.sqlalchemy import Vector
from sqlalchemy import Computed, Integer, String, Text
from sqlalchemy.dialects.postgresql import TSVECTOR, UUID
from sqlalchemy.orm import Mapped, mapped_column

from app.db import Base

EMBEDDING_DIM = 384  # BAAI/bge-small-en-v1.5


class Chunk(Base):
    __tablename__ = "chunks"

    id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True), primary_key=True, default=uuid.uuid4
    )
    case_name: Mapped[str] = mapped_column(Text, nullable=False)
    chunk_index: Mapped[int] = mapped_column(Integer, nullable=False)
    content: Mapped[str] = mapped_column(Text, nullable=False)
    embedding: Mapped[list[float]] = mapped_column(Vector(EMBEDDING_DIM), nullable=False)

    # Stored generated tsvector — kept in sync with content by Postgres.
    ts: Mapped[str] = mapped_column(
        TSVECTOR,
        Computed("to_tsvector('english', content)", persisted=True),
        nullable=True,
    )

    def __repr__(self) -> str:  # pragma: no cover
        return f"<Chunk {self.case_name!r}#{self.chunk_index}>"