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FabledScribe/src/scribe/models/embedding.py
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docs(models): the record-splitting rule gets a findable home — note 3163 (#3128 rec 9)
Spike #3128's fourth question was whether a "when does a record type earn its
own table" rule was worth writing down. It turned out to already exist, in
full, in the RuleEmbedding docstring — the only written statement of a rule
Scribe applies to every record type, sitting where nobody would look for it.

Promoted to note 3163, with the three grounds (scoping different in kind,
machine-written at volume, edge-or-event-not-document), the worked cases
across the whole schema, and the bill: what `rules` had to re-import after
leaving `notes`, including the two cells it left empty on purpose.

The docstring stays put — it is where the decision was made — and now points
at the note.
2026-08-28 13:11:02 -04:00

98 lines
4.6 KiB
Python

from datetime import datetime, timezone
from pgvector.sqlalchemy import Vector
from sqlalchemy import BigInteger, DateTime, ForeignKey, Integer, Text
from sqlalchemy.orm import Mapped, mapped_column
from scribe.models import Base
# bge-small-en-v1.5 produces 384-dim unit-normalized vectors. The column is a
# native pgvector `vector(384)` (see migration 0067) so similarity search runs
# as an indexed `ORDER BY embedding <=> :q LIMIT k` in Postgres rather than a
# full-table Python cosine scan.
EMBEDDING_DIM = 384
class NoteEmbedding(Base):
"""One embedding vector per CHUNK of a note (#280, migration 0077).
The model reads at most 512 tokens, so a single whole-document vector
permanently lost everything past ~400 words. A note now stores one row per
chunk of `embeddings.chunk_document`, and a query matches the note if it
matches ANY chunk — retrieval collapses rows to best-chunk-per-note.
A short note has exactly one row (chunk_index 0) whose text is the
historical `title\\nbody` shape.
"""
__tablename__ = "note_embeddings"
note_id: Mapped[int] = mapped_column(
Integer,
ForeignKey("notes.id", ondelete="CASCADE"),
primary_key=True,
)
chunk_index: Mapped[int] = mapped_column(Integer, primary_key=True)
user_id: Mapped[int] = mapped_column(Integer, nullable=False, index=True)
embedding: Mapped[list] = mapped_column(Vector(EMBEDDING_DIM), nullable=False)
# Exactly what this vector encodes — inspectable when a ranking surprises,
# and the hook for surfacing WHICH section matched, later.
chunk_text: Mapped[str] = mapped_column(Text, nullable=False)
# embeddings.CHUNKER_VERSION at write time. The startup backfill re-embeds
# any note whose rows carry a stale version — shape changes become a
# version bump instead of a table wipe.
chunker_version: Mapped[int] = mapped_column(Integer, nullable=False)
updated_at: Mapped[datetime] = mapped_column(
DateTime(timezone=True),
default=lambda: datetime.now(timezone.utc),
)
class RuleEmbedding(Base):
"""One embedding vector per CHUNK of a rule (milestone 307, note 3026).
A SIBLING of NoteEmbedding rather than a generalisation of it, decided
deliberately. The reasoning below turned out to be the only written
statement of a rule Scribe applies to every record type, so it is now also
NOTE 3163 — "When a record type earns its own table" — with the worked
cases and the cost of leaving `notes`. Read that before splitting a record
type off; this stays here because it is where the decision was made.
- The embedding ROW could have been made polymorphic. The SEARCH could not.
`semantic_search_notes` is a long function of Note-specific scoping —
the visibility clause, the supersession penalty, note_type/task_kind and
system filters — and a rule shares none of it. Rules scope by rulebook
ownership and project applicability instead.
- Generalising the row while still needing two searches is the worst of
both: a polymorphic key with referential integrity to neither table, on
the path every session start runs, to share four columns.
- What is genuinely common is BEHAVIOUR, not storage — get_embedding,
chunk_document, embedding_text and CHUNKER_VERSION are already free
functions and are reused as-is. Sharing those is the DRY win; sharing
the table would have been the DRY costume.
No `user_id`: NoteEmbedding carries one and its own search deliberately
ignores it (scoping on the note instead, or shared records become
unreachable). Rather than repeat a column that exists to be ignored, a
rule's reach is resolved by joining the rule.
"""
__tablename__ = "rule_embeddings"
rule_id: Mapped[int] = mapped_column(
BigInteger,
ForeignKey("rules.id", ondelete="CASCADE"),
primary_key=True,
)
chunk_index: Mapped[int] = mapped_column(Integer, primary_key=True)
embedding: Mapped[list] = mapped_column(Vector(EMBEDDING_DIM), nullable=False)
# Exactly what this vector encodes — inspectable when a ranking surprises.
# For a rule this is the trigger-first document, NOT the rule's `why`:
# `why` is dated incident narrative and would drag every rule toward one
# centroid (measured in note 2485).
chunk_text: Mapped[str] = mapped_column(Text, nullable=False)
chunker_version: Mapped[int] = mapped_column(Integer, nullable=False)
updated_at: Mapped[datetime] = mapped_column(
DateTime(timezone=True),
default=lambda: datetime.now(timezone.utc),
)