A 1536-dimension vector spelled out as JSON decimals is ~31 KB. The same
numbers packed as float32 are 6,144 bytes, and the whole bank is read on
every turn, so those bytes are paid over and over.
It is a format change, not a precision trade: the endpoints compute in
float32 and render that into JSON, so converting back recovers the original
bits exactly. Nothing is re-embedded and no API call is made -- migration 38
is a pure repack of what is already stored.
Unlike migrations 36 and 37 this backfill cannot be expressed in portable
SQL, so it comes through Python, batched, and pays a one-time read of every
vector to stop paying three megabytes a turn.
The JSON column stays, still written through set_vector, so a rollback finds
the vectors intact. Reading from the blob comes next; a follow-up migration
drops the old column once that is verified.
Migration SQL can now be a {dialect: sql} map -- BLOB and BYTEA have no
common spelling, and every Postgres deploy replays this one.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015CYEJKobJ2Re4Dv7qUoSA7
Both egress blowouts this project has had were one query fetching a column
nobody read, and a statement count would have shown nothing wrong in either.
So the meter counts bytes, at the DBAPI cursor -- everything that crosses
that line crossed the wire.
tools/stress_session.py drives a production-shaped adventure through the real
routes with only the network faked. It reproduces both figures measured
directly on production: 426.7 kB for a 200-action page load against 423 KB,
and 3,258.7 kB for one turn against 3,153 kB.
The memory bank is on by default, which is the whole point -- the previous
harness ran without an embedding model, so retrieval returned early and the
heaviest read in a turn never happened. --no-embeddings reproduces that
deliberately, and the gap is 29x.
It also turned up two callers the production SQL could not see: run_post_turn
walks the whole bank again every turn, and Insights pays for it a third time.
A played turn costs ~6.4 MB, not 3.2.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015CYEJKobJ2Re4Dv7qUoSA7
