Sydney Runkle d120f127ca refactor(delta-channel): plain SELECT WHERE replaces recursive CTE ...

The recursive CTE was bottlenecked by a JSON-expression join
(`bl.version = checkpoint->'channel_versions'->>bl.channel`) that the
planner could not index, producing an O(ancestors x blobs) nested-loop.
At depth 1000 it ran ~275 ms and removed ~2M filter rows; the recursion
itself was 2.4 ms.

Switch to three plain indexed SELECTs per delta channel
(checkpoints, checkpoint_writes, checkpoint_blobs); a pure helper on
BasePostgresSaver walks the parent chain and assembles
DeltaChannelWrites. Sync (__init__.py) and async (aio.py) each own
their three-roundtrip I/O wrappers.

Bench numbers (notes/delta_channel_query_bench.md): 3x at depth 50,
15x at depth 200, ~100x at depth 1000. Plain over-fetches sibling rows
when the thread branches but still wins at every realistic depth on
both local and remote postgres.

Multi-channel coalescing dropped — reconstruction is per-channel now.
Same shape as InMemorySaver. Can come back as a SQL-level
optimization later if needed.

2026-04-23 08:21:00 -04:00

..

delta_channel_query_bench.md

refactor(delta-channel): plain SELECT WHERE replaces recursive CTE

2026-04-23 08:21:00 -04:00