---
phase: 02-rust-dict-export-rename
plan: 01
subsystem: rust-bindings
tags: [pyo3, dict-export, microsecond-timestamps, rename]

requires:
  - phase: 01-test-hygiene
    provides: "Clean check-full baseline before bulk renames"
provides:
  - "Rust dict export emits truthful _us keys for microsecond timestamp values"
  - "Source-of-truth naming that Python (Phase 4) and ClickHouse (Phase 3) will follow"
affects: [03-clickhouse-schema-rename, 04-python-sql-rename]

tech-stack:
  added: []
  patterns:
    ["Truthful _us suffix for microsecond timestamp keys in PyO3 dict export"]

key-files:
  created: []
  modified: [src/helpers.rs]

key-decisions:
  - "No value changes needed -- bar.open_time/close_time were already raw microseconds"

patterns-established:
  - "Timestamp dict keys use _us suffix when values are microseconds"

requirements-completed: [RENAME-03]

duration: 2min
completed: 2026-03-25
---

# Phase 02 Plan 01: Rust Dict Export Rename Summary

**Renamed open_time_ms/close_time_ms to open_time_us/close_time_us in helpers.rs PyO3 dict export -- truthful keys matching actual microsecond values**

## Performance

- **Duration:** 2 min
- **Started:** 2026-03-25T01:40:30Z
- **Completed:** 2026-03-25T01:53:00Z
- **Tasks:** 1
- **Files modified:** 1

## Accomplishments

- Renamed `open_time_ms` -> `open_time_us` and `close_time_ms` -> `close_time_us` in `opendeviationbar_to_dict()`
- Updated comment from "column names stay \_ms until CH schema migration" to "truthful_us keys"
- Rebuilt Python extension via `maturin develop` (v13.52.0)
- Verified zero `_ms` timestamp key references remain in helpers.rs

## Task Commits

Each task was committed atomically:

1. **Task 1: Rename dict export keys from \_ms to \_us in helpers.rs** - `8e7d31a` (feat)

## Files Created/Modified

- `src/helpers.rs` - Changed dict key strings and comment for timestamp fields in `opendeviationbar_to_dict()`

## Decisions Made

None - followed plan as specified. Values were already microseconds; only key strings and comment changed.

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered

- `cargo test` on the PyO3 root crate fails with linker errors (pre-existing, not caused by this change). Standard project test command (`cargo nextest run --workspace --exclude opendeviationbar-py`) excludes the root crate. The workspace crates (where all logic lives) are unaffected by dict key string renames.

## User Setup Required

None - no external service configuration required.

## Next Phase Readiness

- Rust dict export now emits `_us` keys, establishing the source-of-truth naming
- Phase 03 (ClickHouse schema rename) and Phase 04 (Python/SQL rename) can proceed
- Python consumers will need updating to read `open_time_us`/`close_time_us` instead of `_ms` variants

---

_Phase: 02-rust-dict-export-rename_
_Completed: 2026-03-25_
