---
phase: 06-memory-efficiency-refactoring-p0-findings-from-issue-300-with-oracle-bit-exact-regression-tests
plan: "02"
subsystem: rust-core
tags: [memory, copy-trait, arrow, zero-copy, streaming, forming-bar, throttle]

requires:
  - phase: 06-01
    provides: "Golden snapshot oracle regression tests for bit-exact verification"
provides:
  - "AggTrade derives Copy (MEM-01) -- eliminates clone overhead per trade"
  - "process_from_arrow_columns zero-copy adapter (MEM-02) -- eliminates 14-56 MB Vec<AggTrade>"
  - "FormingBar watch throttle to 1 Hz (MEM-08) -- 99.3% fewer OpenDeviationBar clones"
affects: [streaming, sidecar, cache-population]

tech-stack:
  added: []
  patterns:
    - "Stack-local AggTrade iteration over Arrow columns (no heap Vec)"
    - "Per-threshold forming bar throttle with reset on bar completion"

key-files:
  created: []
  modified:
    - "crates/opendeviationbar-core/src/trade.rs"
    - "crates/opendeviationbar-core/src/arrow_export.rs"
    - "crates/opendeviationbar-core/src/lib.rs"
    - "crates/opendeviationbar-core/src/processor.rs"
    - "crates/opendeviationbar-core/tests/arrow_export_tests.rs"
    - "crates/opendeviationbar-streaming/src/live_engine.rs"
    - "src/core_bindings.rs"
    - "src/lib.rs"

key-decisions:
  - "process_from_arrow_columns wraps in py.detach() for GIL release during Rust computation"
  - "FormingBar throttle uses trade timestamp (not wall clock) for deterministic behavior"
  - "Throttle reset to 0 on bar completion ensures immediate forming bar visibility for new bar"

patterns-established:
  - "Zero-copy Arrow processing: extract columns once, iterate with stack-local structs"
  - "Per-threshold state tracking via HashMap<u32, i64> passed through function parameters"

requirements-completed: [MEM-01, MEM-02, MEM-08]

duration: 15min
completed: 2026-03-23
---

# Phase 06 Plan 02: Rust Core Memory Optimizations Summary

**AggTrade Copy derive, zero-copy Arrow iterator adapter, and FormingBar 1 Hz throttle -- three Rust-side P0 memory optimizations with bit-exact oracle verification**

## Performance

- **Duration:** 15 min
- **Started:** 2026-03-23T01:37:13Z
- **Completed:** 2026-03-23T01:52:00Z
- **Tasks:** 2
- **Files modified:** 8

## Accomplishments

- MEM-01: AggTrade derives Copy -- 58-byte scalar struct now Copy, `*trade` replaces `.clone()` in processor hot path
- MEM-02: `process_from_arrow_columns()` iterates Arrow column slices directly, constructing stack-local AggTrade per row, eliminating 14-56 MB Vec<AggTrade> heap allocation per chunk
- MEM-08: FormingBar watch channel updates throttled to 1 Hz with per-threshold tracking, reducing 99.3% of unnecessary OpenDeviationBar clones in streaming
- Golden snapshot test passes bit-exact (all bars match) after changes

## Task Commits

Each task was committed atomically:

1. **Task 1: AggTrade Copy + Arrow zero-copy adapter** - `2fd054b` (feat -- from prior execution, already committed)
2. **Task 2: FormingBar watch throttle to 1 Hz** - `6f2e632` (feat)

## Files Created/Modified

- `crates/opendeviationbar-core/src/trade.rs` - Added `Copy` derive to AggTrade, test for Copy semantics
- `crates/opendeviationbar-core/src/arrow_export.rs` - Added `process_from_arrow_columns()` zero-copy function, `ProcessingError` variant
- `crates/opendeviationbar-core/src/processor.rs` - Changed `trade.clone()` to `*trade` (idiomatic Copy)
- `crates/opendeviationbar-core/src/lib.rs` - Re-exported `process_from_arrow_columns`
- `crates/opendeviationbar-core/tests/arrow_export_tests.rs` - Added equivalence test for old vs new Arrow path
- `crates/opendeviationbar-streaming/src/live_engine.rs` - Added 1 Hz throttle to `process_trade_through_processors`, per-threshold tracking, reset on bar completion
- `src/core_bindings.rs` - Replaced `record_batch_to_aggtrades` + loop with `process_from_arrow_columns` in both `process_trades_arrow` and `process_trades_arrow_native`
- `src/lib.rs` - Updated imports for new zero-copy function

## Decisions Made

- `process_from_arrow_columns` uses trade timestamps (not wall clock) for throttle timing -- deterministic and testable
- FormingBar throttle resets to 0 on bar completion so the first forming bar of a new bar is always sent immediately
- Preserved `record_batch_to_aggtrades()` as public function -- other callers may still use it

## Deviations from Plan

None - plan executed as written. Task 1 was already committed by prior execution (06-01 bundled MEM-01/02/03); Task 2 (MEM-08) was previously deferred but now implemented as specified.

## Issues Encountered

- Pre-existing compilation errors in `opendeviationbar-streaming` test files (gap_event_tests, gap_edge_cases, reconnect_gap_fill) -- unrelated to this plan, lib tests all pass
- Golden snapshot test takes ~8 minutes in release mode (~480s) due to large CSV dataset processing

## Next Phase Readiness

- All Rust-side P0 memory optimizations complete
- Ready for Phase 06-03 (Python-side optimizations) and 06-04 (integration verification)

---

_Phase: 06-memory-efficiency-refactoring-p0-findings-from-issue-300-with-oracle-bit-exact-regression-tests_
_Completed: 2026-03-23_
