Phase 02 Plan 01: Train/Test Split Infrastructure Summary

Stratified 80/20 train/test split with sklearn, handling sparse debit account classes, plus embedding model metadata table

Performance

• Duration: 4 min
• Started: 2026-02-20T11:24:34Z
• Completed: 2026-02-20T11:28:40Z
• Tasks: 3
• Files modified: 4

Accomplishments

• Added is_test_set BOOLEAN column to line_item table for clean train/test separation
• Created embedding_model_config table with 3 model configurations (Google, Jina, MiniLM)
• Implemented stratified train/test split module with sklearn handling sparse classes
• Applied split: 4862 train (80%), 1216 test (20%) items with proportional debit account distribution

Task Commits

Each task was committed atomically:

1. Task 1: Add schema for train/test split and model metadata - 5ca209e0 (feat)
2. Task 2: Create train/test split module - 653c0aab (feat)
3. Task 3: Apply schema migration and execute split - f9b9ddaf (fix)

Files Created/Modified

• init.sql - Added is_test_set column and embedding_model_config table
• migrations/001_train_test_split.sql - Migration script for existing database
• src/evaluation/__init__.py - Evaluation package exports
• src/evaluation/train_test_split.py - Stratified split with sparse class handling

Decisions Made

• Used sklearn stratified split to ensure proportional debit account representation in both train and test sets
• Sparse debit account classes (only 1 member) are randomly assigned at test_size probability since sklearn requires 2+ members
• Converted numpy int64 to native Python int for psycopg3 compatibility (mixed types not allowed)

Deviations from Plan

Auto-fixed Issues

1. [Rule 1 - Bug] Fixed stratified split for sparse classes

• Found during: Task 3 (Apply schema migration and execute split)
• Issue: sklearn.train_test_split requires at least 2 members per class for stratification, but 5 debit accounts had only 1 member
• Fix: Separate sparse classes, assign randomly at test_size probability, then merge with stratified results
• Files modified: src/evaluation/train_test_split.py
• Verification: Split executed successfully with 4862 train, 1216 test
• Committed in: f9b9ddaf

2. [Rule 1 - Bug] Fixed numpy int64 type mismatch

• Found during: Task 3 (Apply schema migration and execute split)
• Issue: psycopg3 cannot dump lists of mixed types (int and int64)
• Fix: Convert all IDs to native Python int before passing to SQL
• Files modified: src/evaluation/train_test_split.py
• Verification: UPDATE statement executed successfully
• Committed in: f9b9ddaf

Total deviations: 2 auto-fixed (2 bugs) Impact on plan: Both fixes required for correct execution. No scope creep.

Issues Encountered

None beyond the auto-fixed bugs above.

User Setup Required

None - no external service configuration required.

Next Phase Readiness

• Train/test split complete with 4862 train, 1216 test items
• Both sets have proportional debit account representation (66 unique in train, 57 in test)
• Ready for Phase 02-02: embedding generation with clean evaluation separation
• Model metadata stored in embedding_model_config for runtime lookup

Phase: 02-embedding-generation Completed: 2026-02-20

Self-Check: PASSED

• init.sql exists
• migrations/001_train_test_split.sql exists
• src/evaluation/init.py exists
• src/evaluation/train_test_split.py exists
• Commit 5ca209e0 exists (Task 1)
• Commit 653c0aab exists (Task 2)
• Commit f9b9ddaf exists (Task 3)
• Database has is_test_set column with 80/20 split applied