# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Project Overview

Materia is a commodity data analytics platform built on a modern data engineering stack. The project extracts agricultural commodity data from USDA PSD Online, transforms it through a layered SQL pipeline using SQLMesh, and stores it in DuckDB for analysis.

**Tech Stack:**
- Python 3.13 with `uv` package manager
- SQLMesh for SQL transformation and orchestration
- DuckDB as the analytical database
- Workspace structure with separate extract and transform packages

## Environment Setup

**Install dependencies:**
```bash
uv sync
```

**Setup pre-commit hooks:**
```bash
pre-commit install
```

**Add new dependencies:**
```bash
uv add <package-name>
```

## Project Structure

This is a uv workspace with three main components:

### 1. Extract Layer (`extract/`)
Contains extraction packages for pulling data from external sources.

- **`extract/psdonline/`**: Extracts USDA PSD commodity data from archives dating back to 2006
  - Entry point: `extract_psd` CLI command (defined in `extract/psdonline/src/psdonline/execute.py`)
  - Downloads monthly zip archives to `extract/psdonline/src/psdonline/data/`
  - Uses ETags to avoid re-downloading unchanged files

**Run extraction:**
```bash
extract_psd
```

### 2. Transform Layer (`transform/sqlmesh_materia/`)
SQLMesh project implementing a layered data architecture.

**Working directory:** All SQLMesh commands must be run from `transform/sqlmesh_materia/`

**Key commands:**
```bash
cd transform/sqlmesh_materia

# Plan changes (no prompts, auto-apply enabled in config)
sqlmesh plan

# Run tests
sqlmesh test

# Validate models
sqlmesh validate

# Run audits
sqlmesh audit

# Format SQL
sqlmesh format

# Start UI
sqlmesh ui
```

**Configuration:**
- Config: `transform/sqlmesh_materia/config.yaml`
- Default gateway: `dev` (uses `materia_dev.db`)
- Production gateway: `prod` (uses `materia_prod.db`)
- Auto-apply enabled, no interactive prompts
- DuckDB extensions: zipfs, httpfs, iceberg

### 3. Core Package (`src/materia/`)
Currently minimal; main logic resides in workspace packages.

## Data Architecture

SQLMesh models follow a strict 4-layer architecture defined in `transform/sqlmesh_materia/models/README.md`:

### Layer 1: Raw (`models/raw/`)
- **Purpose:** Immutable archive of source data
- **Pattern:** Directly reads from extraction outputs
- **Example:** `raw.psd_alldata` reads zip files using DuckDB's `read_csv('zip://...')` function
- **Grain:** Defines unique keys for each raw table

### Layer 2: Staging (`models/staging/`)
- **Purpose:** Apply schema, cast types, basic cleansing
- **Pattern:** `stg_[source]__[entity]`
- **Example:** `stg_psdalldata__commodity.sql` casts raw strings to proper types, joins lookup tables
- **Features:**
  - Deduplication using hash keys
  - Extracts metadata (ingest_date) from file paths
  - 1:1 relationship with raw sources

### Layer 3: Cleaned (`models/cleaned/`)
- **Purpose:** Integration, business logic, unified models
- **Pattern:** `cln_[entity]` or `cln_[vault_component]_[entity]`
- **Example:** `cln_psdalldata__commodity_pivoted.sql` pivots commodity attributes into columns

### Layer 4: Serving (`models/serving/`)
- **Purpose:** Analytics-ready models (star schema, aggregates)
- **Patterns:**
  - `dim_[entity]` for dimensions
  - `fct_[process]` for facts
  - `agg_[description]` for aggregates
  - `obt_[description]` for one-big-tables
- **Example:** `obt_commodity_metrics.sql` provides wide table for analysis

## Model Development

**Incremental models:**
- Use `INCREMENTAL_BY_TIME_RANGE` kind
- Define `time_column` (usually `ingest_date`)
- Filter with `WHERE time_column BETWEEN @start_ds AND @end_ds`

**Full refresh models:**
- Use `FULL` kind for small lookup tables and raw sources

**Model properties:**
- `grain`: Define unique key columns for data quality
- `start`: Historical backfill start date (project default: 2025-07-07)
- `cron`: Schedule (project default: '@daily')

## Linting and Formatting

**Run linting:**
```bash
ruff check .
```

**Auto-fix issues:**
```bash
ruff check --fix .
```

**Format code:**
```bash
ruff format .
```

Pre-commit hooks automatically run ruff on commits.

## Testing

**Run SQLMesh tests:**
```bash
cd transform/sqlmesh_materia
sqlmesh test
```

**Run Python tests (if configured):**
```bash
pytest --cov=./ --cov-report=xml
```

## CI/CD Pipeline

GitLab CI runs three stages (`.gitlab-ci.yml`):

1. **Lint:** Runs ruff check and format validation, plus pip-audit
2. **Test:** Runs pytest with coverage
3. **Build:** Creates distribution packages (on tags only)

## Key Design Patterns

**Raw data ingestion:**
- DuckDB reads directly from zip archives using `read_csv('zip://...')`
- `filename=true` captures source file path for metadata
- `union_by_name=true` handles schema evolution

**Deduplication:**
- Use `hash()` function to create unique keys
- Use `any_value()` with `GROUP BY hkey` to deduplicate
- Preserve all metadata in hash key for change detection

**Date handling:**
- Extract ingest dates from file paths: `make_date(split(filename, '/')[-4]::int, split(filename, '/')[-3]::int, 1)`
- Calculate market dates: `last_day(make_date(market_year, month, 1))`

**SQLMesh best practices:**
- Always define `grain` for data quality validation
- Use meaningful model names following layer conventions
- Leverage SQLMesh's built-in time macros (`@start_ds`, `@end_ds`)
- Keep raw layer thin, push transformations to staging+

## Database Location

- **Dev database:** `materia_dev.db` (13GB, in project root)
- **Prod database:** `materia_prod.db` (not yet created)

Note: The dev database is large and should not be committed to git (.gitignore already configured).
- Can you memorize what we discussed