Initialize Warehouse Schema

Generate a comprehensive, user-editable schema reference file for the data warehouse.

Scripts: ../analyzing-data/scripts/ — All CLI commands below are relative to the analyzing-data skill's directory. Before running any scripts/cli.py command, cd to ../analyzing-data/ relative to this file.

What This Does

1. Discovers all databases, schemas, tables, and columns from the warehouse
2. Enriches with codebase context (dbt models, gusty SQL, schema docs)
3. Records row counts and identifies large tables
4. Generates .astro/warehouse.md - a version-controllable, team-shareable reference
5. Enables instant concept→table lookups without warehouse queries

Process

Step 1: Read Warehouse Configuration

cat ~/.astro/agents/warehouse.yml

Get the list of databases to discover (e.g., databases: [HQ, ANALYTICS, RAW]).

Step 2: Search Codebase for Context (Parallel)

Launch a subagent to find business context in code:

Task(
    subagent_type="Explore",
    prompt="""
    Search for data model documentation in the codebase:

    1. dbt models: **/models/**/*.yml, **/schema.yml
       - Extract table descriptions, column descriptions
       - Note primary keys and tests

    2. Gusty/declarative SQL: **/dags/**/*.sql with YAML frontmatter
       - Parse frontmatter for: description, primary_key, tests
       - Note schema mappings

    3. AGENTS.md or CLAUDE.md files with data layer documentation

    Return a mapping of:
      table_name -> {description, primary_key, important_columns, layer}
    """
)

Step 3: Parallel Warehouse Discovery

Launch one subagent per database using the Task tool:

For each database in configured_databases:
    Task(
        subagent_type="general-purpose",
        prompt="""
        Discover all metadata for database {DATABASE}.

        Use the CLI to run SQL queries:
        # Scripts are relative to ../analyzing-data/
        uv run scripts/cli.py exec "df = run_sql('...')"
        uv run scripts/cli.py exec "print(df)"

        1. Query schemas:
           SELECT SCHEMA_NAME FROM {DATABASE}.INFORMATION_SCHEMA.SCHEMATA

        2. Query tables with row counts:
           SELECT TABLE_SCHEMA, TABLE_NAME, ROW_COUNT, COMMENT
           FROM {DATABASE}.INFORMATION_SCHEMA.TABLES
           ORDER BY TABLE_SCHEMA, TABLE_NAME

        3. For important schemas (MODEL_*, METRICS_*, MART_*), query columns:
           SELECT TABLE_NAME, COLUMN_NAME, DATA_TYPE, COMMENT
           FROM {DATABASE}.INFORMATION_SCHEMA.COLUMNS
           WHERE TABLE_SCHEMA = 'X'

        Return a structured summary:
        - Database name
        - List of schemas with table counts
        - For each table: name, row_count, key columns
        - Flag any tables with >100M rows as "large"
        """
    )

Run all subagents in parallel (single message with multiple Task calls).

Step 4: Discover Categorical Value Families

For key categorical columns (like OPERATOR, STATUS, TYPE, FEATURE), discover value families:

uv run cli.py exec "df = run_sql('''
SELECT DISTINCT column_name, COUNT(*) as occurrences
FROM table
WHERE column_name IS NOT NULL
GROUP BY column_name
ORDER BY occurrences DESC
LIMIT 50
''')"
uv run cli.py exec "print(df)"

Group related values into families by common prefix/suffix (e.g., Export* for ExportCSV, ExportJSON, ExportParquet).

Step 5: Merge Results

Combine warehouse metadata + codebase context:

1. Quick Reference table - concept → table mappings (pre-populated from code if found)
2. Categorical Columns - value families for key filter columns
3. Database sections - one per database
4. Schema subsections - tables grouped by schema
5. Table details - columns, row counts, descriptions from code, warnings

Step 6: Generate warehouse.md

Write the file to:

• .astro/warehouse.md (default - project-specific, version-controllable)
• ~/.astro/agents/warehouse.md (if --global flag)

Output Format

# Warehouse Schema

> Generated by `/astronomer-data:warehouse-init` on {DATE}. Edit freely to add business context.

## Quick Reference

| Concept | Table | Key Column | Date Column |
|---------|-------|------------|-------------|
| customers | HQ.MODEL_ASTRO.ORGANIZATIONS | ORG_ID | CREATED_AT |
<!-- Add your concept mappings here -->

## Categorical Columns

When filtering on these columns, explore value families first (values often have variants):

| Table | Column | Value Families |
|-------|--------|----------------|
| {TABLE} | {COLUMN} | `{PREFIX}*` ({VALUE1}, {VALUE2}, ...) |
<!-- Populated by /astronomer-data:warehouse-init from actual warehouse data -->

## Data Layer Hierarchy

Query downstream first: `reporting` > `mart_*` > `metric_*` > `model_*` > `IN_*`

| Layer | Prefix | Purpose |
|-------|--------|---------|
| Reporting | `reporting.*` | Dashboard-optimized |
| Mart | `mart_*` | Combined analytics |
| Metric | `metric_*` | KPIs at various grains |
| Model | `model_*` | Cleansed sources of truth |
| Raw | `IN_*` | Source data - avoid |

## {DATABASE} Database

### {SCHEMA} Schema

#### {TABLE_NAME}
{DESCRIPTION from code if found}

| Column | Type | Description |
|--------|------|-------------|
| COL1 | VARCHAR | {from code or inferred} |

- **Rows:** {ROW_COUNT}
- **Key column:** {PRIMARY_KEY from code or inferred}
{IF ROW_COUNT > 100M: - **⚠️ WARNING:** Large table - always add date filters}

## Relationships

{Inferred relationships based on column names like *_ID}

Command Options

Step 7: Pre-populate Cache

After generating warehouse.md, populate the concept cache:

# Scripts are relative to ../analyzing-data/
uv run cli.py concept import -p .astro/warehouse.md
uv run cli.py concept learn customers HQ.MART_CUST.CURRENT_ASTRO_CUSTS -k ACCT_ID

Step 8: Offer CLAUDE.md Integration (Ask User)

Ask the user:

Would you like to add the Quick Reference table to your CLAUDE.md file?

This ensures the schema mappings are always in context for data queries, improving accuracy from ~25% to ~100% for complex queries.

Options:

1. Yes, add to CLAUDE.md (Recommended) - Append Quick Reference section
2. No, skip - Use warehouse.md and cache only

If user chooses Yes:

1. Check if .claude/CLAUDE.md or CLAUDE.md exists
2. If exists, append the Quick Reference section (avoid duplicates)
3. If not exists, create .claude/CLAUDE.md with just the Quick Reference

Quick Reference section to add:

## Data Warehouse Quick Reference

When querying the warehouse, use these table mappings:

| Concept | Table | Key Column | Date Column |
|---------|-------|------------|-------------|
{rows from warehouse.md Quick Reference}

**Large tables (always filter by date):** {list tables with >100M rows}

> Auto-generated by `/astronomer-data:warehouse-init`. Run `/astronomer-data:warehouse-init --refresh` to update.

If yes: Append the Quick Reference section to .claude/CLAUDE.md or CLAUDE.md.

After Generation

Tell the user:

Generated .astro/warehouse.md

Summary:
  - {N} databases, {N} schemas, {N} tables
  - {N} tables enriched with code descriptions
  - {N} concepts cached for instant lookup

Next steps:
  1. Edit .astro/warehouse.md to add business context
  2. Commit to version cont