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warehouse-init

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by astronomer · part of astronomer/agents

Initialize warehouse schema discovery. Generates .astro/warehouse.md with all table metadata for instant lookups. Run once per project, refresh when schema…

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🧩 One of 7 skills in the astronomer/agents package — works on its own, and pairs well with its siblings.

Initialize warehouse schema discovery. Generates .astro/warehouse.md with all table metadata for instant lookups. Run once per project, refresh when schema…

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This is the exact playbook injected into your agent when the skill activates — shown here so you can audit it before installing. You don't need to read it to use the skill.

by astronomer

Initialize warehouse schema discovery. Generates .astro/warehouse.md with all table metadata for instant lookups. Run once per project, refresh when schema… npx skills add https://github.com/astronomer/agents --skill warehouse-init Download ZIPGitHub397

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

  • Discovers all databases, schemas, tables, and columns from the warehouse

  • Enriches with codebase context (dbt models, gusty SQL, schema docs)

  • Records row counts and identifies large tables

  • Generates .astro/warehouse.md - a version-controllable, team-shareable reference

  • Enables instant concept→table lookups without warehouse queries

Process

Step 1: Read Warehouse Configuration

Copy & paste — that's it
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:

Copy & paste — that's it
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:

Copy & paste — that's it
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:

Copy & paste — that's it
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:

  • Quick Reference table - concept → table mappings (pre-populated from code if found)

  • Categorical Columns - value families for key filter columns

  • Database sections - one per database

  • Schema subsections - tables grouped by schema

  • 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

Copy & paste — that's it
# 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 |

## Categorical Columns

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

| Table | Column | Value Families |
|-------|--------|----------------|
| {TABLE} | {COLUMN} | `{PREFIX}*` ({VALUE1}, {VALUE2}, ...) |

## 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}

Copy & paste — that's it

Command Options

Option Effect /astronomer-data:warehouse-init Generate .astro/warehouse.md /astronomer-data:warehouse-init --refresh Regenerate, preserving user edits /astronomer-data:warehouse-init --database HQ Only discover specific database /astronomer-data:warehouse-init --global Write to ~/.astro/agents/ instead

Step 7: Pre-populate Cache

After generating warehouse.md, populate the concept cache:

Copy & paste — that's it
# 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:

  • Yes, add to CLAUDE.md (Recommended) - Append Quick Reference section

  • No, skip - Use warehouse.md and cache only

If user chooses Yes:

  • Check if .claude/CLAUDE.md or CLAUDE.md exists

  • If exists, append the Quick Reference section (avoid duplicates)

  • If not exists, create .claude/CLAUDE.md with just the Quick Reference

Quick Reference section to add:

Copy & paste — that's it

## 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:

Copy & paste — that's it
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 control
 3. Run /astronomer-data:warehouse-init --refresh when schema changes

Refresh Behavior

When --refresh is specified:

  • Read existing warehouse.md

  • Preserve all HTML comments (<!-- ... -->)

  • Preserve Quick Reference table entries (user-added)

  • Preserve user-added descriptions

  • Update row counts and add new tables

  • Mark removed tables with <!-- REMOVED --> comment

Cache Staleness & Schema Drift

The runtime cache has a 7-day TTL by default. After 7 days, cached entries expire and will be re-discovered on next use.

When to Refresh

Run /astronomer-data:warehouse-init --refresh when:

  • Schema changes: Tables added, renamed, or removed

  • Column changes: New columns added or types changed

  • After deployments: If your data pipeline deploys schema migrations

  • Weekly: As a good practice, even if no known changes

Signs of Stale Cache

Watch for these indicators:

  • Queries fail with "table not found" errors

  • Results seem wrong or outdated

  • New tables aren't being discovered

Manual Cache Reset

If you suspect cache issues:

Copy & paste — that's it
# Scripts are relative to ../analyzing-data/
uv run scripts/cli.py cache status
uv run scripts/cli.py cache clear --stale-only
uv run scripts/cli.py cache clear

Codebase Patterns Recognized

Pattern Source What We Extract **/models/**/*.yml dbt table/column descriptions, tests **/dags/**/*.sql gusty YAML frontmatter (description, primary_key) AGENTS.md, CLAUDE.md docs data layer hierarchy, conventions **/docs/**/*.md docs business context

Example Session

Copy & paste — that's it
User: /astronomer-data:warehouse-init

Agent:
→ Reading warehouse configuration...
→ Found 1 warehouse with databases: HQ, PRODUCT

→ Searching codebase for data documentation...
 Found: AGENTS.md with data layer hierarchy
 Found: 45 SQL files with YAML frontmatter in dags/declarative/

→ Launching parallel warehouse discovery...
 [Database: HQ] Discovering schemas...
 [Database: PRODUCT] Discovering schemas...

→ HQ: Found 29 schemas, 401 tables
→ PRODUCT: Found 1 schema, 0 tables

→ Merging warehouse metadata with code context...
 Enriched 45 tables with descriptions from code

→ Generated .astro/warehouse.md

Summary:
 - 2 databases
 - 30 schemas
 - 401 tables
 - 45 tables enriched with code descriptions
 - 8 large tables flagged (>100M rows)

Next steps:
 1. Review .astro/warehouse.md
 2. Add concept mappings to Quick Reference
 3. Commit to version control
 4. Run /astronomer-data:warehouse-init --refresh when schema changes