refactor: fix mart_patient_360 — eliminate cartesian explosion, hash SSN, add financial metrics

[altimateanas]

Summary

Major refactor of mart_patient_360 to fix critical data quality and HIPAA compliance issues.

Problems Fixed

Issue	Severity	What Changed
Cartesian explosion	🔴 Critical	Raw 1:many joins (patients × encounters × diagnoses × medications × labs) produced millions of duplicate rows. Now pre-aggregates each domain to patient grain before joining.
Missing primary key	🔴 Critical	patient_id was not in the SELECT list. Added as explicit first column.
Raw SSN exposure	🔴 HIPAA	ssn was exposed as plain text. Replaced with sha2(ssn, 256) as ssn_hash.
No financial data	🟡 Gap	Added stg_claims as new upstream + lifetime_charges_dollars / lifetime_paid_dollars using the cents_to_dollars macro (which existed but was never used).
Ambiguous full_name	🟡 Clarity	Renamed to patient_name (from stg_patients). Added primary_provider_name (derived from stg_providers via encounter history).
Missing documentation	🟡 Gap	mart_patient_360 was not listed in _marts.yml at all. Added full column-level documentation.

Column-Level Changes

Change	Column	Details
🟢 ADDED	patient_id	Primary key — was completely missing
🟢 ADDED	primary_provider_name	New column from stg_providers.full_name via encounter join
🟢 ADDED	blood_type, insurance_id	Patient demographics now included
🟢 ADDED	total_encounters, first_encounter_date, last_encounter_date	Aggregated encounter metrics
🟢 ADDED	unique_diagnosis_count, primary_diagnosis_codes	Aggregated diagnosis metrics
🟢 ADDED	unique_medication_count	Aggregated medication metric
🟢 ADDED	total_lab_tests, abnormal_lab_count	Aggregated lab metrics
🟢 ADDED	lifetime_charges_dollars, lifetime_paid_dollars	Financial summary from claims
🟢 ADDED	patient_registered_at	Renamed from created_at for clarity
🟡 RENAMED	full_name → patient_name	Same source (stg_patients), clearer name
🟡 CHANGED	ssn → ssn_hash	Source is still stg_patients.ssn, but now SHA-256 hashed
🔴 REMOVED	diagnosis_code	Raw per-row diagnosis code removed; replaced by aggregated unique_diagnosis_count + primary_diagnosis_codes

New Upstream Dependencies

• stg_providers — to derive primary_provider_name
• stg_claims — to compute financial summary

⚠️ Breaking Changes for Downstream Consumers

Any dashboard, report, or model that reads mart_patient_360 should be checked for:

1. ssn column no longer exists — replaced by ssn_hash
2. full_name column no longer exists — renamed to patient_name
3. diagnosis_code column no longer exists — replaced by aggregated columns
4. Row count will change dramatically — from cartesian explosion (millions of rows) to one row per patient (correct grain)

[github-actions]

SQL Quality Gate Results

Checked SQL files in this PR for common anti-patterns:

• SELECT * (prefer explicit columns)
• Cartesian joins (missing JOIN conditions)
• Non-sargable predicates (functions on columns in WHERE)
• UNION without ALL (unnecessary dedup sort)
• ORDER BY in subqueries (ignored by optimizer)
• Missing LIMIT in analysis queries

See job logs for details.

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