P3D — Birth System B3-P Policy Storage Design rev2

Date: 2026-05-12 Rev: 2 (type compatibility, constraint naming, rollback restore old values)

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1–4. (Unchanged from rev1 — Option A recommended, 6 columns, CHECK constraints, population flow)

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5. Type compatibility rules

Column	Acceptable type	Exact match	On conflict
coverage_status	varchar OR text	Either acceptable	If exists with different type → BLOCKED
coverage_scope_status	varchar OR text	Either acceptable	If exists with different type → BLOCKED
coverage_exemption_reason	text	text only	BLOCKED if different
coverage_review_owner	text	text only	BLOCKED if different
coverage_decided_at	timestamptz	exact	BLOCKED if timestamp without tz
coverage_decided_by	text	text only	BLOCKED if different

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6. CHECK constraint naming convention

chk_<table>_<column>
Example: chk_collection_registry_coverage_status

Before creating: verify no existing constraint with same name. If exists → compare allowed values. Same → OK. Different → BLOCKED_EXISTING_CONFLICT.

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7. Population rollback = restore old values, not blanket NULL

Before UPDATE, Agent captures for EACH row:

(collection_name, old_coverage_status, old_coverage_scope_status, old_coverage_exemption_reason, old_coverage_review_owner, old_coverage_decided_at, old_coverage_decided_by)

Rollback restores these exact old values per row. If old value was NULL → restore to NULL (which is functionally same as blanket NULL, but semantically correct because it's per-row).

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8. (Unchanged — governance role mapping, 2-pass pattern, sequence)

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B3-P Design rev2 | 2026-05-12