Add partial indexes to account for null values

In Postgres 15+, NULLS NOT DISTINCT is supported so that a null value in
the same column is seen as the same value. This is not standard SQL and
Postgres 15 is likely too new to require. This is a workaround to
include partial indexes when some null values are provided.

Signed-off-by: mprahl <[email protected]>

Author: mprahl

controllers/complianceeventsapi/migrations/000001_compliance_history_initial_tables.up.sql

@@ -18,6 +18,20 @@ CREATE TABLE IF NOT EXISTS parent_policies(
    UNIQUE (name, categories, controls, standards)
 );
 
+-- This is required until we only support Postgres 15+ to utilize NULLS NOT DISTINCT.
+-- Partial indexes with 1 null unique field provided (e.g. A, B, C)
+CREATE UNIQUE INDEX parent_policies_null1 ON parent_policies (name, controls, standards) WHERE categories IS NULL;
+CREATE UNIQUE INDEX parent_policies_null2 ON parent_policies (name, categories, standards) WHERE controls IS NULL;
+CREATE UNIQUE INDEX parent_policies_null3 ON parent_policies (name, categories, controls) WHERE standards IS NULL;
+
+-- Partial indexes with 2 null unique field provided (e.g. AB AC BC)
+CREATE UNIQUE INDEX parent_policies_null4 ON parent_policies (name, standards) WHERE categories IS NULL AND controls IS NULL;
+CREATE UNIQUE INDEX parent_policies_null5 ON parent_policies (name, controls) WHERE categories IS NULL AND standards IS NULL;
+CREATE UNIQUE INDEX parent_policies_null6 ON parent_policies (name, categories) WHERE controls IS NULL AND standards IS NULL;
+
+-- Partial index with no null unique fields provided (e.g. ABC)
+CREATE UNIQUE INDEX parent_policies_null7 ON parent_policies (name) WHERE categories IS NULL AND controls IS NULL AND standards IS NULL;
+
 CREATE TABLE IF NOT EXISTS policies(
    id serial PRIMARY KEY,
    kind TEXT NOT NULL,
@@ -35,6 +49,20 @@ CREATE TABLE IF NOT EXISTS policies(
    UNIQUE (kind, api_group, name, namespace, parent_policy_id, spec_hash, severity)
 );
 
+-- This is required until we only support Postgres 15+ to utilize NULLS NOT DISTINCT.
+-- Partial indexes with 1 null unique field provided (e.g. A, B, C)
+CREATE UNIQUE INDEX policies_null1 ON policies (kind, api_group, name, parent_policy_id, spec_hash, severity) WHERE namespace IS NULL;
+CREATE UNIQUE INDEX policies_null2 ON policies (kind, api_group, name, namespace, spec_hash, severity) WHERE parent_policy_id IS NULL;
+CREATE UNIQUE INDEX policies_null3 ON policies (kind, api_group, name, namespace, parent_policy_id, spec_hash) WHERE severity IS NULL;
+
+-- Partial indexes with 2 null unique field provided (e.g. AB AC BC)
+CREATE UNIQUE INDEX policies_null4 ON policies (kind, api_group, name, spec_hash, severity) WHERE namespace IS NULL AND parent_policy_id IS NULL;
+CREATE UNIQUE INDEX policies_null5 ON policies (kind, api_group, name, parent_policy_id, spec_hash) WHERE namespace IS NULL AND severity IS NULL;
+CREATE UNIQUE INDEX policies_null6 ON policies (kind, api_group, name, namespace, spec_hash) WHERE parent_policy_id IS NULL AND severity IS NULL;
+
+-- Partial index with no null unique fields provided (e.g. ABC)
+CREATE UNIQUE INDEX policies_null7 ON policies (kind, api_group, name, spec_hash) WHERE namespace IS NULL AND parent_policy_id IS NULL AND severity IS NULL;
+
 CREATE INDEX IF NOT EXISTS idx_policies_spec_hash ON policies (spec_hash);
 
 CREATE TABLE IF NOT EXISTS compliance_events(