perf(rls): wrap current_setting() in the generated tenant policy for per-statement evaluation

src/RLS/PolicyManagers/TableRLSManager.php

@@ -528,7 +528,7 @@ protected function generateQuery(string $table, array $path): string
 
             if ($table === tenancy()->model()->getTable()) {
                 // Convert tenant key to text to match the session variable type
-                $query .= "{$column}::text = current_setting('{$sessionTenantKey}')\n";
+                $query .= "{$column}::text = (select current_setting('{$sessionTenantKey}'))\n";
                 continue;
             }
 

src/RLS/PolicyManagers/TraitRLSManager.php

@@ -67,7 +67,7 @@ protected function generateDirectRLSPolicyQuery(Model $model): string
 
         return <<<SQL
         CREATE POLICY {$table}_rls_policy ON {$table} USING (
-            {$tenantKeyColumn}::text = current_setting('{$sessionTenantKey}')
+            {$tenantKeyColumn}::text = (select current_setting('{$sessionTenantKey}'))
         );
         SQL;
     }
@@ -87,7 +87,7 @@ protected function generateIndirectRLSPolicyQuery(Model $model, BelongsTo $paren
             {$parentRelationship->getForeignKeyName()} IN (
                 SELECT {$parent->getKeyName()}
                 FROM {$parent->getTable()}
-                WHERE {$tenantKeyColumn}::text = current_setting('{$sessionTenantKey}')
+                WHERE {$tenantKeyColumn}::text = (select current_setting('{$sessionTenantKey}'))
             )
         );
         SQL;

tests/RLS/TableManagerTest.php

@@ -582,15 +582,15 @@
     expect(array_values(app(TableRLSManager::class)->generateQueries()))->toEqualCanonicalizing([
         <<<SQL
         CREATE POLICY authors_rls_policy ON authors USING (
-            tenant_id::text = current_setting('my.current_tenant')
+            tenant_id::text = (select current_setting('my.current_tenant'))
         );
         SQL,
         <<<SQL
         CREATE POLICY posts_rls_policy ON posts USING (
             author_id IN (
                 SELECT id
                 FROM authors
-                WHERE tenant_id::text = current_setting('my.current_tenant')
+                WHERE tenant_id::text = (select current_setting('my.current_tenant'))
             )
         );
         SQL,
@@ -602,7 +602,7 @@
                 WHERE author_id IN (
                     SELECT id
                     FROM authors
-                    WHERE tenant_id::text = current_setting('my.current_tenant')
+                    WHERE tenant_id::text = (select current_setting('my.current_tenant'))
                 )
             )
         );
@@ -652,15 +652,15 @@
     expect(app(TableRLSManager::class)->generateQueries($paths))->toContain(
         <<<SQL
         CREATE POLICY primaries_rls_policy ON primaries USING (
-            tenant_id::text = current_setting('my.current_tenant')
+            tenant_id::text = (select current_setting('my.current_tenant'))
         );
         SQL,
         <<<SQL
         CREATE POLICY secondaries_rls_policy ON secondaries USING (
             primary_id IN (
                 SELECT id
                 FROM primaries
-                WHERE tenant_id::text = current_setting('my.current_tenant')
+                WHERE tenant_id::text = (select current_setting('my.current_tenant'))
             )
         );
         SQL,
@@ -672,7 +672,7 @@
                 WHERE primary_id IN (
                     SELECT id
                     FROM primaries
-                    WHERE tenant_id::text = current_setting('my.current_tenant')
+                    WHERE tenant_id::text = (select current_setting('my.current_tenant'))
                 )
             )
         );

tests/RLS/TraitManagerTest.php

@@ -279,15 +279,15 @@
     expect($manager->generateQueries())->toContain(
         <<<SQL
         CREATE POLICY posts_rls_policy ON posts USING (
-            tenant_id::text = current_setting('my.current_tenant')
+            tenant_id::text = (select current_setting('my.current_tenant'))
         );
         SQL,
         <<<SQL
         CREATE POLICY comments_rls_policy ON comments USING (
             post_id IN (
                 SELECT id
                 FROM posts
-                WHERE tenant_id::text = current_setting('my.current_tenant')
+                WHERE tenant_id::text = (select current_setting('my.current_tenant'))
             )
         );
         SQL,