Family references discriminate through the referenced row's type

Intention: make local <prop>_type columns optional denormalization instead
of an engine requirement — writers should only ever have to say WHO.

Outcomes:
- compile_one_of: a type-strategy family REFERENCE (payer, source, target)
  now selects its polymorphic branch via the referenced row's own type —
  CASE (SELECT type FROM agreego.entity WHERE id = <alias>.<prop>_id) —
  the truth itself, instead of requiring a <prop>_type column beside the
  id. kind-strategy STI and a row's self-discrimination still read locally
  (there is no referenced row to consult). All CASEs are now simple-form,
  so the operand is evaluated once even as a subquery.
- GUC readers guard against the empty string: a rolled-back transaction
  that FIRST-sets a custom GUC leaves it '' session-wide (not unset), and
  COALESCE alone never fires — auth.user_id and punc.external now NULLIF
  first, matching agreego.get_cue's own convention.
- Golden fixtures regenerated via UPDATE_EXPECT; 1286 tests green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

fixtures/queryer.json

@@ -1408,8 +1408,13 @@
               "        'archived', entity_19.archived,",
               "        'created_at', entity_19.created_at,",
               "        'is_primary', contact_21.is_primary,",
-              "        'target', CASE",
-              "          WHEN relationship_20.target_type = 'phone_number' THEN ((",
+              "        'target', CASE (",
+              "          SELECT __fam.type",
+              "          FROM agreego.entity __fam",
+              "          WHERE",
+              "            __fam.id = relationship_20.target_id",
+              "        )",
+              "          WHEN 'phone_number' THEN ((",
               "            SELECT jsonb_build_object(",
               "              'id', entity_22.id,",
               "              'type', entity_22.type,",
@@ -1423,7 +1428,7 @@
               "              NOT entity_22.archived",
               "              AND relationship_20.target_id = entity_22.id",
               "          ))",
-              "          WHEN relationship_20.target_type = 'email_address' THEN ((",
+              "          WHEN 'email_address' THEN ((",
               "            SELECT jsonb_build_object(",
               "              'id', entity_24.id,",
               "              'type', entity_24.type,",
@@ -1437,7 +1442,7 @@
               "              NOT entity_24.archived",
               "              AND relationship_20.target_id = entity_24.id",
               "          ))",
-              "          WHEN relationship_20.target_type = 'address' THEN ((",
+              "          WHEN 'address' THEN ((",
               "            SELECT jsonb_build_object(",
               "              'id', entity_26.id,",
               "              'type', entity_26.type,",
@@ -1659,8 +1664,13 @@
               "        'archived', entity_19.archived,",
               "        'created_at', entity_19.created_at,",
               "        'is_primary', contact_21.is_primary,",
-              "        'target', CASE",
-              "          WHEN relationship_20.target_type = 'phone_number' THEN ((",
+              "        'target', CASE (",
+              "          SELECT __fam.type",
+              "          FROM agreego.entity __fam",
+              "          WHERE",
+              "            __fam.id = relationship_20.target_id",
+              "        )",
+              "          WHEN 'phone_number' THEN ((",
               "            SELECT jsonb_build_object(",
               "              'id', entity_22.id,",
               "              'type', entity_22.type,",
@@ -1674,7 +1684,7 @@
               "              NOT entity_22.archived",
               "              AND relationship_20.target_id = entity_22.id",
               "          ))",
-              "          WHEN relationship_20.target_type = 'email_address' THEN ((",
+              "          WHEN 'email_address' THEN ((",
               "            SELECT jsonb_build_object(",
               "              'id', entity_24.id,",
               "              'type', entity_24.type,",
@@ -1688,7 +1698,7 @@
               "              NOT entity_24.archived",
               "              AND relationship_20.target_id = entity_24.id",
               "          ))",
-              "          WHEN relationship_20.target_type = 'address' THEN ((",
+              "          WHEN 'address' THEN ((",
               "            SELECT jsonb_build_object(",
               "              'id', entity_26.id,",
               "              'type', entity_26.type,",
@@ -1889,8 +1899,8 @@
           "sql": [
             [
               "((SELECT jsonb_strip_nulls((",
-              "  SELECT COALESCE(jsonb_agg(CASE",
-              "    WHEN organization_2.type = 'bot' THEN ((",
+              "  SELECT COALESCE(jsonb_agg(CASE organization_2.type",
+              "    WHEN 'bot' THEN ((",
               "      SELECT jsonb_build_object(",
               "        'id', entity_3.id,",
               "        'type', entity_3.type,",
@@ -1907,7 +1917,7 @@
               "        NOT entity_3.archived",
               "        AND entity_3.id = entity_1.id",
               "    ))",
-              "    WHEN organization_2.type = 'organization' THEN ((",
+              "    WHEN 'organization' THEN ((",
               "      SELECT jsonb_build_object(",
               "        'id', entity_6.id,",
               "        'type', entity_6.type,",
@@ -1921,7 +1931,7 @@
               "        NOT entity_6.archived",
               "        AND entity_6.id = entity_1.id",
               "    ))",
-              "    WHEN organization_2.type = 'person' THEN ((",
+              "    WHEN 'person' THEN ((",
               "      SELECT jsonb_build_object(",
               "        'id', entity_8.id,",
               "        'type', entity_8.type,",
@@ -1959,8 +1969,8 @@
           "sql": [
             [
               "((SELECT jsonb_strip_nulls((",
-              "  SELECT CASE",
-              "    WHEN organization_2.type = 'bot' THEN ((",
+              "  SELECT CASE organization_2.type",
+              "    WHEN 'bot' THEN ((",
               "      SELECT jsonb_build_object(",
               "        'id', entity_3.id,",
               "        'type', entity_3.type,",
@@ -1976,7 +1986,7 @@
               "        NOT entity_3.archived",
               "        AND entity_3.id = entity_1.id",
               "    ))",
-              "    WHEN organization_2.type = 'person' THEN ((",
+              "    WHEN 'person' THEN ((",
               "      SELECT jsonb_build_object(",
               "        'id', entity_6.id,",
               "        'type', entity_6.type,",
@@ -2013,8 +2023,8 @@
           "sql": [
             [
               "((SELECT jsonb_strip_nulls((",
-              "  SELECT CASE",
-              "    WHEN organization_2.type = 'person' THEN ((",
+              "  SELECT CASE organization_2.type",
+              "    WHEN 'person' THEN ((",
               "      SELECT jsonb_build_object(",
               "        'id', entity_3.id,",
               "        'type', entity_3.type,",
@@ -2121,8 +2131,13 @@
               "            'archived', entity_21.archived,",
               "            'created_at', entity_21.created_at,",
               "            'is_primary', contact_23.is_primary,",
-              "            'target', CASE",
-              "              WHEN relationship_22.target_type = 'phone_number' THEN ((",
+              "            'target', CASE (",
+              "              SELECT __fam.type",
+              "              FROM agreego.entity __fam",
+              "              WHERE",
+              "                __fam.id = relationship_22.target_id",
+              "            )",
+              "              WHEN 'phone_number' THEN ((",
               "                SELECT jsonb_build_object(",
               "                  'id', entity_24.id,",
               "                  'type', entity_24.type,",
@@ -2136,7 +2151,7 @@
               "                  NOT entity_24.archived",
               "                  AND relationship_22.target_id = entity_24.id",
               "              ))",
-              "              WHEN relationship_22.target_type = 'email_address' THEN ((",
+              "              WHEN 'email_address' THEN ((",
               "                SELECT jsonb_build_object(",
               "                  'id', entity_26.id,",
               "                  'type', entity_26.type,",
@@ -2150,7 +2165,7 @@
               "                  NOT entity_26.archived",
               "                  AND relationship_22.target_id = entity_26.id",
               "              ))",
-              "              WHEN relationship_22.target_type = 'address' THEN ((",
+              "              WHEN 'address' THEN ((",
               "                SELECT jsonb_build_object(",
               "                  'id', entity_28.id,",
               "                  'type', entity_28.type,",
@@ -2246,15 +2261,15 @@
           "sql": [
             [
               "((SELECT jsonb_strip_nulls((",
-              "  SELECT COALESCE(jsonb_agg(CASE",
-              "    WHEN widget_2.kind = 'stock' THEN (jsonb_build_object(",
+              "  SELECT COALESCE(jsonb_agg(CASE widget_2.kind",
+              "    WHEN 'stock' THEN (jsonb_build_object(",
               "      'id', entity_1.id,",
               "      'type', entity_1.type,",
               "      'archived', entity_1.archived,",
               "      'created_at', entity_1.created_at,",
               "      'kind', widget_2.kind",
               "    ))",
-              "    WHEN widget_2.kind = 'tasks' THEN (jsonb_build_object(",
+              "    WHEN 'tasks' THEN (jsonb_build_object(",
               "      'id', entity_1.id,",
               "      'type', entity_1.type,",
               "      'archived', entity_1.archived,",
@@ -2360,8 +2375,8 @@
               "    'total', order_2.total,",
               "    'customer_id', order_2.customer_id,",
               "    'counterparty', (",
-              "      SELECT CASE",
-              "        WHEN organization_4.type = 'bot' THEN ((",
+              "      SELECT CASE organization_4.type",
+              "        WHEN 'bot' THEN ((",
               "          SELECT jsonb_build_object(",
               "            'id', entity_5.id,",
               "            'type', entity_5.type,",
@@ -2378,7 +2393,7 @@
               "            NOT entity_5.archived",
               "            AND entity_5.id = entity_3.id",
               "        ))",
-              "        WHEN organization_4.type = 'organization' THEN ((",
+              "        WHEN 'organization' THEN ((",
               "          SELECT jsonb_build_object(",
               "            'id', entity_8.id,",
               "            'type', entity_8.type,",
@@ -2392,7 +2407,7 @@
               "            NOT entity_8.archived",
               "            AND entity_8.id = entity_3.id",
               "        ))",
-              "        WHEN organization_4.type = 'person' THEN ((",
+              "        WHEN 'person' THEN ((",
               "          SELECT jsonb_build_object(",
               "            'id', entity_10.id,",
               "            'type', entity_10.type,",

src/database/executors/pgrx.rs

@@ -118,7 +118,7 @@ impl DatabaseExecutor for SpiExecutor {
       Spi::connect(|client| {
         let mut tup_table = client
           .select(
-            "SELECT COALESCE(current_setting('auth.user_id', true), 'ffffffff-ffff-ffff-ffff-ffffffffffff')",
+            "SELECT COALESCE(NULLIF(current_setting('auth.user_id', true), ''), 'ffffffff-ffff-ffff-ffff-ffffffffffff')",
             None,
             &[],
           )
@@ -156,7 +156,7 @@ impl DatabaseExecutor for SpiExecutor {
       Spi::connect(|client| {
         let mut tup_table = client
           .select(
-            "SELECT COALESCE(current_setting('punc.external', true), 'false')::boolean",
+            "SELECT COALESCE(NULLIF(current_setting('punc.external', true), ''), 'false')::boolean",
             None,
             &[],
           )

src/queryer/compiler.rs

@@ -337,10 +337,25 @@ impl<'a> Compiler<'a> {
       .get()
       .ok_or("Missing compiled discriminator for polymorphism")?;
 
-    let type_col = if let Some(prop) = &node.property_name {
-      format!("{}_{}", prop, disc)
+    // The CASE operand that selects the polymorphic branch. For a `type`-strategy
+    // FAMILY REFERENCE (a property like `payer` or `source` pointing at another
+    // entity by `<prop>_id`), discriminate through the referenced row's own type
+    // in agreego.entity — the truth — instead of requiring a local `<prop>_type`
+    // column on the parent. Local `_type` columns thereby become optional
+    // denormalization rather than a requirement of the engine. `kind`-strategy
+    // (single-table STI) and self-discrimination (a row's own `type`) still read
+    // locally: there is no referenced row to consult.
+    let disc_operand = if let Some(prop) = &node.property_name {
+      if disc == "type" {
+        format!(
+          "(SELECT __fam.type FROM agreego.entity __fam WHERE __fam.id = {}.{}_id)",
+          node.parent_alias, prop
+        )
+      } else {
+        format!("{}.{}_{}", node.parent_alias, prop, disc)
+      }
     } else {
-      disc.to_string()
+      format!("{}.{}", node.parent_alias, disc)
     };
 
     for (disc_val, (idx_opt, target_id_opt)) in options {
@@ -369,10 +384,7 @@ impl<'a> Compiler<'a> {
               sql
             };
 
-          case_statements.push(format!(
-            "WHEN {}.{} = '{}' THEN ({})",
-            node.parent_alias, type_col, disc_val, val_sql
-          ));
+          case_statements.push(format!("WHEN '{}' THEN ({})", disc_val, val_sql));
         }
       } else if let Some(idx) = idx_opt {
         if let Some(target_schema) = node
@@ -404,10 +416,7 @@ impl<'a> Compiler<'a> {
               sql
             };
 
-          case_statements.push(format!(
-            "WHEN {}.{} = '{}' THEN ({})",
-            node.parent_alias, type_col, disc_val, val_sql
-          ));
+          case_statements.push(format!("WHEN '{}' THEN ({})", disc_val, val_sql));
         }
       }
     }
@@ -415,7 +424,12 @@ impl<'a> Compiler<'a> {
       return Ok(("NULL".to_string(), "string".to_string()));
     }
 
-    let sql = format!("CASE {} ELSE NULL END", case_statements.join(" "));
+    // Simple CASE: the operand is evaluated once even when it is a subquery.
+    let sql = format!(
+      "CASE {} {} ELSE NULL END",
+      disc_operand,
+      case_statements.join(" ")
+    );
     Ok((sql, "object".to_string()))
   }