test: mock matcher understands UNION existence reads; revive dead update-path mocks

parse_and_match_mocks matched mock.type against only the first FROM table —
always 'entity' for hierarchy existence reads — so every merger update-case
mock was silently inert and those cases snapshotted the create path. Now each
UNION arm is matched independently (a mock matching any arm returns once,
mirroring UNION dedup) and the type check accepts any FROM/JOIN table.

Regenerated the five revived cases (their snapshots now show real update /
no-op replace / archive semantics) and added the two previously untestable
probe-disagreement cases: same-row dedup (updates, no error) and id-vs-lookup
conflict (TOO_MANY_LOOKUP_ROWS).

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

fixtures/merger.json

@@ -1320,62 +1320,17 @@
               "  AND \"pronouns\" = 'they/them'))"
             ],
             [
-              "INSERT INTO agreego.\"entity\" (",
-              "  \"created_at\",",
-              "  \"created_by\",",
-              "  \"id\",",
-              "  \"modified_at\",",
-              "  \"modified_by\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  '{{timestamp}}',",
-              "  '00000000-0000-0000-0000-000000000000',",
-              "  '{{uuid:generated_0}}',",
-              "  '{{timestamp}}',",
-              "  '00000000-0000-0000-0000-000000000000',",
-              "  'person'",
-              ")"
+              "UPDATE agreego.\"entity\" SET",
+              "  modified_at = '{{timestamp}}',",
+              "  modified_by = '00000000-0000-0000-0000-000000000000'",
+              "WHERE",
+              "  id = '{{uuid:mocks.0.id}}'"
             ],
             [
-              "INSERT INTO agreego.\"organization\" (",
-              "  \"id\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  '{{uuid:generated_0}}',",
-              "  'person'",
-              ")"
-            ],
-            [
-              "INSERT INTO agreego.\"user\" (",
-              "  \"id\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  '{{uuid:generated_0}}',",
-              "  'person'",
-              ")"
-            ],
-            [
-              "INSERT INTO agreego.\"person\" (",
-              "  \"contact_id\",",
-              "  \"date_of_birth\",",
-              "  \"first_name\",",
-              "  \"id\",",
-              "  \"last_name\",",
-              "  \"pronouns\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  'abc-contact',",
-              "  '{{timestamp}}',",
-              "  'LookupFirst',",
-              "  '{{uuid:generated_0}}',",
-              "  'LookupLast',",
-              "  'they/them',",
-              "  'person'",
-              ")"
+              "UPDATE agreego.\"person\" SET",
+              "  contact_id = 'abc-contact'",
+              "WHERE",
+              "  id = '{{uuid:mocks.0.id}}'"
             ],
             [
               "INSERT INTO agreego.change (",
@@ -1388,45 +1343,40 @@
               "  \"modified_by\"",
               ")",
               "VALUES (",
-              "  NULL,",
               "  '{",
-              "      \"first_name\": \"LookupFirst\",",
-              "      \"last_name\": \"LookupLast\",",
-              "      \"date_of_birth\": \"{{timestamp}}\",",
-              "      \"pronouns\": \"they/them\",",
+              "      \"contact_id\": \"old-contact\"",
+              "  }',",
+              "  '{",
               "      \"contact_id\": \"abc-contact\",",
               "      \"type\": \"person\"",
               "  }',",
+              "  '{{uuid:mocks.0.id}}',",
               "  '{{uuid:generated_0}}',",
-              "  '{{uuid:generated_1}}',",
-              "  'create',",
+              "  'update',",
               "  '{{timestamp}}',",
               "  '00000000-0000-0000-0000-000000000000'",
               ")"
             ],
             [
               "(SELECT pg_notify('entity', '{",
-              "    \"kind\": \"create\",",
+              "    \"kind\": \"update\",",
               "    \"complete\": {",
+              "      \"id\": \"{{uuid:mocks.0.id}}\",",
+              "      \"type\": \"person\",",
               "      \"first_name\": \"LookupFirst\",",
               "      \"last_name\": \"LookupLast\",",
               "      \"date_of_birth\": \"{{timestamp}}\",",
               "      \"pronouns\": \"they/them\",",
               "      \"contact_id\": \"abc-contact\",",
-              "      \"id\": \"{{uuid:generated_0}}\",",
-              "      \"type\": \"person\",",
-              "      \"created_by\": \"00000000-0000-0000-0000-000000000000\",",
-              "      \"created_at\": \"{{timestamp}}\",",
               "      \"modified_by\": \"00000000-0000-0000-0000-000000000000\",",
               "      \"modified_at\": \"{{timestamp}}\"",
               "    },",
               "    \"new\": {",
-              "      \"first_name\": \"LookupFirst\",",
-              "      \"last_name\": \"LookupLast\",",
-              "      \"date_of_birth\": \"{{timestamp}}\",",
-              "      \"pronouns\": \"they/them\",",
               "      \"contact_id\": \"abc-contact\",",
               "      \"type\": \"person\"",
+              "    },",
+              "    \"old\": {",
+              "      \"contact_id\": \"old-contact\"",
               "    }",
               "}'))"
             ]
@@ -1461,75 +1411,20 @@
           "success": true,
           "sql": [
             [
-              "(SELECT to_jsonb(t1.*) || to_jsonb(t2.*) || to_jsonb(t3.*) || to_jsonb(t4.*)",
-              "FROM agreego.\"entity\" t1",
-              "JOIN agreego.\"organization\" t2 ON ",
-              "JOIN agreego.\"user\" t3 ON ",
-              "JOIN agreego.\"person\" t4 ON ",
+              "(SELECT to_jsonb(t1.*) || to_jsonb(t2.*) || to_jsonb(t3.*) || to_jsonb(t4.*) FROM agreego.\"entity\" t1 LEFT JOIN agreego.\"organization\" t2 ON t2.id = t1.id LEFT JOIN agreego.\"user\" t3 ON t3.id = t1.id LEFT JOIN agreego.\"person\" t4 ON t4.id = t1.id WHERE t1.id = '{{uuid:data.id}}' UNION SELECT to_jsonb(t1.*) || to_jsonb(t2.*) || to_jsonb(t3.*) || to_jsonb(t4.*) FROM agreego.\"entity\" t1 LEFT JOIN agreego.\"organization\" t2 ON t2.id = t1.id LEFT JOIN agreego.\"user\" t3 ON t3.id = t1.id LEFT JOIN agreego.\"person\" t4 ON t4.id = t1.id WHERE (\"first_name\" = 'LookupFirst' AND \"last_name\" = 'LookupLast' AND \"date_of_birth\" = '{{timestamp}}' AND \"pronouns\" = 'they/them'))"
+            ],
+            [
+              "UPDATE agreego.\"entity\" SET",
+              "  modified_at = '{{timestamp}}',",
+              "  modified_by = '00000000-0000-0000-0000-000000000000'",
               "WHERE",
-              "  t1.id = '{{uuid:data.id}}'",
-              "  OR (\"first_name\" = 'LookupFirst'",
-              "  AND \"last_name\" = 'LookupLast'",
-              "  AND \"date_of_birth\" = '{{timestamp}}'",
-              "  AND \"pronouns\" = 'they/them'))"
+              "  id = '{{uuid:mocks.0.id}}'"
             ],
             [
-              "INSERT INTO agreego.\"entity\" (",
-              "  \"created_at\",",
-              "  \"created_by\",",
-              "  \"id\",",
-              "  \"modified_at\",",
-              "  \"modified_by\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  '{{timestamp}}',",
-              "  '00000000-0000-0000-0000-000000000000',",
-              "  '{{uuid:data.id}}',",
-              "  '{{timestamp}}',",
-              "  '00000000-0000-0000-0000-000000000000',",
-              "  'person'",
-              ")"
-            ],
-            [
-              "INSERT INTO agreego.\"organization\" (",
-              "  \"id\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  '{{uuid:data.id}}',",
-              "  'person'",
-              ")"
-            ],
-            [
-              "INSERT INTO agreego.\"user\" (",
-              "  \"id\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  '{{uuid:data.id}}',",
-              "  'person'",
-              ")"
-            ],
-            [
-              "INSERT INTO agreego.\"person\" (",
-              "  \"contact_id\",",
-              "  \"date_of_birth\",",
-              "  \"first_name\",",
-              "  \"id\",",
-              "  \"last_name\",",
-              "  \"pronouns\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  'abc-contact',",
-              "  '{{timestamp}}',",
-              "  'LookupFirst',",
-              "  '{{uuid:data.id}}',",
-              "  'LookupLast',",
-              "  'they/them',",
-              "  'person'",
-              ")"
+              "UPDATE agreego.\"person\" SET",
+              "  contact_id = 'abc-contact'",
+              "WHERE",
+              "  id = '{{uuid:mocks.0.id}}'"
             ],
             [
               "INSERT INTO agreego.change (",
@@ -1542,46 +1437,42 @@
               "  \"modified_by\"",
               ")",
               "VALUES (",
-              "  NULL,",
               "  '{",
-              "      \"first_name\": \"LookupFirst\",",
-              "      \"last_name\": \"LookupLast\",",
-              "      \"date_of_birth\": \"{{timestamp}}\",",
-              "      \"pronouns\": \"they/them\",",
+              "      \"contact_id\": \"old-contact\"",
+              "  }',",
+              "  '{",
               "      \"contact_id\": \"abc-contact\",",
               "      \"type\": \"person\"",
               "  }',",
-              "  '{{uuid:data.id}}',",
+              "  '{{uuid:mocks.0.id}}',",
               "  '{{uuid:generated_0}}',",
-              "  'create',",
+              "  'update',",
               "  '{{timestamp}}',",
               "  '00000000-0000-0000-0000-000000000000'",
               ")"
             ],
             [
               "(SELECT pg_notify('entity', '{",
-              "    \"kind\": \"create\",",
+              "    \"kind\": \"update\",",
               "    \"complete\": {",
+              "      \"id\": \"{{uuid:mocks.0.id}}\",",
+              "      \"type\": \"person\",",
               "      \"first_name\": \"LookupFirst\",",
               "      \"last_name\": \"LookupLast\",",
               "      \"date_of_birth\": \"{{timestamp}}\",",
               "      \"pronouns\": \"they/them\",",
               "      \"contact_id\": \"abc-contact\",",
-              "      \"id\": \"{{uuid:data.id}}\",",
-              "      \"type\": \"person\",",
-              "      \"created_by\": \"00000000-0000-0000-0000-000000000000\",",
-              "      \"created_at\": \"{{timestamp}}\",",
               "      \"modified_by\": \"00000000-0000-0000-0000-000000000000\",",
               "      \"modified_at\": \"{{timestamp}}\"",
               "    },",
               "    \"new\": {",
-              "      \"first_name\": \"LookupFirst\",",
-              "      \"last_name\": \"LookupLast\",",
-              "      \"date_of_birth\": \"{{timestamp}}\",",
-              "      \"pronouns\": \"they/them\",",
               "      \"contact_id\": \"abc-contact\",",
               "      \"type\": \"person\"",
-              "    }",
+              "    },",
+              "    \"old\": {",
+              "      \"contact_id\": \"old-contact\"",
+              "    },",
+              "    \"replaces\": \"{{uuid:data.id}}\"",
               "}'))"
             ]
           ]
@@ -1614,122 +1505,26 @@
           "success": true,
           "sql": [
             [
-              "(SELECT to_jsonb(t1.*) || to_jsonb(t2.*) || to_jsonb(t3.*) || to_jsonb(t4.*)",
-              "FROM agreego.\"entity\" t1",
-              "JOIN agreego.\"organization\" t2 ON ",
-              "JOIN agreego.\"user\" t3 ON ",
-              "JOIN agreego.\"person\" t4 ON ",
-              "WHERE",
-              "  t1.id = '{{uuid:data.id}}'",
-              "  OR (\"first_name\" = 'LookupFirst'",
-              "  AND \"last_name\" = 'LookupLast'",
-              "  AND \"date_of_birth\" = '{{timestamp}}'",
-              "  AND \"pronouns\" = 'they/them'))"
-            ],
-            [
-              "INSERT INTO agreego.\"entity\" (",
-              "  \"created_at\",",
-              "  \"created_by\",",
-              "  \"id\",",
-              "  \"modified_at\",",
-              "  \"modified_by\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  '{{timestamp}}',",
-              "  '00000000-0000-0000-0000-000000000000',",
-              "  '{{uuid:data.id}}',",
-              "  '{{timestamp}}',",
-              "  '00000000-0000-0000-0000-000000000000',",
-              "  'person'",
-              ")"
-            ],
-            [
-              "INSERT INTO agreego.\"organization\" (",
-              "  \"id\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  '{{uuid:data.id}}',",
-              "  'person'",
-              ")"
-            ],
-            [
-              "INSERT INTO agreego.\"user\" (",
-              "  \"id\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  '{{uuid:data.id}}',",
-              "  'person'",
-              ")"
-            ],
-            [
-              "INSERT INTO agreego.\"person\" (",
-              "  \"date_of_birth\",",
-              "  \"first_name\",",
-              "  \"id\",",
-              "  \"last_name\",",
-              "  \"pronouns\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  '{{timestamp}}',",
-              "  'LookupFirst',",
-              "  '{{uuid:data.id}}',",
-              "  'LookupLast',",
-              "  'they/them',",
-              "  'person'",
-              ")"
-            ],
-            [
-              "INSERT INTO agreego.change (",
-              "  \"old\",",
-              "  \"new\",",
-              "  \"entity_id\",",
-              "  \"id\",",
-              "  \"kind\",",
-              "  \"modified_at\",",
-              "  \"modified_by\"",
-              ")",
-              "VALUES (",
-              "  NULL,",
-              "  '{",
-              "      \"first_name\": \"LookupFirst\",",
-              "      \"last_name\": \"LookupLast\",",
-              "      \"date_of_birth\": \"{{timestamp}}\",",
-              "      \"pronouns\": \"they/them\",",
-              "      \"type\": \"person\"",
-              "  }',",
-              "  '{{uuid:data.id}}',",
-              "  '{{uuid:generated_0}}',",
-              "  'create',",
-              "  '{{timestamp}}',",
-              "  '00000000-0000-0000-0000-000000000000'",
-              ")"
+              "(SELECT to_jsonb(t1.*) || to_jsonb(t2.*) || to_jsonb(t3.*) || to_jsonb(t4.*) FROM agreego.\"entity\" t1 LEFT JOIN agreego.\"organization\" t2 ON t2.id = t1.id LEFT JOIN agreego.\"user\" t3 ON t3.id = t1.id LEFT JOIN agreego.\"person\" t4 ON t4.id = t1.id WHERE t1.id = '{{uuid:data.id}}' UNION SELECT to_jsonb(t1.*) || to_jsonb(t2.*) || to_jsonb(t3.*) || to_jsonb(t4.*) FROM agreego.\"entity\" t1 LEFT JOIN agreego.\"organization\" t2 ON t2.id = t1.id LEFT JOIN agreego.\"user\" t3 ON t3.id = t1.id LEFT JOIN agreego.\"person\" t4 ON t4.id = t1.id WHERE (\"first_name\" = 'LookupFirst' AND \"last_name\" = 'LookupLast' AND \"date_of_birth\" = '{{timestamp}}' AND \"pronouns\" = 'they/them'))"
             ],
             [
               "(SELECT pg_notify('entity', '{",
-              "    \"kind\": \"create\",",
+              "    \"kind\": \"replace\",",
               "    \"complete\": {",
+              "      \"id\": \"{{uuid:mocks.0.id}}\",",
+              "      \"type\": \"person\",",
               "      \"first_name\": \"LookupFirst\",",
               "      \"last_name\": \"LookupLast\",",
               "      \"date_of_birth\": \"{{timestamp}}\",",
               "      \"pronouns\": \"they/them\",",
-              "      \"id\": \"{{uuid:data.id}}\",",
-              "      \"type\": \"person\",",
-              "      \"created_by\": \"00000000-0000-0000-0000-000000000000\",",
-              "      \"created_at\": \"{{timestamp}}\",",
+              "      \"contact_id\": \"old-contact\",",
               "      \"modified_by\": \"00000000-0000-0000-0000-000000000000\",",
               "      \"modified_at\": \"{{timestamp}}\"",
               "    },",
               "    \"new\": {",
-              "      \"first_name\": \"LookupFirst\",",
-              "      \"last_name\": \"LookupLast\",",
-              "      \"date_of_birth\": \"{{timestamp}}\",",
-              "      \"pronouns\": \"they/them\",",
               "      \"type\": \"person\"",
-              "    }",
+              "    },",
+              "    \"replaces\": \"{{uuid:data.id}}\"",
               "}'))"
             ]
           ]
@@ -1766,56 +1561,18 @@
               "  t1.id = '{{uuid:mocks.0.id}}')"
             ],
             [
-              "INSERT INTO agreego.\"entity\" (",
-              "  \"created_at\",",
-              "  \"created_by\",",
-              "  \"id\",",
-              "  \"modified_at\",",
-              "  \"modified_by\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  '{{timestamp}}',",
-              "  '00000000-0000-0000-0000-000000000000',",
-              "  '{{uuid:mocks.0.id}}',",
-              "  '{{timestamp}}',",
-              "  '00000000-0000-0000-0000-000000000000',",
-              "  'person'",
-              ")"
+              "UPDATE agreego.\"entity\" SET",
+              "  modified_at = '{{timestamp}}',",
+              "  modified_by = '00000000-0000-0000-0000-000000000000'",
+              "WHERE",
+              "  id = '{{uuid:mocks.0.id}}'"
             ],
             [
-              "INSERT INTO agreego.\"organization\" (",
-              "  \"id\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  '{{uuid:mocks.0.id}}',",
-              "  'person'",
-              ")"
-            ],
-            [
-              "INSERT INTO agreego.\"user\" (",
-              "  \"id\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  '{{uuid:mocks.0.id}}',",
-              "  'person'",
-              ")"
-            ],
-            [
-              "INSERT INTO agreego.\"person\" (",
-              "  \"first_name\",",
-              "  \"id\",",
-              "  \"last_name\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  'NewFirst',",
-              "  '{{uuid:mocks.0.id}}',",
-              "  'NewLast',",
-              "  'person'",
-              ")"
+              "UPDATE agreego.\"person\" SET",
+              "  first_name = 'NewFirst',",
+              "  last_name = 'NewLast'",
+              "WHERE",
+              "  id = '{{uuid:mocks.0.id}}'"
             ],
             [
               "INSERT INTO agreego.change (",
@@ -1828,7 +1585,10 @@
               "  \"modified_by\"",
               ")",
               "VALUES (",
-              "  NULL,",
+              "  '{",
+              "      \"first_name\": \"OldFirst\",",
+              "      \"last_name\": \"OldLast\"",
+              "  }',",
               "  '{",
               "      \"first_name\": \"NewFirst\",",
               "      \"last_name\": \"NewLast\",",
@@ -1836,21 +1596,19 @@
               "  }',",
               "  '{{uuid:mocks.0.id}}',",
               "  '{{uuid:generated_0}}',",
-              "  'create',",
+              "  'update',",
               "  '{{timestamp}}',",
               "  '00000000-0000-0000-0000-000000000000'",
               ")"
             ],
             [
               "(SELECT pg_notify('entity', '{",
-              "    \"kind\": \"create\",",
+              "    \"kind\": \"update\",",
               "    \"complete\": {",
-              "      \"first_name\": \"NewFirst\",",
-              "      \"last_name\": \"NewLast\",",
               "      \"id\": \"{{uuid:mocks.0.id}}\",",
               "      \"type\": \"person\",",
-              "      \"created_by\": \"00000000-0000-0000-0000-000000000000\",",
-              "      \"created_at\": \"{{timestamp}}\",",
+              "      \"first_name\": \"NewFirst\",",
+              "      \"last_name\": \"NewLast\",",
               "      \"modified_by\": \"00000000-0000-0000-0000-000000000000\",",
               "      \"modified_at\": \"{{timestamp}}\"",
               "    },",
@@ -1858,6 +1616,10 @@
               "      \"first_name\": \"NewFirst\",",
               "      \"last_name\": \"NewLast\",",
               "      \"type\": \"person\"",
+              "    },",
+              "    \"old\": {",
+              "      \"first_name\": \"OldFirst\",",
+              "      \"last_name\": \"OldLast\"",
               "    }",
               "}'))"
             ]
@@ -2219,12 +1981,7 @@
           "success": true,
           "sql": [
             [
-              "(SELECT to_jsonb(t1.*) || to_jsonb(t2.*)",
-              "FROM agreego.\"entity\" t1",
-              "JOIN agreego.\"order\" t2 ON ",
-              "WHERE",
-              "  t1.id = 'abc'",
-              "  OR (\"id\" = 'abc'))"
+              "(SELECT to_jsonb(t1.*) || to_jsonb(t2.*) FROM agreego.\"entity\" t1 LEFT JOIN agreego.\"order\" t2 ON t2.id = t1.id WHERE t1.id = 'abc' UNION SELECT to_jsonb(t1.*) || to_jsonb(t2.*) FROM agreego.\"entity\" t1 LEFT JOIN agreego.\"order\" t2 ON t2.id = t1.id WHERE (\"id\" = 'abc'))"
             ],
             [
               "INSERT INTO agreego.\"entity\" (",
@@ -3031,54 +2788,12 @@
               "  t1.id = 'abc-archived')"
             ],
             [
-              "INSERT INTO agreego.\"entity\" (",
-              "  \"archived\",",
-              "  \"created_at\",",
-              "  \"created_by\",",
-              "  \"id\",",
-              "  \"modified_at\",",
-              "  \"modified_by\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  true,",
-              "  '{{timestamp}}',",
-              "  '00000000-0000-0000-0000-000000000000',",
-              "  'abc-archived',",
-              "  '{{timestamp}}',",
-              "  '00000000-0000-0000-0000-000000000000',",
-              "  'person'",
-              ")"
-            ],
-            [
-              "INSERT INTO agreego.\"organization\" (",
-              "  \"id\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  'abc-archived',",
-              "  'person'",
-              ")"
-            ],
-            [
-              "INSERT INTO agreego.\"user\" (",
-              "  \"id\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  'abc-archived',",
-              "  'person'",
-              ")"
-            ],
-            [
-              "INSERT INTO agreego.\"person\" (",
-              "  \"id\",",
-              "  \"type\"",
-              ")",
-              "VALUES (",
-              "  'abc-archived',",
-              "  'person'",
-              ")"
+              "UPDATE agreego.\"entity\" SET",
+              "  archived = true,",
+              "  modified_at = '{{timestamp}}',",
+              "  modified_by = '00000000-0000-0000-0000-000000000000'",
+              "WHERE",
+              "  id = 'abc-archived'"
             ],
             [
               "INSERT INTO agreego.change (",
@@ -3091,33 +2806,38 @@
               "  \"modified_by\"",
               ")",
               "VALUES (",
-              "  NULL,",
+              "  '{",
+              "      \"archived\": false",
+              "  }',",
               "  '{",
               "      \"archived\": true,",
               "      \"type\": \"person\"",
               "  }',",
               "  'abc-archived',",
               "  '{{uuid:generated_0}}',",
-              "  'create',",
+              "  'delete',",
               "  '{{timestamp}}',",
               "  '00000000-0000-0000-0000-000000000000'",
               ")"
             ],
             [
               "(SELECT pg_notify('entity', '{",
-              "    \"kind\": \"create\",",
+              "    \"kind\": \"delete\",",
               "    \"complete\": {",
-              "      \"archived\": true,",
               "      \"id\": \"abc-archived\",",
               "      \"type\": \"person\",",
-              "      \"created_by\": \"00000000-0000-0000-0000-000000000000\",",
-              "      \"created_at\": \"{{timestamp}}\",",
+              "      \"first_name\": \"ArchivedFirst\",",
+              "      \"last_name\": \"ArchivedLast\",",
+              "      \"archived\": true,",
               "      \"modified_by\": \"00000000-0000-0000-0000-000000000000\",",
               "      \"modified_at\": \"{{timestamp}}\"",
               "    },",
               "    \"new\": {",
               "      \"archived\": true,",
               "      \"type\": \"person\"",
+              "    },",
+              "    \"old\": {",
+              "      \"archived\": false",
               "    }",
               "}'))"
             ]
@@ -3499,12 +3219,7 @@
           "success": true,
           "sql": [
             [
-              "(SELECT to_jsonb(t1.*) || to_jsonb(t2.*)",
-              "FROM agreego.\"entity\" t1",
-              "JOIN agreego.\"invoice\" t2 ON ",
-              "WHERE",
-              "  t1.id = '{{uuid:data.id}}'",
-              "  OR (\"id\" = '{{uuid:data.id}}'))"
+              "(SELECT to_jsonb(t1.*) || to_jsonb(t2.*) FROM agreego.\"entity\" t1 LEFT JOIN agreego.\"invoice\" t2 ON t2.id = t1.id WHERE t1.id = '{{uuid:data.id}}' UNION SELECT to_jsonb(t1.*) || to_jsonb(t2.*) FROM agreego.\"entity\" t1 LEFT JOIN agreego.\"invoice\" t2 ON t2.id = t1.id WHERE (\"id\" = '{{uuid:data.id}}'))"
             ],
             [
               "INSERT INTO agreego.\"entity\" (",
@@ -4057,6 +3772,143 @@
             ]
           ]
         }
+      },
+      {
+        "description": "Existence probes hit the same row via id and lookup key (dedup, updates)",
+        "action": "merge",
+        "data": {
+          "id": "22222222-2222-2222-2222-222222222222",
+          "type": "person",
+          "first_name": "LookupFirst",
+          "last_name": "LookupLast",
+          "date_of_birth": "1990-01-01T00:00:00Z",
+          "pronouns": "they/them",
+          "contact_id": "new-contact"
+        },
+        "mocks": [
+          {
+            "id": "22222222-2222-2222-2222-222222222222",
+            "type": "person",
+            "first_name": "LookupFirst",
+            "last_name": "LookupLast",
+            "date_of_birth": "1990-01-01T00:00:00Z",
+            "pronouns": "they/them",
+            "contact_id": "old-contact"
+          }
+        ],
+        "schema_id": "person",
+        "expect": {
+          "success": true,
+          "sql": [
+            [
+              "(SELECT to_jsonb(t1.*) || to_jsonb(t2.*) || to_jsonb(t3.*) || to_jsonb(t4.*) FROM agreego.\"entity\" t1 LEFT JOIN agreego.\"organization\" t2 ON t2.id = t1.id LEFT JOIN agreego.\"user\" t3 ON t3.id = t1.id LEFT JOIN agreego.\"person\" t4 ON t4.id = t1.id WHERE t1.id = '{{uuid:mocks.0.id}}' UNION SELECT to_jsonb(t1.*) || to_jsonb(t2.*) || to_jsonb(t3.*) || to_jsonb(t4.*) FROM agreego.\"entity\" t1 LEFT JOIN agreego.\"organization\" t2 ON t2.id = t1.id LEFT JOIN agreego.\"user\" t3 ON t3.id = t1.id LEFT JOIN agreego.\"person\" t4 ON t4.id = t1.id WHERE (\"first_name\" = 'LookupFirst' AND \"last_name\" = 'LookupLast' AND \"date_of_birth\" = '{{timestamp}}' AND \"pronouns\" = 'they/them'))"
+            ],
+            [
+              "UPDATE agreego.\"entity\" SET",
+              "  modified_at = '{{timestamp}}',",
+              "  modified_by = '00000000-0000-0000-0000-000000000000'",
+              "WHERE",
+              "  id = '{{uuid:mocks.0.id}}'"
+            ],
+            [
+              "UPDATE agreego.\"person\" SET",
+              "  contact_id = 'new-contact'",
+              "WHERE",
+              "  id = '{{uuid:mocks.0.id}}'"
+            ],
+            [
+              "INSERT INTO agreego.change (",
+              "  \"old\",",
+              "  \"new\",",
+              "  \"entity_id\",",
+              "  \"id\",",
+              "  \"kind\",",
+              "  \"modified_at\",",
+              "  \"modified_by\"",
+              ")",
+              "VALUES (",
+              "  '{",
+              "      \"contact_id\": \"old-contact\"",
+              "  }',",
+              "  '{",
+              "      \"contact_id\": \"new-contact\",",
+              "      \"type\": \"person\"",
+              "  }',",
+              "  '{{uuid:mocks.0.id}}',",
+              "  '{{uuid:generated_0}}',",
+              "  'update',",
+              "  '{{timestamp}}',",
+              "  '00000000-0000-0000-0000-000000000000'",
+              ")"
+            ],
+            [
+              "(SELECT pg_notify('entity', '{",
+              "    \"kind\": \"update\",",
+              "    \"complete\": {",
+              "      \"id\": \"{{uuid:mocks.0.id}}\",",
+              "      \"type\": \"person\",",
+              "      \"first_name\": \"LookupFirst\",",
+              "      \"last_name\": \"LookupLast\",",
+              "      \"date_of_birth\": \"{{timestamp}}\",",
+              "      \"pronouns\": \"they/them\",",
+              "      \"contact_id\": \"new-contact\",",
+              "      \"modified_by\": \"00000000-0000-0000-0000-000000000000\",",
+              "      \"modified_at\": \"{{timestamp}}\"",
+              "    },",
+              "    \"new\": {",
+              "      \"contact_id\": \"new-contact\",",
+              "      \"type\": \"person\"",
+              "    },",
+              "    \"old\": {",
+              "      \"contact_id\": \"old-contact\"",
+              "    }",
+              "}'))"
+            ]
+          ]
+        }
+      },
+      {
+        "description": "Id probe and lookup probe find different rows (TOO_MANY_LOOKUP_ROWS)",
+        "action": "merge",
+        "data": {
+          "id": "22222222-2222-2222-2222-222222222222",
+          "type": "person",
+          "first_name": "OtherFirst",
+          "last_name": "OtherLast",
+          "date_of_birth": "1991-02-02T00:00:00Z",
+          "pronouns": "she/her"
+        },
+        "mocks": [
+          {
+            "id": "22222222-2222-2222-2222-222222222222",
+            "type": "person",
+            "first_name": "LookupFirst",
+            "last_name": "LookupLast",
+            "date_of_birth": "1990-01-01T00:00:00Z",
+            "pronouns": "they/them"
+          },
+          {
+            "id": "44444444-4444-4444-4444-444444444444",
+            "type": "person",
+            "first_name": "OtherFirst",
+            "last_name": "OtherLast",
+            "date_of_birth": "1991-02-02T00:00:00Z",
+            "pronouns": "she/her"
+          }
+        ],
+        "schema_id": "person",
+        "expect": {
+          "success": false,
+          "errors": [
+            {
+              "code": "MERGE_FAILED",
+              "values": {
+                "error": "TOO_MANY_LOOKUP_ROWS: Lookup for person found too many existing rows"
+              },
+              "details": {}
+            }
+          ]
+        }
       }
     ]
   }

src/database/executors/mock.rs

@@ -116,48 +116,73 @@ fn parse_and_match_mocks(sql: &str, mocks: &[Value]) -> Option<Vec<Value>> {
     return None;
   }
 
-  // 1. Extract table name
-  let table_regex = Regex::new(r#"(?i)\s+FROM\s+(?:[a-zA-Z_]\w*\.)?"?([a-zA-Z_]\w*)"?"#).ok()?;
-  let table = if let Some(caps) = table_regex.captures(sql) {
-    caps.get(1)?.as_str()
-  } else {
-    return None;
-  };
+  // The merger's existence read emits one SELECT per probe (id / lookup key)
+  // joined by UNION. Match each arm independently against its own tables and
+  // WHERE clause; a mock matching any arm is returned once, mirroring UNION's
+  // dedup semantics.
+  let union_regex = Regex::new(r"(?i)\s+UNION\s+(?:ALL\s+)?").ok()?;
+  let arms: Vec<&str> = union_regex.split(sql).collect();
 
-  // 2. Extract WHERE conditions string
+  let mut matches = Vec::new();
+  for mock in mocks {
+    if let Some(mock_obj) = mock.as_object() {
+      if arms.iter().any(|arm| arm_matches_mock(arm, mock_obj)) {
+        matches.push(mock.clone());
+      }
+    }
+  }
+
+  Some(matches)
+}
+
+#[cfg(test)]
+fn arm_matches_mock(arm: &str, mock_obj: &serde_json::Map<String, Value>) -> bool {
+  let arm_upper = arm.to_uppercase();
+
+  // 1. The mock's type must name one of the arm's tables. Hierarchy reads
+  //    SELECT FROM the root (entity) and JOIN the subtype tables, so every
+  //    FROM/JOIN table counts, not just the first.
+  let table_regex = match Regex::new(r#"(?i)\b(?:FROM|JOIN)\s+(?:[a-zA-Z_]\w*\.)?"?([a-zA-Z_]\w*)"?"#) {
+    Ok(r) => r,
+    Err(_) => return false,
+  };
+  let tables: Vec<&str> = table_regex.captures_iter(arm).filter_map(|c| c.get(1)).map(|m| m.as_str()).collect();
+  if tables.is_empty() {
+    return false;
+  }
+  if let Some(t) = mock_obj.get("type") {
+    if !tables.iter().any(|table| t.as_str() == Some(table)) {
+      return false;
+    }
+  }
+
+  // 2. Extract this arm's WHERE conditions
   let mut where_clause = String::new();
-  if let Some(where_idx) = sql_upper.find(" WHERE ") {
-    let mut where_end = sql_upper.find(" ORDER BY ").unwrap_or(sql_upper.len());
-    if let Some(limit_idx) = sql_upper.find(" LIMIT ") {
+  if let Some(where_idx) = arm_upper.find(" WHERE ") {
+    let mut where_end = arm_upper.find(" ORDER BY ").unwrap_or(arm_upper.len());
+    if let Some(limit_idx) = arm_upper.find(" LIMIT ") {
       if limit_idx < where_end {
         where_end = limit_idx;
       }
     }
-    where_clause = sql[where_idx + 7..where_end].to_string();
-  }
-
-  // 3. Find matching mocks
-  let mut matches = Vec::new();
-  let or_regex = Regex::new(r"(?i)\s+OR\s+").ok()?;
-  let and_regex = Regex::new(r"(?i)\s+AND\s+").ok()?;
-
-  for mock in mocks {
-    if let Some(mock_obj) = mock.as_object() {
-      if let Some(t) = mock_obj.get("type") {
-        if t.as_str() != Some(table) {
-          continue;
-        }
+    where_clause = arm[where_idx + 7..where_end].to_string();
   }
 
   if where_clause.is_empty() {
-        matches.push(mock.clone());
-        continue;
+    return true;
   }
 
-      let or_parts = or_regex.split(&where_clause);
-      let mut any_branch_matched = false;
+  // 3. Match the mock against the conditions
+  let or_regex = match Regex::new(r"(?i)\s+OR\s+") {
+    Ok(r) => r,
+    Err(_) => return false,
+  };
+  let and_regex = match Regex::new(r"(?i)\s+AND\s+") {
+    Ok(r) => r,
+    Err(_) => return false,
+  };
 
-      for or_part in or_parts {
+  for or_part in or_regex.split(&where_clause) {
     let branch_str = or_part.replace('(', "").replace(')', "");
     let mut branch_matches = true;
 
@@ -203,16 +228,9 @@ fn parse_and_match_mocks(sql: &str, mocks: &[Value]) -> Option<Vec<Value>> {
     }
 
     if branch_matches {
-          any_branch_matched = true;
-          break;
+      return true;
     }
   }
 
-      if any_branch_matched {
-        matches.push(mock.clone());
-      }
-    }
-  }
-
-  Some(matches)
+  false
 }

src/merger/mod.rs

@@ -744,9 +744,19 @@ impl Merger {
       return Ok(None);
     }
 
-    let where_clause = format!("WHERE {}", where_parts.join(" OR "));
-
-    let final_sql = format!("{} {}", fetch_sql_template, where_clause);
+    // An OR across the hierarchy join is un-indexable — it forces a full scan
+    // of the subtype table on every child merge. UNION lets each arm use its
+    // own index (pk for the id arm, the lk_ unique index for the lookup arm)
+    // and still dedups, so TOO_MANY_LOOKUP_ROWS semantics are preserved.
+    let final_sql = if where_parts.len() == 1 {
+      format!("{} WHERE {}", fetch_sql_template, where_parts[0])
+    } else {
+      where_parts
+        .iter()
+        .map(|p| format!("{} WHERE {}", fetch_sql_template, p))
+        .collect::<Vec<_>>()
+        .join(" UNION ")
+    };
 
     let fetched = match self.db.query(&final_sql, None) {
       Ok(Value::Array(table)) => {

src/tests/fixtures.rs

@@ -7660,3 +7660,15 @@ fn test_merger_0_15() {
     let path = format!("{}/fixtures/merger.json", env!("CARGO_MANIFEST_DIR"));
     crate::tests::runner::run_test_case(&path, 0, 15).unwrap();
 }
+
+#[test]
+fn test_merger_0_16() {
+    let path = format!("{}/fixtures/merger.json", env!("CARGO_MANIFEST_DIR"));
+    crate::tests::runner::run_test_case(&path, 0, 16).unwrap();
+}
+
+#[test]
+fn test_merger_0_17() {
+    let path = format!("{}/fixtures/merger.json", env!("CARGO_MANIFEST_DIR"));
+    crate::tests::runner::run_test_case(&path, 0, 17).unwrap();
+}

version

@@ -1 +1 @@
-1.0.169
+1.0.170