fix: recognize Valkey Search's missing-index error in exists()

docs/api/exceptions.rst

@@ -168,7 +168,8 @@ Telling "the index is missing" apart from other failures
 Redis Search reports an absent index as an ordinary error reply rather than a distinct
 type, and the wording has changed between versions -- older releases say ``Unknown index
 name``, Redis 8.6 and earlier say ``<name>: no such index``, and Redis 8.8 introduced
-``SEARCH_INDEX_NOT_FOUND Index not found: <name>``. There is no error code to branch on,
+``SEARCH_INDEX_NOT_FOUND Index not found: <name>``. Valkey Search says
+``Index with name '<name>' not found in database <n>``. There is no error code to branch on,
 so code that needs to distinguish "missing" from "something went wrong" has to match the
 message.
 

redisvl/exceptions.py

@@ -64,6 +64,8 @@ def for_svs_vamana(cls, min_redis_version: str):
     "no such index",
     "search_index_not_found",
     "index not found",
+    # Valkey Search: "Index with name '<name>' not found in database <n>"
+    "not found in database",
 )
 
 

tests/unit/test_index_exists.py

@@ -28,12 +28,14 @@
 
 # Every wording Redis Search has used for an absent index. 8.8 replaced the
 # older prose with an error code, so a match on any single one of these would
-# break exists() on some supported server.
+# break exists() on some supported server. Valkey Search words it differently
+# again, with the index name between "Index" and "not found".
 MISSING_INDEX_MESSAGES = [
     "Unknown index name",
     f"{INDEX_NAME}: no such index",
     f"SEARCH_INDEX_NOT_FOUND Index not found: {INDEX_NAME}",
     "Index not found",
+    f"Index with name '{INDEX_NAME}' not found in database 0",
 ]
 
 # Failures that must never be read as "the index is absent": reporting False