[BUG] is_default_schema does not do a space check for defaults or #embedding (#5787)

## Description of changes

_Summarize the changes made by this PR._

- Improvements & Bug fixes
- There is a bug in schema where is_default_schema does not check the
space when confirming if the schema is default. This was hidden by our
e2e tests, since we used an ef with a default space of cosine. therefore
the configuration was cosine and was automatically converted into the
schema and tests passed. this PR adds a new test to confirm the basic
space setting scenario works
- New functionality
  - ...

## Test plan

_How are these changes tested?_

- [ ] Tests pass locally with `pytest` for python, `yarn test` for js,
`cargo test` for rust

## Migration plan

_Are there any migrations, or any forwards/backwards compatibility
changes needed in order to make sure this change deploys reliably?_

## Observability plan

_What is the plan to instrument and monitor this change?_

## Documentation Changes

_Are all docstrings for user-facing APIs updated if required? Do we need
to make documentation changes in the [docs
section](https://github.com/chroma-core/chroma/tree/main/docs/docs.trychroma.com)?_

Author: jairad26

chromadb/test/api/test_schema_e2e.py

@@ -107,6 +107,64 @@ def test_schema_vector_config_persistence(
 
     collection_name = f"schema_spann_{uuid4().hex}"
 
+    schema = Schema()
+    schema.create_index(
+        config=VectorIndexConfig(
+            space="cosine",
+            spann=SpannIndexConfig(
+                search_nprobe=16,
+                write_nprobe=32,
+                ef_construction=120,
+                max_neighbors=24,
+            ),
+        )
+    )
+
+    collection = client.get_or_create_collection(
+        name=collection_name,
+        schema=schema,
+    )
+
+    persisted_schema = collection.schema
+    assert persisted_schema is not None
+
+    print(persisted_schema.serialize_to_json())
+
+    embedding_override = persisted_schema.keys["#embedding"].float_list
+    assert embedding_override is not None
+    vector_index = embedding_override.vector_index
+    assert vector_index is not None
+    assert vector_index.enabled is True
+    assert vector_index.config is not None
+    assert vector_index.config.space is not None
+    assert vector_index.config.space == "cosine"
+
+    client_reloaded = client_factories.create_client_from_system()
+    reloaded_collection = client_reloaded.get_collection(
+        name=collection_name,
+    )
+
+    reloaded_schema = reloaded_collection.schema
+    assert reloaded_schema is not None
+    reloaded_embedding_override = reloaded_schema.keys["#embedding"].float_list
+    assert reloaded_embedding_override is not None
+    reloaded_vector_index = reloaded_embedding_override.vector_index
+    assert reloaded_vector_index is not None
+    assert reloaded_vector_index.config is not None
+    assert reloaded_vector_index.config.space is not None
+    assert reloaded_vector_index.config.space == "cosine"
+
+
+def test_schema_vector_config_persistence_with_ef(
+    client_factories: "ClientFactories",
+) -> None:
+    """Ensure schema-provided SPANN settings persist across client restarts."""
+
+    client = client_factories.create_client_from_system()
+    client.reset()
+
+    collection_name = f"schema_spann_{uuid4().hex}"
+
     schema = Schema()
     embedding_function = SimpleEmbeddingFunction(dim=6)
     schema.create_index(

rust/types/src/collection_schema.rs

@@ -1547,8 +1547,13 @@ impl Schema {
                 if vector_index.enabled {
                     return false;
                 }
+                if !is_embedding_function_default(&vector_index.config.embedding_function) {
+                    return false;
+                }
+                if !is_space_default(&vector_index.config.space) {
+                    return false;
+                }
                 // Check that the config has default structure
-                // We allow space and embedding_function to vary, but check structure
                 if vector_index.config.source_key.is_some() {
                     return false;
                 }
@@ -1613,6 +1618,9 @@ impl Schema {
                 if !vector_index.enabled {
                     return false;
                 }
+                if !is_space_default(&vector_index.config.space) {
+                    return false;
+                }
                 // Check that embedding_function is default
                 if !is_embedding_function_default(&vector_index.config.embedding_function) {
                     return false;
@@ -3804,6 +3812,63 @@ mod tests {
         assert!(!schema_with_extra_overrides.is_default());
     }
 
+    #[test]
+    fn test_is_schema_default_with_space() {
+        let schema = Schema::new_default(KnnIndex::Hnsw);
+        assert!(schema.is_default());
+
+        let mut schema_with_space = Schema::new_default(KnnIndex::Hnsw);
+        if let Some(ref mut float_list) = schema_with_space.defaults.float_list {
+            if let Some(ref mut vector_index) = float_list.vector_index {
+                vector_index.config.space = Some(Space::Cosine);
+            }
+        }
+        assert!(!schema_with_space.is_default());
+
+        let mut schema_with_space_in_embedding_key = Schema::new_default(KnnIndex::Spann);
+        if let Some(ref mut embedding_key) = schema_with_space_in_embedding_key
+            .keys
+            .get_mut(EMBEDDING_KEY)
+        {
+            if let Some(ref mut float_list) = embedding_key.float_list {
+                if let Some(ref mut vector_index) = float_list.vector_index {
+                    vector_index.config.space = Some(Space::Cosine);
+                }
+            }
+        }
+        assert!(!schema_with_space_in_embedding_key.is_default());
+    }
+
+    #[test]
+    fn test_is_schema_default_with_embedding_function() {
+        let schema = Schema::new_default(KnnIndex::Hnsw);
+        assert!(schema.is_default());
+
+        let mut schema_with_embedding_function = Schema::new_default(KnnIndex::Hnsw);
+        if let Some(ref mut float_list) = schema_with_embedding_function.defaults.float_list {
+            if let Some(ref mut vector_index) = float_list.vector_index {
+                vector_index.config.embedding_function =
+                    Some(EmbeddingFunctionConfiguration::Legacy);
+            }
+        }
+        assert!(!schema_with_embedding_function.is_default());
+
+        let mut schema_with_embedding_function_in_embedding_key =
+            Schema::new_default(KnnIndex::Spann);
+        if let Some(ref mut embedding_key) = schema_with_embedding_function_in_embedding_key
+            .keys
+            .get_mut(EMBEDDING_KEY)
+        {
+            if let Some(ref mut float_list) = embedding_key.float_list {
+                if let Some(ref mut vector_index) = float_list.vector_index {
+                    vector_index.config.embedding_function =
+                        Some(EmbeddingFunctionConfiguration::Legacy);
+                }
+            }
+        }
+        assert!(!schema_with_embedding_function_in_embedding_key.is_default());
+    }
+
     #[test]
     fn test_add_merges_keys_by_value_type() {
         let mut schema_a = Schema::new_default(KnnIndex::Hnsw);