CREATE VECTOR INDEX statement not supported

[pdarulewski]

It looks like it's not possible to create a vector index using the emulator.

To reproduce

> gcloud --project local spanner databases ddl update local-database --instance local-instance --ddl="CREATE VECTOR INDEX embeddings_idx ON a_table(embeddings) OPTIONS (distance_type = 'COSINE', tree_depth = 2, num_leaves = 100, num_branches = 10);"

Expected behaviour

The vector index is created

Actual behaviour

The following error is returned:

ERROR: (gcloud.spanner.databases.ddl.update) HTTPError 400: {"code":3,"message":"Error parsing Spanner DDL statement: CREATE VECTOR INDEX text_embeddings ON non_existent_table(text_embeddings) OPTIONS (distance_type = 'COSINE', tree_depth = 2, num_leaves = 100, num_branches = 10) : Syntax error on line 1, column 8: Encountered 'VECTOR' while parsing: create_statement"}