Constant SEMANTIC_PER_TABLE_INDEX_KEY 

pub const SEMANTIC_PER_TABLE_INDEX_KEY: &str = "greptime.internal.semantic.per_table_index";

Internal QueryContext extension key carrying the per-table semantic index (a {table_name -> {semantic_key: value}} JSON blob) from the ingestion encode path to the auto-create site. Deliberately OUTSIDE SEMANTIC_PREFIX so it is not a valid table option and never leaks into a table’s options.