Spanner Batch Reader
SpannerBatchReader is identical to Incremental Batch Reader, minus the Username and Password properties, plus the Augment Query Clause property.
Specify the connection URL as jdbc:cloudspanner:/projects/<project ID>/instances/<instance ID>/databases/<database name>?credentials=<service account key>. See Spanner Writer for a detailed description of the service account key.
Optionally, use the Augment Query Clause property to specify FORCE_INDEX directives (see Table hints) using the syntax:
{"<table name>": {"tablehints": {"FORCE_INDEX": "<index name>"}}You may specify multiple indexes (no more than one per table) separated by commas, for example:
{"order": {"tablehints": {"FORCE_INDEX": "order_amount_index"}},
{"customer": {"tablehints": {"FORCE_INDEX": "customer_ID_index"}}