> ## Documentation Index
> Fetch the complete documentation index at: https://docs.pg-sharding.tech/llms.txt
> Use this file to discover all available pages before exploring further.

# Cross-shard queries

SPQR is optimized for single-shard OLTP queries but supports limited cross-shard operations:

* `SELECT * FROM` without `WHERE` clause and DDL commands (best-effort with no snapshot isolation, see [Distributed Transactions](/sharding/distributed_transactions))
* [Bulk operations](/sharding/bulk) (COPY, batch INSERT)

Disable with `query_routing.default_route_behaviour: BLOCK` in router config.