On a distributed database, queries and DML can be routed to the shards for processing with or without a sharding key. If a key is provided by the application a database request is routed directly to the shards, but if no key is provided the request is processed by the shard catalog, and then directed to the necessary shards for processing.

Topics:

• How Database Requests are Routed to the Shards
• Connecting to the Query Coordinator
• Query Coordinator Operation
• Query Processing for Single-Shard Queries
• Query Processing for Multi-Shard Queries
• Multi-Shard Query Coordinator Availability and Scalability
• Pushing PL/SQL Function Queries to the Shards
• Gathering Optimizer Statistics on Sharded Tables
• Supported Query Constructs and Example Query Shapes
• Supported DMLs and Examples