CRDTs Overview v5

Introduction to CRDTs

Conflict-free replicated data types (CRDTs) support merging values from concurrently modified rows instead of discarding one of the rows as the traditional resolution does.

Each CRDT type is implemented as a separate PostgreSQL data type with an extra callback added to the bdr.crdt_handlers catalog. The merge process happens inside the PGD writer on the apply side without any user action needed.

CRDTs require the table to have column-level conflict resolution enabled, as described in Column-level conflict resolution.

CRDTs in PostgreSQL

The CRDTs are installed as part of bdr into the bdr schema. For convenience, the basic operators (+, #, and !) and a number of common aggregate functions (min, max, sum, and avg) are created in pg_catalog. Thus they are available without having to tweak search_path.

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• Introduction to CRDTs
• CRDTs in PostgreSQL