An alternative to sharding by sequence number is to create a shard ID based on the individual database and table. The shardbytable filter achieves this at a row level by combining the schema and table information to form the shard ID. For all other events, including statement based events, the shard ID #UNKNOWN is used.

The key part of the filter is the extraction and construction of the ID, which occurs during row processing:

oneRowChange = rowChanges.get(j);
schemaName = oneRowChange.getSchemaName();
tableName  = oneRowChange.getTableName();

id = schemaName + "_" + tableName;
if (proposedShardId == null)
{
  proposedShardId = id;
}