PostgreSQL 12 High Availability Cookbook - Third Edition

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If we wanted to use our new ID generator in a table, then we could do it very simply. Assuming that we already have our myapp.msg_log table, we could create a new table based on it with the following SQL statement:

CREATE SCHEMA myapp1; 
CREATE TABLE myapp1.msg_log ( 
    LIKE myapp.msg_log INCLUDING INDEXES 
); 
 
ALTER TABLE myapp1.msg_log 
ALTER id TYPE BIGINT, 
ALTER id SET DEFAULT shard.next_unique_id(1); 

This structure would correspond with shard number 1. All we need to do is modify the id column so that it can store our 64-bit integer and then set the default value to invoke our next_unique_id function. By doing so, we can create up to 2,048 schemas holding tables like this, and every generated ID will be unique across all of ...