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Creating a Snowflake Sequence in a New Cluster

Before using Snowflake sequences, each node in your cluster must be assigned a unique snowflake.node identity in the postgresql.conf file. There are three ways to set the value of snowflake.node. You can:

  • use the pgedge spock node-create command.
  • use the pgedge db guc-set snowflake.node command.
  • manually modify the postgresql.conf file.

If your cluster has 9 nodes (or fewer), and you use the node naming convention N1, N2, N3 for your nodes, the pgedge spock node-create command will set the snowflake.node value for you. When you invoke the pgedge spock node-create command to define a new node, the value of snowflake.node is displayed after the command confirmation:

[pgedge]$ ./pgedge spock node-create n2 'host=10.2.1.2 user=pgedge port=5432 dbname=acctg' acctg

[
  {
    "node_create": 560818415
  }
]
  new: snowflake.node = 2

If you have a cluster with more than 9 nodes or a different node naming convention (other than N1, N2, etc.), you can use the pgedge db guc-set command to manually set snowflake.node to a numeric value that is unique within your cluster. The syntax is:

[pgedge]$ ./pgedge database_name guc-set snowflake.node node_number

Where

node_number is a unique number associated with the node. For example, the following command sets the snowflake.node value to 10:

[pgedge]$ ./pgedge acctg guc-set snowflake.node 10
You also have the option to manually edit the postgresql.conf file, adding the value of snowflake.node. For example, you can add the following statement at the end of the file to identify the host as node 11:

snowflake.node = 11

After setting the node identifier, you need to reload the server before using a Snowflake sequence. You can use the pgedge reload command:

[pgedge]$ ./pgedge reload pg16
pg16 reloading

or use the pg_ctl reload command to reload the server:

[pgedge]$ /home/pgedge/pg16/bin/pg_ctl reload -D "/home/pgedge/data/pg16"
server signaled