Forcing a merge

The URL /admin/datastore?op=merge command can also be used to force a merge.

Manually forcing a merge is considered a one-time version, because after the merge operation is performed (via a temporary aggressive change to the merge policy), the merge policy reverts to its previous setting.

The one-time version of the merge command is used to perform a complete merge of all generations without making a change to the default merge policy.

Forcing a merge implies starting a full merge of all generations of data files. When running this command, be aware of the following considerations:

Memory requirements. Forcing a complete merge utilizes the server's memory. If the amount of memory reaches the amount of RAM that is available, the merge operation will continue to work, but could run substantially slower and have a higher impact on query performance.
Disk space requirements. Forcing a merge requires provisioning three times the amount of disk space as the current size of the data files for the particular data store. If not enough disk space is provisioned, it could be disruptive to force a complete merge. This consideration is especially important for running this command on the Oracle Endeca Server in a production environment.

In a cluster of nodes, you can use this command only on the Endeca data store whose Dgraph process is configured as the leader node.

The format of the one-time version of the command is:

/admin/datastore?op=merge&mergepolicy=<version>

The following example assumes that the Dgraph process of the data store is using a balanced merge policy, and you want to temporarily apply an aggressive policy so that the merging can be performed.

http://localhost:7770/admin/books?op=merge&mergepolicy=aggressive

When you issue the command, the resulting Web page will look like this example:

Dgraph admin, OK.
Dgraph Manual merge started at Sat March 31 09:52:47 2012

After the merging is performed, the merge policy reverts to its previous setting.