detach_data_node()

Detach a data node from one hypertable or from all hypertables.

Reasons for detaching a data node:

  • A data node should no longer be used by a hypertable and needs to be removed from all hypertables that use it
  • You want to have fewer data nodes for a distributed hypertable to partition across

Required Arguments

NameTypeDescription
node_nameTEXTName of data node to detach from the distributed hypertable

Optional Arguments

NameTypeDescription
hypertableREGCLASSName of the distributed hypertable where the data node should be detached. If NULL, the data node will be detached from all hypertables.
if_attachedBOOLEANPrevent error if the data node is not attached. Defaults to false.
forceBOOLEANForce detach of the data node even if that means that the replication factor is reduced below what was set. Note that it will never be allowed to reduce the replication factor below 1 since that would cause data loss.
repartitionBOOLEANMake the number of space partitions equal to the new number of data nodes (if such partitioning exists). This ensures that the remaining data nodes are used evenly. Defaults to true.

Returns

The number of hypertables the data node was detached from.

Errors

Detaching a node is not permitted:

  • If it would result in data loss for the hypertable due to the data node containing chunks that are not replicated on other data nodes
  • If it would result in under-replicated chunks for the distributed hypertable (without the force argument)
tip
Replication is currently experimental, and not a supported feature

Detaching a data node is under no circumstances possible if that would mean data loss for the hypertable. Nor is it possible to detach a data node, unless forced, if that would mean that the distributed hypertable would end up with under-replicated chunks.

The only safe way to detach a data node is to first safely delete any data on it or replicate it to another data node.

Sample Usage

Detach data node dn3 from conditions:

SELECT detach_data_node('dn3', 'conditions');

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