Using APOC periodic iterate to delete large numbers of nodes

When deleting a large number of nodes (1000+), it's important to stagger the delete operations so as not to overwhelm the database.

When learning Neo4j you may have used this query  

MATCH (n) DETACH DELETE(n) 

This is not suited for large data set as listed in the documentation. 

Instead, APOC's periodic iterate function can handle this for you in a better way.

For example, you can do it like this (not an optimal version):

CALL apoc.periodic.iterate(
"MATCH (n) RETURN n",
"DETACH DELETE n",
{batchSize:10000, parallel:false})

Note setting parallel to true can lead to contention. We advise you start setting it to false.

Since Aura has some safeguards for its query memory and is running a database version greater than 4.x  you should use this improved method instead:

call apoc.periodic.iterate(
"MATCH (p) return id(p) AS id", 
"MATCH (n) WHERE id(n) = id DETACH DELETE n", 
{batchSize:1000})

If you have dense nodes it may be more efficient to delete the relationships separately then the nodes to avoid any contention/locking;

CALL apoc.periodic.iterate(
'MATCH ()-[r]->() RETURN id(r) AS id', 
'MATCH ()-[r]->() WHERE id(r)=id DELETE r', 
{batchSize: 5000});

CALL apoc.periodic.iterate(
'MATCH (n) RETURN id(n) AS id', 
'MATCH (n) WHERE id(n)=id DELETE n', 
{batchSize: 5000});