periodic

The periodic module enables users to execute a query periodically in batches. In this case, the name periodic doesn't indicate that the query is executed after a time interval, but rather that, due to the complexity of the query, the results of some input source are batched to speed up execution.

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Procedures

iterate(input_query, running_query, params)

Input:

• input_query: string ➡ the input query which will yield the results that need to be batched
• running_query: string ➡ query which will be executed on the batched results
• params: Map[string, string] ➡ parameters for the procedure
  • batch_size: Integer ➡ key specifying how many results should a batch contain

Output:

• success: boolean ➡ true if the procedure executed successfully, false otherwise
• number_of_executed_batches: Integer ➡ number of executed batches (possibly a fraction of the full number if the procedure returned success: false)

Usage:

CALL periodic.iterate(
  "LOAD CSV FROM '/tmp/file.csv' WITH HEADER AS row RETURN row.node_id AS node_id, row.supernode_id AS supernode_id", 
  "MATCH (s:SuperNode {supernode_id: supernode_id}), (n:Node {node_id: node_id}) CREATE (s)-[:HAS_REL_TO]->(n)", 
  {batch_size: 5000}) 
YIELD * RETURN *;

Example

CREATE INDEX ON :SuperNode;
CREATE INDEX ON :SuperNode(supernode_id);
CREATE INDEX ON :Node;
CREATE INDEX ON :Node(node_id);
 
CREATE (:SuperNode {supernode_id: 1});
FOREACH (i IN range(1, 1000000) | CREATE (:Node {id: i}));

supernode_id,node_id
1,1
1,2
1,3
1,4
1,5
1,6
...
1,999998
1,999999
1,1000000

CALL periodic.iterate(
  "LOAD CSV FROM '/tmp/file.csv' WITH HEADER AS row RETURN row.node_id AS node_id, row.supernode_id AS supernode_id",
  "MATCH (s:SuperNode {supernode_id: supernode_id}), (n:Node {node_id: node_id}) CREATE (s)-[:HAS_REL_TO]->(n)",
  {batch_size: 5000})
YIELD * RETURN *;

+------------------+----------------------------+
| success          | number_of_executed_batches |
+------------------+----------------------------+
| true             | 200                        |
+------------------+----------------------------+