Reviewing plan operators

We will take a look at a few important operators that we will encounter most often while tuning queries.

These operators impact query performance the most and are listed as follows:

• AllNodesScan: This means the database is looking at all the nodes. Most often than not, this means the user forgot to provide a label. There are scenarios where this might be the intention. Most users when they are beginning with Cypher add the label name but forget to add ":" before the label. An example looks like this:

  MATCH (Drug {code: '1234'} RETURN *

We might have thought we provided the label name, but since we don’t have ":" before the label, it will be treated as a variable, and we will see all nodes are being looked at.

• CartesianProduct: This is a scenario when we have multiple MATCH statements without the WITH clause between them. A sample of such a scenario looks like this:

  MATCH (p:Patient)

  MATCH (d:Drug)

  RETURN...