Deleting Data

await gom.delete(Person, uuid);                                                  // returns how many: 1 or 0
await gom.delete(Issue, uuid, { where: (q) => q.state.eq('closed') });           // only if it meets the condition
await gom.deleteAll(Issue, (q) => ({ where: q.state.eq('closed') }));            // what a load with the filter finds
await gom.deleteAll(RaisedAndAssignedIssue, (q) => ({ where: q.assignedTo.name.eq('Former Employee') }));
await gom.deleteAll(Issue, 'n.locked = true');                                   // a predicate of your own, over n

A delete removes the root and its relationships. The nodes they led to stay, unless the delete cascades. Deleting a view by id can also delete the nodes it reaches:

await gom.delete(SessionView, sessionId);                                          // NONE: the root only
await gom.delete(SessionView, sessionId, { cascade: CascadeType.DELETE_ORPHAN });  // and each node nothing outside it needs
await gom.delete(SessionView, sessionId, { cascade: CascadeType.DELETE_ALL });     // and every node in the view

The cascade follows the relationships a save of the view writes, through nested views; a node outside the view is never deleted. So it leaves what a read-only field loads (a @ReadOnly() field, a @GraphPath, and a list of fragments read over several hops): other code writes those nodes. A view that contains itself is not read-only, so each of its levels is deleted. DELETE_ALL deletes nodes others may still point at, so use it for nodes the root owns. DELETE_ORPHAN keeps a node in the view that a node outside it still refers to, at any level, together with everything the view holds below it: a bookmarked message keeps its attachments, and a pinned sub-session keeps its messages and its own sub-sessions. The rest of the view is deleted, including the session that held a kept message. DELETE_ORPHAN isn’t available on Memgraph.

A view that contains itself (parts: SessionTree[], with a maxDepth) deletes what a load of it reads: the nodes at every level, and what each level holds through the view’s other relationships a save writes. A cascade never stops short: if the relationship reaches below its maxDepth, the delete throws a DrivineError before anything is written, saying how deep the view reads. Raise the maxDepth to cover the deepest level.