Anchors

It is possible to define the start time of an activity directive as relative to the start or end time of another directive. This is known as "Anchoring".

Anchor to Another Activity Directive

Anchors can be declared while inserting an activity directive:

mutation InsertDirectiveWithAnchor(
  $plan_id: Int!
  $name: String!
  $tags: _text
  $type: String!
  $arguments: jsonb!
  $metadata: jsonb
  $anchor_id: Int
  $anchored_to_start: Boolean!
  $start_offset: interval!
) {
  insert_activity_directive(
    objects: {
      plan_id: $plan_id
      name: $name
      tags: $tags
      type: $type
      arguments: $arguments
      metadata: $metadata
      anchor_id: $anchor_id
      anchored_to_start: $anchored_to_start
      start_offset: $start_offset
    }
  ) {
    returning {
      id
      plan_id
      name
      type
      created_at
      anchor_id
      anchored_to_start
      start_offset
      anchor_validations {
        reason_invalid
      }
    }
  }
}

Or can be added as an update to an existing directive:

mutation UpdateAnchor(
  $id: Int!
  $plan_id: Int!
  $anchor_id: Int
  $anchored_to_start: Boolean!
  $start_offset: interval!
) {
  update_activity_directive_by_pk(
    pk_columns: { id: $id, plan_id: $plan_id }
    _set: { anchor_id: $anchor_id, anchored_to_start: $anchored_to_start, start_offset: $start_offset }
  ) {
    id
    anchor_id
    anchored_to_start
    start_offset
    anchor_validations {
      reason_invalid
    }
  }
}

If you have previously anchored an activity directive to another directive and wish to remove the anchor, you can anchor it back to plan by setting its anchor_id to null.

Invalid Anchors

For ease of use, Aerie allows anchors that are not able to be simulated to exist. These anchors are considered to be invalid.

Note

A plan cannot be simulated or scheduled while there are invalid anchors.

To get all invalid anchors for a plan, along with the reason why each anchor is invalid, use the following query:

query QueryAllInvalidAnchors($plan_id: Int!) {
  anchor_validation_status(
    where: { plan_id: { _eq: $plan_id }, _and: { reason_invalid: { _neq: "" } } }
    order_by: { activity_id: asc }
  ) {
    activity_id
    reason_invalid
  }
}

Delete Activity Directive with Anchors

If an activity directive has other directives anchored to it, it cannot be deleted directly. Instead, all anchors onto it must either be manually removed from the dependent directives or handled in bulk using one of the following options:

Delete Entire Subtree

This option deletes both the directive and all directives anchored to it at once.

mutation DeleteSubtree($plan_id: Int!, $activity_id: Int!) {
  delete_activity_by_pk_delete_subtree(args: { _plan_id: $plan_id, _activity_id: $activity_id }) {
    change_type
    affected_row
  }
}

Reanchor Subtree

This option keeps the directives that were anchored to the activity directive to be deleted (referred to here as the "root directive"), but modifies their anchors so they are no longer anchored to the root directive. It then deletes the root directive.

caution

When reanchoring the subtrees, Aerie does not account for the duration the root directive might have when simulated. If any activity directives were anchored to the end of the root directive, they may be simulated earlier than expected.

Reanchor Subtree to Plan Start

mutation ReanchorPlanStart($plan_id: Int!, $activity_id: Int!) {
  delete_activity_by_pk_reanchor_plan_start(args: { _plan_id: $plan_id, _activity_id: $activity_id }) {
    change_type
    affected_row
  }
}

Reanchor Subtree to Root Directive's Anchor

If the root directive was anchored to another activity directive, you can choose to reanchor the subtrees to that directive.

mutation ReanchorRootAnchor($plan_id: Int!, $activity_id: Int!) {
  delete_activity_by_pk_reanchor_to_anchor(args: { _plan_id: $plan_id, _activity_id: $activity_id }) {
    change_type
    affected_row
  }
}