Delete-Time Reference Warning

Deleting a resource that others consume says so before it happens. The confirmation that already asks before every delete adds a warning when any of the owner's other resources reference what is going: "Used by 2 other resources, which will show it as missing until restored", followed by each one's name and type. Airtable's field manager answers the same question, what depends on this, before a field is deleted. A delete with no consumers looks exactly as it did.

How it works

ResourceConsumersWarning sits in both delete confirmations: the blade header's, for the resource the page is open on, and the list's, for one row or a whole selection. It mounts with the confirmation, so the read happens only when a delete is being asked about, and useQuery fires resource.readResourceConsumers with the ids. A query's input rides its URL, and a few hundred ids would pass the server's header limit, so a large selection is read READ_RESOURCE_CONSUMERS_IDS_MAX_LENGTH ids at a time, each chunk its own request. Each chunk leaves out only its own ids, so the warning drops a consumer that another chunk is deleting, and names once a consumer that several chunks found.

The procedure is one lookup of the resource-link index by target. It returns the caller's live resources that hold a link to any of the ids, of any role (a dashboard's or an email's Dataset, a program's Email or Survey), ordered by name. Three kinds of resource are left out, each for its own reason:

• A resource being deleted alongside. Deleting a dashboard together with its sheet leaves no reference behind to miss.
• A resource already in the recycle bin. It reads nothing until it is restored, and its own restore would show the source missing then.
• Another owner's resource. Its reference never resolves to the caller's resource (cross-owner references), and naming it would hand the caller its name.

flowchart LR
  OPEN["Delete confirmation opens"] -->|"ids"| READ["readResourceConsumers"]
  READ -->|"targetId in ids"| LINKS[("resourceLinks")]
  LINKS -->|"sourceId"| FILTER{"the caller's own, live,<br/>not being deleted?"}
  FILTER -->|"none"| PLAIN["plain confirmation"]
  FILTER -->|"some"| WARN["warning naming each consumer"]
  WARN --> CONFIRM["Delete moves to the bin;<br/>each consumer shows its source missing"]
  CONFIRM -->|"Restore"| HEAL["every consumer reads it again"]

The warning is advisory. Delete stays enabled, because the delete is a soft one: the toast after it offers Restore, and a restore heals every consumer at once, since nothing rewrote their content in the meantime (dangling reference cleanup). Each consumer says its source is missing where the reference is picked (datasets).

Key files

Notes

• The index is written by every save, and it shipped before any consumer held content, so the warning never undercounts a resource saved before it existed (resource links).
• Each chunk's read is capped at the list read limit, which is far past the consumers a selection has.

Sources

• Airtable, "Field manager and field dependencies" — which objects depend on a field, identified before it is changed or deleted: https://support.airtable.com/docs/field-manager-and-field-dependencies