Skip to content

Safely edit a record (GET-modify-PUT)

Goal: change or delete varFields on a patron (or item) record without corrupting the fields you didn't touch.

A PUT with varFields replaces one fieldTag group at a time: for every fieldTag you send, Sierra rewrites that tag's whole group with exactly what you sent, and leaves tags you send nothing of untouched (see PUT varFields replaces per fieldTag group). You still fetch the whole record and edit in memory — both so an update keeps each field's identity instead of duplicating it, and because deleting a field means either dropping it while still sending its same-tag siblings, or (patrons only) blanking its content.

Before you start

  • A SierraRESTClient authenticated against your deployment.
  • The record number (record_num) of the record you're editing.

1. GET the full record

Use the bare-comma fields=, form to get all fields — without it you get a minimal response that's missing the varFields you need to preserve.

resp = client.request("GET", f"patrons/{record_num}", params={"fields": ","})
record = resp.json()
varfields = record.get("varFields", [])

2. Modify varFields in memory

Edit the list you fetched, leaving every entry you don't intend to change untouched.

  • To change a field: edit its content in place.
  • To delete a field:
    • if it shares its fieldTag with fields you're keeping → just leave it out; sending the siblings rewrites that tag-group without it (works on any record type).
    • if it's the only field of its tag → set content to "" (patrons remove it; items/bibs only blank it — no clean removal there). Don't expect leaving the sole field of a tag out of the array to delete it — that sends zero of the tag, so Sierra leaves it untouched.
  • If you don't want a deletion, drop empty-content entries before sending so you don't blank a patron field by accident:
varfields = [vf for vf in varfields if vf.get("content")]   # avoid accidental empty-content deletes
# ... make your edits to varfields here ...

3. PUT only the mutable subset

Send just {"varFields": [...]} — the complete array. Do not echo the whole GET response back: Sierra rejects ~9 read-only top-level fields (id, homeLibrary, updatedDate, createdDate, deleted, …) with 400 Invalid JSON : field(s) unknown.

resp = client.request("PUT", f"patrons/{record_num}", json={"varFields": varfields})

4. Check for 204, not 200

A successful update returns 204 No Content with no body. Don't call .json() on it.

if resp.status_code == 204:
    ...  # success
elif resp.status_code == 404:
    ...  # "ghost record": GET worked but PUT 404s — skip it, non-fatal
else:
    resp.raise_for_status()

Gotchas this recipe already handles

  • Per-tag-group replace — omitting a field deletes it only if you still send another field of the same fieldTag; the sole field of a tag survives omission. Delete singletons by blanking content (patrons only). Step 1's fields=, + PUT-back preserves each field's identity so edits don't create duplicates.
  • Empty-content drop — step 2 pre-filters so it doesn't surprise your verification.
  • Read-only fields — step 3 sends only varFields, avoiding the 400.
  • 204 not 200 — step 4 checks the right status and never parses an empty body.
  • Ghost records — step 4 treats a PUT 404 after a successful GET as a non-fatal skip.
  • Don't send top-level phones — it appends instead of replacing; manage phone data through varFields, which this recipe does by construction.

Verify

After the PUT, GET the record again with fields=, and compare the underlying varFields — not the top-level emails/phones/names arrays, which Sierra re-renders on every write and will always look "changed".

Underlying behavior (reference):

Why this is necessary: Why writes have side effects