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Version: 1.0.8

Annotations New in 1.0.8

An annotation is a note written on the history of one or more tags: "Filter changed" at a moment, or "Line stopped for CIP" across a period. Every Historian chart that shows one of those tags draws it, wherever that chart is. The note belongs to the tag's history, not to the chart it was written on.

Who sees and writes them​

ViewerReadsAddsEdits or deletes
A LiveView operator signed in to this project✅✅Their own
A platform user with View Namespace✅✅Their own
An administrator: a platform admin, or an operator at the Admin write level✅✅Any
An anonymous visitor of a public trend❌❌❌

Annotations are for signed-in viewers only. An anonymous visitor of a public trend sees the trend, with no annotations and no Annotations button. The identity comes from the viewer's session, never from anything the page sends, and writes are rate-limited.

Placing one​

  1. On a Historian chart, open Annotations in the toolbar. The panel lists the notes in the window.
  2. Press Add. The plot switches to placing mode, with a crosshair and the hint Click a moment or drag across a period to annotate. Esc cancels.
  3. Click for a moment, or drag across a period. The form opens with the time already set.
  4. Write the Note (up to 2,000 characters), check Moment or Period and its times, pick the Tags it belongs to, and Save.

Shortcut: Ctrl + click or Ctrl + drag (⌘ on a Mac) places a note without opening the panel first. Placing never zooms the chart or pins the crosshair.

A note on an alarm. A moment placed within a few pixels of an alarm event on the chart snaps to that event's exact time, for "why did this trip?". Its badge sits just below the alarm triangle, and the tooltip names both.

On the chart​

  • A moment is a strong dashed guide with a round badge on top of the line.
  • A period is a tinted band with solid edges and a bar from the badge to its end.
  • Hover a badge to read the note, its author and its time. Click it to open the note in the panel, highlighted, where its author or an administrator can Edit or Delete it. Delete asks first.
  • Annotations have their own colour (violet), distinct from the alarm palette and the quality shading.
  • Settings → Annotations → Show annotations hides them for this viewer. The chart's settings.annotations property sets the default (on).

A window shows at most the newest 1,000 notes; the panel says so when there are more.

Two people, one note​

If someone changed a note after you opened it, your edit or delete is refused. The panel says who changed it, and the chart reloads the current version. Nothing is silently overwritten.

Where they are kept​

Annotations live in their own table, historian_annotation, on the designated historian's QuestDB, beside the history they describe. QuestDB cannot update or delete a row, so a note is append-only: an edit or a delete is a new revision of the same note, and the newest revision is the note. That also records who changed what, and when.

  • Annotations have no retention. They outlive the raw history they describe.
  • Moving the historian keeps them. A chart reads the notes from every store its window spans, and the newest revision of each note wins wherever it was written.
  • Reads are served from memory, refreshed from QuestDB at most once a second. A chart with many notes costs QuestDB nothing per pan or zoom.

→ Querying history · Historian component