Historian Configuration

1. Create a QuestDB connection

The historian needs a QuestDB instance with both ports reachable:

Port	Protocol	Used for
8812	Postgres wire	Queries
9009	Line protocol (ILP)	Ingestion

→ QuestDB connection

2. Designate it as the historian

The designation lives in Settings → Historian. Reading it needs View connections; changing it needs Edit connections.

Exactly one connection can hold the designation. Changing it opens a new epoch rather than truncating existing history.

Before accepting a store, QUBIQ pre-flights it: it looks inside for an existing historian table and checks its shape, rather than issuing a CREATE TABLE IF NOT EXISTS that silently no-ops against a table it did not create.

3. Tune ingestion

Setting	Effect	Guidance
Worker count	Parallel ILP senders	1–4; more only helps at high tag counts
Auto-flush rows	Flush after N rows	Higher = more throughput, later visibility
Auto-flush interval	Flush after N ms	Bounds visibility latency on slow plants
Deduplication	QuestDB DEDUP UPSERT KEYS	Leave on — makes replays idempotent
Partition	Base table partition unit	DAY suits most plants
Rollup partition	Rollup partition unit	Coarser than the base table
Rollup refresh every	Re-aggregation cadence	Balance freshness against load

Deduplication matters more than it looks. Store-and-forward can replay a batch that was flushed but not acknowledged — a crash in exactly that window. With dedup on, the replay overwrites identical rows; with it off, it duplicates them.

4. Enable history on tags

Per tag: Enable history, plus a deadband and optionally a store interval.

Be deliberate. For each tag ask:

• Will anyone trend this, or is the live value enough?
• What deadband makes the trend honest without storing noise?
• Does a frozen signal need a store interval to prove it was alive?

A 0.5–1% of span deadband typically removes 90%+ of the rows and changes no chart a human can read.

5. Set retention

The sweep runs daily, dropping whole partitions past the configured age. Because partition drops are metadata-only in QuestDB, retention costs essentially nothing.

The first sweep waits for a warm-up period after boot, so it does not race schema creation.

Sizing:

rows ≈ tags × changes-per-second × 86,400 × retention-days

Apply QuestDB's compression to that, then add headroom. If the number is uncomfortable, revisit deadbands before revisiting retention — a value you never stored costs nothing to keep.

Repairing a store

Schema drift

QuestDB auto-creates a table for an ILP line naming a table that does not exist — with a schema QUBIQ did not choose: the designated timestamp named timestamp instead of ts, no dedup keys, no index, and val_* columns appearing lazily as each type first arrives. Every read path expects ts, so the historian goes silent with Invalid column: ts.

QUBIQ detects this and alarms. To repair:

Use Rebuild table on the connection (needs Edit connections).

QuestDB refuses to rename a designated timestamp column, so repair-in-place is impossible; the data is copied into a correctly-shaped table.

Stale rollup

Use Rebuild rollup on the connection (needs Edit connections). It re-aggregates the 1-minute rollup. The automatic rebuild declines above a size threshold — this is the deliberate counterpart, run when you can accept the load.

Suspended tables

If QuestDB's WAL apply job fails unrecoverably, the table is suspended: rows land in the WAL, nothing is applied, and charts go silent while ingestion appears healthy.

The WAL supervisor distinguishes a recoverable stall (resumed automatically) from a poison or missing segment after a disk event or unclean restart (alarmed, because blindly resuming would loop). A suspended-table alarm means: look at QuestDB's own logs.

Ownership conflict

An ownership banner means another installation claims this store. Confirm the previous owner is retired, then:

Use Take ownership on the connection (needs Edit connections). This is audited. Do not do it to silence a banner on a store another live system is writing to.

Migrating the historian

1. Create and test the new QuestDB connection.
2. Change the designation in Settings → Historian.
3. QUBIQ closes the old epoch and opens a new one.
4. Charts spanning the changeover query both stores and stitch the timeline.
5. Retire the old store only when its epoch is no longer within any window you need to read.

No export/import step, and no truncated trends.

Monitoring

What	Where
Ingestion buffer status	The Status panel (needs View connections)
Buffer pressure	The buffer-pressure alarm
Series cache statistics	The Status panel's historian view
Schema drift, suspension, ownership	Historian alarms

Troubleshooting

Symptom	Cause	Action
No data for a tag	History not enabled on the tag	Enable it
No data at all	No designated historian, or ILP unreachable	Check designation and port 9009
Invalid column: ts	Schema drift	Rebuild the table
Charts stop, ingestion looks fine	Table suspended	Check QuestDB logs; the supervisor alarms
Ownership banner	Another installation claims the store	Verify, then take ownership
Data appears seconds late	Auto-flush interval too high	Lower it, or rely on the live-tail merge
Disk filling faster than expected	Deadbands missing, or history on chattering tags	Set deadbands
Long-range charts slow	Rollup stale	Rebuild the rollup

Next

→ Querying history