Stored NULL values come back as 0.0 from history queries (SQL Historian and SDK historians)

Ignition
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We're building a custom historian module for timescaledb on the 8.3 Historian SDK (gateway 8.3.3) and got a bug report that NULL values in history read back as 0.0. After digging in, it turns out this isn't specific to our module.

What we tested:

  1. Stored three good float points (1.5, 2.5, 3.5) with system.historian.storeDataPoints, then inserted two rows with NULL values directly in the database: one with good quality (192) and one with the bad quality code we observed Ignition itself produce for a failing tag (-2147483136). Queried the range with system.historian.queryRawPoints. Result: 1.5, 0.0, 2.5, 0.0, 3.5. The qualities come back unchanged (192 for the good NULL, -2147483136 for the bad one), but both NULLs turned into 0.0. The good quality NULL is now indistinguishable from a real measured zero.

  2. Our module keeps the value as null the whole way: we check ResultSet.wasNull() and hand the null to DataPointFactory.createAtomicPoint, which internally routes to createNullPoint. So the 0.0 appears later, when the platform assembles the query result dataset. As far as we can tell no historian implementation can return a NULL through that layer.

  3. For comparison we looked at the stock SQL Historian (historian-sql 1.3.3). In PartitionDataLoader.getValueFromRS the numeric columns are read with rs.getLong / rs.getDouble without a wasNull() check, so there a NULL already becomes 0/0.0 at the JDBC level.

Questions:

  1. Is the null to 0.0 coercion in query result assembly intended? If so, what is createNullPoint meant for?
  2. Is there a recommended way for a historian to return "no value at this timestamp" so clients see a gap instead of a fabricated zero?
  3. Should the missing wasNull() checks in the stock SQL Historian be filed as a bug through support?

Setup: Ignition 8.3.3 in Docker, queries via a WebDev endpoint calling system.historian.queryRawPoints, per-point qualities read with getQualityAt.

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