BentsiLeviav opened a new issue, #38466:
URL: https://github.com/apache/beam/issues/38466
### What would you like to happen?
**Title:** ClickHouseIO: Add `DateTime64` support for sub-second timestamp
precision
### Problem
The ClickHouse IO currently supports only `DateTime` (second precision)
via `TypeName.DATETIME`, which maps to Beam's `Schema.FieldType.DATETIME`
(millisecond precision Joda `Instant`).
ClickHouse's `DateTime64(precision, [timezone])` type — which supports
millisecond, microsecond, and nanosecond precision — is not recognized by
`TableSchema` or the column type parser, so users
cannot write sub-second timestamps to ClickHouse tables that use
`DateTime64` columns.
This is becoming a blocker for users whose pipelines emit events with
sub-second timestamps (e.g. log/event ingestion, financial data).
### Proposed solution
1. **Schema model**
- Add `TypeName.DATETIME64`.
- Extend `ColumnType` with a `precision` field (0–9) and an optional
`timezone` string, plus a factory `ColumnType.dateTime64(int precision,
@Nullable String timezone)`.
2. **Parser**
- Add a grammar rule for `DateTime64(<precision>[, '<timezone>'])` to
`ColumnTypeParser.jj`.
3. **Beam field type mapping**
- For `precision <= 3`, continue mapping to `Schema.FieldType.DATETIME`
(Joda `Instant`, ms precision) for backward compatibility.
- For `precision > 3`, map to a Beam logical type that preserves
sub-second precision — `SqlTypes.TIMESTAMP` (`java.time.Instant`-backed, nanos)
is the natural fit.
4. **Writer**
- In `ClickHouseWriter`, serialize `DateTime64` as a little-endian
`Int64` containing `epoch_seconds * 10^precision + sub_second_units`, matching
the ClickHouse native protocol.
5. **Tests**
- Round-trip tests for precisions 3, 6, 9 against a ClickHouse test
container, plus parser unit tests covering `DateTime64(3)`, `DateTime64(6,
'UTC')`, and the `Nullable(DateTime64(...))`
wrapper.
### Issue Priority
Priority: 2 (default / most feature requests should be filed as P2)
### Issue Components
- [ ] Component: Python SDK
- [ ] Component: Java SDK
- [ ] Component: Go SDK
- [ ] Component: Typescript SDK
- [x] Component: IO connector
- [ ] Component: Beam YAML
- [ ] Component: Beam examples
- [ ] Component: Beam playground
- [ ] Component: Beam katas
- [ ] Component: Website
- [ ] Component: Infrastructure
- [ ] Component: Spark Runner
- [ ] Component: Flink Runner
- [ ] Component: Prism Runner
- [ ] Component: Twister2 Runner
- [ ] Component: Hazelcast Jet Runner
- [ ] Component: Google Cloud Dataflow Runner
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