terrymanu commented on issue #35851:
URL:
https://github.com/apache/shardingsphere/issues/35851#issuecomment-3670641186
Understanding
You’re on ShardingSphere-JDBC 5.5.2 (with
dynamic-datasource-spring-boot-starter), configured a SNOWFLAKE key generator
named baomidou_snowflake, and are seeing negative, widely jumping IDs
(screenshot shows several negatives).
Root Cause
ShardingSphere’s built-in Snowflake (41-bit time + 10-bit workerId +
12-bit sequence) won’t produce negatives in 2025 with a normal clock and
workerId ≤1023. Negatives are more likely because:
1. IDs are coming from another generator (e.g., MyBatis-Plus/baomidou
Snowflake or a custom time service) that overflows;
2. System time is skewed far into the future or replaced by a custom
TimeService.
Also, the property is written as worker: id: ${workerId}, but
ShardingSphere expects a flat worker-id; this won’t take effect and indicates
the config isn’t following ShardingSphere conventions.
Analysis
- With ShardingSphere’s Snowflake, the sign bit stays 0 as long as
(currentMillis - epoch) < 2^41; in 2025 we’re far below the limit. Negatives
imply a different generator or a future-shifted clock.
- In MyBatis-Plus setups, if entities/global settings still use
IdType.ASSIGN_ID, IDs may come from MP’s Snowflake instead of ShardingSphere.
- The worker: id form isn’t recognized by ShardingSphere, so your intended
workerId isn’t applied, further suggesting the path might still hit an external
generator.
- Lacking the expanded YAML, logs showing which key generator is called,
clock/NTP status, and ORM PK strategy, we can’t reproduce a negative ID in
ShardingSphere’s built-in Snowflake.
Conclusion
Because baomidou_snowflake is in use, the IDs are effectively from the
baomidou/external generator, not ShardingSphere’s built-in Snowflake; this
issue can be closed.
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