Non-serializable execution (lost update) when a recode is deleted about scalardb HOT 3 CLOSED

Cheap solution: randomize initial version.
Precise solution: check tx_id and tx_version in the prepare phase.

Randomizing initial version almost fix the issue except 1/2^32 of collision.

tx_id is a UUIDv4 value newly generated for each transaction, so the collision is neglectable. Checking two values may impact the performance, although it might not be significant.

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@Yonezawa-T2 Thanks. That randomize solution sounds a bit tricky and makes verification more difficult.
Checking tx_id additionally might be good enough for this.

I feel introducing logical delete and guaranteeing monotonic version increase would probably be good from many perspectives as well. Physical delete is a bit scary from verification perspective actually. (it depends how well C*/underlining conditional delete is implemented)

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It is closed since it is fixed.
@Yonezawa-T2 Thank you very much for the report.

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