BsoBird commented on issue #11765:
URL: https://github.com/apache/iceberg/issues/11765#issuecomment-2541708695
@RussellSpitzer
Sir. I am using Spark version 3.5.1, and the Iceberg version is 1.7.1/1.6.1.
Sql:
```
merge into target_iceberg_table t using
(
select primark_key,modified_time
from (
select prikaey_key,modified_time,row_number() over(partition by
primary_key order by modified_time desc) as rank
from ods_table
) s1 where rank=1
) s
when matched when s.modified_time > t.modified_time then update set
t.modified_time = s.modified_time
when not matched then insert *
```
In this SQL, target_iceberg_table is a COW (Copy-On-Write) table.
However, sir, I might have discovered some issues. When executing the
COW-MERGE-INTO command, Spark needs to use the ods_table twice. The first time
is to match data files based on incremental records, and the second time is to
perform the actual data merge. If the data in the ods_table changes between the
first and second usage, I would like to know if this could lead to abnormal
execution results? What would happen if the data in the ods_table suddenly
increases? What about if the data in the ods_table suddenly decreases?
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