[ARORO-3289] Avoid calling getMixedTablePartitionSpecById in the scan loop

[7hong]

Why are the changes needed?

Close #3289 .

How was this patch tested?

In my environment, there is a table with many partitions waiting to be merged. Each plan is very time-consuming. After optimization, the time-consuming is significantly reduced

[7hong]

@zhoujinsong @majin1102 Do you have time to review it? Thanks

[baiyangtx]

Will the old code trigger a reload of TableMetadata?

It seems that if the reloading of TableMetadata is not triggered, the performance of the new code is the same as that of the old code.

Iceberg TableMetadata also returns Specs Map objects from memory

[7hong]

@baiyangtx
Yes, the old code will refresh the TableMetadata. Especially when calling the getUGI method in an environment with Kerberos enabled, it will enter a synchronous blocking state.

[czy006]

If there are Fire flame Graph or some unit test cases, it would be best.

[7hong]

@czy006
Flame graph before optimization：

Flame graph after optimization:

[zhoujinsong]

Based on the information provided by the flame graph, Table#specs does not reload table metadata. From its internal implementation, this process is controlled by the shouldRefresh variable. However, this call does trigger the Kerberos relogin check logic, which is unnecessary.

So, I am +1 with this improvement.