What problem does this PR solve?

Issue Number: close #9561

Problem Summary:

select col, gen_col from t;

gen_col is a virtual generated column. The current approach is that TiFlash generates an empty column and places it in the block. Then, it passes the block to TiDB, allowing TiDB to calculate and populate the column.

I’ve named this column generated_xxx.

The information about this column is marked in tipb_table_scan.columns with a flag. When TiFlash sees this flag, it automatically adds a generated_xxx column.

However, this situation has an issue when a remote read occurs: the block returned from the remote read, when parsed, assigns names to each column based on RemoteRequest.schema. For example, if TiFlash-1 receives a block from TiFlash-2, it will parse it as <col, gen_col>.

But TiFlash-1, in the table scan's projection, expects the block to be <col, generated_xxx>. So, when projecting the block from the remote read, an error occurs because it cannot find the generated_xxx column.

What is changed and how it works?

make the column name of local read and remote read be same

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

fix virtual column not found when remote read happens