## Proposed changes
support parallel result sink

This PR changed result sink logic:
#36053
Need to change the show column stats get row batch logic to avoid NPE.

## Proposed changes
optimization for parallel result sink #36053

## Proposed changes
optimization for parallel result sink apache#36053

This PR changed result sink logic:
#36053
Need to change the show column stats get row batch logic to avoid NPE.

## Proposed changes
optimization for parallel result sink #36053

… and dry_run_query=true. (#53653)

Related PR: #36053 && #53209

Problem Summary:

Fixed the issue that the result of `dry_run_query=true` is wrong in
multi-be scenarios (the number of rows is less)

I think this may be related to the multi result sink introduced in pr
#36053 && #53209.
Reason:
```cpp
vmysql_result_writer.cpp
GetResultBatchCtx::on_close() {
    ...
    statistics->set_returned_rows(returned_rows);  // Set only once per result_writer.
    ...
}
```
``` java
if (connectContext != null && connectContext.getSessionVariable().dryRunQuery) {
    if (resultBatch.isEos()) {     // This will only be counted once. 
        numReceivedRows += resultBatch.getQueryStatistics().getReturnedRows();
    }
} else if (resultBatch.getBatch() != null) {
    numReceivedRows += resultBatch.getBatch().getRowsSize();
}
```
If there are multiple be, there will be multiple result sinks, and each
result sink will update its own row count at the end. Since
`resultBatch.isEos()` is only triggered once, the row count information
is less.

… and dry_run_query=true. (apache#53653)

Related PR: apache#36053 && apache#53209

Problem Summary:

Fixed the issue that the result of `dry_run_query=true` is wrong in
multi-be scenarios (the number of rows is less)

I think this may be related to the multi result sink introduced in pr
apache#36053 && apache#53209.
Reason:
```cpp
vmysql_result_writer.cpp
GetResultBatchCtx::on_close() {
    ...
    statistics->set_returned_rows(returned_rows);  // Set only once per result_writer.
    ...
}
```
``` java
if (connectContext != null && connectContext.getSessionVariable().dryRunQuery) {
    if (resultBatch.isEos()) {     // This will only be counted once. 
        numReceivedRows += resultBatch.getQueryStatistics().getReturnedRows();
    }
} else if (resultBatch.getBatch() != null) {
    numReceivedRows += resultBatch.getBatch().getRowsSize();
}
```
If there are multiple be, there will be multiple result sinks, and each
result sink will update its own row count at the end. Since
`resultBatch.isEos()` is only triggered once, the row count information
is less.