[cherry-pick] pr #13909 fix some unhandled error and redundant codes

[m-schen]

What type of PR is this?

• API-change
• BUG
• Improvement
• Documentation
• Feature
• Test and CI
• Code Refactoring

Which issue(s) this PR fixes:

issue #13908

What this PR does / why we need it:

some error was unhandled and it may cause hung.
removed some unused codes like redundant type conversion.

[matrix-meow]

@m-schen Thanks for your contributions!

Review:

Title: [cherry-pick] pr #13909 fix some unhandled error and redundant codes

Body:

• The PR is marked as a BUG fix.
• It fixes issue [Bug]: some error was unhandled in the package compile #13908.
• The PR addresses unhandled errors and removes redundant code.

Changes:

• In pkg/sql/compile/compile.go, the code now checks for errors when submitting tasks to the ants pool and handles the error by sending it to the errC channel and calling wg.Done().
• In pkg/sql/compile/ddl.go, the code removes unnecessary type conversion when appending addIndex to newCt.Cts.
• In pkg/sql/compile/ddl.go, the code now assigns the result of dbSource.Truncate to a variable err and checks for errors.
• In pkg/sql/compile/ddl.go, the code removes unnecessary type conversion when comparing startNum with preStartWith.
• In pkg/sql/compile/fuzzyCheck.go, the code now checks for errors when writing to the all buffer and returns the error if any.
• In pkg/sql/compile/runtime_filter.go, the code assigns filter.Data directly to Zm without unnecessary type conversion.
• In pkg/sql/compile/scope.go, the code now checks for errors when submitting tasks to the ants pool and handles the error by sending it to the errChan channel and calling wg.Done().
• In pkg/sql/compile/util.go, the code now calls cancelFunc() after assigning index_id to handle the context cancellation properly.

Overall, the changes made in this pull request address the unhandled errors and remove redundant code. However, there are a few suggestions for further improvement:

1. Error handling in pkg/sql/compile/compile.go and pkg/sql/compile/scope.go:

   • Instead of sending the error to the errC and errChan channels and calling wg.Done() separately, it would be more efficient to use a defer statement to handle the error and call wg.Done() in a single place.
   • Example:

     errSubmit := ants.Submit(func() {
         defer func() {
             if e := recover(); e != nil {
                 err := moerr.ConvertPanicError(c.ctx, e)
                 errC <- err
             }
             wg.Done()
         }()
         // Task logic here
     })
     

2. Redundant type conversion in pkg/sql/compile/ddl.go:

   • The type conversion in the comparison startNum < preStartWith is unnecessary since startNum and preStartWith are already of the same type. The comparison can be simplified to startNum < preStartWith.

3. Error handling in pkg/sql/compile/fuzzyCheck.go:

   • Instead of returning the error immediately when writing to the all buffer, it would be better to accumulate the errors in a slice and return them all at once. This way, the caller can handle multiple errors if they occur.

4. Context cancellation in pkg/sql/compile/util.go:

   • The cancelFunc() should be called before returning from the function to ensure proper cancellation of the context. It can be moved outside the if err != nil block.

These suggestions will help improve the code quality and optimize the changes made in the pull request.

[m-schen]

chatgpt好像越活越倒退了。。

1，2，4点就是我改的内容。
第三点纯纯乱讲 😠😠