feat: implement batch processing for MSSQL with improved structure and logging

cmd/go_migrate/extractor-error-handler.go

@@ -0,0 +1,66 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/google/uuid"
+)
+
+type ExtractorError struct {
+	Batch
+	LastId    int64
+	HasLastId bool
+	Msg       string
+}
+
+func (e *ExtractorError) Error() string {
+	return e.Msg
+}
+
+const maxRetryAttempts = 3
+
+func extractorErrorHandler(chErrorsIn <-chan ExtractorError, chBatchesOut chan<- Batch, chGlobalErrorsOut chan<- error) {
+	for err := range chErrorsIn {
+		if err.RetryCounter >= maxRetryAttempts {
+			chGlobalErrorsOut <- fmt.Errorf("batch %v reached max retries (%d): %s", err.Id, maxRetryAttempts, err.Msg)
+			continue
+		}
+
+		newBatch := err.Batch
+		newBatch.RetryCounter++
+
+		if err.HasLastId {
+			newBatch.ParentId = err.Id
+			newBatch.Id = uuid.New()
+			newBatch.LowerLimit = err.LastId
+			newBatch.IsLowerLimitInclusive = false
+		}
+
+		chBatchesOut <- newBatch
+	}
+}
+
+func ExtractorErrorFromLastRowMssql(lastRow UnknownRowValues, indexPrimaryKey int, batch *Batch, previousError error) ExtractorError {
+	lastIdRawValue := lastRow[indexPrimaryKey]
+
+	lastId, ok := ToInt64(lastIdRawValue)
+	if !ok {
+		currentBatch := *batch
+		currentBatch.RetryCounter = maxRetryAttempts
+		exError := ExtractorError{
+			Batch:     currentBatch,
+			HasLastId: true,
+			Msg:       fmt.Sprintf("Couldn't cast last id value as int: %s", previousError.Error()),
+		}
+		return exError
+
+	}
+
+	exError := ExtractorError{
+		Batch:     *batch,
+		HasLastId: true,
+		LastId:    lastId,
+		Msg:       previousError.Error(),
+	}
+	return exError
+}