refactor: update extractor interfaces to return row counts instead of using pointers for rows read

internal/app/etl/extractors/mssql.go

@@ -73,14 +73,14 @@ func buildExtractQueryMssql(
 func errorFromLastRow(
 	lastRow models.UnknownRowValues,
 	indexPrimaryKey int,
-	partition *models.Partition,
+	partition models.Partition,
 	previousError error,
 ) *custom_errors.ExtractorError {
 	lastIdRawValue := lastRow[indexPrimaryKey]
 
 	lastId, ok := convert.ToInt64(lastIdRawValue)
 	if !ok {
-		currentPartition := *partition
+		currentPartition := partition
 		currentPartition.RetryCounter = 3
 		return &custom_errors.ExtractorError{
 			Partition: currentPartition,
@@ -91,7 +91,7 @@ func errorFromLastRow(
 	}
 
 	return &custom_errors.ExtractorError{
-		Partition: *partition,
+		Partition: partition,
 		HasLastId: true,
 		LastId:    lastId,
 		Msg:       previousError.Error(),
@@ -106,8 +106,7 @@ func (mssqlEx *MssqlExtractor) ProcessPartition(
 	partition models.Partition,
 	indexPrimaryKey int,
 	chBatchesOut chan<- models.Batch,
-	rowsRead *int64,
-) error {
+) (int, error) {
 	query := buildExtractQueryMssql(tableInfo, columns, partition.ShouldUseRange, partition.IsLowerLimitInclusive)
 
 	var queryArgs []any
@@ -118,9 +117,10 @@ func (mssqlEx *MssqlExtractor) ProcessPartition(
 		)
 	}
 
+	rowsRead := 0
 	rows, err := mssqlEx.db.QueryContext(ctx, query, queryArgs...)
 	if err != nil {
-		return &custom_errors.ExtractorError{Partition: partition, HasLastId: false, Msg: err.Error()}
+		return rowsRead, &custom_errors.ExtractorError{Partition: partition, HasLastId: false, Msg: err.Error()}
 	}
 	defer rows.Close()
 
@@ -136,7 +136,7 @@ func (mssqlEx *MssqlExtractor) ProcessPartition(
 
 		if err := rows.Scan(scanArgs...); err != nil {
 			if len(batchRows) == 0 {
-				return &custom_errors.ExtractorError{Partition: partition, HasLastId: false, Msg: err.Error()}
+				return rowsRead, &custom_errors.ExtractorError{Partition: partition, HasLastId: false, Msg: err.Error()}
 			}
 
 			lastRow := batchRows[len(batchRows)-1]
@@ -144,52 +144,48 @@ func (mssqlEx *MssqlExtractor) ProcessPartition(
 			select {
 			case chBatchesOut <- models.Batch{Id: uuid.New(), PartitionId: partition.Id, Rows: batchRows, RetryCounter: 0}:
 			case <-ctx.Done():
-				return nil
+				return rowsRead, ctx.Err()
 			}
 
-			atomic.AddInt64(rowsRead, int64(len(batchRows)))
-
-			return errorFromLastRow(lastRow, indexPrimaryKey, &partition, err)
+			return rowsRead, errorFromLastRow(lastRow, indexPrimaryKey, partition, err)
 		}
+		rowsRead++
 
 		batchRows = append(batchRows, rowValues)
-
 		if len(batchRows) >= batchSize {
 			select {
 			case chBatchesOut <- models.Batch{Id: uuid.New(), PartitionId: partition.Id, Rows: batchRows, RetryCounter: 0}:
 			case <-ctx.Done():
-				return nil
+				return rowsRead, ctx.Err()
 			}
 
-			atomic.AddInt64(rowsRead, int64(len(batchRows)))
 			batchRows = make([]models.UnknownRowValues, 0, batchSize)
 		}
+
 	}
 
 	if err := rows.Err(); err != nil {
 		if errors.Is(err, ctx.Err()) {
-			return ctx.Err()
+			return rowsRead, ctx.Err()
 		}
 
-		if len(batchRows) == 0 {
-			return &custom_errors.ExtractorError{Partition: partition, HasLastId: false, Msg: err.Error()}
+		if len(batchRows) > 0 {
+			lastRow := batchRows[len(batchRows)-1]
+			return rowsRead, errorFromLastRow(lastRow, indexPrimaryKey, partition, err)
 		}
 
-		lastRow := batchRows[len(batchRows)-1]
-		return errorFromLastRow(lastRow, indexPrimaryKey, &partition, err)
+		return rowsRead, &custom_errors.ExtractorError{Partition: partition, HasLastId: false, Msg: err.Error()}
 	}
 
 	if len(batchRows) > 0 {
 		select {
 		case chBatchesOut <- models.Batch{Id: uuid.New(), PartitionId: partition.Id, Rows: batchRows, RetryCounter: 0}:
 		case <-ctx.Done():
-			return nil
+			return rowsRead, ctx.Err()
 		}
-
-		atomic.AddInt64(rowsRead, int64(len(batchRows)))
 	}
 
-	return nil
+	return rowsRead, nil
 }
 
 func (mssqlEx *MssqlExtractor) Exec(
@@ -234,7 +230,7 @@ func (mssqlEx *MssqlExtractor) Exec(
 				return
 			}
 
-			err := mssqlEx.ProcessPartition(
+			rowsReadResult, err := mssqlEx.ProcessPartition(
 				ctx,
 				tableInfo,
 				columns,
@@ -242,9 +238,12 @@ func (mssqlEx *MssqlExtractor) Exec(
 				partition,
 				indexPrimaryKey,
 				chBatchesOut,
-				rowsRead,
 			)
 
+			if rowsReadResult > 0 {
+				atomic.AddInt64(rowsRead, int64(rowsReadResult))
+			}
+
 			if err != nil {
 				var exError *custom_errors.ExtractorError
 				var jobError *custom_errors.JobError