Improving Transfer's comments.

clients/snowflake/staging.go

@@ -27,12 +27,6 @@ func castColValStaging(colVal any, colKind columns.Column, additionalDateFmts []
 	return values.ToString(colVal, colKind, additionalDateFmts)
 }
 
-// PrepareTemporaryTable does the following:
-// 1) Create the temporary table
-// 2) Load in-memory table -> CSV
-// 3) Runs PUT to upload CSV to Snowflake staging (auto-compression with GZIP)
-// 4) Runs COPY INTO with the columns specified into temporary table
-// 5) Deletes CSV generated from (2)
 func (s *Store) PrepareTemporaryTable(tableData *optimization.TableData, tableConfig *types.DwhTableConfig, tempTableName string, additionalSettings types.AdditionalSettings, createTempTable bool) error {
 	if createTempTable {
 		tempAlterTableArgs := ddl.AlterTableArgs{
@@ -51,6 +45,7 @@ func (s *Store) PrepareTemporaryTable(tableData *optimization.TableData, tableCo
 		}
 	}
 
+	// Write data into CSV
 	fp, err := s.loadTemporaryTable(tableData, tempTableName)
 	if err != nil {
 		return fmt.Errorf("failed to load temporary table: %w", err)
@@ -63,26 +58,25 @@ func (s *Store) PrepareTemporaryTable(tableData *optimization.TableData, tableCo
 		}
 	}()
 
+	// Upload the CSV file to Snowflake
 	if _, err = s.Exec(fmt.Sprintf("PUT file://%s @%s AUTO_COMPRESS=TRUE", fp, addPrefixToTableName(tempTableName, "%"))); err != nil {
 		return fmt.Errorf("failed to run PUT for temporary table: %w", err)
 	}
 
+	// COPY the CSV file (in Snowflake) into a table
 	copyCommand := fmt.Sprintf("COPY INTO %s (%s) FROM (SELECT %s FROM @%s)",
-		// Copy into temporary tables (column ...)
 		tempTableName, strings.Join(tableData.ReadOnlyInMemoryCols().GetColumnsToUpdate(s.config.SharedDestinationConfig.UppercaseEscapedNames, &sql.NameArgs{
 			Escape:   true,
 			DestKind: s.Label(),
 		}), ","),
-		// Escaped columns, TABLE NAME
 		escapeColumns(tableData.ReadOnlyInMemoryCols(), ","), addPrefixToTableName(tempTableName, "%"))
 
 	if additionalSettings.AdditionalCopyClause != "" {
 		copyCommand += " " + additionalSettings.AdditionalCopyClause
 	}
 
-	_, err = s.Exec(copyCommand)
-	if err != nil {
-		return fmt.Errorf("failed to load staging file into temporary table: %w", err)
+	if _, err = s.Exec(copyCommand); err != nil {
+		return fmt.Errorf("failed to run copy into temporary table: %w", err)
 	}
 
 	return nil