Reading default values (#912)

clients/mssql/queries.go

@@ -14,7 +14,8 @@ SELECT
 		ELSE
 		DATA_TYPE
 	END AS DATA_TYPE,
-    CHARACTER_MAXIMUM_LENGTH
+    CHARACTER_MAXIMUM_LENGTH,
+    COLUMN_DEFAULT AS DEFAULT_VALUE
 FROM
     INFORMATION_SCHEMA.COLUMNS
 WHERE

clients/mssql/store.go

@@ -72,7 +72,6 @@ func (s *Store) Dedupe(_ sql.TableIdentifier, _ []string, _ bool) error {
 }
 
 func (s *Store) GetTableConfig(tableData *optimization.TableData) (*types.DwhTableConfig, error) {
-	// TODO: Figure out how to leave a comment.
 	tableID := s.specificIdentifierFor(tableData.TopicConfig(), tableData.Name())
 	query, args := describeTableQuery(tableID)
 	return shared.GetTableCfgArgs{

clients/shared/table_config.go

@@ -15,6 +15,8 @@ import (
 	"github.com/artie-labs/transfer/lib/typing/columns"
 )
 
+// TODO: Simplify this function
+
 type GetTableCfgArgs struct {
 	Dwh       destination.DataWarehouse
 	TableID   sql.TableIdentifier
@@ -104,14 +106,24 @@ func (g GetTableCfgArgs) GetTableConfig() (*types.DwhTableConfig, error) {
 		}
 
 		col := columns.NewColumn(row[g.ColumnNameForName], kindDetails)
-		// We need to check to make sure the comment is not an empty string
-		if comment, isOk := row[g.ColumnNameForComment]; isOk && comment != "" {
-			var _colComment constants.ColComment
-			if err = json.Unmarshal([]byte(comment), &_colComment); err != nil {
-				return nil, fmt.Errorf("failed to unmarshal comment %q: %w", comment, err)
+		strategy := g.Dwh.Dialect().GetDefaultValueStrategy()
+		switch strategy {
+		case sql.Backfill:
+			// We need to check to make sure the comment is not an empty string
+			if comment, isOk := row[g.ColumnNameForComment]; isOk && comment != "" {
+				var _colComment constants.ColComment
+				if err = json.Unmarshal([]byte(comment), &_colComment); err != nil {
+					return nil, fmt.Errorf("failed to unmarshal comment %q: %w", comment, err)
+				}
+
+				col.SetBackfilled(_colComment.Backfilled)
 			}
-
-			col.SetBackfilled(_colComment.Backfilled)
+		case sql.Native:
+			if value, isOk := row["default_value"]; isOk && value != "" {
+				col.SetBackfilled(true)
+			}
+		default:
+			return nil, fmt.Errorf("unknown default value strategy: %q", strategy)
 		}
 
 		cols.AddColumn(col)

lib/typing/columns/columns.go

@@ -26,7 +26,8 @@ type Column struct {
 	// Whenever we see the same column where there's an opposite value in `toastColumn`, we will trigger a flush
 	ToastColumn  bool
 	defaultValue any
-	backfilled   bool
+	// TODO: Instead of using a boolean, we should be setting the value at some point.
+	backfilled bool
 }
 
 func (c *Column) PrimaryKey() bool {