func (d *ddl) addColumn(tblInfo *model.TableInfo, colInfo *model.ColumnInfo, pos *ColumnPosition) (*model.ColumnInfo, int, error) {
// Check column name duplicate.
cols := tblInfo.Columns
position := len(cols)
// Get column position.
if pos.Type == ColumnPositionFirst {
position = 0
} else if pos.Type == ColumnPositionAfter {
c := findCol(cols, pos.RelativeColumn)
if c == nil {
return nil, 0, errors.Errorf("No such column: %v", pos.RelativeColumn)
}
// Insert position is after the mentioned column.
position = c.Offset + 1
}
colInfo.State = model.StateNone
// To support add column asynchronous, we should mark its offset as the last column.
// So that we can use origin column offset to get value from row.
colInfo.Offset = len(cols)
// Insert col into the right place of the column list.
newCols := make([]*model.ColumnInfo, 0, len(cols)+1)
newCols = append(newCols, cols[:position]...)
newCols = append(newCols, colInfo)
newCols = append(newCols, cols[position:]...)
tblInfo.Columns = newCols
return colInfo, position, nil
}
func (d *ddl) createColumnInfo(tblInfo *model.TableInfo, colInfo *model.ColumnInfo, pos *ast.ColumnPosition) (*model.ColumnInfo, int, error) {
// Check column name duplicate.
cols := tblInfo.Columns
position := len(cols)
// Get column position.
if pos.Tp == ast.ColumnPositionFirst {
position = 0
} else if pos.Tp == ast.ColumnPositionAfter {
c := findCol(cols, pos.RelativeColumn.Name.L)
if c == nil {
return nil, 0, infoschema.ErrColumnNotExists.GenByArgs(pos.RelativeColumn, tblInfo.Name)
}
// Insert position is after the mentioned column.
position = c.Offset + 1
}
colInfo.ID = allocateColumnID(tblInfo)
colInfo.State = model.StateNone
// To support add column asynchronous, we should mark its offset as the last column.
// So that we can use origin column offset to get value from row.
colInfo.Offset = len(cols)
// Insert col into the right place of the column list.
newCols := make([]*model.ColumnInfo, 0, len(cols)+1)
newCols = append(newCols, cols[:position]...)
newCols = append(newCols, colInfo)
newCols = append(newCols, cols[position:]...)
tblInfo.Columns = newCols
return colInfo, position, nil
}