// Adds a new column.
func (table *Table) Add(name string, length int) int {
_, exists := table.Columns[name]
if exists {
return st.ColumnAlreadyExists
}
if len(name) > constant.MaxColumnNameLength {
return st.ColumnNameTooLong
}
if length <= 0 {
return st.InvalidColumnLength
}
var numberOfRows int
numberOfRows, status := table.NumberOfRows()
if status == st.OK && numberOfRows > 0 {
// Rebuild data file if there are already rows in the table.
// (To leave space for the new column)
status = table.RebuildDataFile(name, length)
table.pushNewColumn(name, length)
} else {
newColumn := table.pushNewColumn(name, length)
// Write definition of the new column into definition file.
_, err := table.DefFile.Seek(0, 2)
if err != nil {
logg.Err("table", "Add", err.Error())
return st.CannotSeekTableDefFile
}
_, err = table.DefFile.WriteString(column.ColumnToDef(newColumn))
if err != nil {
logg.Err("table", "Add", err.Error())
return st.CannotWriteTableDefFile
}
}
table.RowLength += length
return st.OK
}
// Removes a column.
func (table *Table) Remove(name string) int {
var theColumn *column.Column
// Find index of the column.
var columnIndex int
for i, column := range table.ColumnsInOrder {
if column.Name == name {
theColumn = table.ColumnsInOrder[i]
columnIndex = i
break
}
}
if theColumn == nil {
return st.ColumnNameNotFound
}
if strings.HasPrefix(name, "~") {
return st.CannotRemoveSpecialColumn
}
length := theColumn.Length
// Remove the column from columns array.
table.ColumnsInOrder = append(table.ColumnsInOrder[:columnIndex], table.ColumnsInOrder[columnIndex+1:]...)
// Remove the column from columns map.
// table.Columns[name] = nil, true
delete(table.Columns, name)
numberOfRows, status := table.NumberOfRows()
if status != st.OK {
return status
}
if numberOfRows > 0 {
// Rebuild data file if there are already rows in the table.
// (To remove data in the deleted column)
status = table.RebuildDataFile("", 0)
} else {
status = util.RemoveLine(table.DefFilePath, column.ColumnToDef(theColumn))
}
table.RowLength -= length
if status != st.OK {
return status
}
return st.OK
}