func (tr *Transaction) Update(t *table.Table, rowNumber int, row map[string]string) int {
// Execute "before update" triggers.
beforeTable, status := tr.DB.Get("~before")
if status != st.OK {
return status
}
original, status := t.Read(rowNumber)
if status != st.OK {
return status
}
triggerRA := ra.New()
_, status = triggerRA.Load(beforeTable)
if status != st.OK {
return status
}
_, status = triggerRA.Select("TABLE", filter.Eq{}, t.Name)
if status != st.OK {
return status
}
status = trigger.ExecuteTrigger(tr.DB, t, triggerRA, "UP", row, original)
if status != st.OK {
return status
}
// Update the row.
status = t.Update(rowNumber, row)
if status != st.OK {
return status
}
// Execute "after update" triggers.
afterTable, status := tr.DB.Get("~after")
if status != st.OK {
return status
}
triggerRA = ra.New()
_, status = triggerRA.Load(afterTable)
if status != st.OK {
return status
}
_, status = triggerRA.Select("TABLE", filter.Eq{}, t.Name)
if status != st.OK {
return status
}
status = trigger.ExecuteTrigger(tr.DB, t, triggerRA, "UP", row, original)
if status != st.OK {
return status
}
// Log the updated row.
tr.Log(&UndoUpdate{t, rowNumber, original})
return st.OK
}
func (tr *Transaction) Delete(t *table.Table, rowNumber int) int {
// Execute "before delete" triggers.
beforeTable, status := tr.DB.Get("~before")
if status != st.OK {
return status
}
row, status := t.Read(rowNumber)
if status != st.OK {
return status
}
triggerRA := ra.New()
_, status = triggerRA.Load(beforeTable)
if status != st.OK {
return status
}
_, status = triggerRA.Select("TABLE", filter.Eq{}, t.Name)
if status != st.OK {
return status
}
status = trigger.ExecuteTrigger(tr.DB, t, triggerRA, "DE", row, nil)
if status != st.OK {
return status
}
// Update the row.
status = t.Delete(rowNumber)
if status != st.OK {
return status
}
// Execute "after delete" triggers.
afterTable, status := tr.DB.Get("~after")
if status != st.OK {
return status
}
triggerRA = ra.New()
_, status = triggerRA.Load(afterTable)
if status != st.OK {
return status
}
_, status = triggerRA.Select("TABLE", filter.Eq{}, t.Name)
if status != st.OK {
return status
}
status = trigger.ExecuteTrigger(tr.DB, t, triggerRA, "DE", row, nil)
if status != st.OK {
return status
}
// Log the deleted row.
tr.Log(&UndoDelete{t, rowNumber})
return st.OK
}
// Look for a value in a table's column, returns true if the value is found.
func find(column, value string, t *table.Table) (bool, int) {
numberOfRows, status := t.NumberOfRows()
if status != st.OK {
return false, status
}
for i := 0; i < numberOfRows; i++ {
row, status := t.Read(i)
if status != st.OK {
return false, status
}
if row[column] == value {
return true, st.OK
}
}
return false, st.OK
}
// Relational algebra join using nested loops.
func (r *Result) NLJoin(alias string, t2 *table.Table, name string) (*Result, int) {
// t1 is the table in RA result.
t1Column := r.Aliases[alias].ColumnName
t1 := r.Tables[r.Aliases[alias].TableName]
t2RowNumbers := make([]int, 0)
// t2 is the external table.
t2NumberOfRows, status := t2.NumberOfRows()
if status != st.OK {
return r, status
}
// Prepare to re-arrange the sequence of row numbers of all existing tables in RA result.
newRowNumbers := make(map[string][]int)
for name, _ := range r.Tables {
newRowNumbers[name] = make([]int, 0)
}
// NL begins.
for i, t1RowNumber := range t1.RowNumbers {
for t2RowNumber := 0; t2RowNumber < t2NumberOfRows; t2RowNumber++ {
t1Row, status := t1.Table.Read(t1RowNumber)
if status != st.OK {
return r, status
}
t2Row, status := t2.Read(t2RowNumber)
if status != st.OK {
return r, status
}
if t1Row["~del"] != "y" && t2Row["~del"] != "y" && t1Row[t1Column] == t2Row[name] {
for name, _ := range newRowNumbers {
newRowNumbers[name] = append(newRowNumbers[name][:], r.Tables[name].RowNumbers[i])
}
t2RowNumbers = append(t2RowNumbers[:], t2RowNumber)
}
}
}
// Re-arrange the sequence of row numbers of all existing tables in RA result.
for name, rowNumbers := range newRowNumbers {
r.Tables[name].RowNumbers = rowNumbers
}
// Load columns of t2 into RA result.
r.Load(t2)
t2Table := r.Tables[t2.Name]
t2Table.RowNumbers = t2RowNumbers
return r, st.OK
}