def main(cls, args):
db = SimpleDB("studentdb")
tx = db.newTx()
mdm = db.mdMgr()
# Open a scan on the data table.
studentplan = TablePlan(tx, "student", mdm)
studentscan = studentplan.open()
# Open the index on MajorId.
indexes = mdm.getIndexInfo("student", tx)
ii = indexes.get("majorid")
idx = ii.open()
# Retrieve all index records having a dataval of 20.
idx.beforeFirst(Constant(20))
while idx.next():
# Use the datarid to go to the corresponding STUDENT record.
datarid = idx.getDataRid()
studentscan.moveToRid(datarid)
print(studentscan.getString("sname"))
# Close the index and the data table.
idx.close()
studentscan.close()
tx.commit()
def executeModify(self, data, tx):
tblname = data.tableName()
fldname = data.targetField()
p = TablePlan(tx, tblname, self.mdm)
p = SelectPlan(p, data.pred())
ii = self.mdm.getIndexInfo(tblname, tx).get(fldname)
idx = None if (ii is None) else ii.open()
s = p.open()
count = 0
while s.next():
# first, update the record
newval = data.newValue().evaluate(s)
oldval = s.getVal(fldname)
s.setVal(data.targetField(), newval)
# then update the appropriate index, if it exists
if idx is not None:
rid = s.getRid()
idx.delete(oldval, rid)
idx.insert(newval, rid)
count += 1
if idx is not None:
idx.close()
s.close()
return count
def test2():
db = SimpleDB("studentdb")
mdm = db.mdMgr()
tx = db.newTx()
p1 = TablePlan(tx, "student", mdm)
s = p1.open()
while s.next():
print(s.getString("sname"), s.getInt("gradyear"))
def main(cls, args):
db = SimpleDB("studentdb")
tx = db.newTx()
mdm = db.mdMgr()
studentplan = TablePlan(tx, "student", mdm)
studentscan = studentplan.open()
# Create a map containing all indexes for STUDENT.
indexes = {}
idxinfo = mdm.getIndexInfo("student", tx)
for fldname in idxinfo.keySet():
idx = idxinfo.get(fldname).open()
indexes[fldname] = idx
# Task 1: insert a new STUDENT record for Sam
# First, insert the record into STUDENT.
studentscan.insert()
studentscan.setInt("sid", 11)
studentscan.setString("sname", "sam")
studentscan.setInt("gradyear", 2023)
studentscan.setInt("majorid", 30)
# Then insert a record into each of the indexes.
datarid = studentscan.getRid()
for fldname in indexes.keys():
dataval = studentscan.getVal(fldname)
idx = indexes.get(fldname)
idx.insert(dataval, datarid)
# Task 2: find and delete Joe's record
studentscan.beforeFirst()
while studentscan.next():
if studentscan.getString("sname") == "joe":
# First, delete the index records for Joe.
joeRid = studentscan.getRid()
for fldname in indexes.keys():
dataval = studentscan.getVal(fldname)
idx = indexes.get(fldname)
idx.delete(dataval, joeRid)
# Then delete Joe's record in STUDENT.
studentscan.delete()
break
# Print the records to verify the updates.
studentscan.beforeFirst()
while studentscan.next():
print(
studentscan.getString("sname") + " " +
str(studentscan.getInt("sid")))
studentscan.close()
for idx in indexes.values():
idx.close()
tx.commit()
def executeInsert(self, data, tx):
p = TablePlan(tx, data.tableName(), self.mdm)
us = p.open()
us.insert()
iterator = data.vals().__iter__()
for fldname in data.fields():
val = iterator.__next__()
us.setVal(fldname, val)
us.close()
return 1
def executeDelete(self, data, tx):
p = TablePlan(tx, data.tableName(), self.mdm)
p = SelectPlan(p, data.pred())
us = p.open()
count = 0
while us.next():
us.delete()
count += 1
us.close()
return count
def executeModify(self, data, tx):
p = TablePlan(tx, data.tableName(), self.mdm)
p = SelectPlan(p, data.pred())
us = p.open()
count = 0
while us.next():
val = data.newValue().evaluate(us)
us.setVal(data.targetField(), val)
count += 1
us.close()
return count
def executeDelete(self, data, tx):
tblname = data.tableName()
p = TablePlan(tx, tblname, self.mdm)
p = SelectPlan(p, data.pred())
indexes = self.mdm.getIndexInfo(tblname, tx)
s = p.open()
count = 0
while s.next():
# first, delete the record's RID from every index
rid = s.getRid()
for fldname in indexes.keys():
val = s.getVal(fldname)
idx = indexes.get(fldname).open()
idx.delete(val, rid)
idx.close()
# then delete the record
s.delete()
count += 1
s.close()
return count
def executeInsert(self, data, tx):
tblname = data.tableName()
p = TablePlan(tx, tblname, self.mdm)
# first, insert the record
s = p.open()
s.insert()
rid = s.getRid()
# then modify each field, inserting an index record if appropriate
indexes = self.mdm.getIndexInfo(tblname, tx)
valIter = data.vals().__iter__()
for fldname in data.fields():
val = valIter.__next__()
s.setVal(fldname, val)
ii = indexes.get(fldname)
if ii is not None:
idx = ii.open()
idx.insert(val, rid)
idx.close()
s.close()
return 1