class Query:
"""
# Creates a Query object that can perform different queries on the specified table
"""
def __init__(self, table):
self.table = table
self.idx = Index(table)
pass
"""
# delete a record with specified key
"""
def delete(self, key):
rids = self.idx.locate(key)
for rid in rids:
self.table.invalidate_record(rid)
self.idx.delete(key)
pass
"""
# Insert a record with specified columns
"""
def insert(self, *columns):
rid = self.table.insert_base_record(*columns)
self.idx.add_key(rid,self.table.key)
pass
"""
# Read a record with specified key. will return an empty list if query
# cannot be completed or if no records are found
"""
def select(self, key, query_columns):
if len(query_columns) is not self.table.num_columns:
print('error: number of queried columns must match number of columns in table')
return []
rids = self.idx.locate(key)
if len(rids) is not 0:
records = self.table.get_records(rids, query_columns, key)
return records
else:
return []
pass
"""
# Update a record with specified key and columns
"""
def update(self, key, *columns):
rids = self.idx.locate(key)
if len(rids) is not 0:
for rid in rids:
self.table.update_record(rid, columns)
if columns[self.table.key] != None:
self.idx.update_index(rid, key, columns[self.table.key])
pass
"""
:param start_range: int # Start of the key range to aggregate
:param end_range: int # End of the key range to aggregate
:param aggregate_columns: int # Index of desired column to aggregate
"""
def sum(self, start_range, end_range, aggregate_column_index):
column_sum = 0
query_columns = [0]*self.table.num_columns
query_columns[aggregate_column_index] = 1
for key in range(start_range, end_range+1):
rids = self.idx.locate(key)
if len(rids) is not 0:
records = self.table.get_records(rids, query_columns, key)
for record in records:
column_sum += record.columns[aggregate_column_index]
return column_sum
pass
