class SQL_Statement:
def __init__(self, sql_string):
self.sql_string_array = sql_string.split()
self.statement_type = self.sql_string_array[0]
self.command_executions = {
'insert': self.handle_insert_command,
'select': self.handle_select_command
}
self.vm = VM()
def execute(self, table):
if self.statement_type not in self.command_executions:
print(self.statement_type + " is not a valid command")
return
self.command_executions[self.statement_type](table)
def handle_insert_command(self, table):
# format the row to insert
row = self.get_row_from_insert_command()
if not row:
return
self.vm.insert_row(row, table)
def handle_select_command(self, table):
if (self.validate_select_command()):
self.vm.select_all_rows(table)
def get_row_from_insert_command(self):
if len(self.sql_string_array) != 4:
print(
"PREPARE_SYNTAX_ERROR: the insert command takes three arguments - insert 1 name [email protected]"
)
return False
## validate input ID
try:
user_id = int(self.sql_string_array[1])
if (user_id <= 0):
print("row ID must be positive")
return False
except ValueError:
print("Second argument must be an integer")
return False
## validate input name
name = self.sql_string_array[2]
if (len(name) > constants.NAME_FIELD_SIZE):
print("name too long: " + name)
return False
## validate input email
email = self.sql_string_array[3]
if (len(email) > constants.EMAIL_FIELD_SIZE):
print("email too long: " + email)
return False
row = Row(user_id, name, email)
row.serialize()
return row
def validate_select_command(self):
if len(self.sql_string_array) != 1:
print(
"PREPARE_SYNTAX_ERROR: the select command takes no arguments")
return False
return True