def optimize(syntax_tree, sql):
if syntax_tree.operator == 'SELECT':
condition = syntax_tree.condition
sql = condition.split('&')
relation = []
for i in range(len(sql)):
if search(sql[i]) is not None:
relation.append(search(sql[i]))
syntax_tree = optimize(syntax_tree.left_child, sql)
elif syntax_tree.operator == 'PROJECTION':
syntax_tree.left_child = optimize(syntax_tree.left_child, sql)
elif syntax_tree.operator == 'JOIN':
first_tree = SyntaxTree()
first_tree.operator = 'SELECT'
first_tree.condition = sql[0]
first_tree.left_child = syntax_tree.left_child
syntax_tree.left_child = first_tree
if len(sql) == 1:
return syntax_tree
second_tree = SyntaxTree()
second_tree.operator = 'SELECT'
second_tree.condition = sql[1]
second_tree.right_child = syntax_tree.right_child
syntax_tree.right_child = second_tree
return syntax_tree
def parse(sql_statement):
sql = sql_statement.split()
execute_tree = SyntaxTree()
index = 0
while True:
if index >= len(sql):
break
#处理一元运算符
elif sql[index] == 'SELECT' or sql[index] == 'PROJECTION':
execute_tree.operator = sql[index]
index += 2 # 从[开始到]里面的全部记录下来
condition = ''
while sql[index] != ']':
condition += sql[index]
condition += ' '
index += 1
index += 1
execute_tree.condition = condition
#处理二元运算符
elif sql[index] == 'JOIN':
# 连接操作需要创建子树，所以分开写
execute_tree.operator = sql[index]
execute_tree.left_child = SyntaxTree()
execute_tree.left_child.attribute = sql[index - 1]
execute_tree.right_child = SyntaxTree()
execute_tree.right_child.attribute = sql[index + 1]
index += 1
#处理子查询，进行递归
elif sql[index] == '(':
index += 1
statement = ''
while index < len(sql) and sql[index] != ')':
statement += sql[index]
statement += ' '
index += 1
index += 1
execute_tree.left_child = parse(statement)
else:
index += 1
return execute_tree
def parse(sql_statement):
sql = sql_statement.split()
execute_tree = SyntaxTree()
index = 0
while True:
if index >= len(sql):
break
elif sql[index] == 'SELECT' or sql[index] == 'PROJECTION':
execute_tree.operator = sql[index]
index += 2 # 从[开始到]里面的全部记录下来
condition = ''
while sql[index] != ']':
condition += sql[index]
condition += ' '
index += 1
index += 1
execute_tree.condition = condition
elif sql[index] == 'JOIN':
# 连接操作需要创建子树，所以分开写
execute_tree.operator = sql[index]
execute_tree.left_child = SyntaxTree()
execute_tree.left_child.attribute = sql[index - 1]
execute_tree.right_child = SyntaxTree()
execute_tree.right_child.attribute = sql[index + 1]
index += 1
elif sql[index] == '(':
# 每次遇到这个说明需要创建一棵子树，由于题目中的查询都是只有一个分支，所以可以直接进入下一个子树中
index += 1
statement = ''
while index < len(sql) and sql[index] != ')':
statement += sql[index]
statement += ' '
index += 1
index += 1
execute_tree.left_child = parse(statement)
else:
index += 1
return execute_tree