将mysql查询语句转化为查询树
任选下列查询语句中的三条，将其转化为对应的查询执行树，并且根据设计的查询优化算法，对生成的查询执行树进行优化。
SELECT [ ENAME = ’Mary’ & DNAME = ’Research’ ] ( EMPLOYEE JOIN DEPARTMENT )
PROJECTION [ BDATE ] ( SELECT [ ENAME = ’John’ & DNAME = ’ Research’ ] ( EMPLOYEE JOIN DEPARTMENT) )
SELECT [ ESSN = ’01’ ] ( PROJECTION [ ESSN, PNAME ] ( WORKS_ON JOIN PROJECT ) )
PROJECTION [ ENAME ] ( SELECT [ SALARY < 3000 ] ( EMPLOYEE JOIN SELECT [ PNO = ’P1’ ] ( WORKS_ON JOIN PROJECT ) )
PROJECTION [ DNAME, SALARY ] ( AVG [ SALARY ] ( SELECT [ DNAME = ’ Research’ ] ( EMPLOYEE JOIN DEPART MENT) )
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from pptree import *
def parser(sentence):
'''
将输入的数据库查询序列解析成表tables的list，选择条件selects的list，投影projections的list
假设以上三个list中的元素按list的角标对应
以及绘制查询树并优化
:param sentence:sql查询语句
:return: tables,selects,projections 三个list组成的list
return example：
[['EMPLOYEE', 'DEPARTMENT'], [['ENAME', '=', 'Mary'], ['DNAME', '=', 'ENAME']], []]
'''
temp = sentence.replace("[", "").replace("]", "").replace("(", "").replace(")", "").replace("’", "").replace(",",
"").split(
" ")
temp_0 = []
for i in range(len(temp)):
if temp[i] != "":
temp_0.append(temp[i])
tables = []
for i in range(len(temp_0)):
if temp_0[i] == "JOIN":
tables.append(temp_0[i - 1])
tables.append(temp_0[i + 1])
temp_1 = temp_0[0: i - 2]
# sequence = 1 表示select在projection之前，为0则相反，为-1表示没有projection
sequence = -2
selects = []
projections = []
if not temp_1.__contains__("PROJECTION"):
sequence = -1
and_flag = 0
for i in range(len(temp_1)):
if (temp_1[i] == "&"):
selects.append([temp_1[i - 3], temp_1[i - 2], temp_1[i - 1]])
selects.append([temp_1[i + 1], temp_1[i + 2], temp_1[i - 3]])
and_flag = 1
if and_flag == 0:
for i in range(len(temp_1)):
if (temp_1[i] == "SELECT"):
selects.append([temp_1[i + 1], temp_1[i + 2], temp_1[i + 3]])
for i in range(len(temp_1)):
if (temp_1[i] == "PROJECTION"):
if i + 1 <= len(temp_1):
if temp_1[i + 2] == "SELECT":
projections.append(temp_1[i + 1])
sequence = 0
else:
projections.append(temp_1[i + 1])
projections.append(temp_1[i + 2])
sequence = 1
print("lexer : " + str(temp_0))
print("tables : " + str(tables))
print("selects : " + str(selects))
print("projections : " + str(projections))
# print(sequence)
amend = 1
if sequence == -1:
root_1 = "SELECT " + "".join(selects[0])
if len(selects) == 2:
root_1 = root_1 + " " + "".join(selects[1])
paint_root = Node(root_1)
paint_join = Node("JOIN", paint_root)
for i in range(len(tables)):
Node(str(tables[i]), paint_join)
print("原始查询树 :")
print_tree(paint_root, horizontal=False)
children = []
paint_root = Node("JOIN")
for i in range(len(selects)):
children.append(Node("SELECT " + "".join(selects[i]), paint_root))
Node(str(tables[i]), children[i])
print("改进查询树(%d) :" % (amend))
amend = amend + 1
print_tree(paint_root, horizontal=False)
if sequence == 0:
root_1 = "PROJECTION " + "".join(projections[0])
if len(projections) == 2:
root_1 = root_1 + " " + "".join(selects[1])
paint_root = Node(root_1)
select_1 = "SELECT " + "".join(selects[0])
if len(selects) == 2:
select_1 = select_1 + " " + "".join(selects[1])
paint_select = Node(select_1, paint_root)
paint_join = Node("JOIN", paint_select)
for i in range(len(tables)):
Node(str(tables[i]), paint_join)
print("原始查询树 :")
print_tree(paint_root, horizontal=False)
root_1 = "PROJECTION " + "".join(projections[0])
if len(projections) == 2:
root_1 = root_1 + " " + "".join(selects[1])
paint_root = Node(root_1)
select_1 = "SELECT " + "".join(selects[0])
paint_select_1 = Node(select_1, paint_root)
if len(selects) == 2:
select_2 = "SELECT " + " " + "".join(selects[1])
paint_select_2 = Node(select_2, paint_select_1)
paint_join = Node("JOIN", paint_select_2)
for i in range(len(tables)):
Node(str(tables[i]), paint_join)
else:
paint_join = Node("JOIN", paint_select_1)
for i in range(len(tables)):
Node(str(tables[i]), paint_join)
print("改进查询树(%d) :" % (amend))
amend = amend + 1
print_tree(paint_root, horizontal=False)
root_1 = "PROJECTION " + "".join(projections[0])
if len(projections) == 2:
root_1 = root_1 + " " + "".join(selects[1])
paint_root = Node(root_1)
paint_join = Node("JOIN", paint_root)
join_children = []
for i in range(len(selects)):
join_children.append(Node("SELECT " + "".join(selects[i]), paint_join))
Node(str(tables[i]), join_children[i])
print("改进查询树(%d) :" % (amend))
amend = amend + 1
print_tree(paint_root, horizontal=False)
root_1 = "PROJECTION " + "".join(projections[0])
if len(projections) == 2:
root_1 = root_1 + " " + "".join(selects[1])
paint_root = Node(root_1)
paint_join = Node("JOIN", paint_root)
join_children = []
join_children.append(Node(root_1 + " DNO", paint_join))
Node(str(tables[0]), Node("SELECT " + "".join(selects[0]), join_children[0]))
join_children.append(Node("PROJECTION DNO", paint_join))
Node(str(tables[1]), Node("SELECT " + "".join(selects[1]), join_children[1]))
print("改进查询树(%d) :" % (amend))
print("假设BDATE为EMPLOYEE的属性,假设DNO为EMPLOYEE和DEPARTMENT的共同属性,代表部门编号")
amend = amend + 1
print_tree(paint_root, horizontal=False)
if sequence == 1:
root_1 = "SELECT " + "".join(selects[0])
if len(selects) == 2:
root_1 = root_1 + " " + "".join(selects[1])
paint_root = Node(root_1)
str_projections = "PROJECTION " + "".join(projections[0])
if len(projections) == 2:
str_projections = str_projections + " " + "".join(projections[1])
paint_projection = Node(str_projections, paint_root)
paint_join = Node("JOIN", paint_projection)
for i in range(len(tables)):
Node(str(tables[i]), paint_join)
print("原始查询树 :")
print_tree(paint_root, horizontal=False)
str_projections = "PROJECTION " + "".join(projections[0])
if len(projections) == 2:
str_projections = str_projections + " " + "".join(projections[1])
paint_root = Node(str_projections)
str_select = "SELECT " + "".join(selects[0])
if len(selects) == 2:
str_select = str_select + " " + "".join(selects[1])
paint_select = Node(str_select, paint_root)
paint_join = Node("JOIN", paint_select)
for i in range(len(tables)):
Node(str(tables[i]), paint_join)
print("改进查询树(%d) :" % (amend))
amend = amend + 1
print_tree(paint_root, horizontal=False)
str_projections = "PROJECTION " + "".join(projections[0])
if len(projections) == 2:
str_projections = str_projections + " " + "".join(projections[1])
paint_root = Node(str_projections)
paint_join = Node("JOIN", paint_root)
str_select = "SELECT " + "".join(selects[0])
if len(selects) == 2:
str_select = str_select + " " + "".join(selects[1])
Node(str(tables[0]), Node(str_select, paint_join))
Node(str(tables[1]), paint_join)
print("改进查询树(%d) :" % (amend))
print("假设ESSN是WORKS_ON的属性")
amend = amend + 1
print_tree(paint_root, horizontal=False)
str_projections = "PROJECTION " + "".join(projections[0])
if len(projections) == 2:
str_projections = str_projections + " " + "".join(projections[1])
paint_root = Node(str_projections)
paint_join = Node("JOIN", paint_root)
str_select = "SELECT " + "".join(selects[0])
paint_projection = []
for i in range(len(projections)):
paint_projection.append(Node("PROJECTION " + str(projections[i]) + " PNO ", paint_join))
Node(str(tables[0]), Node(str_select, paint_projection[0]))
Node(str(tables[1]), paint_projection[1])
print("改进查询树(%d) :" % (amend))
print("假设ESSN是WORKS_ON的属性，假设PNO为WORKS_ON和PROJECT的共同属性")
amend = amend + 1
print_tree(paint_root, horizontal=False)
print("")
return [tables, selects, projections]
if __name__ == '__main__':
assignments = []
assignments.append("SELECT [ ENAME = ’Mary’ & DNAME = ’Research’ ] ( EMPLOYEE JOIN DEPARTMENT )")
# 假设BDATE为 EMPLOYEE的属性,假设DNO为EMPLOYEE和DEPARTMENT的共同属性,代表部门编号
assignments.append(
"PROJECTION [ BDATE ] ( SELECT [ ENAME = ’John’ & DNAME = ’ Research’ ] ( EMPLOYEE JOIN DEPARTMENT) )")
# 假设ESSN是WORKS_ON的属性，假设PNO为WORKS_ON和PROJECT的共同属性
assignments.append("SELECT [ ESSN = ’01’ ] ( PROJECTION [ ESSN, PNAME ] ( WORKS_ON JOIN PROJECT ) )")
for i in range(3):
parser(assignments[i])
This post is licensed under CC BY 4.0 by the author.