pyodbc 游标的回滚功能

Question

使用 pyodbc 我正在更新三个数据库表。更新最后一个表时遇到错误，我正在调用 rollback() 函数。即使在 rollback() 上，第二个表也会保留其更新的值；第一个和第三个表没有按预期更新。为什么它会这样？

dbCursor.execute("insert into table1(item11, item12, item13, item14, item15, item16) values(?,?,?,?,?,?)", value1, value2, value3, value4, value5, value6)

dbCursor.execute("update into table2(item21, item22, item23, item24, item25, item26) values(?,?,?,?,?,?)", value1, value2, value3, value4, value5, value6)
---> two rows in the table get updated

dbCursor.execute("select item from table2 where unit_no = ?", unit_number)

tempVal = dbCursor.fetchone()

dbCursor.execute("update table3 set item31=?, item32=? where unit=?", val1, val2, tempVal)
---> Nothing gets updated as there is no tempVal found

if dbCursor.rowcount is 0:
    dbCursor.rollback()

预计rollback()会导致三个表都回滚，但是table2保留了值。

connection.getinfo(pyodbc.SQL_DRIVER_NAME)  --> iclit09b.dll
connection.getinfo(pyodbc.SQL_DRIVER_VER)   --> 4.10.FC4DE

Answer 1

使用 'autocommit = False' 的快速测试显示回滚工作正常：

使用以下命令创建测试表：

informix@irk:/data/informix/IBM/OpenInformix/pyodbc# cat p.sql
drop table table1;
drop table table2;
drop table table3;
create table table1(item11 integer, item12 integer, item13 integer, item14 integer, item15 integer, item16 integer)     ;
create table table2(item11 integer, item12 integer, item13 integer, item14 integer, item15 integer, item16 integer)     ;
create table table3(item31 integer, item32 integer, item13 integer, unit integer, item15 integer, item16 integer)       ;
insert into  table2 values (1,1,1,1,1,1);
insert into  table2 values (1,1,1,1,1,1);

informix@irk:/data/informix/IBM/OpenInformix/pyodbc# dbaccess stores7 p
Database selected.
Table dropped.
Table dropped.
Table dropped.
Table created.
Table created.
Table created.
1 row(s) inserted.
1 row(s) inserted.
Database closed.
informix@irk:/data/informix/IBM/OpenInformix/pyodbc# 

'table2' 的两行都有“1,1,1,1,1,1”

下面的python代码将输出'table2'中的数据，关闭AutoCommit并尝试更新。

informix@irk:/data/informix/IBM/OpenInformix/pyodbc# cat p.py 
import pyodbc

cnxn = pyodbc.connect('DSN=irk1210')
dbCursor = cnxn.cursor()

value1          = "2"
value2          = "2"
unit_number     = "1"
val1            = "2"
val2            = "2"
tempVal         = "2"

print("before update")
dbCursor.execute("select item11,item12 from table2")
row = dbCursor.fetchone()
if row:
    print(row)

#Set AutoCommit off
cnxn.autocommit = False

dbCursor.execute("insert into table1(item11, item12) values (?,?)", value1, value2)
dbCursor.execute("update table2 set item11=?, item12=?", value1, value2)

print("after update")
dbCursor.execute("select item11,item12 from table2")
row = dbCursor.fetchone()
if row:
    print(row)

dbCursor.execute("select item11 from table2 where item12 = ?", unit_number)
tempVal = dbCursor.fetchone()
dbCursor.execute("update table3 set item31=?, item32=? where unit=?", val1, val2, tempVal)
if dbCursor.rowcount is 0:
    dbCursor.rollback()

print("after rollback")
dbCursor.execute("select item11,item12 from table2")
row = dbCursor.fetchone()
if row:
    print(row)

informix@irk:/data/informix/IBM/OpenInformix/pyodbc# 

输出：

informix@irk:/data/informix/IBM/OpenInformix/pyodbc# python3 p.py 
before update
(1, 1)
after update
(2, 2)
after rollback
(1, 1)
informix@irk:/data/informix/IBM/OpenInformix/pyodbc# 

最后一个选择显示更新操作已按预期回滚。 两行的值和更新前一样(1,1)