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问题 I'm not sure if I'm asking the correct question to begin with, apologies in advanced. Question I am wondering if it is possible to have some type of handler to rollback an erroneous transaction in Hibernate. I am having a problem which, whenever an error comes up during a batch update from Hibernate the "SET TRANSACTION must be first statement of transaction" error comes up and I would not be able to do any other query after that. Thanks :) 回答1: Hibernate don't have an automatic transaction

问题 This is a very general computer science based question, but one that doesn't seem intuitive based on the literature about how they work. It's a language agnostic question, but relates to how a Set data type works internally. I have used them many times, and it is recommended to use them to store unique values and quickly access them. Supposedly in Big-O notation its time and complexity is O(1) every time the Set is accessed. How is that possibly if the Set may contain thousands of items? Even

问题 What is the best way to generate a set of bitarray-like objects so that I can test for membership efficiently. The naive way doesn't seem to work as I expect: >>> from bitarray import bitarray >>> >>> bitarray_set = set([bitarray('0000'), bitarray('0001')]) >>> bitarray_set set([bitarray('0001'), bitarray('0000')]) >>> >>> bitarray('0000') in bitarray_set False A workaround is to keep a separate set of strings or other more friendly object as keys. Then convert a bitarray to a string and test

问题 This is a follow question from an earlier post. After clarifying my earlier question, it was recommended that I make a new post as the question had shifted dramatically, which was a good suggestion. Here is the original question: Why doesn't this LINQ Select expression work The updated question is as follows. What I want is to get every permutation whereby each new group is made of only one element from a list of lists. As an example: List<List<int>> oldList = {{1,2},{3,4}}; List<List<int>>

问题 I am beginner in SQL Server My query in SAP B1 is DECLARE @FROMDATE AS DATETIME SET @FROMDATE= [%0] DECLARE @TODATE AS DATETIME SET @TODATE= [%1] DECLARE @ACCNUM AS NVARCHAR(100) SET @ACCNUM= [%2] get the account name, number for every transaction of an account SELECT T4.[ACCOUNT] AS 'A/C NUM', T4.[ACCTNAME] AS 'A/C NAME', T4.[TransId] AS 'KEY', SUM(VEL_DB) AS 'VEL DB', SUM(VEL_CR) AS 'VEL CR', SUM(DEF_DB) AS 'DEF_DB', SUM(DEF_CR) AS 'DEF CR', T4.[LINEMEMO], T1.[U_Naaration] FROM OJDT T1 for

问题 Given some sets (or lists) of numbers, I would like to iterate through the cross product of these sets in the order determined by the sum of the returned numbers. For example, if the given sets are { 1,2,3 }, { 2,4 }, { 5 }, then I would like to retrieve the cross-products in the order <3,4,5>, <2,4,5>, <3,2,5> or <1,4,5>, <2,2,5>, <1,2,5> I can't compute all the cross-products first and then sort them, because there are way too many. Is there any clever way to achieve this with an iterator?

问题 Suppose I have a data.table like this: Table: V1 V2 A B C D C A B A D C I want each row to be regarded as a set, which means that B A and A B are the same. So after the process, I want to get: V1 V2 A B C D C A In order to do that, I have to first sort the table row-by-row and then use unique to remove the duplicates. The sorting process is quite slow if I have millions of rows. So is there an easy way to remove the duplicates without sorting? 回答1: For just two columns you can use the

问题 I require help in an approach to check through sets within a set where each sub-set must be present in the list before returning true. init(){ let list1 : Set<Int> = [1,2] let list2 : Set<Int> = [3,4] let list3 : Set<Int> = [5,6,7] let list4 : Set<Int> = [8,9] listGroups = [list1,list2,list3,list4] } func checklist(_ list: [Numbers]) -> Bool { //I want to check that each sub set(list1-list4) elements exist //E.G. if list contains 2, 3, 7, 8 it will return true //and if list contain 1, 4, 7,

问题 I need to remove duplicates values in a list, but with set() or for ... if not in... loop I only get partially correct decisions. For example for ['asd', 'dsa', 1, '1', 1.0] I get: ['asd', 'dsa', 1, '1'] but the required result is: ['asd', 'dsa', 1, '1', 1.0] How can I achieve this? 回答1: You can try In [3]: [value for _, value in frozenset((type(x), x) for x in l)] Out[3]: [1.0, '1', 1, 'dsa', 'asd'] We create a (temporary) frozenset of tuples containing both element and its type - to keep

问题 I am iterating over a Set in Python. In my application I prefer that the iteration be in a random order each time. However what I see is that I get the same order each time I run the program. This isn't fatal but is there a way to ensure randomized iteration over a Set? 回答1: Use random.shuffle on a list of the set. >>> import random >>> s = set('abcdefghijklmnopqrstuvwxyz') >>> for i in range(5): #5 tries l = list(s) random.shuffle(l) print ''.join(l) #iteration nguoqbiwjvelmxdyazptcfhsrk