752 questions
0
votes
1
answer
44
views
How to preprocess date in Isolation Forest sklearn [closed]
I am using sklearn's IsolationForest model to detect anomalies on a time-series dataset. One of the features is date with the format MM-YYYY, the other features are numeric values.
What is the best ...
- 21
0
votes
2
answers
73
views
Strange behavior of Update Statement
The thing is about a very simple update statement:
UPDATE `user` SET fans = fans +1 where id = 8;
(because it will not cause any concurrency issue when just single[auto commit] use it, so I want to ...
- 81
-1
votes
1
answer
63
views
Postgres DB throws max_pred_locks_per_transaction exceeded
We are using an Azure postgresql flexible server DB for doing our performance testing. On max load of around 50 tps, all our queries are failing with
[ERROR: out of shared memory Hint: You might need ...
- 1
0
votes
0
answers
26
views
System.Data.Entity.Infrastructure.CommitFailedException
System.Data.Entity.Infrastructure.CommitFailedException: An error was reported while committing a database transaction but it could not be determined whether the transaction succeeded or failed on the ...
0
votes
0
answers
32
views
Can `select` in reads a partially updated row in MySQL with the Read Uncommited isolation level?
Suppose the following two statements are executed in parallel:
-- before: col1=val1, col2=val2
UPDATE my_table SET col1=new_val1,col2=new_val2 WHERE col3=val3
SELECT col1,col2 FROM my_table WHERE ...
- 9,440
0
votes
0
answers
23
views
What is the relationship between conflict serializable schedule and the serializable isolation level
So if a schedule is conflict-serializable, then it is conflict-equivalent to a serial schedule, which should have no anomalies since serial schedules have no anomalies.
If your DBMS runs transactions ...
- 1,052
-1
votes
1
answer
79
views
Dirty reads happening in RCSI in Azure SQL Server
Although my database isolation level is set to READ_COMMITTED_SNAPSHOT, I am still getting dirty (uncommited) reads.
SELECT COUNT([random_string]) NoTx FROM [dbo].[IncTesting5];
BEGIN TRANSACTION;
...
- 95
0
votes
0
answers
8
views
Repeatable reads transaction level
-- TRANSACTION 1
set transaction isolation level REPEATABLE READ
BEGIN TRANSACTION
select name from student where id=1
waitfor delay '00:00:15'
update Student set name='abc' where id=1
commit ...
- 29
0
votes
0
answers
13
views
Is lost update possible with serializable transaction isolation?
It is often stated serializable transactions prevents all read phenomena including lost update and phantoms. But is this the case when read committed transaction (A) and serializable transaction (B) ...
- 23.6k
1
vote
1
answer
34
views
When sanpshot is taken into consideration in transactions?
When is the snapshot actually taken in transactions? On BEGIN TRANSACTION or on the first operation?
I've been experimenting with transactions in both MySQL and PostgreSQL using the REPEATABLE READ ...
0
votes
0
answers
51
views
@Transactional propagation and isolation levels in Spring Boot
I have a question regarding @Transactional annotation.
In our project we have a REST controller that receives events from the message bus and calls a UseCase(@Service) to save the changes to the ...
- 1
1
vote
1
answer
67
views
consistency by isolation levels, while SELECT SUM(...) million records, UPDATE some records
I was testing READ UNCOMITTED and READ COMITTED. For this, using 2.5 million row records, I tried the followings.
First, at Session A:
BEGIN;
SELECT SUM(salary) FROM salaries;
then immediately (...
- 2,062
1
vote
1
answer
43
views
Does using a transaction for read queries provide benefits under Read Committed Isolation Level in PostgreSQL?
I'm using Prisma with PostgreSQL. As I read about the transaction isolations in PostgreSQL, I wondered if I am using transactions without any benefits or if I understood the subject correctly.
async ...
0
votes
1
answer
127
views
Postgres serializable isolation level confusion
I'm learning about database isolation levels and I'm attempting to walk through an example of when the serializable isolation level would cause concurrent transactions to error.
I have come up with ...
- 73
0
votes
0
answers
40
views
Read one table write to another data race SQL solution
I'm currently learning about database transactions, isolation levels, and SQL in general. I've thought up a problem which involves a potential data race and can't seem to figure out the solution ...
- 73