locking

问题 I have a table into which multiple processes insert data very rapidly throughout the day. Assume that at least one process is performing an insert at any given moment. I need to read from this table during the day, while the inserts are happening. I need to read every row but I only need to read each row once. My questions are: Is it possible for a single process to read from the table this way without affecting insert performance? Could there be more than one process reading data from the

问题 I need to use a table for a queuing system. The table will be constantly be updated. For example, multiple users on my website, will add their files for process, and I heard that when updates occur simultaneously from multiple users, the table becomes non responsive or something like that. so do I need locking tables in this situation ? how do i apply a lock to a mysql table ? 回答1: When you do several updates at once, you can get into a deadlock situation. Engines such as InnoDB will detect

问题 Hey StackOverflow VB.NET members, After running the following code (which locks the computer), what code must I be applying to see if the user has successfully logged into the computer and that "Lock Screen" I'd so called has disappeared? Private Declare Function LockWorkStation Lib "user32.dll" () As Long Private Function LockComputer() LockWorkStation() End Function I will call "LockComputer", after that what do I do to see if the Lock screen so called by this function (after say 2 minutes)

问题 Background information I am trying to understand how postgresql well enough so that I can ensure that my web app will not fail when users are simultaneously trying to update the same record. For testing purposes, I have created two scripts - one script creates / defines the transaction block and the second script simulates load (and attempts to create conflicts) by calling script 1. Code Here's what script 1 looks like: http://pastebin.com/6BKyx1dW And here's what script two looks like: http:

问题 Building on the query in this answer (please note/assume that the GROUP_CONCAT s are now also held in user defined variables), when and what will InnoDB lock on table1 ? I'd prefer that it only lock the table1 row that it's currently updating and release it upon starting on the next row. I'd also prefer that when it locks table2 (or its' rows) that SELECT s will at least be able to read it. The column being updated is not PK or even indexed. How can this be achieved, or is it already doing

问题 Trying to implement document locking in a small database. We use it in XPiNC. I found Julian Boss's excellent answer in in which he provides a javascript function that seems to have everything I need. So in a small test database I added the script library and added as a resource. In my edit button I have the following code: var ntdDoc:NotesDocument = document1.getDocument(); documentLocking.lockDoc(ntdDoc) But this throws the following error: Script interpreter error, line=2, col=17:

问题 When I try to run a code I have this mistake: java.lang.Exception: Lock wait timeout exceeded; try restarting transaction. I have see the inoodb status and I get this. How can I translate this into a language which I know?. How can I modify the time for the innodb variable?. Thanks mysql> show engine innodb status\g | InnoDB | | ===================================== 130117 13:25:22 INNODB MONITOR OUTPUT ===================================== Per second averages calculated from the last 19

问题 Documentation: SELECT ... LOCK IN SHARE MODE sets a shared mode lock on any rows that are read. Other sessions can read the rows, but cannot modify them until your transaction commits. If any of these rows were changed by another transaction that has not yet committed, your query waits until that transaction ends and then uses the latest values. However, some experimentation suggests that it locks more than the rows that are read. CREATE TABLE example (a int); START TRANSACTION; SELECT a FROM

问题 Is there a way of ensure that a set of methods operating on a volatile static member variable via one thread will be done and over with before other threads access this member variable? I am trying something like this, but I am not sure if it would work. public class MyClass { private static final Object lock = new Object(); public static volatile MyObj mo; //assume null will be checked before access public static void initialize() { if (mo == null) { synchronized(lock) { mo = new MyObj(); mo

问题 I use Hibernate version 4. We have a problem in batch process. Our system works as below Select set of records which are in 'PENDING' state Update immediately to 'IN PROGRESS' state Process it and update to 'COMPLETED' state The problem when we have two servers and executing at same time, we fear of having concurrency issue. So we would like to implement DB Lock for first two steps. We used query.setLockOptions() , but it seems not working. Is there any other to have table level lock or Row