A mechanism for managing concurrent access to shared data or resources by granting temporarily exclusive access to the processes requesting the lock.

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1answer
37 views

MySql timeouts waiting for table lock, no apparent deadlocks

I started having the following error on two different applications that write to the same database and table: Lock wait timeout exceeded; try restarting transaction At the beginning I thought it ...
2
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1answer
41 views

Is there a way to determine locks that a given query might apply on SQL objects?

Consider a simple query, as simple as a select statement: select * from Teachers where Name like N'%John%' As soon as I start this query, it finishes. Thus, I get no chance to see sp_who2 to find ...
0
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1answer
52 views

improving performance of concurrent inserts on innodb with randomized primary

I was looking at my design for primary keys which is based on my own incrementing BIGINT key generator. It is designed to generate batches of 50 numbers for use on that process, but mostly it ends up ...
0
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1answer
42 views

ORA-02049 Timeout: Distributed Transaction Waiting for Lock Solution needed

We are cleaning up the last year's transactions from our primary database. We use public database link to delete the records a day by day from another database. Each days records are around 30-40k, ...
5
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1answer
27 views

During rollback, is lock escalation reversed

Generally, SQL Server will take locks during updates. It also supports Lock Escalation: Lock escalation is the process of converting many fine-grain locks into fewer coarse-grain locks, reducing ...
0
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1answer
68 views

Locking in stored procedures [closed]

If a stored procedure has multiple statements, will the lock acquired for the first statement be released once its executed or will it hold on till entire stored procedure is complete? I am running ...
6
votes
1answer
51 views

Does issuing DDL against a view in PostgreSQL take out the same locks as issuing DDL against a table?

I understand that views are implemented using the rule system but I'm unclear if this has any advantages/disadvantages when running transactional DDL against them. Does issuing CREATE OR REPLACE VIEW ...
2
votes
0answers
10 views

In PostgreSQL, can you read from an index during a ALTER INDEX … SET TABLESPACE operation?

I have a PostgreSQL 9.3 server, and there's a large index that I want to move to another tablespace on another disk, because I want to free up space on the original disk. However this is a production ...
0
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1answer
21 views

pg_stat_activity shows lots of easy queries running for minutes

After application server start its connection pool fills quickly and application can't work properly. I went through pg_stat_activity and noticed lots of queries running for minutes: But postgres's ...
2
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0answers
35 views

How to avoid row locks on both tables joined in an update?

I have little knowledge about MySQL internals, but I'm experiencing that in a query like: UPDATE t1 JOIN t2 ON t1.id = t2.id SET t1.a = x, t1.b = y, [, ...] WHERE [ ... ] rows from both t1 and ...
3
votes
0answers
44 views

MySQL queries waiting for other queries to finish

We have 30-40 different projects in Python and PHP that update, insert and select more than 1 million rows of data in MySQL DB every day. Currently we use InnoDB Engine for our tables. The problem: ...
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1answer
53 views

MySQL INSERT … SELECT Performance

I know that this query will lock table2: UPDATE table1... SELECT .. FROM table2 How about this query ? INSERT INTO table1... SELECT .. FROM table2 Does this query also create a lock on table2?
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1answer
36 views

`ON CONFLICT DO UPDATE` causing deadlocks?

I have a project where I'm trying to use the PostgreSQL ON CONFLICT DO UPDATE clause, and I'm having huge numbers of deadlocking issues. My schema is as follows: webarchive=# \d web_pages ...
1
vote
1answer
61 views

Sybase 12 to behave like Oracle and SQL Server 2014 - non blocking transaction read

We utilize an ODBC connection so our code can access various databases - namely Oracle, Sybase 12 and SQL Server 2014. NOTE : We have a table called which we use for locks. This table only ever has ...
3
votes
1answer
44 views

What is the impact of temporarily setting ALLOW_PAGE_LOCKS ON

The MSDN ALTER INDEX page says "An index cannot be reorganized when ALLOW_PAGE_LOCKS is set to OFF." I'm modifying our index reorg/rebuild process to be sensitive to indexes that have ...
2
votes
1answer
49 views

Update with CTE & OUTPUT blocks on concurrent calls

I was having deadlock issues, so I started using this CTE trick that I read somewhere. No more deadlocks. But now each client that I add slows down (blocks?) the sproc. E.g. a 1-2 second update with ...
2
votes
2answers
29 views

MySQL lock on MEMORY storage engine, when does it apply?

I want to use MySQL MEMORY storage engine to handle my PHP session variables (actually I already implemented it but since all my tests are being done by a single user, me, I am unable to notice this). ...
2
votes
2answers
80 views

Percona 5.7 tokudb poor query performance - wrong (non-clustered) index chosen

I have a table with about 8.5m rows in it. The table is tokudb and it has the indexes described below. I'm experiencing dismal performance when trying to run update statements like the following: ...
0
votes
1answer
14 views

Does MariaDB require aliases for subquery table locks?

MySQL suffers from a bug (which they claim is not a bug) that prevents a table lock from working on a sub-query unless you create a table alias for each mention of the table name. See: ...
1
vote
1answer
89 views

InnoDB MVCC vs Locking

From what I understand you InnoDB supports Row Level Locking MVCC (Multiversion Concurrency Control) Row Level Locking Locking is for when multiple writers are trying to update the same ...
3
votes
2answers
48 views

SQL Server - What access do I have during a transaction rollback?

As the title says, do I have read/write access to my entire database while it is rolling back a transaction? Or read/write access to only the tables that the transaction did not write to? What is the ...
0
votes
1answer
20 views

Mysql locking - How to acquire a lock in the DB for each userId

Hi I have a J2EE Server(clustered) that executes requests from multiple users. I would like that each request of a given user will be handled like so: { acquireLockForUser(userId); // i.e. insert ...
18
votes
6answers
385 views

Can I rely on reading SQL Server Identity values in order?

TL;DR: The question below boils down to: When inserting a row, is there a window of opportunity between the generation of a new Identity value and the locking of the corresponding row key in the ...
2
votes
1answer
68 views

Hold exclusive lock on a whole DB

As I explained in Set a filegroup to readonly, I wanna set some tables readonly, to have better performance. These tables are only written by an ETL that runs daily, then they are only read. ...
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2answers
64 views

Select query on an index column with gap locking

I am trying to understand in which cases will a select query make a gap locking on an indexed column select. What I read so far: Select queries use the repeatable read mode in InnoDB and will not ...
1
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1answer
33 views

Innodb Isolation levels and locking performance

I am reading a lot about locking and isolation levels in MySQL and InnoDB. I understood the technical differences and basic approach, but I still fail to understand a situation where for example READ ...
2
votes
1answer
26 views

How do I find what keys mysql will use for a query?

I just had a query encounter a deadlock, where the lock it was trying to acquire was for an index. But when I used explain to visualize the query, I saw that a different index was listed under key and ...
0
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0answers
32 views

PostgreSQL not running every update on my script

I'm running a dozen update statements on a loop and some updates just won't happen (they return 0 affected rows), If i recall the script it will slowly update the rows, I don't know how to debug ...
1
vote
1answer
10 views

What happens during RCSI while tempdb is being populated?

Our database/application utilizes Read Committed Snapshot Isolation so that readers are not blocked by writers, and writers are not blocked by readers. Of course that means when a row/page/table lock ...
0
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1answer
54 views

Log Shipping- Can I alter the schema of a table that is being used in the secondary instance?

We have two SQL Server instances with log shipping set on a database. Can I alter the schema (add columns, remove columns etc.) of the table in the Primary instance/db while the table is being used in ...
0
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1answer
38 views

avoid lock and allow two scripts to insert data in one table

I have a database called db1 and I'm filling it with other two different databases, let's call db2 and db3. I connect db2 and db3 to db1 using postgres_fdw and now I'm running scripst like this: ...
0
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0answers
24 views

MySQL lock on READ and concurrent execution

I'm building a small application (in Java) and I have arrived to a point where, depending on a field in one my database table the action to be executed has to be completely unique. I have a ...
2
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0answers
25 views

Does Disabling Page Level Locking Have an Adverse Effect on Other DBs

I got the following from a vendor about what their software (“IM”) needs: “IM needs its own SQL Server Instance if the DB is installed on a shared SQL server. This is a mandatory prerequisite because ...
1
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1answer
88 views

PostgreSQL optimistic reads (equivalent to SQL Server's Read Committed Snapshot)

Does PostgreSQL provide a built-in optimistic concurrency control mechanism such as SQL Server's Read Committed Snapshot Isolation? Readers can read all the rows without blocking, but writes will ...
2
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0answers
64 views

SQL Server Check Constraint Lock Order

I'm having problems with SQL Server 2012 filetable. Filetable defines an check constraint on a path_locator field with definition as: /*ParentsAreDirectories*/ ...
3
votes
1answer
393 views

How to get SQL insert and/or update to not lock entire table on MS SQL Server

Very much a newbie on DB work, so appreciate your patience with a basic question. I'm running SQL Server 2014 on my local machine, and I have a small table and a basic client application to test ...
1
vote
2answers
81 views

SELECT…FOR UPDATE - Will only an UPDATE release the lock?

I'm using a SELECT ...FOR UPDATE in a Java PreparedStatement. I may or may not need to execute the update depending on the results of the SELECT. If I execute a rs.close(); or pStmt.close(); without ...
10
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2answers
388 views

Good reasons to use SELECT… WITH XLOCK?

I am facing some re-occurring deadlocks, one of which is a Keylock and contains a SELECT query with XLOCK hint that becomes the deadlock victim. The other statement is an INSERT into one of the tables ...
1
vote
2answers
73 views

How can I ensure that only one user at a time can call a stored procedure? Can I lock an SP?

I have a procedure that generates reports basis user requests. The request is such that at a time only one user can call the procedure. Is there any way I can handle this using DB2? Like place a lock ...
13
votes
1answer
207 views

Massive INSERTs blocking SELECTs

I have a problem with a massive amount of INSERTs that are blocking my SELECT operations. Schema I have a table like this: CREATE TABLE [InverterData]( [InverterID] [bigint] NOT NULL, ...
0
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0answers
14 views

ReportServerTempDB - SessionLock table Locked [duplicate]

When a number of SSRS reports are run in a short period of time, I see a number of locks occur on the ReportServerTempDB. The table locked is dbo.SessionLock. The locks sit there until I restart the ...
4
votes
1answer
80 views

Deadlock best practices

We are running Postgres 9.3, and we have occasional deadlock issues. Currently someone notices and will manually kill off the processes. Is there a best practice in dealing with these when they ...
6
votes
1answer
369 views

What happens when we add an index to an existing table with a large amount of data?

I've a table which will contain around ~15 Million records. Now I need to add an index to the table. Adding an index will take some time to update every entry in the table. I'm quite confused ...
6
votes
1answer
170 views

Does UPDLOCK guarantee concurrency

I have a table called tblOrderNumber which has 1 row and 1 column. This table stores what the next order number will be for my ecommerce website. It is ABSOLUTELY VITAL that the same order number is ...
1
vote
0answers
46 views

How to make a PostgreSQL trigger thread-safe

I want to make my PostgreSQL trigger function do something like incrementing counters etc (something complex with multiple queries etc) thread-safely (so the same function triggered concurrently won't ...
0
votes
1answer
39 views

Generate incrementing IDs without sequences

Suppose there's a multi-tenant application where users can create some kind of documents with basic structure like CREATE TABLE users (id SERIAL PRIMARY KEY, email TEXT); CREATE TABLE documents ( ...
0
votes
1answer
27 views

Putting an order in the way how locks are aquired in MySQL

From MySQL documentation: A locking read, an UPDATE, or a DELETE generally set record locks on every index record that is scanned in the processing of the SQL statement. It does not matter whether ...
1
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1answer
39 views

Help understanding InnoDB Deadlock Detection

I have a deadlock occurring when executing an Update and a Select in seperate threads but I'm not sure what can be done about it. Previously my understanding was that this could happen in parallel but ...
2
votes
1answer
34 views

Which Table Will Get Locked With This Query

INSERT INTO stats.cps (time_stamp,entries,cust_id) select start_time, count(*) , c_id from gb.str where start_time between '$DATE10' and '$DATE' group by start_time, src_id order by start_time ASC ...
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2answers
266 views

How to force SQL server to use row locking for specific update/delete statements

I read this great response to a similar question How to force the use of row locks but I was looking for a per update/delete statement instead of permanently putting the rowlock restriction on an ...