For questions about issues arising when multiple users or processes concurrently access or modify shared information in a database system.

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concurrent insertion in mutually exclusive tables in oracle

There are three tables: create table C(id_row integer primary key) create TABLE A(col_a1,col_a2,col_a3,..., id_row integer primary key, constraint fk_a_c foreign key (id_row) references C(id_row)) ...
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45 views

InnoDB index concurrent inserts

I have an InnoDB table with an index on it. I have a few million rows to insert, so I thought I might take advantage of the row-level locking and do it in parallel. I'm inserting in batches of 10000, ...
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175 views

SSIS: FTP task - concurrent connections

I have created an SSIS package for downloading file from FTP server. When I debug the package, everything goes fine. But when I shedule the package as Job step, it sometimes fails to connect. The job ...
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89 views

How to safely take an SQL job out of the schedule?

There is a table | jobID | status | startTime | endTime | and a job, that is scheduled to run every X seconds, it will take the first undone job ID, put it in stored proc and run it. Stored proc takes ...
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27 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 ...
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527 views

How to identify concurrency issues in Oracle 11g?

For a short period in time we had a concurrency issue that lead to subsequent faults in our application (Java, Spring, Hibernate). Since we are using dictionary managed tablespaces, I first thought ...
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200 views

Handling concurrent updates, inserting if and only if no record already exists

I'm writing a Java application to update a relational database (currently H2, but we'll likely switch to PostgreSQL at some point). I have a process which does the following: Poll an external system ...
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234 views

UPLOCK to avoid multiple reads

Given the following table structure... Orders ====== OrderId int PK OrderEvent =========== OrderEventId int PK OrderId int FK EventTypeId int FK I've got multiple concurrent processes SELECT-ing ...
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How to lock tables in a stored program if I can’t say LOCK TABLES? (in an ancient version of MySql)

MySQL does not allow LOCK TABLES in stored programs. But this is my problem: I have a large stored function to control “phases”. The function advances to next phase, if needed (rarely so), and ...
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PostgreSQL - Are CREATE FUNCTION and DROP FUNCTION locking when used inside different transactions?

I'm having a locking issue on PostgreSQL 9.4.5. I run two or more transactions simultaneously (generally there are 2 running at the same time, but 2+ may happen sometimes) reading from the same tables ...
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51 views

How to determine if a schedule is non serializable?

How to determine if a schedule is non serializable? I am aware that a schedule is serializable if there is a concurrent schedule which gets an output same as a serial schedule. But how do you ...
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28 views

Understanding Serializeable vs conflict-serializable

I am having hard time wrapping my head around this concept of serializable. I know that if a schedule is conflict-serializeable then it is a conflict-equivalent to some serial schedule. But then does ...
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57 views

MYSQL- concurrency issue

I use JDBC to connect to MySQL. order_items table order_item_id order_id quantity unit_price shipping_price business_id workflow_id delivery_id item_id Orders table billing_address_id ...
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52 views

Is it a good idea to have too many named locks?

I am using MySQL as a data store and a Java App on the top. There are many state changes that happen, and I am seeing some concurrency bugs in there. I wanted to know if I can use named locks ...
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33 views

Can a slow SELECT statement in READ COMMITTED isolation level read content from concurrent committed UPDATE?

Let's say we have a big table with hundreds of million of rows (or more). On one connection, we perform a query requiring full table scan under READ COMMITTED isolation level: SELECT * FROM ...
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82 views

How can I obtain concurrent deletes for this table?

We have a program that is currently doing something to the effect of: SET TRANSACTION ISOLATION LEVEL READ COMMITTED BEGIN TRANSACTION UPDATE [Source].[dbo].[SourceTable] SET [ProcessedOn] = ...
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84 views

Why does the delete/update block each other in this case?

The following drives me crazy. I have: session1>begin; session2>begin; session2>update dummy set salary=1000 where id=11; session1>delete from dummy where id=1; id is the PK ...
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86 views

MySQL Multiple threads inserting *SAME* record a Bad Thing?

Okay, as I've noted in other questions, I'm not a sophisticated database user even though I took my first course in relational algebra from ted Codd. I've now inherited an application that ...
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48 views

Oracle User Profile for REST API

What sort of profile would you recommend for an Oracle user that is manifested through a RESTful API; particularly where there will be a lot of asynchronous requests? So we're talking about a ...