An evaluation of whether a system works well enough to be fit for purpose. Normally performance refers to the speed with which a system completes an operation or set of operations over time.

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How can I reduce recursion in Couchbase?

Sometimes, you need to access a certain document (A), but you do not know the key for that document (A), as that data is stored in a different document (B). So now, if you want to fetch A, it looks ...
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1answer
51 views

How to optimise very simple query with subquery that only needs to execute once

SELECT products_id, products_model, products_iban_no, products_allocation_number FROM products WHERE products_model IN (SELECT products_model FROM products GROUP BY products_model HAVING ...
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259 views

Do OR conditions in Oracle SQL queries spoil index use / cause full table scan?

I have a query on Oracle 11g of the following type, which results in a series of highly inefficient full table scans: select t.Id, t.ObjectId, t...[other Tasks columns] , od1...[ObjectData1 ...
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1answer
583 views

How to configure my.cnf for Mysql 5.1, which is using too much CPU?

I am new Database engineer. I am having trouble in my server which is using too much CPU on database query(simple count statement). I have googled about it, so i found out it depends on system ...
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1answer
129 views

Redo log size results into performance degrade

We are continuously doing heavy insert and update query, but after 10 hours data base is returning answer late in minutes normally it takes around 1 ms. I observed that "free buffer wait" and "redo ...
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1answer
421 views

Slow delete caused by many foreign keys

My DB has about 90 tables. Most of the tables have an UpdatedBy and AddedBy column that have foreign keys pointing back to the user table. With even moderate amounts of data spread throughout the ...
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24 views

Approaching multiple values in same column

I'm developing an Android-application that scrapes the schedule for my university and presents it nicely since the current system is a nightmare. I'm processing a lot of data and it gets down to ...
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1answer
636 views

How to know which process is causing high memory usage on DB?

I've got one Onesight alert mail stating below: Short Description: Onesight Alert: ZEUS DB Monitor (zeus04) Description: Solaris 5.8: vmstat memory(free) - Free Memory for zeus04 2065112 8:06:02 ...
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1answer
694 views

Slower queries after upgrade from mysql-5.5 to mysql-5.6

There is lots written about how MySql 5.6 is faster than MySql 5.5 (e.g. http://dev.mysql.com/tech-resources/articles/mysql-5.6.html) but we upgraded our Amazon RDS instance (using the new upgrade ...
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19 views

Storing generated documents that can not be updated by changes in relationships

I have a system running with PostgreSQL and Yii Framework, which generates a few medical documents that, once ready, can't be changed. For example: If my full name comes out on this document today, ...
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1answer
66 views

MySQL from table to table data transfer

I've got some problem with my MySQL. I have the database with many many data. Well, there is only one table actually with huge ammount of data, over 1 billion rows. For some reasons I need to create ...
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2answers
60 views

SQL Server Backup and Query Execution

Is SQL Server Backup affects the query execution performance? Is there an effect while running the SQL Server backup in remote query execution? Thanks.
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52 views

Oracle 9i Low performance on Windows Server Enterprise 2003

I'm facing some problems with performance with my Oracle database running on a virtual machine with Microsoft Windows Server Enterprise 2003 with 8GB RAM. It works pretty well after the database is ...
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0answers
128 views

MySQL: after query optimization the CPU is still over 100%

my first time here! First of all I want to say that I'm not a DBA and I have a very little experience with MySQL but I like to study and understand what I'm doing. I have a virtual machine (2gb RAM, ...
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69 views

Oracle after insert trigger vs update performance in plsql block

I want to know whether an after insert trigger is better than an insertion statement followed by update statement in plsql block.
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1answer
32 views

Why does AttachDBFile make everything slower?

In my ASP.NET app, I had tested a query against a 200.000 rows table with two connection strings, one connect to a remote SQL Server and once use AttachDBFile to attach to a database file in App_Data. ...
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2answers
184 views

Oracle 11.2 using too few memory

it is about one year that I have changed my server from Oracle 10g to 11.2g (and also changed the hardware and Windows from 2003R2 to 2012). The problem is that with more than doubled cpu power, ...
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1answer
57 views

Is array serialization always bad idea?

I'm making form-generating app in php. I have Widget table with type_id (html input) field, and I would like to add options field, like width/height, step, range, etc. Different widgets do have ...
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42 views

Querying number of tries since last successful log, checking IP as well as user

I asked this question before on stackoverflow, but it might fit better here, since it is mainly about database performance. The actual question With performance in mind, how would you go about ...
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1answer
357 views

SQL Server “TOP 101” much slower than “TOP 100”

SQL Server shows huge decrease in performance when query is written like: select top 101 name from Dogs order by name compared to select top 100. As far as I know, this happens for the reason that ...
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1answer
188 views

inserting large quantity of data into mysql table

I need to insert about 400 000 000 rows of test data into the InnoDB table. Table is quite simple: CREATE TABLE IF NOT EXISTS `tgt` ( `id_1` int(10) unsigned NOT NULL, `id_2` int(10) unsigned NOT ...
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1answer
746 views

SQL Server 2012 performance degradation

We are running SQL Server 2012 SP1 on Windows Server 2012. The issue we have is that after some time the server automatically reboots. Checking the logs did not show any errors. When looking into ...
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0answers
71 views

Significant difference between duration for querys in SHOW PROFILE and SHOW PROFILES?

I have use mysql profiler to optimize an opencart query which takes more than 10 seconds to executes. mysql> SHOW PROFILES; ...
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2answers
120 views

Slow INSERT/UPDATE on InnoDB

I have a problem with the performance of my MySQL server, let me explain: I instaled a MySQL server, version 5.5.20 Server version: 5.5.20-log Source distribution SELECT queries runs fast on ...
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76 views

Why is this query stuck if there are no waits?

I am working with a vendor's activity logging system. One of the tables has 70+ million records and is constantly increasing at several hundred records per minute. They have a utility to delete old ...
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1answer
79 views

Oracle: index vs. table stats [closed]

In Oracle, when would I want to gather index stats, instead of just gathering stats on the table? In which use case would index stats make a difference?
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1answer
814 views

Improve MySQL Query Performance - Too many records

I am using MySQL RDMS for a contact management system. Now a days my database grew in size and contains more than 1 million records. Checking duplicate phone numbers became a big issue during ...
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1answer
720 views

MongoDB insert performance rapidly dropping

I'm currently experiencing a rapid decrease of the insert Performance. I have a rather simple data model { "Id": "ObjectId", "SomeProp": "xy", "SomeTags": [ { "key": ...
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84 views

Oracle: separate column histograms for partitions

I have a partitioned table like MY_TABLE(PART_KEY, DATE_KEY, ...) with a local partitioned index on (PART_KEY, DATE_KEY). When I collect stats on the table, I end up with a HEIGHT BALANCED histogram ...
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119 views

SLEEP_TASK and PAGELATCH_XX peaking after upgrade to R2 SP1

I wanted to just add a comment to this question: SLEEP_TASK Wait Type in SQL Server - What does it indicate? But I'm having not only SLEEP_TASK wait but also PAGELATCH_SH and PAGELATCH_EX wait types. ...
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2answers
337 views

DBCC CheckDB causing high values for resource_semaphore wait type

On one of our production server, where SQL Server 2008R2 (Service Pack 2) is installed with 24 GB memory and 24 CPU cores grouped into two NUMA nodes, we are facing high counts for resource_semaphore ...
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1answer
227 views

Oracle using index on partitioned table when full scan would have been better

Trying to make some sense out of this observation in Oracle. Query: SELECT ... FROM MY_TABLE WHERE PART_KEY=x and DT_KEY between 20120101 and 20120731 Uses an index scan on PART_KEY/DT_KEY, even ...
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2answers
101 views

Seeking help to test a use case on sql server memory

This is a question which came out of curiosity to know of how sql server handles memory. Assume I set a very low value for max server memory and I increase my workload like running dbcc checkdb, ...
2
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1answer
148 views

poor and/or unreliable InnoDB performance

I recognize that there are a ton of posts like this, but after reading up on InnoDB performance problems, nothing I tried has helped. I have a database containing four InnoDB tables. The largest ...
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26 views

How can I determine the performance (rows/second) for a certain query on one of my tables?

I want to find the performance (rows/second) for an UPDATE query on one of my tables so I can adjust my WHERE clause to select an appropriate number of records. The table has around 10 million rows. ...
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1answer
90 views

Slow queries InnoDB occasionaly

I have the next table: CREATE TABLE `sessions` ( `session_id` char(32) COLLATE utf8_unicode_ci NOT NULL, `session_expires` int(11) NOT NULL DEFAULT '0', `session_data` varchar(10000) COLLATE ...
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2answers
140 views

Disk I/O Activity

Resource Monitor on our SQL Server DB server shows very high fluctuating disk activity that I cannot understand. I then check Activity Monitor and the Database I/O looks ok. Any ideas why I am seeing ...
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1answer
58 views

Insert (write) performance

We are trying to speed up the queries in our application and in the process identified all queries which took more than 100ms. We noticed that there were few insert statements which took more than ...
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1answer
45 views

Why is logging “slow”?

On an empty transient table, inserting a single row took 50ms before changing it to UNLOGGED, 1ms afterwards. Why is this exactly? If the table structure is necessary, I'll post it, but it's only ...
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3answers
309 views

MySQL: How to avoid case sensitivity in SQL queries when migrate from Windows to Linux?

I have migrated my Database from Windows to Linux server. In many places, query has been written without focusing their cases (uppercase / lowercase). So, these queries are not getting executed and ...
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1answer
992 views

Does SQL Server allow INSERTs into tables and indexes to be written in parallel?

If I have a table that has many indexes, and I run a statement that inserts rows into the table, will SQL Server insert rows one-at-a-time, or will the rows be inserted using parallelism?
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1answer
54 views

Is it OK to duplicate parent field in child table for performance?

I have a very complicated query which involve more than 10 tables. Some parent tables are loaded only to search on one field. I wonder if I can copy this field in the child table (this data is never ...
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0answers
31 views

Performance Metrics for TempDB [duplicate]

I've been tasked with gathering performance metrics on a few database servers that have one TempDB data file. It seems prevailing wisdom is to have one TempDB data file per core up to a certain ...
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1answer
144 views

How to speed up looped INSERT INTO statements?

I currently use the following statement, for 10,000 rows it takes about 150 seconds. I tried removing the index on the target table, but this didn't help. Running the loop without the INSERT INTO ...
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1answer
1k views

Is SQL*Net message from dblink > 30% a performance issue?

I have a Java web-application running under Glassfish. App accesses Oracle using JPA (eclipselink). Last 2 days I'm observing some perfomance issues: some messages about long running queries (10 to ...
2
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1answer
129 views

Do triggers affect DB performance

I have a database with 250 small and medium sized tables. These tables are related with both MyISAM and InnoDB storage engines. There are multiple triggers that have been created on different tables. ...
2
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1answer
94 views

Will adding more indexes speed up using RedGate SQL DATA compare?

We want to use RedGate's SQL Data Compare to migrate user data from one DB to a DB on a completely different provider. This will be a time-sensitive operation as we do not want our site offline for ...
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1answer
868 views

Database design for handling 1 billion rows and counting

We receive real-time GPS data at a rate of around 5000 pr. minute (from 4 TCP servers). Each server uses a single connection to insert the data, and buffers data in between inserts. Every 15 minutes ...
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1answer
186 views

Optimizing a large number of INSERT … SELECT statements

I have a MySQL InnoDB database with two tables related by a foreign key. Each time a row is inserted into one it uses an INSERT ... SELECT statement from the other to get the corresponding foreign ...
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1answer
2k views

SQL Server PerfMon: Compilations/sec > Batch Requests/sec

I've been looking at various PerfMon metrics on one of our client's SQL Server instances trying to get a good gauge of where our database (or server) could use improvements. One measure that has me ...