Improving the performance characteristics of a database application or system.

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Tuning SQL Query which returns REF CURSOR

I am using reference cursor in function to return values. This function is getting called recursively for different input values. My package Definition is as follows. create or replace PACKAGE ...
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22 views

Query plan reads vs statistics io reads

I have a very strange problem. When I run a query with SET STATISTICS IO ON, it shows that I had a total of 183 reads. But when I look at the query plan dmv it shows I did 555,132 reads. I cleared the ...
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15 views

Best ratio for files and file groups for a highly partitioned table

I have a number of tables with exactly 1000 partitions. Each table can be up to 200G with 100M rows and cannot be compressed. Data in partitions distributed quite equally. The SQL Server has 8 ...
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49 views

Optimizing intersect query in MySQL

I'm facing a performances problem in our MariaDB server. We have a table linking users to pages, a user belongs to 1+ pages. I have a page that have users and I want to get the 10 best pages based ...
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48 views

Is my SQL Job causing the High Disk usage?

I have a concern regarding High Average disk queue length for one of my server with below configuration: Version: SQL 2005 with SP3, standard edition. windows: version 2003 r2 SP2 No Processors= 4 ...
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55 views

Using Database Engine Tuning Advisor in production

I have a SQL Server 2008R2 OLTP database which is experiencing performance issues during work hours. I would like to run Database Engine Tuning Advisor on this instance but I don't know how it will ...
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32 views

Why does retrieving fewer rows take longer? [duplicate]

I have a view that (left outer) joins multiple recursive CTEs. There are about 10k rows. The results of running SELECT * FROM MyView ORDER BY MyPrimaryKey, with statistics time and io on: SQL Server ...
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36 views

reporting space consumption to files in filegroup - how to reverse-engineer the algorythm spreading data across files

First question, so be gentle ;) I would like to know how to be able to calculate the distribution of data consumed per file in a filegroup, back to the index (HEAP, CLUSTERED, NONCLUSTERED) storing ...
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1answer
65 views

OS Paging too high in sql server

For one of my servers with below configuration: Total RAM: 32 GB CPU: 8 Max Server Mem: 22.5 GB Min Server:: 4 GB Edition: Enterprise Edition with 2k8R2 installed on SP3 ...
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1answer
36 views

Select two aggregate functions on the same column using different criteria - performance

Dear stack exchange users, first question here. The database in question is a service database where a user hires a service. Now I would like to show the person that was hired an overview of how many ...
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2answers
114 views

Do I need to reindex mysql table after bulk delete?

I have a table in MySQL with a lot of INSERT and SELECT at every second. And there is a bulk delete of some older data once in a day. Do I need to reindex the table after delete? I want to increase ...
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64 views

Do I need to reindex my table in mysql after delete?

I have a table in mysql with a lot of INSERT and SELECT at every second. And there is a bulk delete of some older data once in a day. Do I need to reindex the table after delete? I want to increase ...
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63 views

Query optimization for multiple joins postgres

ER Diagram Brief description The database to be used is postgres. The database might contain upto 2 million AccountHolder records. Since the AccountHolder table is accessed and updated frequently ...
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21 views

Intermittent MySQL 5.17 issues - extremely slow queries

I am experiencing major issues with intermittent mySQL issues. To give some background the website runs optimally for the majority of the time, however 3-4 times a day queries that should take a split ...
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22 views

PostgreSQL buffer page size limitations - rebuild with larger size?

We just ran into a limit on indexing due to the 'index size cannot be more than 1/3 of page size (2712)' error. This indicates the buffer page size is 8192 (8k). This seems awfully small during the ...
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2answers
249 views

Hyperthreading & MySQL InnoDB Thread Concurrency Performance

I have a dedicated DB Server with the following specs" Ubuntu 12.04 LTS Server Intel(R) Xeon(R) CPU X5670 @ 2.93GHz 12 Cores MySQL 5.5.29 64 GB RAM RAID10 We are currently doing Hyperthreading ...
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395 views

SQL SERVER – Find Most Expensive Queries

I am running the following script to find most expensive queries. However I want to narrow it down to only queries ran on Saturday 18th October 2014 Is there any way to do this? SELECT TOP 50 ...
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1answer
43 views

What do these pstart and pstop values mean?

I'm attempting to tune a query and I want to be able to tell if partition pruning is happening. On one part of the query, the I'm getting a Pstart and Pstop value = "KEY": | Id | Operation ...
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67 views

Window function sorting performance

For background, I am on an instance of SQL Server 2012 Enterprise Edition. I have three tables that join on the same set of three keys - all of them are INT. All tables have their keys clustered in ...
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2answers
166 views

Very high load avg for MySQL database [closed]

I have a backend server which response to my clients app, it has more than 20k~25k hit per second and this make my server load average very high, I believe that my MySQL config is not appropriate. In ...
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28 views

is there any limit of MySQL status variable value?

As we know MySQL status variable is a counter variable since the service start. MySQL service in my DB server restart every week (on sunday). Below is my observation since last few week: Suddenly ...
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1answer
47 views

MySQL: What do we mean by 0 value in in_use column of show open tables statement?

If I run show open tables command, system return 73 records. But, in_use column value for every record is 0. What does this mean? Are these tables available in cache but not used by any thread?
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26 views

How to handle too many instances of multiple tables?

If there is a table accessed by multiple DB threads ( for example 100) at a time then how many instances of that table will be opened? If I run show open tables and see that in_use column value of a ...
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65 views

MySQL: What should I do if too many tables opened during peak hours?

In Peak hours: When I run below statement, I found around 100 tables out of 250 have opened. show open tables where in_use>0; There are around 10 tables for which in_use value are >50. Storage ...
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1answer
26 views

Do threads in cache still use memory?

I was studying about how and how much memory allocated to each connection thread and found below MySQL tutorial: http://dev.mysql.com/doc/refman/5.1/en/memory-use.html There is a point mentioned as ...
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17 views

SSIS Performance tunning [duplicate]

I have few questions on SSIS Performance tunning. Suppose My system has 8GB RAM and I have installed SQL Server 2012 along with DataTools. SQL Server uses 7GB memory. Will SSIS uses the 7GB memory or ...
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100 views

Identifying cause of high I/O

I'm trying to diagnose the bottleneck for high-write I/O activity on a percona master (with replication to a slave). The pattern of behaviour is roughly cyclic and regular: 60 mins of 75-90% ...
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66 views

DB Design: Looking for Performance improvement with a Column used in all SQL Queries

I recently got added to a new ASP .NET Project(A web application) .There were recent performance issues with the application, and I am in a team with their current task to Optimize some slow running ...
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80 views

Very Slow MySql Stored Procedure

I'm working with a web app running on MySQL. It uses stored procedures for all database-related tasks. The original web app and the database were designed by another developer; I'm only maintaining it ...
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38 views

Tuning MySQL On Azure Windows Server Setup

I have a MySQL 5.5 running on Azure VM Windows Server 2012. Once per second the log db gets about 2K inserts through LOAD DATA INFILE... once a day I need to run stats and when the stats are crunching ...
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130 views

Lower performance on newest servers

We have several db servers on production, 4 of them with very similar hardware configuration. Dell PowerEdge R620, only difference is that 2 newest ones (bought and configured 3 months ago) have RAID ...
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1answer
106 views

Searching a big table for a few results without scanning the whole table

I need to search a very big PostgreSQL table (500+M rows), I want to limit the returned search results, but using the "limit" keyword cant prevent the search over the whole set of data(is it correct?) ...
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80 views

Tuning Mysql and Monitoring

I would like to know if anybody can point me towards a tool/way for MySQL database tuning ... Actualy the tunning of my.cnf is like below My database is in MyISAM | Mysql 5.1.73 key_buffer = 500M ...
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13 views

Multiple Trace Files or Replay

I am just wondering how useful the replay functionality of SQL profiler is. The issue I have is that I can capture a workload from production with little overhead, however I would not be able to ...
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58 views

MongoDB read performance

I have an ingestion process which loads data into a specific collection at a very high rate. Some of these documents have to be loaded into another system in batches of 100K . Means as soon as I find ...
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47 views

MySQL: How turning off the logging affect the performance?

OS: RHEL5 DB: MySQL 5.1.73 community edition DB size: ~1GB I have setup a testing environment and turned off all logging - general logs, binary logs, slow query logs etc. I am using Oracle ...
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61 views

same query different servers,different execution plan and time

I have this query and it runs less than 2 minutes on Test but on Prod it takes 10 minutes. Both are the same version,CPU,RAM,OS the same. I have four tempdb files on Prod but one one Test. I ...
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416 views

Collecting Wait Stats

We currently use a monitoring tool which shows us our top wait stats either by number of waiting tasks or total wait time. Below are the wait stats by number of tasks waiting and also wait time per ...
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272 views

Oracle average active sessions high threshold

I am trying make sense of the DB load from the AWR report for a period handed over to me by DBA. Researching a bit, I see the "Average active sessions" is a metric widely used to measure DB load. It ...
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296 views

Optimization Tips For MYSQL Tuner/Primer

So I have a site that has a crap ton of traffic. I see a decent amount of latency when the site has over 1,000 active visitors on it. I have new relic installed and it seems Im only using 10% of the ...
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261 views

What to do with unused RAM on a MySQL database server?

For years I have been running dedicated servers with more or less limited ressources, resulting in unsatisfying performance of the web application (Drupal). Tools like Matthew Montgomery's MySQL ...
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1answer
34 views

Need DDL for an Oracle Table that would be 1 row = 1 8K Block

For performance testing in our performance environment we want a means to turn over SGA the way production does. Our performance environment is a fraction of production and production's very nature ...
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1answer
317 views

Optimize MySQL query_cache_min_res_unit

My query cache settings are the following: mysql> SHOW GLOBAL STATUS LIKE 'Q%'; +-------------------------+----------+ | Variable_name | Value | +-------------------------+----------+ ...
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1answer
859 views

Understanding pagefile.sys % Usage performance monitor (perfmon) counter correctly

Lately we run into performance inssues and I started tracking some recommended sql, memory, disk and cpu counters. I informed myself about the recommended values and numbers to look at. One of the ...
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263 views

Cannot tune database any further; what next?

We have a vendor-supplied application. It is under support and we are talking to their developers (we have their largest database size by an order of magnitude), but in the meantime, we have the ...
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1answer
166 views

Sort Warnings, finding out the query behind them

I'm troubleshooting a SQL Server 2012 that has started timing out as of a few weeks ago. The server is filled with thousands of sort warnings, at a rate of about 15 warnings per minute. To get the ...
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1answer
122 views

High I/O for part of query

I have a large query that I'm trying to tune. I write lots of queries but haven't done a lot of tuning. I've included a screenshot from SQL Sentry Plan Explorer Free (SSPEF): In the above part of ...
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1answer
136 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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2answers
114 views

Need help performance tuning a query

Basically, here is the design of the table (the part that is necessary): id | dt -------- 1 | 2014-05-13 2 | 1900-01-01 3 | 1900-01-01 4 | 2014-05-12 5 | 1900-01-01 So what I am trying to do ...
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1answer
802 views

Understanding sys.dm_exec_query_stats execution_count vs creation_time

I've just downloaded the SQL Server 2012 'Performance Dashboard Reports' and am having some issues interpreting the data shown by one of the results and linking it back to the DMV ...