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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Performance: order of tables in joined statement

I have the following SQL statement, running on a SQLite database on a Windows mobile device. SELECT table1.uniqueidentifier1, table1.int1, table1.varchar1, table1.decimal1, table1.decimal2 ...
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3answers
140 views

How do you see which database on a Server uses most resources

I have a database server with a couple of databases on it. How can I see where any resource pressure may come from? I would like to get a table of: Database Name Batch Requests per second CPU ...
5
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1answer
546 views

Possibilities to speed up InnoDB INSERTs and UPDATEs

My website retains user sessions in an innodb table. This usually works well, but a few hundred times a day, the INSERT and particularly the UPDATE statements run slower. I'm monitoring when, and it ...
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2answers
2k views

MySQL not using indexes when joining against another table

I have two tables, the first table contains all articles / blog posts within a CMS. Some of these articles may also appear in a magazine, in which case they have a foreign key relationship with ...
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1answer
128 views

Entity with >150 attributes: One table or many tables with relationships

I have entity with 170 attributes. It's data from vehicle monitoring. Every entity has datatime label and unique id of gps terminal. Datetime and id of terminal - these are conditions for GROUP BY ...
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2answers
1k views

Oracle query is slower the second time

I have a general question about something I'm seeing in performance tuning in Oracle. I have a query that I'm testing. It's too big and complex for me to provide a simple example, sorry! (I tried ...
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1answer
64 views

Should I be concerned about excessive Com_change_db commands?

I installed MONyog recently to check for problems on a MySQL server that I admin. Most of the information was useful and helpful, but there's one warning I am not sure is worth fixing. It reports ...
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4answers
820 views

Sql server full text search performance with additional conditions

We have a performance problem with SQL Server (2008 R2) Full text search. When we have additional where conditions to full-text search condition, it gets too slow. Here is my simplified query: ...
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1answer
156 views

filtered index null and > 0 disparity — need explanation

I'm getting behavior in a query plan I cannot explain. The difference is between two filtered indexes I'm testing with. One uses a where id is not null and the other uses where id > 0. In my ...
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0answers
527 views

Mysql slow writes

i have a strange problem with mysql. My selects goes fast. My insert/create/delete/drop/update go very slow. I have done some tests on 2 machines. My old machine and my new machine. Old is worst ...
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202 views

How to increase MySQL performance with joins

I have a MySQL database with InnoDB engine. Particularly one of my queries became very slow. The query is shown below: SELECT t1.`ARTREF1` FROM `lijnen` AS t3 INNER JOIN (`kortingen` AS t2, ...
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1answer
62 views

Do regular ALTERs weaken the performance?

In a project, we need to frequently ALTER the tables to delete or add columns. I wonder if this weakens the database performance in long term. If it has a considerable negative impact, what is the ...
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1k views

Oracle: Truncate large table takes forever

Problem I'm truncating a very large table ( +210 million rows ). It's been hours since it started and I have no idea when it will be done. There're several tables like that, that I want to ...
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3answers
2k views

How to optimization database for heavy I/O from updates (software and hardware)

The situation I have a postgresql 9.2 database which is quite heavily updated all the time. The system is hence I/O bound, and I'm currently considering making another upgrade, I just need some ...
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0answers
105 views

MongoDB advantages [closed]

I am actually can not understand the real advatage or killer feature of MongoDB storage. As I understand currently MongoDB implements exclusive per-database write lock that is even worse from the ...
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2answers
966 views

SQL Server: Additional cpus slow down batch

I'm running SQL Server 2012 in Windows 2008R2 in a virtualized environment. I've observed the following under both VMware Workstation 9 and Hyper-V 2012R1 and I don't know how to address it. I've ...
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42 views

Is it better performance wise to check if a field needs update if you know the record does

In the queries we use all the records in one table that has data which needs to be placed in a another system had a Insert, Update and Delete flags (i, u, d being 1 in the record), this way we can ...
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59 views

designing mysql for large tables

Currently I've been assigned the task to research ways to speed up an existing project. It's going to be rebuild so we can start from scratch, the current implementation has been build by another ...
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1answer
94 views

A query executed in a backup of a database is performing better than if executed in the original database

We have two databases with the same data, let's call it Database A which is the original and Database B which is the backup from Database A. A query is performing much better in Database B for example ...
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1answer
57 views

What ways are there to limit the processor / ram requirements of a specific query?

Every once in a while, I need to run some very expensive query on a production server. Think spaghetti joins. This is likely to affect the server operation, and I don't want that. What ways are there ...
2
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1answer
158 views

Creating indexes on AutoId and time column

My table structure is as follows Events( AutoId int identity(1,1) //Primay Key, clustered index EventTime datetime // non unique, non clustered index FileName nvarchar(1000) ...
4
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1answer
190 views

Plan cache memory: parameterized SQL vs stored procedures

In making a case to disallow parameterized SQL in my company's development environment the lead developer related a story about how the last time they used parameterized SQL the server had major ...
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1answer
97 views

Query_cache doesn't work with join

I have a simple join query, but for some reason query_cache won't cache it! SELECT id, news, approve, FIXED, DATE, allow_main FROM post LEFT JOIN post_plus ON post.id = post_plus.news_id WHERE ...
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1answer
1k views

Postgresql vs MySQL - Which is better for join queries & writing data(inserts) [closed]

I have to design a database which will end up with 50M records in a single table(there will be other tables with lesser number of records). I'm more concerned with join queries & writing ...
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53 views

Postgresql function taking long time on newly restored database

I have developed one function in my PostgreSQL database. It was taking 12-15 seconds to execute. Now I have restored a new PostgreSQL 9.0 dump using following command: pg_restore -hx.x.x.x -p5432 -d ...
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0answers
81 views

Oracle specifying join order hint

Oracle 2 node RAC 11G R2 I have a query (this is a simplified version, but still exhibits the same issue as the larger query) that looks like this: SELECT t1.trip_id, t1.origin, ...
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1answer
111 views

Benefit to keeping a record in the database, rather than deleting it, for performance issues?

So I have a client that I am building a Rails app for....I am using PostgreSQL. He made this comment about preferring to hide records, rather than delete them, and given that this is the first time I ...
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2answers
2k views

When to make changes to the cost threshold for parallelism

While examining a performance issue , I have seen an influx on CXPACKETS suggesting I might need to look at the cost threshold for parallelism and perhaps the MAXDOP. Before making any drastic ...
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2answers
131 views

Splitting up tables with similar structures since they contain unrelated data? (huge numbers)

Is my reasoning correct in splitting up tables with similar structures since they contain unrelated data? I'll explain the situation with an example : Suppose there is a server which hosts an online ...
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1answer
162 views

Data center from scratch which way to go

My budget for a data center (hardware,OS licences, SQL Licences WithOut CALS ) is around $50K~$60K. I have needs for around 200 users and my apps works only works in Microsoft environment (Window ...
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1answer
62 views

Does limit impact affected rows or not?

I have this table: CREATE TABLE IF NOT EXISTS `usergroups` ( `id` int(11) unsigned NOT NULL AUTO_INCREMENT, `user_id` int(11) unsigned NOT NULL, `group_id` smallint(5) unsigned NOT ...
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1answer
101 views

How to -create- performance issues? - oracle [closed]

I want to dedicate some time to learn more about performance and tuning issues. I assign for that a clean DB. I want to know how can I load into it some data and performance-problem queries/DML/DDL? ...
2
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1answer
264 views

Getting the most out of SQL Server with a million rows a day [closed]

I have a windows service that is inserting 1000 rows at 1 minute intervals to a SQL Server 2008 Standard database table that looks like: id, datetime, key_id, value key_id is a foreign key to ...
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1answer
221 views

Slow query and Insert with trigger

I have vehicle tracking system application based on PHP, SQL Server 2008 R2 Enterprise Edition with XEON HP Z800 Server. My database is growing day by day in millions and it makes it very slow to ...
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2answers
121 views

Why doesn't running a full sample *always* improve query performance

Conventional wisdom would suggest that running a full sample of statistics would provide SQL with the optimum information to make the best decisions when forming a query plan for execution and ...
4
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2answers
1k views

Does a TRIGGER improve the performance?

I understand that TRIGGERs are useful, as they take care of subsequent queries, but do they have an advantage from performance point of view too? Replacing two or three queries as INSERT INTO table1 ...
2
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1answer
237 views

MySQL / Fusion IO Configuration Question

I need a little configuration optimization. I think what I have is pretty good but feel like there's still room for improvement. Current Config [mysqld] user=mysql datadir=/var/lib/mysql ...
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1answer
901 views

Why do large tables slow down queries in databases?

Kind of a generic question; but I have noticed that large tables in certain CMS's can slow them down to a crawl. The solutions for this I've seen are to just truncate those tables. Why do large ...
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2answers
241 views

Optimize simple query using ORDER BY date and text

I have a query to a table in Postgres with an order based on a date field and a number field, this table has 1000000 records The data types of the table are: fcv_id = serial fcv_fecha_comprobante = ...
2
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2answers
122 views

Large number of VLF and shrinking the log

If there are lot number of VLF then it will effect the performance of the queries. I saw that solution is to shrink the log file. But shrinking the file is also bad. So how to take control of whole ...
4
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2answers
349 views

Trace flag and which need to be turned off and Why

In SQL server there are so many trace flags. Why some of them need to be turned off. Some where i saw that trace flag 8017 need to be turned off. So i want to know which trace flag need to be tuned ...
2
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2answers
460 views

How can you tell when a query plan reuse is causing performance problems

When investigating a performance issue, a workmate suggested running DBCC FREEPROCCACHE to clear the plan cache. He came to this conclusion after noticing performance improved after a reboot. This ...
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2answers
402 views

Oracle intermittent performance problem

I have some complex queries that are usually fast (< 1 sec), but occasionally slow (> 10 sec, even minutes). How do I track this down or identify what condition is causing it? One theory was ...
2
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1answer
265 views

What database and setup can handle several million inserts per minute? [closed]

We have come to a point where for a few of our customers' systems, at peak times, events are generated at that crazy rate. That is, millions of new events per minute (between 1M and 2M). The ...
4
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1answer
264 views

performance issue caused by IO?

Just curious to get an issue sanity checked . . . I'm trying to ascertain whether a performance issue experienced by users is the result of the app, server it sits on or SQL Server. Looking at ...
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2answers
4k views

Splitting a large table to improve performance

This is a follow-up to an earlier question. I have a SQL Server 2008 R2 Standard server, that holds a single database, which itself has almost nothing except a large table. The table is 100+ million ...
4
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1answer
241 views

View with fallback (performance/optimization question)

I have a table with tariffs for stuff; the tariffs table is not important in this scenario, the "tariff values" are. In this Demonstration SQL Fiddle the tariff_plan is the FK to the tariffplans table ...
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43 views

Creating a dedicated HD parition at beginning of disk for data files, benefits and draw backs?

I am thinking of creating a dedicated partition on the harddisk for the mysql database data files in /var/lib/mysql , while considering those 2 points: a dedicated partition will avoid any file ...
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2answers
78 views

Understanding multiple indexes with MySQL (and performance)

I have a "phones" table with around 120 000 records, it contains phone_id, phone_number, phone_user_name, phone_last_contacted, etc. The phone_id is index and looks like: 1,2,3,4 ... 120 000. But I ...
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1answer
87 views

Why isn't the rows of an EXPLAIN accurate?

I have the following table: mysql> select count(*) from employees; +----------+ | count(*) | +----------+ | 10000 | +----------+ 1 row in set (0.03 sec) I do an EXPLAIN: ...