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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23 views

Optimal config for a small vserver with ispconfig

I have a vserver with debian wheezy, 1GHz CPU single core, 512MB RAM and only 8GB HDD. Owncloud is running, but has its own database-engine How should I configure Mysql so it doesn't slow down the ...
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4answers
3k views

Slow query on large table with GROUP BY and ORDER BY

I have a table with 7.2 million tuples which looks like this: table public.methods column | type | attributes ...
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36 views

Query slower than the sum of its parts

I have a query with the following pseudo outline 1. CREATE TABLE #Temp 2. INSERT INTO #Temp 3. INSERT INTO A --90% of time spent here 4. INSERT INTO B --10% of time spent here 5. INSERT ...
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1answer
527 views

Select * from statement execute very slowly, innodb io read speed is low

I have a very simple query " select * from ap_statistic " running in my servers. the servers have the same hardware and software configuration (CPU 8 core, mem :32G, OS: redhat 5.5, mysql version: ...
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2answers
5k views

exist (select * from my table)

My colleague suggests that Query 1 should run faster than Query 2. If it's true, please anyone explain me the reason. Thanks. Query (1): IF ( SELECT COUNT(UnitTrustCounterId) FROM ...
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1answer
22 views

Is 'internallength' always useful in custom type definition in Postgres?

In our database we use a custom type to store 3D locations: CREATE TYPE float3d AS ( x real, y real, z real); In many examples I see INTERNALLENGTH used as a parameter with the definition of ...
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2answers
504 views

What is faster, one big query or many small queries?

I have been working for different companies, and I have noticed that some of them prefer to have views that will join a table with all its "relatives". But then on the application some times, we only ...
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64 views

Will I still benefit from provisioned IOPS in RDS on a smaller non-PIOPS-Optimized instance type?

Quote from the docs: If you are using Provisioned IOPS storage, we recommend that you use the db.m3.xlarge, db.m3.2xlarge, db.m1.large, db.m1.xlarge, db.m2.2xlarge, db.m2.4xlarge, ...
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1answer
93 views

Why isn't this index helping my InnoDB MySQL query?

I'm having trouble understanding why an index I have on one of my tables is doing nothing to help the performance of a JOIN, even when forcing the index. Here is the query: EXPLAIN SELECT * FROM ...
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1answer
15 views

“Approximately equal” between Sync and Async operations for PageCleaners

The documentation of num_iocleaners says: The parameter can be reduced if both of the following conditions are true: pool_data_writes is approximately equal to pool_async_data_writes ...
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25 views

Oracle - physical writes to an index

We have a large UPDATE (affects about 200K records) on a huge table (80M records). Due to a coding mistake, the UPDATE updates the same set of rows (200K) all over again with the exact same value. ...
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121 views

General error: 1615 Prepared statement needs to be re-prepared

I have been running into this issue every time I try and sync a medium size JSON object to my database so we can perform some reporting on it. From looking into what can cause it I have come across ...
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1answer
47 views

Optimal way of loading, registering, indexing and querying a huge XMLDB

I've got 35 million highly structured XML documents, with a total size of 500 GB. An XSD is available for this data, and the end goal is to transform the data into an RDB. All fields can be considered ...
8
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2answers
6k views

Optimizing bulk update performance in PostgreSQL

Using PG 9.1 on Ubuntu 12.04. It currently takes up to 24h for us to run a large set of UPDATE statements on a database, which are of the form: UPDATE table SET field1 = constant1, field2 = ...
2
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0answers
31 views

longitude lattitude performance

I have to store frequently (at least every min) the position (longitude, latitude) of animals in a DB, and perform for each update a search in order to determinate if ananother animal is near to it. ...
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1answer
173 views

Execution plan index suggestion - difference between similar queries

I am trying to analyze queries on this table: CREATE TABLE [dbo].[Values]( [tid] [smallint] NOT NULL, [t] [datetime2](3) NOT NULL, [v] [real] NOT NULL, CONSTRAINT [PK_Values_Unique] ...
2
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2answers
280 views

Inserting to table: Insert rows with Left Outer Join or Insert rows then Update?

I have a table of Orders and another table of Deliveries. The Orders table will contain a reference to the Deliveries table if there is a corresponding row. Not every row in Orders will have a row in ...
2
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1answer
87 views

What is running on my server every night?

My data disk queue is high every night at about 1:00 AM UTC. I did sql profiler trace and found that there are many queries running at the same time similar to these: Can someone tell me what is ...
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1answer
123 views

What is the fastest way to clone/copy oracle databases on the same machine?

I want to clone oracle 11g databases on the same machine and I need to change user etc. from e.g. PROD to DEV. For that I use expdp/impdp, but this tends to be slow with increasing database size. I ...
3
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4answers
4k views

Why is optimistic locking faster than pessimistic locking?

Both forms of locking cause a process to wait for a correct copy of the record if its currently in use by another process. With pessimistic locking, the lock mechanism comes from the DB itself (a ...
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0answers
18 views

Joining 2 big tables turn into a server down problem

Recently I was using a database (MySQL with Workbench) in the company that I work for (I'm a business analyst, not a DBA), and wrongly I created a query joining 2 tables that basically are the same. ...
2
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2answers
52 views

Does the system process slow down my Database access?

I have a Fairly large DB containing mostly html documents. I wrote a python script that fetches always 1000 html documents at once from my database cur.execute("SELECT id,url,html_file FROM html ORDER ...
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0answers
56 views

Why would call to scalar function inside a Table Value Function be slower than outside the TVF?

I am writing a Table Value Function, calling the function takes 10x as long as directly running the code. I traced this to a call to a multi-line scalar function inside the TVF. The call to the ...
2
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1answer
47 views

Which database technologies to consider for a data search application?

I'm designing an application that only does read queries to some database tables (it's a kind of search application); the queried data is updated at night by the system (so speed is less critical, ...
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1answer
39 views

Print, transaction and cursor performance in Transact-sql

I'm having some performance issues when I run a script. I was reading about the problem with print and its performance, but I cannot figure out how to reduce the impact. The algorithm is O(n^2). The ...
3
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1answer
361 views

Optimizing large database query (25+ million rows, using max() and GROUP BY)

I'm using Postgres 9.3.5 and I have a large table in the database, currently it has over 25 million rows and it tends to get even larger rapidly. I'm trying to select specific rows (all unit_ids with ...
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0answers
22 views

How to figure out how to split a table using the proper scheme

If you have a big table that you want to partition and you have 2 candidates as the partitioning key (in the sense that 50% of the queries use one column and 50% of the queries use the other column ...
3
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2answers
154 views

Enhance performance of update query

I have a query that is running against a table with 50 million rows. The phone number is stored as a CHAR(10) and an ETL process is changing the phone number if it has certain values. We are seeing ...
8
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4answers
12k views

Fastest way to check if InnoDB table has changed

My application is very database intensive. Currently, I'm running MySQL 5.5.19 and using MyISAM, but I'm in the process of migrating to InnoDB. The only problem left is checksum performance. My ...
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0answers
52 views

is this dead simple query too slow?

I have added and removed a few indexes from my user table and, while testing, didn't see the performance gains I had hoped. As a result, I removed the indexes and tried a simple query to see what my ...
18
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2answers
4k views

Is a composite index also good for queries on the first field?

Let's say I have a table with fields A and B. I make regular queries on A+B, so I created a composite index on (A,B). Would queries on only A also be fully optimized by the composite index? ...
6
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1answer
220 views

Huge differences of performance of MySQL in two servers

We have a MySQL server installed in two different machines, a testing server and a production server, both windows, which is used by a web application. The problem is that there are HUGE performance ...
7
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1answer
128 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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0answers
22 views

Mysql performance tunning [closed]

I have 2 VM : one x.x.x.22 "16G RAM" and "Intel(R) Xeon(R) CPU E5620 @ 2.40GHz 8Core " and one x.x.x.21 "8G RAM" and "Intel(R) Xeon(R) CPU E5620 @ 2.40GHz 8core" Now , app is installed ...
3
votes
1answer
291 views

Is there any performance difference in using a unique index on primary key?

I know there are lost of similar questions to this one, but none that really answers this: Is there ANY difference in performance in using an unique index in a primary key, using a MyISAM table on a ...
1
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2answers
126 views

How do I maintain high INSERT-performance on PostgreSQL

I'm working on a project which is parsing data from measurement files into a Posgres 9.3.5 database. At the core is a table (partitioned by month) which contains a row for each measurement point: ...
2
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2answers
100 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
101 views

MySQL CPU & Memory Spikes

Every couple of days, my server's CPU and memory usage spikes up to 100%, making our vBulletin forum almost unusable for 5-10 minutes. CPU is typically at 1-2, Memory at 3GB. During the spikes, CPU ...
3
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2answers
3k views

How much do foreign keys affect performance?

I'm reviewing an SQL Server 2008R2 installation having large performance problems. Currently I'm looking into its indexes and foreign keys and have found out that none of the tables have any foreign ...
3
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1answer
130 views

Why does my query end up with two seeks instead of one and how do I fix that?

I have these two tables: CREATE TABLE [TaskItems] ( [ItemId] UNIQUEIDENTIFIER NOT NULL UNIQUE PRIMARY KEY, [LastOperationTime] DATETIME NULL DEFAULT GETUTCDATE(), [OwnerId] ...
0
votes
1answer
79 views

Is normalization advisable on transactional data?

I have read a lot of articles about normalized vs denormalized schemas, but I find very little mention of the cost of row insertion. I am considering the impact of converting a 100% denormalized ...
0
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0answers
16 views

RAID configuration for mysql [closed]

I attached 4 10G disks to mysql Server and I used RAID 0 but still same mysql performance the same, Do I have to change configuration in my.cnf to let mysql know about RAID 0
8
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2answers
330 views

Why are simple SELECTs on InnoDB 100x slower than on MyISAM?

I have quite an annoying problem. I want to use INNODB as my main database engine and give up on MyISAM as I need the former for using galera-cluster for redundancy. I copied (description follows) ...
0
votes
1answer
30 views

Stored Procedure Performance Issue in Sharepoint Report

We have a report stored procedure that runs in about 1 minute in production; however, when executed from the Sharepoint it populates, it rus for over 20 minutes, with exactly the same parameters. ...
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2answers
200 views

RAID configuration for mysql

I attached 4 10G disks to mysql Server and I used RAID 0 but still same mysql performance the same, Do I have to change configuration in my.cnf to let mysql know about RAID 0. this is my mount ...
1
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2answers
144 views

Changing compatibility level of database causes performance improvement of stored procedure

We have a Web Application in a Windows Server 2012 Datacenter (IIS 8), running under .NET Framework 4.0, which connects to another Windows Server 2012 Datacenter with SQL Server 2012. My Database has ...
0
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1answer
98 views

Multi-Column Full Text Search Going Very Slow

I have a full text index on a table articles for the columns content, title and keywords When doing the search on each of the columns, like so select count(1) from articles where ...
2
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1answer
58 views

Innodb DB Consuming IO even when no operations are being done

I am currently doing some stress testing where I am pushing inserts to the database as fast as I can. The simulation inserts 10000 records per second. After inserting around 200 million records I ...
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0answers
57 views

MySQL DATE vs DATETIME read/write performace

Did anyone perform accurate read/write performance comparisons of MySQL's DATE vs DATETIME column types? Please do not bother writing "It should be faster" or "I think it's faster". I am looking for ...
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2answers
99 views

Table design for multi-type data

The information model I am modelling from includes an "any type". For example a customer can have zero or more 'entries' each of which can have a number of values. Each value could be a either date, ...