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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1answer
82 views

MySQL Config for server with 8gb RAM and 4 cpus

I have a server with 8gb ram and 4 cpus. I don't have enough time for testing and bench marking so I would like to get the advise of experts like you guys, let me know if something is wrong with my ...
0
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0answers
19 views

Need some advice on db layout

I have some data that gets exported from a different system that I want to suck into mysql for some analysis. Currently, the export consists of 2 files, essentially file1 is the list of transactions ...
0
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1answer
39 views

Does LIMIT 1 still have effect on a unique column

I know that adding LIMIT 1 when searching for only one record makes a lot of difference when it comes to performance. But does it still have any effect when we search a column with a unique ...
3
votes
1answer
159 views

MS SQL Server CPU load goes up dramatically when turning on 2014 features by setting compatibility level

I'm running some Microsoft SQL Server 2014 load testing on a decently spec'ed machine. I'm certainly not an expert on the SQL Server tuning specifics, but with the bits an pieces I've gathered from ...
99
votes
7answers
100k views

How can I optimize a mysqldump of a large database?

I have a symfony application with an InnoDB database that is ~2GB with 57 tables. The majority of the size of the database resides in a single table (~1.2GB). I am currently using mysqldump to ...
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0answers
25 views

Does extending datafiles affect performance

We have an Oracle 10.2.0.3.0 on Windows 2003 Server which is scheduled for upgrade within the next six months. One tablespace is about 2TB in size with over 250 data files. Some of these were ...
10
votes
1answer
992 views

Why are multiple COUNT faster than one SUM with CASE?

I wanted to know which of the following two approaches is faster: 1) Three COUNT: SELECT Approved = (SELECT COUNT(*) FROM dbo.Claims d WHERE d.Status = 'Approved'), Valid ...
3
votes
1answer
185 views

What are possible causes for consistently volatile INSERT performance in MySQL tables?

I have a Java program running on a VM that is sequentially feeding a queue of single row INSERTs through a single connection to a MySQL server on the same VM. The queue execution is not artificially ...
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0answers
20 views

Performance issue for daily calculations - Sybase Adaptive Server

I need an advice from the community, there is no wrong answer I'd like to have as many advice that I can ! I manage a process that does every day a lot of financial calculations and they are ...
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1answer
37 views

Consultants using old version of Hibernate ORM for new application - should I be concerned?

My company currently has consultants developing a Java-based application. They are using Hibernate ORM 3.5 (released 5 1/2 years ago in 2010) in this application. The back-end is SQL Server 2012. ...
0
votes
1answer
24 views

Large Sleep counts causing THREADPOOL wait?

When I run sp_whoisactive throughout the day, I usually see we have around 500-700 connections on our server. We are occasionally getting threadpool waits and high signal wait ratios (so we are thread ...
2
votes
3answers
92 views

Why do large images stored in database hurt performance [closed]

I have read on the internet that it is better to keep large images on file systems since storing them in the database hurts performance. My question is why do large images hurt db performance?
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votes
2answers
82 views

Merge two huge tables keeping only the unique rows

I have two tables: table1 with 61 million rows and table2 with 59 millions rows. The columns in both are the same (name and type). Both are imported from backup files. I want to merge these two ...
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votes
3answers
3k views

How is LIKE implemented?

Can anyone explain how the LIKE operator is implemented in current database systems (e.g. MySQL or Postgres)? or point me to some references that explain it? The naive approach would be to inspect ...
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vote
2answers
126 views

Faster query when joining data from multiple tables

I’m looking for a way to make a database query faster. The table parts has over 6 million rows. Each part row is associated with the manufacturers table (a couple hundred rows) by ID. When searching ...
1
vote
1answer
66 views

SQL Server - High Performance Record Comparison [closed]

Scenario : I have a collection of records to be inserted/updated into a table. Each record before getting inserted/updated in the table must be checked with the other rows in the table so as to find ...
2
votes
2answers
60 views

How to retrieve Oracle Key Performance Indicators in 5 minute intervals within a time range

I have Oracle 11g attached to a Performance Test environment. A performance test runs for two hours. After the run I want to programmatically extract a variety of in key indicators from the database ...
8
votes
2answers
138 views

Why is TOP operation in SQL execution plan

After searching for a while, I decided to post this question for lack of finding an answer and apologize if there is a similar question/answer out there. When running the query below on two similarly ...
0
votes
1answer
47 views

Slow query log on production?

What are the best practices regarding the slow query log? Should it be active in production environment? If so, what would be a reasonable long query time? I know its different for every application, ...
5
votes
1answer
2k views

Performance difference between SQL Server Linked Server and direct query

A Management Studio query pane connected directly to a remote sql server executes and displays a simple table query of (SELECT * FROM table) in just under 2 seconds. The same Management Studio but ...
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0answers
48 views

MySQL query hanging while copying to tmp table

I have a query that ran in 10+ seconds last week, but now is hanging even after 10 minutes. I'm running this in a test environment so the data hasn't changed much and I am baffled at what could be ...
2
votes
2answers
18k views

Where all can the /*+ PARALLEL */ hint be used?

It works with SELECT and UPDATE statements. Are there some more statements with which it works? I was able to use it with create, but am not sure if the hint was actually considered. SQL> create ...
3
votes
1answer
94 views

Select performance problems with conditional index vs non-conditional on large volume table

We are trying to change some indexes on a large-volume table to be conditional indexes (function-based indexes) to reduce how much space is being used for indexes against this table. When testing the ...
2
votes
1answer
2k views

'Incorrect datetime value: for column 'last_login' at row 1'

i am getting below error: Last_SQL_Errno: 1292 Last_SQL_Error: Error 'Incorrect datetime value: '2013-03-10 02:00:00' for column 'last_login' at row 1' on query. Default database: 'platform'. ...
0
votes
1answer
75 views

SQL Server Memory Cap reached its maximum state and threw an Out Of Memory Exception

We have set a memory cap limit of 43GB in SQL server instance, so thereafter it keeps 42 GB near about and keeps near about 1 GB for its processing operations. But then we received near about 500,000 ...
4
votes
5answers
409 views

How to optimize very slow SELECT with LEFT JOINs over big tables

I was googling, self-educating & looking for solution for hours but with no luck. I found a few similar questions here but not this case. My tables: persons (~10M rows) attributes (location, ...
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0answers
25 views

Any risks to pure inserts + delete duplicates, instead of insert/ update for SQL Server?

I saw a related question but it was more of the how vs. the why. I'm wondering in SQL Server why one would attempt an "insert/ update" with incoming data ... instead of just running pure inserts ... ...
4
votes
1answer
224 views

Should I use UUID as well as ID

I've been using UUIDs in my systems for a while now for a variety of reasons ranging from logging to delayed correlation. The formats I used changed as I became less naive from: VARCHAR(255) ...
0
votes
1answer
54 views

Is it possible to break down query time?

We have a setup of a few cloud servers that connect to a MySQL cluster on dedicated servers over Rackspace's Rack Connect network. We have noticed recently that the time for database queries (via PHP) ...
0
votes
0answers
41 views

MySQL database hangs but less CPU

I create an application for 30 concurrent users using C# and InnoDB of MySQL (mysql-5.1.35). The size of database is more than 100M lines (~20GB). Most of data is come from 7 active table (2M ...
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vote
0answers
77 views

Mongodb Huge Number of Open Connections and Write Locks

We are seeing around 800 open connections to our Mongodb. To clarify our issue: We have 5 different clients who write the data into Mongodb. Each of these clients - write four different type of ...
4
votes
0answers
154 views

Performance inner join vs left join involving parallelism

I have a query which takes about 8 hours to finish. Simplified, the query looks something like this: SELECT [Some attributes, inconsequential] FROM RBM.Financial_Events RFE INNER JOIN ...
2
votes
2answers
52 views

How to optimize performance of backup process? Servers go down during backup

The context - So I am an intern (So I'll appreciate a more noob friendly response) and we have several websites on a server of which we do a backup daily, at midnight. We use MongoDB and there's a ...
3
votes
2answers
450 views

Optimise huge Postgres table for fast read

I'm about to create a Postgres table with 1.5 billion rows. The table will just have a single TEXT column. The table is effectively a blacklist. When a user of my software saves certain data, this ...
2
votes
0answers
87 views

Materialized View - vs. New Calculated table for performance [closed]

I have a problem - I'm trying to de-normalize data tables in a data warehouse in preparation for use in the Business Intelligence/ Presentation layer. By denormalize I mean create a series of joins. ...
1
vote
0answers
113 views

CPU Time Slower in SQL Server 2014 than in SQL Server 2008

We’re upgrading a virtualized database server from an old SQL Server 2008 R2 Standard (vmware) to a new shiny SQL Server 2014 Standard server (hyper-v). We were doing some performance testing and to ...
0
votes
2answers
72 views

Improving performance on a join query

I have the following MySQL query that I am attempting to run against a set of tables prepopulated with data: $sql = sprintf(' SELECT video.id, video.name, video.created_at, video.duration, ...
4
votes
1answer
193 views

MySQL Write performance bottleneck

We are trying to diagnose a MySQL Bottleneck, specifically for data writes. Basically, we have a single process that picks files from a folder and load into a MySQL table X using LOAD DATA CONCURRENT ...
2
votes
0answers
24 views

Implications of many materialized views in Postgres?

I'm working on a system that includes a scheduling component, which has support for recurring events. After reading many, many posts on storing recurring events, it was suggested that they be ...
0
votes
0answers
38 views

How to tune a sql server for a specific process in particular?

I have a specific process that I am want to tune for in a sql server DEV server. The DEV server and the LIVE server are equal, just the DEV has less memory. Both LIVE and DEV read data from the same ...
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vote
1answer
198 views

Heavy load of one of shards in MongoDB

I have a problem with one of our shards. For some reason I'm getting the next usage: 15:38:42 up 4 days, 10:28, 1 user, load average: 3.67, 3.50, 3.56 In the mean time all other shards are ok. ...
0
votes
0answers
32 views

Increasing system load due to multiple inserts every millisecond

In my project I need to do multiple database inserts every millisecond and thus Postgres takes huge amount of CPU. I need to find a way to reduce CPU load as I need to process about millions of rows. ...
0
votes
1answer
83 views

What's the biggest bottleneck (time) in writing data to a SQL database?

I'm running an ETL process that is writing about 2 million rows to a SQL Server database. I'm trying to optimize the time it takes for pure inserts (I guess updates is a different story). I'm ...
11
votes
2answers
3k views

Placing Transaction Log on Separate Volume [solid state]?

Transaction logs are often isolated on a separate volume. The rationale for this practice, as I understand it, is that the transaction log's data is written sequentially -- and hard drives can execute ...
0
votes
0answers
87 views

Performance: Postgres (Read-Committed) vs MySQL (Read-Uncommitted)

I have a workload that involves very frequent writes and reads. It is very performance sensitive, but not accuracy-sensitive. Hence, to maximize performance and minimize locking-delays, my plan was to ...
0
votes
0answers
11 views

with innodb engine, connection timed out & MySQL server has gone away error occured [duplicate]

I have created chat application which ping server every sec for messages. Currently I have done load test with httperf, with 500 request/sec. "Connection timed out & MySQL server has gone away ...
3
votes
1answer
556 views

Is a clustered index on column A the same as creating a table ordered by A?

Reading the official PostgreSQL documentation for version 9.0 I read an interesting escamotage that performs better than CLUSTER for big tables: The CLUSTER command reorders the original table by ...
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0answers
49 views

Improve performance of count(*) with two exists

I need some help improve performance of this query that runs in Postgresql 9.4 at Amazon RDS: SELECT count(*) AS total FROM people WHERE EXISTS ( SELECT 1 FROM person_values WHERE ...
8
votes
3answers
162 views

Poor cardinality estimate disqualifies INSERT from minimal logging?

Why is the second INSERT statement ~5x slower than the first? From the amount of log data generated, I think that the second is not qualifying for minimal logging. However, the documentation in the ...
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0answers
49 views

Inexplicable differences between 2 almost identical databases on the same server

Our situation is as follows: We've got 1 MySQL (5.5.44) database server. The server hosts 2 databases. 1 database is the production database. The other is a copy database that gets copied from ...