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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45 views

PostgreSQL queries slower than before?

I am using PostgreSQL 9.3 server on my production server. Everything had been working fine for the past couple of months. But since the past week or so, PostgreSQL seems to have becomes very slow with ...
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1answer
55 views

Localization: One table or multiple tables? (MySQL)

I need to be able to store string messages in various languages. I guess I need a column for each language string. For example my columns could be: ID | message_EN | message_DE | message_FR Now, I ...
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2answers
40 views

SQL Performance: COUNT or extra attribute?

If I want to count the number of a multivalued attribute, which way is faster: a) using COUNT(attribute) on a whole table or b) adding an extra attribute which counts these stored values (to be ...
6
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2answers
479 views

Transaction speed benchmarks for mySQL v5.6 replication - seems very slow

I'm trying to select the best configuration for our new infrastructure but got a bit confused about the results. I used sysbench v0.5 for the tests: prepare data sysbench ...
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0answers
56 views

Multiple databases with medium tables or Single database with huge tables

I've developed a shop management software using Postgresql and JAVA. I would like to know which of the solutions below is the best one for my specific situation: Only one database with huge tables ...
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1answer
45 views

Will switching from Concrete Table Inheritance to Single Table Inheritance improve the performance of my queries?

I currently have an application that allows people to view and share 10 different types of posts (ex SportsPost, WorldNewsPost, TechnologyPost, etc). All posts types are conceptually the same, but ...
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1answer
63 views

Simple query is slow on 4M-rows table

I have in production a MySQL table pageviews with 4M rows that records page views of users on posts. I need to know which posts a specific user have read, but this request takes up to 15 seconds to ...
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0answers
43 views

Looking for a recipe to merge multiple rows to single row

I have a aggregation table that is written by multiple processors (around 20). Each row has a composite key - location-id, campaign-id,... and aggregate stats about it. I need to merge the ...
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5answers
16k views

SQL Server 2012 slower than 2008

I migrated a large website and database from an older server (Windows 2008 / SQL Server 2008 / 16 GB RAM / 2 x 2.5 GHz Quad Core / SAS disks) to a newer, much better server (Windows 2008 R2 / SQL ...
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1answer
66 views

SQLAnywhere: Visualize in real time CPU and RAM consumption of sql connections

I want to keep track of which connection use most of resources. Within Sybase Central (SQL Anywhere 9, 12), for each server and database, we have pane to check in real time All Connected Users and ...
3
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2answers
573 views

Dramatic decrease in SQL Azure performance after scaling to new edition

Yesterday, we scaled one of our databases in Azure from the old Business edition to the new Standard one (S2). Since then, it has been behaving rather erratically. We have a relatively simple table ...
1
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1answer
45 views

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

I want to clone oracle 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 need ...
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3answers
6k views

When a previously-fast SQL query starts running slow, where do I look to find the source of the issue?

Background I have a query running against SQL Server 2008 R2 that joins and/or left-joins about 12 different "tables". The database is fairly large with many tables over 50 million rows and about 300 ...
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1answer
102 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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2answers
128 views

Is there a faster way to get UNION ALL behavior in Postgres?

I have a table (t0), in my Postgres DB, with data that looks something like this: t1_id t2_id 1 1 2 1 2 1 4 null 4 null 5 null And I have a query to return my ...
2
votes
2answers
1k views

Redis takes up all the Memory and Crashes

A redis server v2.8.4 is running on a Ubuntu 14.04 VPS with 8 GB RAM and 16 GB swap space (on SSDs). However htop shows that redis alone is taking up 22.4 G of memory! redis-server eventually crashed ...
0
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1answer
27 views

MYSQL improve query performance when using OR

I have a very simple MYSQL table with 2 columns and I run this query: SELECT * FROM table WHERE (col1 = '123' AND col2 = '456') OR (col1 = '456' AND col2 = '123') Col1 and ...
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2answers
27 views

MySQL improve query syntax

I have this simple MySQL query: SELECT * FROM table1 INNER JOIN table2 ON table2.col = table1.id WHERE table1.id = '123' id is the primary key in table1. table2 has composite primary key of two ...
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0answers
57 views

Can High CPU be triggered by Login Failures?

On our SQL Server (used for TFS) we have recently had the CPU pegged at 100% (with a few occasional dips) for nearly a day and a half. Looking at the SQL Logs, there appears to be a correlation in ...
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1answer
37 views

Mathematical or Computing Alternatives for MySQL Combination Queries operating toward their Performance Limit

We regularly run a contest that is becoming quite popular. In the contest, we need to select the combinations of contestants from 8 groups whose cost is under a threshold, and who combined have the ...
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0answers
42 views

Billion records mysql performance with large result sets

I'm currently developing an application which will have several mysql tables where 3 of them have very large amounts of records. The thing is that my app will have to sync each account on a hourly ...
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2answers
74 views

Signal wait always high

I'm not sure if this is the right place to ask this question, so apologies in advance if not. Problem I'm facing is: One of my server's signal wait floats at around %35 and won't go down. Top 3 ...
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3answers
404 views

Keeping default max memory 2147483647 MB value in SQL Server, a bad practice?

Based on that msdn page : server memory settings it's a good practice to keep the default values for SQL-Servers min and max memory to keep it dynamic... From what I learned through tutorials you ...
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3answers
2k 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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2answers
87 views

PostgreSQL and storing configs

The problem is to store and use global configs such as currency/date format etc. Since this functions are commonly called I'm concerned with the performance impact. Lets take currency as an example. ...
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3answers
247 views

SQL Server clustered index, index balancing and insert performance using NewID

I have a large (6db) trace table. It has a clustered key (DateTime) which is created through GETDATE(). The connection pool for connections to this database/table rises as high as 50 on average ...
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2answers
16k views

When To Update Statistics?

I've inherited a Maintenance Plans that does the following: Cleanup old data Checks DB integrity Performs Database and Transaction Log Backups Reorganizes Our indexes Updates Statistics Delete old ...
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1answer
23 views

Effects of monolothic databases on performance and security?

Please note: although I'm specifically calling out MySQL here, I would also appreciate/entertain generic answers that apply to all/most relational systems. As a developer I don't see the design ...
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0answers
54 views

MySQL Crash due to “InnoDB Assertion” after Query

Current setup: Ubuntu 12.04 LTS MySQL 5.5.31 Current Use: Slave - Only ETL queries 64 GB RAM Intel(R) Xeon(R) CPU X5670 @ 2.93GHz - 12 Cores - Hyperthreaded (24 Logical) MySQL Main Settings: ...
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2answers
43 views

Is there anything wrong with creating a very large log file?

I've been given the task of finding out why our server is slow. First of all I did not set this server up. Is there anything wrong with setting the initial log file size to 70GB? That's what ours is ...
2
votes
1answer
44 views

Can autoshrink permanently damage a database? [duplicate]

I've been given the task of finding out why our server is slow. I ran a stored procedure I downloaded called sp_Blitz. It let me know that our database had auto-shrink enabled, and to disable it. So, ...
0
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0answers
30 views

MySQL performance_schema not working properly?

I have MySQL 5.6.19 community server running on my Ubuntu 14.04. Lately I have been trying to monitor MySQL server using performance_schema. Previously I used to do this by running SHOW FULL ...
0
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1answer
28 views

Query perfomance with multiple JOINs on MyISAM-based DB

I'm working with Enron Email Dataset in MySQL database. After I executed data import from dump-file into MyISAM-based DB, I got the set of tables without any connections between them via foreign keys. ...
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1answer
19 views

MySQL query performance of Date sorted data

I found some articles and questions on this issue but not sure if I got the answer. very new to db modeling so please bear with me My use case is: Save user activities: I'm doing this by creating a ...
0
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1answer
33 views

How to model efficient permission checks for a social network?

The goal is to build a facebook like permission system. So that users can grant other users access on objects based on a direct assignment (allow user X to see posts) or allow users to access them ...
4
votes
1answer
105 views

Proving the usefulness of a specific index

I'm looking for a way to prove that some recently added indexes are positively impacting a production system. I've collected some dmv statistics to show that the indexes are indeed being used ...
0
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1answer
17 views

Can I use MySQL-SERVER tunning variables in MYSQL CLUSTER?

When tunning MySQL-SERVER for best performance, the edition is done down my.cnf file. Such as: max_connections = 500 wait_timeout = 600 sort_buffer_size = 2M Can I improve MySQL CLUSTER ...
3
votes
1answer
61 views

PL/pgSQL - Indexes vs Collation vs Pattern Ops

I'm using PostgreSQL 9.3. Having already read articles and answers on DBA stackexchange: Why would you index text pattern ops on a text column PostgreSQL documentation: Indexes - Opclass Pattern ...
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2answers
69 views

Optimizing for data that does not fit in memory

We have a database that contains around 235 GB of data (calculcated using pg_total_relation_size for each table) on a server with around 77GB of memory. The server is used for nothing else (aside from ...
2
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2answers
158 views

Partition : understanding files and file groups

We are trying to partition a large history table. Being new to partitioning, I was trying to understand the concept of files and file groups. File groups can be set up in following three ways : 1. ...
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3answers
106 views

500 databases or 1 database with 500 tables or just 1 table with all the records? [closed]

I currently have an application that is used by a single end customer. For ease of discussion assume the application only needs a single database table for all records. I now need to support ...
0
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1answer
61 views

How to check SQL database files for physical fragmentation?

I search the Internet and did not find clear explanation if I have to try defragmenting physical database files when my DB resides on SAN. I understand that there are tools and procedures inside some ...
0
votes
1answer
49 views

Problem with procedure performance

I'm having problem in Oracle, where I have two procedures that are executed one after the other. Where the first procedure, I have a cursor that does insert into a table. This insert has about 30 ...
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vote
2answers
108 views

Upgrading hardware for MySQL. If we get SSDs, are CPUs likely to become a bottleneck

We are upgrading hardware for a MySQL database server (DB is around 200GB). We're getting 4x Samsung 850 Pro SSDs and are planning to run them in a RAID10 configuration. Also, 128GB of RAM. The ...
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0answers
17 views

Is there a faster way to get UNION ALL behavior in Postgres? [duplicate]

I have a table (t0), in my Postgres DB, with data that looks something like this: t1_id t2_id 1 1 2 1 2 1 4 null 4 null 5 null And I have a query to return my ...
1
vote
1answer
31 views

Can I build relationships in existing system without breaking it?

This is my first question here, so I would love help to make it work for SO:DBA. I inherited an older relational system that is sitting on a SQL Server 2005 box and the database is at SQL2000 ...
14
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2answers
15k views

How to optimize a query that's running slow on Nested Loops (Inner Join)

TL;DR Since this question keeps getting views, I'll summarize it here so newcomers don't have to suffer the history: JOIN table t ON t.member = @value1 OR t.member = @value2 -- this is slow as hell ...
1
vote
1answer
49 views

Is there a faster way to get OR behavior in Postgres?

Is there a faster way to do an inner join with an OR clause. I have a query that looks something like this: INNER JOIN (select u_id, b_id from t1) AS t2 ON t2.u_id = t1.u_id OR (t2.b_id = ...
10
votes
3answers
5k views

general memory requirements for sql server 2008 r2

I'm not experienced with DBA work, but I'm trying to make a case for requesting additional resources for our sql server and was hoping I could get some smart folks to provide a rough rough estimate of ...
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0answers
22 views

MySQL Cluster Disk Data Tables - worth it?

I'm working on improving the performance of our 4-node MySQL cluster for a webapp with lots of DB writes. We've got a Solr index sitting 'on top' of the SQL in order to give us fast querying, and we ...