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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MySQL - Server collation utf8_unicode_ci vs table collation utf8_bin: compatibility and performance

I'm not sure whether this belongs to SE DBA, but it sounds more logical ... Our MySQL 5.5.32 on Ubuntu 12.04 64 uses utf8_unicode_ci for the Server collation and some tables, like phpBB3, uses ...
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335 views

TCP sockets bottleneck with InnoDB/Debian?

We have a big mysql performance issue on a production environment with 18 "front" servers sending mysql queries to a unique mysql server. We are using Redis on each front server for a number of ...
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129 views

SQL queries are very slow

I have noticed that my queries are getting slower. Some update queries take about 48-50 seconds. Here's how it looks: [root@db-1 ~]# tail /var/lib/mysql/mysql-slow.log # Time: 131113 17:09:48 # ...
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25 views

optimizing a CTE Hierarchy [duplicate]

I have a table of accounts with a typical acct/parent account architecture to represent a hierarchy of accounts (SQL Server 2012). I created a VIEW using a CTE to hash out the hierarchy, and on the ...
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1k views

Slow MySql Server Performance - What and How to check?

start:disclaimer I'm not a MySql Server DBA; I know mostly of MSSQL - which is why i need your help end:disclaimer I've been asked to check why the MySql server engine is performing poorly - i have ...
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2answers
9k views

MySQL creates temporary tables on disk. How do I stop it?

We are running a site (Moodle) that the users currently find slow. I think I have tracked down the problem to MySQL creating temporary tables on disk. I watch the variable created_tmp_disk_tables in ...
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1answer
62 views

Can SQL Server WebAdmin degrade the performance of my site?

Once upon a time a had to use the Parallels WebAdmin interface. After contacting the support team that hosts my website and informing them that I must use the Webadmin, they informed me that: MS ...
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342 views

SQL Server: Batch Requests/sec showed increase in performance, but performance actually decreased

We are currently on SQL Server 2005, with a plan to move to SQL 2012. To make this move we have to test new database drivers for the application (Java). We performed 2 load tests using the 2 different ...
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190 views

Which is better? A join or a SELECT IN? [closed]

I have a set of ids that I extract using a join of 2 tables. Now I need some information from 2 other tables. What would normally be the best approach? So a SELECT IN using the set of ids I already ...
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322 views

Should NOT IN be avoided?

Among SQL Server developers, it's a widely held belief that NOT IN is terribly slow, and queries should be rewritten so that they return the same result but do not use the "evil" keywords. (Example) ...
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129 views

MySql - is possible that performance issues are caused by dynamic SQL?

We have this MySQL SP, which uses dynamic SQL. It seems it does NOT perform well under load. It is possible that this SP becomes slow under load because it uses dynamic SQL? Can dynamic SQL cause ...
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76 views

How is the number of records on a select determined as high or low by optimizer?

What is the threshold between using the index and doing an direct access to the database? I assume this decision is related to the number of index access (and subsequent access to the tables). If this ...
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57 views

Can MySql nested SP be a bottleneck?

We have this MySQL SP, which calls a nested SP. It seems it does NOT perform well under load. It is possible that this SP becomes slow under load because it calls a nested SP and uses temporary ...
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1answer
893 views

Table-valued function runs fast, but slow from another function [closed]

Disclaimer: I'm a senior sysadmin who's trying to help our development team speed up the production database. Our users are hurting, bad. Please don't shoot me for not being great with SQL The ...
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4answers
213 views

Which of these queries is best for performance?

Which of these queries are best for performance ? Sometimes I wonder if SHORT scripts really is the best thing to focus on. These scripts performs the same task. With left joins i can achieve what i ...
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431 views

Fastest way to perform simple operations on 1 million rows

I have a simple table with more than 1 million rows in an InnoDB MySQL table. Here are the steps that I need to perform on each row: SELECT * FROM tbl where work_done=0 make some data processings ...
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74 views

Find Most active databases that can be offloaded from a busy server

I am in the process of identifying the most active databases on the server and will be moving the databases off the current server to alleviate the load. The reason to do it is that our servers are ...
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2answers
109 views

Running a simple logging program, how to diagnose spikes mongod's CPU activity?

I'm running mongodb 1.4.7 - I've a node server set up which logs incoming requests in a logs collection: {'u':'user123', 'l':'log data'} In addition, once the request happens, the server will check ...
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74 views

Can XML columns in Oracle/MS SQL Server replace document oriented databases to some extent?

Just a strategic question: I am currently working with frequently changing data schemas and it takes a lot to keep track of versions and specific content. I do, however, have a classic OLTP ...
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54 views

MySQL showing non-linear behavior for a simple insert

I've come across a symptom in MySQL which got me baffled. First, the time it takes to INSERT a certain amount of records changes non-linearily with the amount of records. Second, the time also depends ...
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113 views

My queries are slow under load

I am performing a load test for my application. All my SQL queries which are fired from my application, individually look better and perform fast. The same SQL are becoming bottleneck when they are ...
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1answer
69 views

Restoring with replace going incredibly quickly [duplicate]

So I have a database (on a SQL Server 2008 R2 SP2 instance) that is 2TB uncompressed, with a .bak file that is 500GB compressed. As I have been toying with the fastest way to restore this database ...
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2answers
1k views

GROUP BY with MAX versus just MAX

I am a programmer, dealing with a big table which the following scheme: UpdateTime, PK, datetime, notnull Name, PK, char(14), notnull TheData, float There is a clustered index on Name, UpdateTime ...
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185 views

Using coalesce on an index column

Does doing a COALESCE on an indexed columns in a WHERE clause e.g. WHERE COALESCE(table1.indexed_column, '9999-01-01') > table2.other_date_column affect indexing in a bad way? I think that it ...
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123 views

mysqldump & upload to mysql speed impact due to SSD and innoDb?

I am testing an AWS Medium Instance with CentOS (AWS AMI) and comparing it with Hetzner's EX40-SSD (http://www.hetzner.de/hosting/produkte_rootserver/ex40ssd). Software setup on both is comparable( ...
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134 views

Best read performance when every query is known, and the data doesn't change

I'm trying to maximise performance on an underpowered PostGIS server - 1 core, 4 CPUs. The data (OpenStreetMap) will be infrequently (monthly?) loaded, and never changes otherwise. Each of the 30 or ...
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129 views

Why does removing a RID by creating a clustered index lose parallelism and slow down execution by 2X

If I remove a RID lookup by replacing 2 non-clustered indices (non unique) with 2 identical clustered indicies (non-unique) where there weren't any before, why does this query slow down by a factor ...
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2answers
585 views

MySQL - Add index to low cardinality text column?

I'm working on project where an enum column is being converted into a text column (I cannot change this). The cardinality of the column is low (7 unique values). Would I gain a performance increase by ...
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2answers
701 views

Does using LIMIT improve the performance and is it noticeable?

I want to understand the following. Assume that I have a complicated query with let's say a join of 5 tables a group by summations and order by. Letting aside any optimizations to the query itself ...
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1answer
531 views

How to “warm up” a cold DB server?

1st setup was a DB slave that was used by customers. That was sufficiently fast. 2nd setup (now) is replication of a DB slave that is just used by me. The current setup is slower on query execution ...
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2answers
302 views

Slow query responce on different mysql versions, percona, MariaDB

LEFT JOIN is supposed to be faster than a NOT IN query. This is what I've read online. But practically, this seems to be opposite. I have the following query here, INSERT IGNORE INTO callrequests ...
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2answers
2k views

Efficient query to get greatest value per group from big table

Given the table: Column | Type id | integer latitude | numeric(9,6) longitude | numeric(9,6) ...
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285 views

Simple PostgreSQL lookup table is inexplicably slow

I'm trying PostgreSQL 8.4.14 for storing triples, pieces of data of the form (String, String, String). For speed, I'm not repeatedly storing strings but rather using two tables: main table triples ...
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3answers
411 views

Performance of primary key IDs with gaps (but in sequential order)

I know that having non-sequential IDs is bad for index performance. But assuming all my IDs are created in correct order, but with large gaps: i.e: 154300000 283700000 351300000 464200000 ...will ...
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141 views

PostgreSQL 9.2 (PostGIS) performance problem

A month ago i got acquainted with PostgreSQL and only now i've noticed that some of my queries are pretty slow. Well, for example, i have table: CREATE TABLE sometable ( gid serial NOT NULL, geom ...
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185 views

Improve Speed of MySQL Database Import

I'm importing around 44 GB (14 million rows) of information into an InnoDB MySQL database, and I'd like to do so in a reasonable timeframe. Since I'm doing this on a personal computer, I only have 8 ...
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112 views

Slow query with ORDER BY with index created (more than 4mins on 0.6million records

I ran into a very weird query performance situation. If I run this query without order by, it finish in millsecs, with order by, it ends up with more than 4mins. EXPLAIN SELECT `book_book`.`id`, ...
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3answers
997 views

Conditional Join - Specific Column Select

I have tables like these: Table Employee ( Emp_Id, Full_Name, ...) Table Order ( Submitter_Id, Recipient_Id, ...) Then say that I have conditional join like this: select isnull(Emp.Full_Name, ...
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226 views

What is Required to use Oracle Performance Manager to monitor SQL Server?

I am working with a customer who has several SQL Server and Oracle DBMS server instances. My customer would like to setup up performance data collection, monitoring and alerting for all of their ...
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100 views

SQL server taking too much time in opening properties in SSMS

I am using sql server express 2008 r2 SP2 from about 2 years. Now a days when i try to check properties of database using sql server management studio it takes too much time(25 to 30 seconds) to open ...
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1answer
406 views

Extremely Slow StatMan query issue with #SP2010 farm

The issue I’m experiencing is explained in a blog-post I created for this, (easy to refer to and to manage the responses / solutions in 1 location) which can be found here: ...
4
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1answer
171 views

Disk usage spikes: good, bad or indifferent?

I'm working on a project where we're receiving data from multiple sources, that needs to be saved into various tables in our database. Fast. I've played with various methods, and the fastest I've ...
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335 views

Is it possible to optimize a range query so an explain statement would state “using index” instead of “using index condition”?

I have a very large table where specific queries made by my application are timing out. The table looks something like this: LargeTable ------------ Id [BIGINT(20)] UtcTimestamp [BIGINT(20)] Pivot ...
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1answer
123 views

Get unmatched rows for foreign key

Consider two tables: CREATE TABLE Users( id INT PRIMARY KEY, name VARCHAR(128) ) Engine=InnoDB CREATE TABLE Tags( id INT PRIMARY KEY, user REFERENCES Users(id), tag VARCHAR(128) ) ...
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87 views

What is the most efficient way to create new MySQL database

I need to setup a development environment for several developers. Each of them needs to test the software with a "fresh" MySQL database. There is a SQL file with many CREATE, ALTER and INSERT queries. ...
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198 views

MySQL select by primary key against 100M of records within 30ms

I have no expirience with MySQL and database performance tuning in general. Wondering whether it is possible to perform a large number of selects against 100 millions of records by primary key within ...
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1answer
603 views

TPS too high in PostgreSQL

I created a table: CREATE TABLE foo ( id integer primary key, bar integer NOT NULL ); and inserted one row: INSERT INTO foo (id, bar) VALUES (1, 1); and ran a pgbench of the following ...
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82 views

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
142 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 ...
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1answer
636 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 ...