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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Troubleshoot of WRITELOG on new machine running very slow? [closed]

I recently moved away from an old Intel 2,4 GHZ Dual Core dev. machine with 4 GB RAM and SSD to a XEON 2.8 GHZ, 8 GB SSD machine Both machines running Win 7 pro. My trouble is that this new machine ...
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1answer
189 views

Finding reason behind high write IOPS on MySQL (RDS) server

I am having performance issues with an AWS RDS instance (running MySQL 5.6). This is the backend db to an XMPP server called Tigase. According to Tigase Inc. this type of db instance should be able ...
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1answer
49 views

If a query contains two identical subqueries, will they both run?

Say I have a SELECT query that contains two identical subqueries, like the below: SELECT (SELECT SUM(Price) FROM Product p WHERE p.GroupID = g.GroupID) AS 'TotalCost', (SELECT SUM(Price) ...
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1answer
28 views

Optimizing bulk update performance in Postgresql with dependencies

Basically my question is the same as this one, but WITH dependencies, so drop/renaming the table is not a trivial option (I assume). We are refactoring a large, poorly designed table which has many ...
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37 views

How do triggers work on partitioned tables?

I have partitioned a table on the basis of a column. This column can either have 0 or 1. So, only two partitions (p0, p1) have been created internally. On this table there are 3 triggers which execute ...
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27 views

Performance implications of mixing VARCHAR and CHAR fields in MySQL Table

I read the following answers in this forum: What is the performance impact of using CHAR vs VARCHAR on a fixed-size field? MySQL: Does the order of the fields in a table make a difference in ...
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2answers
222 views

Can I update every datetime in bulk?

The current database assumes all times are local to the user. Now we're changing this so the database stores everything in UTC and our application converts the UTC time in the database to the correct ...
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1answer
85 views

If an INNER JOIN in a query returns no rows, do additional INNER JOINS add a significant performance overhead?

If I make a query as follows: SELECT * FROM TableA A INNER JOIN TableB B ON A.AID = B.AID INNER JOIN TableC C ON B.BID = C.BID Does the INNER JOIN with TableC add significantly to the performance ...
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2answers
239 views

MySQL performance problem using indexed datetime column

I tried to solve the following problem for about one hour now and still didn't get any further with it. Okay, I have a table (MyISAM): ...
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113 views

sql query takes too long to execute [closed]

I am having trouble with this query. It takes 10 hours to execute. WITH CONSUM AS ( SELECT C.ID_MEASURER,C.ID_MEASURING_POINT,C.CONSUM_TYPE FROM GCGT_RE_CONSUM_H_E C WHERE C.DAY ...
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35 views

Bulk update performance

I have a several process that aggregate some statistics on items (how much was shown, clicked ... around 30 factors). Once in a 5 minutes i flush the aggregate data to postgres (9.1). I have 250K ...
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1answer
47 views

Does it make sense to order condition in where query?

We have a clustered index in table Tbl with order of A,B,C. Does it make senses to write a query to have WHERE A = @a, B = @b, C = @c or it'll be as same as WHERE C = @c, B = @b, A = @a Does the ...
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2answers
84 views

Should I drop a foreign key if I use a soft delete?

"ON UPDATE" scenario never happens in my application. As soft delete is used, "ON DELETE" cascade and restrict scenario never happen as well now. Then, should I just drop foreign key because I have ...
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2answers
92 views

Do MySQL optimizations hold for MariaDB also?

I am a developer who will be starting a new project soon in which database performance will be crucial. The current candidate for the backend is MariaDB. I have worked with MySQL and MariaDB before in ...
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1answer
163 views

Database design for a table with both bulk insert and single row insert

I have to design a table where records will be inserted in two ways. Bulk insert from a batch process from a delimited text file between 2 - 3 million rows in a short burst. Later the same records ...
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1answer
37 views

MySQL: What is SQL profiler, does it different for MySQL?

Whenever SQL profiling comes in mind, focus goes to two below sections: GUI tools like - MONyog, Neor Profile SQL set profiling =1; Execute Query; show profiles; show profile; I am really confuse ...
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1answer
132 views

MySQL: Which join is better between left outer join and inner join

Which join is better peforming if all of them provides the same result? For example, I have a two tables employees(emp_id,name, address, designation, age, sex) and work_log(emp_id,date,hours_wored). ...
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1answer
73 views

MySQL: How index speed up query execution

I have read multiple articles about MySQL indexes. Some of the important pages are below: http://dev.mysql.com/doc/refman/5.6/en/mysql-indexes.html ...
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1answer
162 views

Amazon RDS CPU Usage keep increasing without any long running process in Show Processlist

We are using Amazon RDS(db.m2.2xlarge), CPU usage is suddenly increasing gradually even after we reboot the DB Server. This is happening just past 2 days and we didn't give any new build recently. I ...
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1answer
29 views

MySQL server performance plummets

Part of our software solution is responsible for processing files that get uploaded to us by our clients. We want to process them as quickly as we can. Our system is architected so that there's a ...
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1answer
20 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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3answers
223 views

InnoDB import performance

I'm struggling with bulk importing a quite big InnoDB-Table consisting of roughly 10 Million rows (or 7GB) (which for me is the biggest table I've worked with so far). I did some research how to ...
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1answer
42 views

MySQL: How turning off the logging affect the performance?

OS: RHEL5 DB: MySQL 5.1.73 community edition DB size: ~1GB I have setup a testing environment and turned off all logging - general logs, binary logs, slow query logs etc. I am using Oracle ...
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1answer
58 views

What is FT BATCH CMPLETE in the cmd column for sysprocesses?

I was trying to figure out what was causing high cpu usage in our sql server and found two processes that were consuming high CPU. When I queried sysprocesses to see what the spid was doing, it had ...
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1answer
14 views

How to minimize the writes needed to update a counter field multiple times

I need to minimize the number of queries that are executed just for updating a counter field. One of my example counter fields is raised by 1 everytime a page is visited, I was wondering what could ...
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2answers
441 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 ...
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2answers
3k views

Why would SELECT * be magnitudes faster than SELECT foo?

Consider a table of values and hashes, like so: +------------+----------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | ...
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1answer
53 views

Migration query taking time

I'm doing a migration from Oracle to SQL Server and, for one of the tables where we have 3 million records, it is taking a lot of time to complete. When I check the activity monitor, I can see the a ...
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62 views

How can I decrease FULLTEXT initialization time?

I'm trying to decrease execution time of the a query. Using SHOW PROFILE, FULLTEXT initialization takes about 0.3, which is too high. Other values are at normal level. How can I decrease FULLTEXT ...
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2answers
208 views

SQL 2008 Server - performance loss possibly connected with a very large table

Migrated from http://serverfault.com/questions/615129/sql-2008-server-performance-loss-possibly-connected-with-a-very-large-table We have SQL Server 2008 with 3 active databases running on it. DB1 ...
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2answers
58 views

Optimize rows to columns conversion

I have a big Oracle table (around 40 million rows) that looks like this: ID Name Question Answer Reason 3 Name1 1 Yes blah blah 3 Name1 2 No NA 3 Name1 3 ...
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2answers
63 views

How do dirty reads at both the transaction and table level provide increased performance?

I ran the following code past our architect as I thought there may have been a tautology between the isolation level and table hint: SET NOCOUNT ON SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED ...
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2answers
469 views

Explanation requested for slow DELETE with SQL Server

I would like to get some extra insights/reasoning for SQL Server delete behavior. We have a fairly large database of over 1800 GB. In there are some very shallow tables (only a few integer columns) ...
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1answer
97 views

Perl - MySQL/MariaDB - slow with no identifiable bottleneck

I am running a Perl script (using DBI) which reads from raw files from a hard disk, and updates MySQL database (which is on a separate SSD). My performance is rather slow (1000 files processed in ...
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1answer
129 views

Tuning Mongo (TokuMX) for fastest bulk reads

What options do I have for tuning MongoDB / TokuMX for reading the results of queries with large result sets? I'm currently on a single server (no sharding) with the data on an SSD drive. My queries ...
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0answers
64 views

firebird update very slow

I am writing a stored procedure for Firebird 2.5 in which I sometimes need to update a single row in a data table more than once in the same transaction. However, I have noticed that the performance ...
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39 views

performance questions in database design

I need to describe a set of studies that are practiced to a patient, every patient have a "Clinical History", that are described in another table called "Clinical History Lines"(hclines) Every visit ...
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18 views

What is the optimal way to get a tabular view from an Entity-Attribute-Model table?

Following up on my previous question, I have created a table for storing measurements of different physical quantities. The schema looks like this: CREATE TABLE sensorreadings ( time TIMESTAMP, ...
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56 views

Database design for large incoming data

I've been tasked to design a database to handle a large volume of incoming traffic from sensor readings, possibly 1,000s an hour when it's at full strength. Each reading will be relatively short - ...
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1answer
42 views

Disable MongoDB journaling?

Are there any benefits in disabling mongodb journaling besides performance gain? I know journaling provides write durability and crash resiliency. But I can tune syncdelay parameter to make data files ...
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2answers
167 views

Rapidly increasing TempDB write latency

We have two servers that were set very similarly, but not identically. These two servers have hugely different performance running the same application. On server A the application runs successfully ...
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1answer
100 views

Handling a chat room in a database

I have been searching all day to find a better answer to my question but those I found was useful but do not critically analyse my question. I am building a chat room using php, mysql, jquery and ...
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60 views

A working view now starts timing out

I have 2 identical databases (one larger, one smaller) with identical views. Recently a view on the smaller DB started timing out. Google searches seems to point to deadlocking of some sorts. If I ...
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1answer
36 views

mongodb - “replication oplog window” possibly reduced due to profiling - when profiling disabled no change?

PROBLEM I have a 3 member replica set (no sharding) running mongodb version 2.4.8. Using MMS (Mongo Monitoring) I can see that on 7th July 2014 at 12:00 my "replication oplog window" dropped from ...
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2answers
92 views

SQL Server Baseline and Performance Optimization

I've been struggling a little bit around Performance Troubleshooting including baseline and troubleshooting of SQL Performance. Could anyone help with this or point me to where I can possibly get a ...
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1answer
121 views

Why is this second query more expensive than the first?

While reading Graph Databases book, I came across this excerpt: I can't figure out why the second query is more expensive than the first. Indeed, both filter on the Bob person. May anyone ...
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2answers
51 views

Does leaving a connection open for a matter of seconds cause deadlocks?

I have been testing a system application and have noticed that it is slow when it connects to the database overseas. This is to be expected to some extent, but there is a big difference with the ...
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2answers
291 views

Optimizing large MySQL SELECT WHERE IN clauses

How can the following SELECT WHERE IN case be optimized? I have a table with over 100 million rows with only 3 columns. The primary key (col1) is a 127 varchar. I am performing a SELECT col1 WHERE ...
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33 views

Mysql table with only two columns, nothing unique: Will an index increase search performance?

If my table only has two columns (username, groupname) and a million or so rows, will an index improve performance at all? Wouldn't it take just as long to search the index file as it would to search ...
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1answer
127 views

How performance schema in mysql 5.6 improve performance?

Since MySQL 5.5 performance_schema database has been added likewise information_schema. As we know that tables in information_schema contains statistical information like tables, plugins, partitions, ...