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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14
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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 ...
1
vote
3answers
880 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 ...
4
votes
1answer
11k views

Mysql slowly uses memory until it starts to use swap

I am running a 1gb of RAM rackspace database server. For some reason in about 2 days the memory usage goes from using very little swap, to using 100mb. If I don't restart sql it will keep using more ...
1
vote
1answer
53 views

Disk Read IO Throttle not showing in perfmon Windows Server 2012 r2

I am working on Windows Server 2012r2,SQL Server 2014. I am trying to create a new data collector to review Disk IO in perfmon. When I get to the step to add the available counters there is no Disk ...
1
vote
3answers
182 views

Are TEXT fields stored separately from the row in MySQL-ISAM?

We have a "notes" table and some of the queries are getting very slow even though we're not searching on the note contents. We're wondering if moving the note content into a separate table would speed ...
0
votes
1answer
95 views

SQL Server Data File/Log File poor performance

I've been asked to look at a database/application server that's "performing slow". No one could really tell me what was performing slow (except for the database backups) so this has been a discovery ...
1
vote
2answers
121 views

Slow “CREATE TABLE” and “TRUNCATE” on MySQL / MariaDB

I am fighting with performance issues on a local MariaDB instance. Fun thing: I previously had problems with all my INSERT and UPDATE and DELETE queries. This got signigicantly faster (~40ms -> less ...
66
votes
6answers
39k views

How to determine if an Index is required or necessary

I've been running an auto-index tool on our MS SQL database (I modified a script originating from Microsoft that looks at the index statistics tables - Automated Auto Indexing). From the stats, I now ...
1
vote
2answers
71 views

High SOS_SCHEDULER_YIELD and Signal Waits

I have run Paul Randals wait script and can see SOS_SCHEDULER_YIELD is at 60% with an average signal wait of 10ms. I have also run a script to find out the what percentage of my waits are signal ...
0
votes
0answers
1k views

Using something better than UNION for combining multiple queries

I have one big query which is based on 12 smaller queries that I have put together using UNION. A relative simple example of my query: (SELECT 'type1' AS 'type', fieldOne AS someField, ...
1
vote
1answer
200 views

Indexed VIEW in SQL Server with PIVOT

A simplified version of my problem is as follows: I have three tables Records, Inputs, and Outputs. Records Id DTS   1  2015-01-01 00:00 ... Inputs Id RecordId ...
0
votes
0answers
64 views

Database too slow after CHARSET Conversion [closed]

I have an Oracle database which runs on version 9.0.1 with WE8859P1 charset and i'm trying to migrate it to the version 9.2i which has the WE8MSWIN1252 charset. The conversion is made without any ...
1
vote
0answers
180 views

Multi-Table Join to Single Destination [closed]

I am having a serious performance issue with join together four tables and placing the results (in a certain permutation) into one destination table. I am using MSSQL 2008 and good ole T-SQL. To ...
0
votes
0answers
64 views

Tuning a Postgres INSERT only database

I am designing a database which will have many inserts and selects, but no updates. Are there any considerations to take (in order to have high query performance) while knowing no tuple updates will ...
1
vote
0answers
153 views

SQL Server and Perfmon [duplicate]

Possible Duplicate: SQL 2008 Server agent cant see perfmon counters I'm trying to setup SQL Server Perfmon counters on a Windows Server 2003 with SQL Server 2005 SP3. I'd like to run ...
1
vote
2answers
51 views

Will frequent small select queries slow down frequent write queries in InnoDB table in MySQL?

I'm running a MySQL database with tens of tables in remote server. To monitor the data, I write a small program to query to database via VPN connection every 10 seconds. Each query is a union of 20+ ...
0
votes
1answer
37 views

mysql Quiz leaderboard filter by points, time taken

I have a quiz report table which shows a report for every quiz a user takes. I need to create a leaderboard from this, which shows the top users best score, filtering by points and then time taken. ...
0
votes
0answers
258 views

Oracle - Slow queries without prepending schema name or providing hint

I am logged in as the schema owner in Oracle 11gR2 on Linux. I have 55 million rows in table. select max(col) from table; - takes 300 seconds (index full scan) select max(col) from schema.table; - ...
1
vote
1answer
45 views

MongoLab: Does hardware effect performance of a find() query [closed]

I asked a pervious question on StackOverflow about if document size affected the performance of fetching that document (the document is 3MB in size) ...
4
votes
1answer
216 views

Sudden poor SELECT performance on a large table with existing indexes

My company uses a software suite in which the only thing I can truly modify is the database. We've always had performance issues (mostly hardware problems that we hope to resolve soon), but lately ...
1
vote
1answer
49 views

Migration from SQL Server 2012 Ent to SQL Server 2014 STD

We recently migrated from a traditional hosting environment with a back end of SQL Server 2012 ENT to an Azure VM running SQL Server 2014 STD. We did all the cool stuff with BPEs on SSD, etc. The ...
0
votes
2answers
106 views

How to calculate mysql server reads per second,writes per second?

Can anyone let me know how to calculate mysql server writes,reads,deletes,updates per second.
0
votes
1answer
50 views

Load & traffic balance best practices

I am about to design an enterprise solution for a large scale application in which a windows service, MVC, and many other projects will use a database, so I am thinking about load balancing and best ...
1
vote
1answer
315 views

Improve the insertion rate of mongo sharded cluster

I can't disable the write concern while i mongorestore with .bson file. It totally damages the insertion rate (insert/sec). This is my sharding status. mongos> sh.status() --- Sharding Status --- ...
1
vote
2answers
346 views

MySQL/MariaDB Limitations

we're running MariaDB on our DB server. We have to install multiple databases on each DB instance (in fact each DB server runs multiple MariaDB instances) because each database must be separated. ...
2
votes
3answers
57 views

Is database performance optimization independent of the size of a database or a table?

If by rewriting an operation or a piece of code the performance has increased by 30% in a program reading and writing to a table with 100,000 records, does that optimization remains same if the table ...
4
votes
1answer
6k views

Very slow DELETE in PostgreSQL, workaround?

I have a database on PostgreSQL 9.2 that has a main schema with around 70 tables and a variable number of identically structured per-client schemas of 30 tables each. The client schemas have foreign ...
6
votes
1answer
100 views

Capture and Replay workload

We have a new server which we are migrating too and want to see the potential benefits of the hardware. So the idea is that we capture a workload and replay this against our new box. My question is ...
0
votes
1answer
107 views

Optimizing key lookup in subquery with UNION ALL

I am trying to optimize following query (little bit more complex actually, but this is important part): SELECT Id, StatusDate, [...Lot Of Columns...] FROM ( ( SELECT Id, StatusDate, [...Lot ...
3
votes
0answers
40 views

SQL Server Disk IO Performace appears different between otherwise identical servers [closed]

I have two identical servers each running Microsoft SQL Server and performing a batch processing job. Server #2 keeps timing out while processing while server #1 appears to be running smoothly. I ...
2
votes
1answer
191 views

How can I compare the server impact of transaction replication

We are developing a system that must extract data from an existing SQL Server 2008 R2 cluster. One of our design goals is to limit the performance impact on that cluster as much as is practical. ...
3
votes
1answer
110 views

How to monitor load on database server

Could anybody please suggest me a way to monitor the load on my database server? What perfmon counters should I monitor on daily basis and confirm that load on the server is increasing day by day [or] ...
2
votes
2answers
109 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, ...
3
votes
2answers
375 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 ...
0
votes
1answer
38 views

SQL Server data, logs, backups files in mounted foldersin C:\

I know that is a good practice to have data, logs and backups files of SQL Server in diferent disk, for example D:\ for Data files, E:\ for Logs files, F:\ for backup files. But if I want to use this ...
0
votes
3answers
87 views

SQL Server Compact - Will it perform well with heavier traffic sites? [closed]

I'm using Orchard CMS, and on initial setup, the default setting is to use SQL Server Compact. I'm not too knowledgeable about different database types and performance. So, will SQL Server Compact be ...
2
votes
1answer
75 views

Postgresql performance issues when issuing many small inserts and updates one at a time

I have a production web server with postgresql database. My server gets data from another server every hour on the hour. The other server wakes up and sends many requests to my server, each result in ...
1
vote
1answer
475 views

Calculating a running balance to store with transactions

I need to put a read-only copy of balance and transaction data from a legacy system, which will only be used to view/print statements. Balance | id | member_id | product_id | balance | | 1 | ...
3
votes
1answer
129 views

Pagination performance, with subquery, inner join and where

I am trying to optimize following query (this is most simplified version I could came up with): SELECT tr.Id, StatusDate FROM ( SELECT tr.Id, tr.StatusDate FROM mon.ArchivedTaskResults_201504 ...
3
votes
2answers
657 views

Query planner thinks doing a sequential scan on a very large table is faster than using an index?

I've got a query that selects the most favorited photo for each of the last 12 editions for a particular domain (this is just a segment of a larger query, but the problem seems to stem from here): ...
0
votes
1answer
44 views

how big of a role does hardware play? [closed]

I'm the developer, not the DBA. I don't know much about setting up databases but i'm concern of the setup at my current work. The server is installed on desktop PC hardware(i7, 16GB RAM, 1 TB SATA ...
1
vote
1answer
48 views

Is there something I can do to make this UPDATE run faster?

I have a relation EnumeratedSensorReading that includes a siteid and a quantityid column. I want to replace these two columns with a single sensorid column. I have added this column, and it is ...
1
vote
2answers
140 views

Merge faster than Insert

Are there any advantages/disadvantages of making use of a merge over a insert function? Can an insert statement make use of the `OUTPUT' Note: the ON clause for the merge is set to 1=0 (always ...
46
votes
4answers
75k views

Possible to make MySQL use more than one core?

I've been presented with some dedicated MySQL servers that never use more than a single core. I'm more developer then DBA for MySQL so need some help Setup The servers are quite hefty with an ...
4
votes
1answer
243 views

AlwaysON : Log_Send_Queue_Size is increasing but the log_send_rate keeps decreasing?

Question Why, despite the increasingly log_send_queue_size for these two databases, did the log_send_rate keep decreasing? There were no bandwidth issues on the network at this time, and no other ...
198
votes
15answers
78k views

Can MySQL reasonably perform queries on billions of rows?

I am planning on storing scans from a mass spectrometer in a MySQL database and would like to know whether storing and analyzing this amount of data is remotely feasible. I know performance varies ...
4
votes
2answers
3k views

Hibernate Query Running Slow

I am currently facing a problem with a slow running Hibernate query that is being kicked off from a Java program. It is making a call to Oracle 11g at the back end. This query is taking anything from ...
4
votes
0answers
555 views

SQL server query is slow *without* including execution plan [closed]

I have just set up fresh installation of SQL Server 2012 on a new server and I'm experiencing very strange performance problems. Long story short, for some reason not including execution plan makes my ...
1
vote
1answer
114 views

Tune Performance by putting large tables into the KEEP Pool

We currently have a database with 20GB SGA space. SQL has been optimized but has to statisfy its use cases as well and some queries are very, very slow, specifically when large result sets are ...
3
votes
2answers
70 views

Is copy/rename a good way to improve temp table performance?

An application I am working with contains this sequence of queries at the end of constructing a large temp table; I believe it is an attempt to improve performance by pruning dead tuples - create ...