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.

learn more… | top users | synonyms

5
votes
3answers
242 views

SQL Server how to test filegroup IO

We have a customer who is switching from SAN storage to directly attached storage. Our SQL Server database has several filegroups all of which has been deployed on the same LUN. In order to determine ...
5
votes
4answers
4k views

Optimising join on large table

I am trying to coax some more performance out of a query that is accessing a table with ~250-million records. From my reading of the actual (not estimated) execution plan, the first bottleneck is a ...
5
votes
1answer
169 views

Is my function nondeterministic one

I have two functions: fn_Without_Param and fn_With_Param CREATE FUNCTION [dbo].[fn_Without_Param] ( ) ... INNER JOIN .. ON .. AND SubmitDate = CONVERT( varchar(10), GETUTCDATE(), 101 ) and /* ...
5
votes
2answers
313 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) ...
5
votes
2answers
1k 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) ...
5
votes
2answers
565 views

SQL Server performing slow

I have a Microsoft SQL Server running on an IBM server with 10 cores and 64 GB RAM. I have from 100 to 300 users working concurrently on the server. Users complain about slowness of the application. ...
5
votes
2answers
2k views

Rebuilding index has impact on mdf/ldf files SQL Server 2008

While rebuilding index have used option 'SORT_IN_TEMPDB = ON' in order to avoid unnecessary growing your user database files. What does it exactly means? Is complete process done on TempDB and does ...
5
votes
1answer
374 views

how to improve performance by using or not using table variables

I have a table variable: DECLARE @to_process TABLE ( [Id] [bigint] NOT NULL, [SequenceId] [bigint] NOT NULL, ... ) INSERT INTO @to_process ( Id , SequenceId ... ) SELECT ...
5
votes
4answers
3k views

MySQL: Index when joining to tables not being used (Performance optimizing question)

I need to optimize the following query: SELECT /* [things omitted] */ articles.blogpost_id, articles.id AS articleid FROM blogposts JOIN articles ON articles.blogpost_id = blogposts.id WHERE ...
5
votes
1answer
404 views

IO_STALL question and understanding

I am collecting IO_STALLS from sys.dm_io_virtual_file_stats every 5minutes and then doing a delta to see which files are being affected most by IO. In one 5min period I get a delta of 5826331 ms ...
5
votes
1answer
2k views

Troubleshooting SOS_SCHEDULER_YIELD wait

Running our corporate ERP (Dynamics AX 2012), I noticed our production environment seemed much slower than our development systems. After performing the same activities in both the development and ...
5
votes
2answers
785 views

Performance impact of waiting on a service broker message

I have a situation where multiple client apps send messages via the Service Broker (utilizing stored procs). These messages are picked up by yet another client app and then processed. The way the ...
5
votes
2answers
891 views

Speed up INSERTs

I need to have a way to insert to a table, fast, synchronous, with minimal duration. What I've tried ("blind") is : Have no index on the table whatsoever Switch to simple logging (from full logging) ...
5
votes
2answers
512 views

Unexpected extremely long query time (~5 minutes using nested WHEN-INs)

For the first time, I am running up against a horrifically long execution time of a MySQL query (~5 minutes). The data in the database is highly (and not arbitrarily) normalized. It very efficient ...
5
votes
2answers
881 views

Using totals on aggregates to improve performance

I have two tables: details and totals of these details. Details (Slow solution): select OrderId = r.OrderId , TotalQty = SUM(r.Quantity) , ...
5
votes
2answers
1k views

Postgresql 8.3: Limit resource consumption per query

I'm using PostgreSQL 8.3+PostGIS 1.3 to store geospatial data on Ubuntu 8.04 Hardy. This particular version of PostGIS has a bug when calculating a buffer() on very complex segments, which causes ...
5
votes
3answers
3k views

Why does this Entity Framework query perform so bad in MySQL?

Let me give you a little setup. We have a InnoDB table on MySQL 5.1 with close to 20 million records, no foreign keys, and proper indexes for queries we do. We are using the latest 6.3.5 MySQL ...
5
votes
1answer
929 views

MySQL 5.1 to 5.6: massive performance hit

Okay, this is possibly three questions. I want to move my existing MySQL 5.1 database using MyISAM to 5.6 using InnoDB for what I think are a host of obvious -- and possibly even good -- reasons. ...
5
votes
2answers
1k views

MySQL replication: most important config parameters for performance on slave server?

I'm setting up a mysql master-slave configuration, where slave is located on a much weaker sever. Since, if I understand correctly, slave only works on updates/inserts, what are the most critical ...
5
votes
1answer
201 views

Sql server snapshot isolation overhead when read_committed_snapshot is enabled

When SQL Server's read committed snapshot is on (and thus some amount of row versioning is necessary), is there any additional overhead caused merely by enabling snapshot isolation? Snapshot ...
5
votes
1answer
520 views

Denormalized table designs in normalized database?

There was a discussion between the developers and DBA's last week on set of tables that the developers were creating with more than 400 columns in our OLTP environment with combinations of VARCHARs, ...
5
votes
3answers
1k views

CPU usage on RDS instance monotonically increasing with no change to query volume

I have two RDS instances: a R/W master and a read-only replica. On 29th June, the replica stopped registering replication data - not sure if this is related. On July 3rd, the master's CPU usage ...
5
votes
1answer
308 views

How can I benchmark the performance of UDFs to figure out which one is faster?

Basically I have two scalar UDFs that output the same data, one that uses a cursor and one that uses a recursive CTE. I want to determine which one should be used and discard the other; I'd prefer to ...
5
votes
1answer
201 views

RESOURCE_SEMAPHORE_QUERY_COMPILER waits in Microsoft SQL Server 2008 Enterprise

Could fragmented indexes on Microsoft SQL Server 2008 Enterprise cause RESOURCE_SEMAPHORE_QUERY_COMPILER waits? The last two weeks one of our applications has had downtime due to ...
5
votes
1answer
3k views

What's the difference between POINT(X,Y) and GeomFromText(“POINT(X Y)”)?

I'd like to store some geometric positions in my MySQL database. For this I use the POINT datatype. Almost everywhere I read that the function GeomFromText should be used to insert data in the table. ...
5
votes
1answer
913 views

Oracle aggregate functions slows query down massively

I have a table with ~12M rows of data in it. Here is the table structure: SYSTEM_ID BATCH_ID MEASUREMENT_INDEX, PARAMETER_ONE, PARAMETER_TWO The primary key is made up of the first three columns. I ...
5
votes
2answers
622 views

How can I save a severely fragmented database/table?

I've recently made a discovery that might explain my slow SQL run times. I found out that the default in SSMS is to allow mdf growth of 1MB at a time. When the size of one table alone is roughly 23 ...
5
votes
3answers
9k views

How to get the most out of MySQL on a QuadCore machine with 16 GB of RAM?

I'm running a MySQL 5.5 server on my workstation for scientific data analysis and wonder how to configure MySQL in order to get the most out of it performance-wise. The types of query that I typically ...
5
votes
1answer
3k views

Capabilities of InnoDB INSERT Performance

Hi I am running the most recent version of Percona Server. Server version: 5.5.24-55 Percona Server (GPL), Release 26.0 I have a 10 cpu box of these characteristics. processor : 0 vendor_id ...
5
votes
3answers
461 views

Just how much is a query supposed to slow down the whole system?

This is similar to my earlier question but more generic. I have a system with 16GB of memory, 16 cores, supposedly quality hard drives, RHEL 5, MySQL 5.0.x. Yes, I know, we're working on upgrading ...
5
votes
1answer
136 views

Why would SQL cast have to be expensive if used on a join column?

I see that sql join internally functions always on some of the three basic operations : nested loops join, merge join and hash join. From multiple articles on the internet I see SQL casting is said ...
5
votes
1answer
769 views

How to determine if there are [idle connections with] uncommitted transactions in PostgreSQL?

According to a comment on this question I asked about idle connections in PostgreSQL 9.2, some uncommitted transactions (possibly related to some of those idle connections) might cause some ...
5
votes
1answer
173 views

How do I find out who is the resource hog in SQL Server 2008?

We have a SQL Server 2008 installation on a machine with 24+GB of RAM and 16 cores. Plus fast drives, etc. A large machine by our standards. Anyway, that machine is 100% devoted to SQL Server and ...
5
votes
1answer
2k views

Oracle's Merge v. Select->Update/Insert

What is the faster statement? A MERGE or Select->Update/Insert depending on if it returns a value? I'm trying to optimize a database, but I haven't found any speed tests comparing the two. I found ...
5
votes
1answer
491 views

Indications from obscenely high Operator Costs in Query Plan?

I have a monthly ETL process that's too complicated to explain here, but basically we get a large amount of customer data, bulk load it into various tables, then run a series of build processes. The ...
5
votes
3answers
352 views

MyISAM Performance: Join Decomposition

in High Performance MySQL on page 159 they talk about breaking up complex queries into simple ones: Converting SELECT * FROM tag JOIN tag_post ON tag_post.tag_id=tag.id JOIN post ON ...
5
votes
1answer
3k views

MongoDB performance vs. PostgreSQL with 5.5 million rows / documents

Can someone help me compare these queries and explain why the PostgreSQL query executes in just under 2000ms and the MongoDB aggregate query takes almost 9000ms and sometimes as high as 130K ms? ...
5
votes
1answer
538 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 ...
5
votes
1answer
197 views

Sudden increase in log_file_sync waits

I'm on Oracle 11gR2 with a 2 node RAC system. It's shared fiber storage to an EMC Clariion. Last friday things went bad..fast. All of the sudden processes that normally ran fine for years became ...
5
votes
1answer
354 views

PostgreSQL: Recommendation size for shared_buffers

I am rather new to PostgreSQL. I started migrating some MySQL databases to PostgreSQL one month ago. I am looking for help about the proper memory values for the configuration file. Currently, I ...
5
votes
2answers
624 views

Teradata: How to design table to be normalized with many foreign key columns?

I am designing a table in Teradata with about 30 columns. These columns are going to need to store several time-interval-style values such as Daily, Monthly, Weekly, etc. It is bad design to store ...
5
votes
2answers
491 views

Large accounting table, best way to partitioning by two dates

I need to create a log table to stores the connections to out network (last 3 years, after that the log will go into backup). The hardware/software used is proprietary, and for accounting it just call ...
5
votes
2answers
3k views

What are the potential causes for a sudden MySQL slowdown?

A few days ago mysql became suddenly very slow with queries taking more than 10s to complete when they used to complete under 100ms... It lasted about an hour and then the speed was normal again. What ...
5
votes
1answer
3k views

MySQL INNODB SELECT query hanging on copying to tmp table

I have a query that is hanging (seemingly) randomly on a specific query. Most of my website users do not have a problem when this query runs but a few users are having timeout issues on the website ...
5
votes
1answer
320 views

MySQL and Solid State Disks on EMC

Since all writes and sequential reads are cached by the EMC storage system, the best use for solid state disk is to store data that has a random READ pattern. On Oracle, that is the temp tablespace ...
5
votes
1answer
913 views

NESTING_TRANSACTION_FULL latch

Production SQL Server 2008 performance is far below expectations. Simple single-table queries sometimes are working for 5 seconds in the mid-day compared to 250ms after hours. We cannot find which ...
5
votes
1answer
793 views

How to calculate cache misses for PostgreSQL

I'm administering a server where a tool using a PostgreSQL runs. The tool takes care of most PostgreSQL configurations by itself, but I'm observing some performance problems. I could confirm at OS ...
5
votes
0answers
361 views

SQL Server 2012 performance issues (maybe due to linked server) [closed]

Summary of the problem We've spit our one database server environment into two servers. We are now having intermittent performance issues I am hoping someone can offer clues - perhaps direction ...
5
votes
0answers
338 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
votes
3answers
139 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 ...