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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MS SQL Server 2008: How to improve performance after deleting transaction log file

Due to the size of transaction log file (it grew up to 200 GB) I had to delete it because the disk was running out of space. I know this is not a good practice but anyway after that the performance is ...
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4answers
853 views

Advice on choosing a really fast DBMS

I am working on a project that does real-time monitoring of data being transmitted, and logs if there are any of the various type of errors, etc. The CRUD operations are real-time. We initially ...
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5answers
2k views

How to determine why a MySQL server has become slow and requests sometimes time out?

I'm working on my first project that makes heavy use of a MySQL database and am struggling to understand performance issues I'm having. Most of the time, responses are returned quickly from the ...
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3answers
137 views

Performance difference between searching table with 350 columns and searching table with 25 columns

I am currently doing some hibernate performance test. My requirement is to search for data in a particular column of a table containing 8 million rows and 350 columns. Currently, I don't have the ...
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4answers
478 views

Help understanding SQL Server 2005 execution plan

One of my stored procedure has long execution time (average around 4 to 7 minutes). Now I trying to tweak it an make it run faster. I am looking at execution plan and two things I see that using ...
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3answers
784 views

SQL server disk write queue dramatically grows sometimes

I have SQL Server 2008 and a single database with full recovery model. Usually, the queue length is less than 1. But sometimes it grows up to several thousands (3000!!) for a few seconds. At this time ...
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4answers
2k views

One table with many rows or many tables with a few rows

I'm having a question rounding my mind. It's better to create one table and store a lot of rows there or create various tables and have a few rows on them? What's the performance and the I/O saved at ...
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1answer
427 views

Query takes hours

Up until now all queries in my PostgreSQL application were fast. During the last days, sometimes a query takes several hours. Index are healthy, because after dump, restore, vacuum -z, it is still the ...
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5answers
2k views

Setting up a Redundant Sql Server 2008 Configuration While Retaining High Performance and Minimal Downtime

We have a situation where we are moving to a new hosting facility and are attempting to configure our new database environment. However, none of us are formal DBA's so a lot of what we are doing is ...
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2answers
66 views

query plan caching (sql server)

Is there a measure of time frame as to which the execution plan of inline queries will cached?
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3answers
296 views

What affects the speed of a count(*) besides the number of records

I have a query like SELECT COUNT(*) FROM Foo Where Bar = 1 AND Baz = 2 the table has 12934600 records of which 1000001 match that predicate Looking at the query statistics I see (1 row(s) ...
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2answers
845 views

How can you tell when a query plan reuse is causing performance problems

When investigating a performance issue, a workmate suggested running DBCC FREEPROCCACHE to clear the plan cache. He came to this conclusion after noticing performance improved after a reboot. This ...
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2answers
2k views

How to tune mysql to be inmemory-like

I've given MySQL 5GB of memory (I use innodb), but when I insert lots of data (dumpfile is 1GB), hard drive I/O is still a bottleneck (CPU is not busy and hard drive is). Is it possible to force ...
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2answers
904 views

PostgreSQL performance degradation over time on a write intensive db

I have observed a weird situation that over time the performance of a query (a combination of queries explained below) degrades, meaning at the start of testing (for a few minutes) the time of the ...
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2answers
7k views

Most efficient way to add a serial column to a huge table

What's the fastest way to add a BIGSERIAL column to a huge table (~3 Bil. rows, ~ 174Gb)? EDIT: I want the column to be incremented values for existing rows (NOT NULL). I didn't set a fillfactor ...
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3answers
3k views

Improve `Update` performance (rows locking issue)

I am running 30 scripts (PHP CLI) on Linux , each script are updating (loop) the data in the MySQL database. When I typed 'mysqladmin proc' in terminal, I can see a lot of rows has been locked for ...
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1answer
566 views

Disk Latency vs Throughput

I've searched the web for a little while and haven't found an answer I'm confortable with. I am testing a SQL Server on a VM that was presented new disc. If disk latency is reduced, shouldn't ...
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2answers
205 views

Large number of VLF and shrinking the log

If there are lot number of VLF then it will effect the performance of the queries. I saw that solution is to shrink the log file. But shrinking the file is also bad. So how to take control of whole ...
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2answers
9k views

Splitting a large table to improve performance

This is a follow-up to an earlier question. I have a SQL Server 2008 R2 Standard server, that holds a single database, which itself has almost nothing except a large table. The table is 100+ million ...
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4answers
935 views

When do I use another type index than integer? (eg string) [integer vs string index]

I was reading about relational databases like sqlite and I always see the schema for user storage like: UserID (index) | Username | Password but wouldn't it be actually much faster to use Username ...
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4answers
1k views

Spread SQL Server data files across devices to improve performance?

Would it improve performance of a database in SQL Server if I place the .mdf (rows data) and .ldf (log) files on separate sets of raided disks, as opposed to having both files on the same set of ...
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2answers
2k views

MongoDB - Should I separate the journal and the data to different drives?

I have seen and heard from multiple sources that it can be a good idea, performance-wise, to write your db journal and your data files to separate disks. What's the recommended way to do this (e.g. ...
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3answers
13k views

which mysql version to use - 5.1 or 5.5?

I am designing a new database. There are going to be around 1000 write queries per second. There may be as much as 10000 read per second. Which MySQL version is recommended? I came across a post on ...
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2answers
615 views

Is it a good idea to move high-volume and highly-accessed tables to a separate database?

Ours is a web-based application (built on multi-tenant architecture) running PostgreSQL v9.1.3. There are about 450 tables in our application, out of which 2-3 tables, specific to a module in the ...
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3answers
33k views

SQL Server 2008 R2 High memory usage

I have SQL Server 2008 R2 that runs multiple jobs over night, the problem is SQL Server will eat up all RAM and CPU, then it will not release the RAM resources after the job finishes, as a workaround ...
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1answer
107 views

SQL Server - Data and Log Separation

We have a SQL Server 2008 R2 which has, among others, a 12K RPM HDD and a 7.2K RPM HDD. The original intention was to store the data files on the 12K drive and the log files on the 7.2K drive, as is ...
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3answers
185 views

How to make stored procedures more readable without harming performance

I come from OOP background, and I need to write and maintain huge stored procedures. Naturally, the sprocs become quite unreadable very quickly, no matter how much I try formatting, giving readable ...
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2answers
627 views

Optimize simple query using ORDER BY date and text

I have a query to a table in Postgres with an order based on a date field and a number field, this table has 1000000 records The data types of the table are: fcv_id = serial fcv_fecha_comprobante = ...
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3answers
4k views

When to periodically RESTART SQL SERVER 2008 R2? [closed]

So I've read that it's really a bad practice to restart SQL Server on a production environment.. Does restarting SQL Server speed it up? Automatically restart SQL Server 2008 Why are periodic ...
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1answer
280 views

How do you figure out what planner cost constants to use in Postgres?

I'm using Postgres 8.4 right now. Performance has started to become an issue as our tables have grown in size and our queries in complexity, so I've started to look into some performance tuning, but I ...
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2answers
3k views

Will altering order of columns in GROUP BY affect performance?

I have a SQL query like this: SELECT A, B, (CASE WHEN C=0 THEN 0 ELSE 1 END), COUNT(D) FROM SomeTable GROUP BY A, B, (CASE WHEN C=0 THEN 0 ELSE 1 END) On a huge dataset the actual execution plan ...
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2answers
1k views

Does it ever make sense to use RAM Disk to force RAM allocation for tempdb with SQL Server 2008

If I give all RAM to SQL Server, it will use it's own pattern to determine what RAM to allocate for what. If I allocate portion of RAM as RAM Disk and put tempdb into that disk it will force RAM ...
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2answers
1k views

Trying to optimize query for performance (MySQL)

So I have this table that has a lot of foreign keys but when I will a record, I need to join all on those tables because I generally need those fields for the record to make any sense. The basic ...
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1answer
574 views

Maintenance Plan Takes Too Long - Locks Tables - Indexing To Blame

System: I have a Maintenance Plan that Rebuilds Indexes for Several Tables (10 tables, 50M records total). Issue: During the Index Rebuild (~20 minutes), we fail to insert data into the DB ...
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1answer
2k views

Postgres multiple joins slow query, how to store default child record

Ive got a small database in Postgres, about 10,000 records storing company customers. I have a "slow" performing query (about half a second) which is performed very frequently, and my boss wants me to ...
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2answers
382 views

How to quantify TEMPDB usage in relation to other databases hosted on same hardware?

Working on a project to decide if configuration 1 or 2 is the best way to organise disks for my SAN: Config1 (sql 2008): 8 disks @ raid 10 data 2 disks @ raid 1 logs 2 disks @ raid 1 tempdb 2 disks ...
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3answers
431 views

Express union which is dependent on other results

I would like to make a union of two tables that are actually in a hierarchical constellation. How would I write that in relational algebra? Say table A is the parent of B in a 1:n relationship. ...
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2answers
3k views

Solving high page load time using SQL Profiler

I'm looking into a performance of a login page taking 10-13 seconds to load. I'm using a DEMO database to test the performance and tweak to see any improvement. I'm using SQL Profiler to capture what ...
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1answer
160 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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1answer
251 views

How to speed up looped INSERT INTO statements?

I currently use the following statement, for 10,000 rows it takes about 150 seconds. I tried removing the index on the target table, but this didn't help. Running the loop without the INSERT INTO ...
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1answer
621 views

Will certain Database Compatibility cause performance degradation?

I'm running a variety of SQL Servers from 2005 to 2012 across several machines. I have many of these databases running in SQL Server 2000 compatibility mode. Will using an older compatibility in a ...
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2answers
296 views

Performance effect of indexing foreign keys

My database is for an HR application with performance reviews and I am interested in whether I should index my foreign key. There are two tables involved. The first is a ratings table with 2 columns: ...
2
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1answer
183 views

excessive CPU utilization by SQL server

I have an issue with SQL server 2000. Its CPU utilization is high from 9.00 AM to 5.00 PM. Three applications use this server through three different instances but when the CPU utilization is high one ...
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1answer
278 views

Log all than queries taking more than X seconds

I have a database Microsoft SQL Server 2008r2. I have some applications in different programming languages. I would like to log all the queries that take more than X seconds. I guess that the I ...
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3answers
306 views

How can I identify and fix bottlenecks in an Oracle11gR2 import

I've recently been tasked with moving our Oracle 11g database from a linux CentOS desktop to a windows 2008 server. Given I've not done much behind the scenes stuff with oracle before I'm a bit out of ...
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2answers
865 views

Closed loops in database model, does it affect the performance?

I have heard that having loops in the database relational model should be avoided. From what I can think of, it is not a good practice, because there will be more than one different pathes to get the ...
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1answer
3k views

Why Is oracle ignoring my index?

This query is not too complex: select trunc(created_date, 'MONTH') as created_date, al.op_name, al.region, al.alarm_type, COUNT(1) as total_new, SUM( (SELECT ...
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2answers
3k views

Querying a database efficiently for a huge chunk of data

Here is my query SELECT * FROM ( SELECT a.*, rownum rnum FROM ( SELECT id, data FROM t ORDER BY id ) a ...
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1answer
2k views

Prevent a single query from hogging all resources

I have a production database server running SQL Server 2008 R2. How can I keep a user query on one database from hogging all the system resources and bogging down all the databases on the server? The ...
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1answer
1k views

Performance Inserting and Updating Millions of rows into a table

We have a CSV the user imports into the Application. After inspecting the CSV, validating and applying some business logic, we got Inserts and Updates operations we should perform into a ...