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

1
vote
2answers
128 views

Improving MySQL efficiency

I have a table now containing over 43 million records. To execute SELECT, I usually select records with the same field, say A. Will it be more efficient to divide the table into several tables by ...
1
vote
3answers
1k views

SQL Server 2008 Partitioning Evaluation

I'm trying to do a performance comparison of a table with partitioning and the same table without partitioning. So we have Subcriber and SubscriberPartitioned tables. Tables structure is: ...
4
votes
2answers
7k views

Is InnoDB Engine up to speed against Memory Engine?

I am exploring the efficiency of different database engines in MySQL version 5.5.18 to see which is best suited for use with a range query on a dataset of 5 million rows: SELECT P.col1, P.col2, ...
3
votes
1answer
743 views

Can you have a WHERE clause with a greater than operator on a composite key?

I'm a web developer (not DB admin!) having performance problems processing a 1.7m record table on MySQL. Here is that table : CREATE TABLE `bbcmapimp_pc_raw` ( `postcode` char(8) NOT NULL, ...
1
vote
2answers
606 views

All columns of table should be indexed or not mysql database?

I am having one table with 4 columns. I that one is primary key and other three columns are references to columns of other tables. I am using join of these four tables for search filter. These joins ...
10
votes
1answer
7k views

Order by column should have index or not?

I have added indexes to table which are used for searching result. I am showing results by ASC or DESC order. So that column should have index or not? I have 2 more indexes on that table. How ...
5
votes
1answer
867 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 ...
1
vote
0answers
355 views

Best database for INSERT 2 millions of records around 3 hours and query data at the same time [closed]

I have a voting application. This voting process takes about 3 hours to complete. After 3 hours there will be 2 millions of records in the database. At the same time application needs to query the ...
2
votes
0answers
111 views

MySQL MEMORY table has high Lock Wait Ratio [duplicate]

Possible Duplicate: Mysql Memory table getting many locks on my site I log every pageview (date,ip,referrer,page,etc) in a simple mysql table. This table gets very little selects (3 per ...
19
votes
4answers
16k views

Pattern matching with LIKE, SIMILAR TO or regular expressions in PostgreSQL

I had to write a simple query where I go looking for people's name that start with a B or a D : SELECT s.name FROM spelers s WHERE s.name LIKE 'B%' OR s.name LIKE 'D%' ORDER BY 1 I was wondering ...
6
votes
3answers
2k views

Why performance degradation with query hint FIRST_ROWS(1000)? [closed]

I have a query with user supplied arguments that can produce a very high amount of rows depending on the user's input. In case the user supplies very unselective arguments, the query takes a lot of ...
3
votes
1answer
5k views

Query performance with subquery and IN clause

I am trying to select a range of data for multiple devices (unique serial numbers) from a historical table and was wondering why there is such a big difference in time for the following queries: ...
1
vote
2answers
138 views

why doesn't time for a simple update scale linearly with the number of records?

I am running some performance tests and I started with a dataset of 900.000 records the update took 10 seconds or about 90000 records per second. Then I increased the number of records to 9.000.000 ...
2
votes
1answer
414 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 ...
3
votes
3answers
1k views

Does ORDER BY on a clustered key effect performance?

Say I have a table clustered on PrimaryKey, and in all cases I want my results to be ordered by PrimaryKey so I additionally always ORDER BY PrimaryKey in all queries. Does this ORDER BY affect ...
4
votes
2answers
3k views

MySql - How can I speed up this query

I have the following tables: CREATE TABLE `users` ( `id` int(11) NOT NULL AUTO_INCREMENT, `first_name` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL, `last_name` varchar(255) COLLATE ...
4
votes
1answer
280 views

Is there a way to make SQL Server's Database Tuning Advisor use more than one core?

I'm using SQL Server's Database Engine Tuning Advisor to generate recommendations for performance improvements on my database server. For the "consuming workload" step, it appears to use all ...
15
votes
3answers
8k views

Configuring PostgreSQL for write performance

One of my PostgreSQL servers hosts several (1-3) databases which receive a constant stream of data. The data is not particularly structured, it amounts to the current time and a variety of observed ...
5
votes
1answer
946 views

Nested queries or temp (#) tables in SQL Server

I have written a web application which aggregates and presents data from a SQL Server. The data involved is large, and there is a lot of aggregation involved. Currently, under advice from an 'expert' ...
8
votes
5answers
1k views

Inclusion of ORDER BY on query that returns no rows drastically affects performance

Given a simple three table join, query performance changes drastically when ORDER BY is included even with no rows returned. Actual problem scenario take 30 seconds to return zero rows but is instant ...
6
votes
4answers
812 views

Four db servers all identical, one is much slower than the others

The setup We have an application loading a lot of transaction data for later querying. It's sharded on 4 SQL Server 2008R2 Enterprise Edition on Windows Server 2008 64 bits. All servers are ...
2
votes
2answers
3k views

Mysql consumes a lot of memory

Here is my situation. I have an ubuntu server monitored by nagios. recently nagios sends alarms regarding the memory consumption on the server. I logged into the server and executed the top command ...
4
votes
1answer
758 views

Database as a service (DbaaS) over dimensions--performance, scalability, & reliability?

MySql Database as a service: Amazon Xeround Another eg. PostgreSQL Database-as-a-Service. You can get the list of similar products here. Does anyone have details on their performance, ...
1
vote
2answers
999 views

Oracle 11. Updating BLOB field. Db file sequential read inappropriately slow?

I've and Oracle (11 Enterprise) schema with a table CREATE TABLE USER.WSP_BUNDLE ( NODE_ID RAW(16) NOT NULL, BUNDLE_DATA BLOB NOT NULL ); CREATE UNIQUE INDEX USER.WSP_BUNDLE_IDX ...
2
votes
2answers
1k views

Tuning SQL Server Performance

While profiling my application against SQL Server 2008 running against a JDBC Application most of the time consumed were by following COMMIT TRAN FETCH API_CURSOR & exec sp_cursorfetch I ...
3
votes
2answers
509 views

Performance gain by moving a large table from a database and referencing with a synonym

We have SQL Server 2008 R2 database which is currently about 80Gb. About 10Gb of this is down to one table, and I wondered if there would be a performance gain if I moved this table into it's own ...
2
votes
1answer
1k views

MySQL Config for Large MyISAM tables

I have to do some updates on myisam tables which have around 20 M records. Our server has 24GB of ram and 2 quad core xeon with 24 MB of cache. I want to know how I can change the my.ini file so I get ...
8
votes
4answers
13k views

Fastest way to check if InnoDB table has changed

My application is very database intensive. Currently, I'm running MySQL 5.5.19 and using MyISAM, but I'm in the process of migrating to InnoDB. The only problem left is checksum performance. My ...
2
votes
3answers
2k 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 ...
3
votes
1answer
50 views

Is time to deliver data included in time measured for a Slow Query

I'm looking at some horrible numbers in a SLOW_QUERY_LOG (one example) Count: 2563 Time=23.21s (59498s) Lock=0.00s (1s) Rows=21.4 (54857) This is for a simple SELECT statement that runs for less ...
3
votes
1answer
2k views

How to find the detail cpu high process name which occupying most resource in the SQL Server database?

I'm running into a problem when using the following SQL to identify CPU usage in the production SQL Server 2005 env. DECLARE @ts_now bigint; SELECT @ts_now = cpu_ticks / CONVERT(float, ...
3
votes
1answer
236 views

Possible to add KEEPFIXED PLAN option to reduce the recompile in SqlServer2k5 on Production Env?

I'm not sure if it is good to enable the KEEPFIXED PLAN to reduce the impact of recompilation in the Production Env? I'd know if we may gain performance after that or on the other hand it will be ...
1
vote
1answer
1k views

What are some good methods of structuring a MySQL audit trail to be both immutable, and perform well for usage?

In one application, we have an audit table that uses the ArchiveEngine in conjunction with a few triggers to capture 100% of the changes that occur. The upside to this is that 20+ million rows ...
1
vote
4answers
683 views

Top 2 rows per partition from an absolute value date difference

I have a database of security camera footage in a denormalized database. I have Locations which have multiple Cameras which take multiple images. Location + Camera + image capture_date is the ...
5
votes
3answers
128 views

Dynamic temporary index creation

In my undergrad databases course, my professor mentioned that some DBMS software is so advanced that it can detect when a long-running query would benefit from an index. The DBMS can then create that ...
7
votes
2answers
1k views

PostgreSQL: reuse of complex intermediate result in same query

Using PostgreSQL (8.4), I'm creating a view that summarizes various results from a few tables (e.g creating columns a, b, c in the view), and then I need to combine some of these results together in ...
6
votes
3answers
302 views

Query performance

Why SELECT Barraportfolioname FROM portfolio WHERE id IN (SELECT DISTINCT i1.portfolioid FROM Import i1 LEFT OUTER JOIN Import i2 ON ...
0
votes
2answers
825 views

How to find out the activity which increasing the response time of the Sql Server?

We are using SQL Server 2008 as our database server. Recently we came to know, by using a 3rd party tool, that the response time of our database server is increasing at a specific time for example at ...
4
votes
2answers
1k views

SSAS queries time out when Windows File System Cache drops

We have a SQL 2008 Analysis Services instance on Windows 2003 that is experiencing near-daily performance issues (query timeouts) during peak activity. A second identical instance queried from the ...
2
votes
2answers
9k views

Improve BLOB Writing Performance in Oracle 11g

I have an application that writes a lot of rows into a table that contains a blob column. The average size of the blob is 3k bytes. Is there any buffer that i can resize to improve inserts into this ...
1
vote
2answers
144 views

Restore backup in order to write datafile sequentially in disk

I have just come to a new company and we have one database which was created with standard initial size and autogrowth parameters for data and log files (1 MB autogrowth for data / 10% for log). The ...
2
votes
3answers
1k views

Loading a FACT table per day

I have a database with 13 billion rows, per day I have around 20-30 mio rows. On top of this I have one cube, one of its dimensions is DateTime that goes down to milliseconds. To load the fact table I ...
6
votes
3answers
2k views

Performance issue with xpath in SQL Server 2008

I have a table with lots of large xml-documents. When I run xpath expressions to select data from those documents I run into a peculiar performance issue. My query is SELECT p.n.value('.', 'int') ...
5
votes
2answers
2k views

Compare Microsoft SQL server performance between virtual and dedicated server

I have a dedicated windows 2008 r2 server at the moment and I am thinking about migrating to a virtual server because of the costs. Now I know that SQL should be on a dedicated server, but the ...
5
votes
3answers
4k views

MySQL general query log performance effects

One of our customers who has a somewhat problematic web application would like us to log all the queries for a period of 24 hours. I wouldn't know how much data it will actually write. The amount ...
2
votes
2answers
387 views

Slow SSD on Dell 710

We recently upgraded our Dell T110 server to a Dell T710 with a 100GB SSD drive. We were hoping that we would see a tremendous improvement in mysql select performance, but unfortunately the new ...
3
votes
1answer
491 views

MySQL query 'going away' on executing INSERT ON DUPLICATE UPDATE statement with a 12524 character blob

I have a mysql insert on update query like so insert into table (col1, col2, col3) values (1,2,'huge blob with 12524 chars') on duplicate key update col3 = 'huge blob with 12524 chars'; col1, col2 ...
2
votes
1answer
467 views

Fastest key-value store for random disk reads?

I want a key-value store, with records stored on disk. (There are too many for memory.) I want to use a single machine. What key-value store will provide the fastest random reads (off disk)?
3
votes
1answer
119 views

Database performance for determining entities assigned to users

I am interested in insight in improving performance in the following instance: I am currently working on an application that has a hierarchical entity structure where, depending on a user’s level ...
10
votes
3answers
5k views

What's better for large changes to a table: DELETE and INSERT every time or UPDATE existing?

I am making a project where I need to change around 36K records in one table daily. I'm wondering what will perform better: delete rows and insert new ones, or update already existing rows For me ...