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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0
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3answers
49 views

Should frequently accessed tables containing large blobs with one-to-one relationships be normalized and columns split into two tables?

I have a frequently accessed table containing 3 columns of blobs, and 4 columns of extra data that is not used in the query, but just sent as result to PHP. There are 6 small columns (big int, small ...
0
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0answers
71 views

Order before Group

I have this query: SELECT HOTEL.hotelname AS NAME, HOTEL.`boardbasis` AS board, HOTEL.`engine`, HOTEL.`itemcode`, Group_concat(Round(((hotel.cheapestprice / 2) + ...
3
votes
1answer
127 views

PostgreSQL: When should I use fillfactor < 100 for tables on SSD?

PostgreSQL documentation says that choosing smaller fillfactor lets table reserve space for future updates on the same page and "This gives UPDATE a chance to place the updated copy of a row on ...
2
votes
3answers
140 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 ...
3
votes
1answer
45 views

How to show the related (suggested) keywords?

We do a program for cataloging images by assigning keywords (tags) to them. An image has the following keywords "John", "Jane", "Portrait". Another image has the following keywords "John", "Jane", ...
1
vote
1answer
476 views

Delete data from huge InnoDB table from MySQL Master and Slaves

We have some huge tables in MySQL database, We have already archived/deleted data older than 2012 in 2013, Now we need to archive/delete data older than 2013 means we need to archive data for year ...
1
vote
1answer
39 views

Do the showplan (any or all) events add more overhead than a tuning trace should have

How long (order of magnitude) do the various showplan events take to record? Also is the time these events require counted as part of the "duration" column of the corresponding SQL query?
2
votes
3answers
279 views

MySQL query extremely slow after server restart

I am managing a very large database for a custom application I wrote to keep track of visitors. The DB server was rebooted for the first time in over a year - not even to install any updates, but ...
0
votes
0answers
58 views

Performance difference search on INT or TEXT in SQLite 3

I'm a little bit confused about SQLite 3 type system. SQLite 2 was typeless with only exception of INTEGER PRIMARY KEY. I don't get if SQLite 3 are same or not.. I have in my table PRIMARY KEY of INT ...
2
votes
1answer
67 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. ...
0
votes
0answers
328 views

hstore vs redis performance wise (without durability) [closed]

How do PostgreSQL's Hstore and Redis compare performance-wise? This question was asked here, but I would like to compare with a PostgreSQL configuration without durability guarantee, i.e. with ...
3
votes
2answers
630 views

What can cause slow queries with low resource usage?

I am writing an application which builds a database on a SQL server. The application loads data into some staging tables, then executes a series of stored procedures which merge the staging tables ...
0
votes
4answers
307 views

Can migration from MS Access to SQL Server or … make database faster? [closed]

A company asked me to migrate their database from MS Access to SQL Server or MySQL because they think that on those engines their database will run faster. But I wonder if their problem isn't because ...
0
votes
1answer
80 views

How can it take longer to replay a captured trace than to capture it

I am attempting to use trace captures to determine how much of a performance issue was database related and how much was code related. However, the trace is taking longer to replay that it took to ...
2
votes
1answer
71 views

Clustered Index / Index Oriented Table performance in join, worse than nonclustered?

Can a clustered index (or IOT in Oracle) be detrimental, when to be used on a very "broad" table, but only few columns are used? In this case, the "Product" table is used only like a junction table ...
2
votes
0answers
48 views

Identical query & instance but other execution plans & performance [duplicate]

I have 2 identical queries . One is executed with parameters, the other is executed with hardcoded values. Somehow sql server is creating 2 different execution plans for the 2 queries. The first one ...
0
votes
0answers
105 views

MySQL Load Avg High — CPU bound or IO Bound or Memory Issues

We are using MySQL 5.5 and the database is approximately 10TB. The load avg is constantly high during day time. Following are the configurations and a snap shot of a 'top' command. I wanted ...
1
vote
1answer
170 views

MySQL with high CPU and memory usage

here we have a VPS with 3.2GHz quadcore processor with 2GB of RAM and 4GB of SWAP which need to work with a high intensive legacy system (read: bad coded). The main problem is that the CPU (~80 - ...
1
vote
1answer
441 views

Using OFFSET in a large table by a simple sub-query

The slow performance for using OFFSET in large table has been widely discussed in various blogs, and the most efficient way is to use an INNER JOIN as SELECT * FROM table INNER JOIN ( SELECT id FROM ...
0
votes
0answers
26 views

MySQL cluster with RAID0

I use several EC2 (M1.LARGE) instances with ephemeral storage. Would RAID0 improve write and read performance? I'am only interested in performance. Has someone experience? Is the speedup=2??
1
vote
1answer
38 views

Moving large database to another drive, how to measure performance before, and setup some type of replication for fast fail back?

Sorry if this is kind of more than question at a time, but here goes. Running SQL Server 2008 on windows server 2008 as well. We have a large database just over 200gb right now (it holds images of ...
0
votes
1answer
35 views

Should the value of a select max be indexed when the where clause is already indexed

I have a customer_orders table in a schema designed to be shared between multiple companies. Each customer_order has an invoice number that should always start at 1 and increment based on company ...
1
vote
1answer
88 views

How to isolate that network is issue of bad query performance [closed]

I would like to know how to isolate SQL Server bad query performance is caused by NETWORK and not the SQL Server. Are there any specific tips and tricks in SSMS, wait types, or specific PerfMon ...
1
vote
0answers
65 views

What to look for in query execution plans? [closed]

Assuming the query execution is slow, I have collected the xml plan. What should I look for in the actual execution plan. What are the top 10 things I need to watch out for? I know this is a broad ...
0
votes
1answer
129 views

Does the recovery model affect query speed?

Would using the Full Recovery model make something like a long running DELETE operation slower than it would be under the Simple Recovery model?
1
vote
1answer
1k views

Lazy Writes Performance Issues

My SQL Server sometimes reports high Lazy Writes e.g. "Lazy Writes per second is 119 Writes/sec" What should I be checking to find out why this is high? What are potential causes? Thanks.
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0answers
38 views

Why does a scrambled junction table destroy the speed of my query?

I have two schema in a MySQL database, one containing raw data in MyISAM tables and the other containing the results of some processing tasks performed on the raw data, also in MyISAM tables. For ...
5
votes
1answer
145 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 ...
2
votes
2answers
162 views

Improve Performance -Update query with OR in WHERE

How do we improve this Update query Performance as currently it is taking 1 Minute to update 17643 Rows. Query -> Declare @date datetime = '09-Dec-2013' update #tmp_sp_abc set ...
0
votes
0answers
29 views

MySQL: system variables and status variables related with Disk I/O

How disk I/O is related with MySQL performance improvement. I have a MySQL-5.1.58 based Intranet application equipped with Windows 2008 server and 8 GB RAM. Even, When my application face performance ...
-2
votes
1answer
98 views

Maximum dataset size for a well-performing SQL Server 2012? [closed]

We're planning a project using SQL Server 2012 for storing about a billion records over less than 50 fields. Assuming good hardware, is SQL Server up to that task? Roughly how many request/second can ...
0
votes
0answers
73 views

MySQL cluster performance very poor on Amazon

We have currently a project running where we need to store 1 to 20,30 million 500B to 2kB records. We need to use MySQL cluster on 4 EC2 instances (8GB Ram, 2 cores) and ephemeral storage (Records ...
1
vote
1answer
48 views

Patterns/Designs to help with concurrency/performance [closed]

I'm working on a SQL Server 2008 R2 DB and I'm experiencing some performance/concurrency issues with probably the main table in the DB. Problems like slow reads, deadlocks, poor performance in ...
2
votes
1answer
161 views

Is this amount of disk IO expected with MySQL?

I am running MySQL 5.5.34 on an Amazon EC2 micro instance with EBS (elastic block storage). The instance has been running for around 10 days and according to Amazon I've accumulated around 8.5 ...
3
votes
2answers
162 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): ...
1
vote
1answer
187 views

Internal query on CDEF$ and CON$ very CPU bound

I am checking an application (Infor ERP LN) that loads a lot of data into an oracle 10.2 database. While checking one of the user sessions with SQL_TRACE and its output with tkprof, I found that the ...
0
votes
0answers
145 views

MySQl: slow query is not using index in joining

Below is the configuration of my DB server: Apache version : Apache/2.2.22 (Win32) mod_ssl/2.2.22 OpenSSL/0.9.8 PHP version : 5.3.13 MySQL version : mysqlnd 5.1.11 Windows Server 2008 Standard ...
1
vote
1answer
111 views

Slow queries related to subqueries using aggregation

Here's a simplified version of the queries I am running: select ... from editions join edition_events on edition_events.edition_id = editions.id join events on events.id = ...
0
votes
0answers
142 views

how I can set tmp_table_size for 16GB long table?

I am posting the same question as I posted in SO, but somebody advice me to post it here. I have a 16GB big table with 8 partition. And RAM 4 GB. I am running a query - SELECT ...
0
votes
0answers
14 views

how I can set tmp_table_size for 16GB long table? [duplicate]

I have a 16GB big table with 8 partition. And RAM 4 GB. I am running a query - SELECT c.eveDate,SUM(c.dataVolumeDownLink)+SUM(c.dataVolumeUpLink) FROM cdr c WHERE c.evedate>='2013-10-01' GROUP ...
0
votes
2answers
48 views

Preventing sysquerymetrics from being created ASE 15.7

Can I prevent Sybase ASE 15.7 from creating the sysquerymetrics view for a database upon creation? And also, if the view is dropped how can it be added later?
0
votes
1answer
44 views

Suggest performance tradeoffs

I have a an inner query that needs outer query column values as input. It looks something like this CREATE TABLE TISSET( COL1 int ,COL2 int,COL3 int) INSERT INTO TISSET VALUES (1,1,1); INSERT ...
2
votes
0answers
76 views

SQL Server 2012 STIntersects

I have one table, T_PIN, with 300,000 pins and another, T_POLYGON, with 36,000 polygons. T_PIN has this index : CREATE SPATIAL INDEX [T_PIN_COORD] ON [dbo].[T_PIN] ( [Coord] )USING GEOGRAPHY_GRID ...
1
vote
1answer
83 views

Restore With Move has poor performance

As part of our regular development cycle we need to take a copy of production into development databases. To do this, we take a copy of production backups and move them to the Development Server. ...
4
votes
2answers
198 views

Architectural Help Needed - MySQL or NoSQL for a table with 54 million records

We have a table with 54 million records. Here is the table structure. CREATE TABLE `metaplay` ( `track_id` int(11) NOT NULL DEFAULT '0', `user_id` int(11) DEFAULT NULL, `completed` int(11) ...
1
vote
2answers
78 views

distinguish single-block vs multi-block reads in Oracle explain plan

If I am looking at a query plan in Oracle 11g, is there any way I can tell which operations will result in single-block reads and which will result in multi-block?
2
votes
1answer
215 views

Performance issue with TOP (1) on a nullable column

I need help to identify the reason for a performance issue. Actually following query sits in a scalar-valued-function but that is not the reason for the issue since it needs the same time as query: ...
0
votes
1answer
64 views

SQL Server 2000 Replication, Performance, and Query Priorities

I'm a developer and wanting to confirm the following: Does anyone here have experience with SQL Server Replication (transactional) on 2000? We are trying to convince the DBAs to allow this in a ...
0
votes
0answers
94 views

Postgres chooses a bad query plan

The following query finishes in 1.5s (which is ok, the table contains about 500M rows): explain (analyze, buffers) select sales.* from sales join product on (product.id = sales.productid) join date ...
5
votes
0answers
375 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 ...