Tagged Questions
1
vote
1answer
21 views
How un-clustered is a CLUSTER USING table in Postgres
I have some tables which benefit greatly from CLUSTER ON/CLUSTER USING in Postgres. Data accessed at the same time is "defragmented" into a small number of disk blocks:
# CLUSTER table USING ...
0
votes
0answers
41 views
Hierarchical data best practices
I'm looking for a best practicies\databases to solve our problem:
Currently we are using SQL Server 2008 R2 with HierarchyId. It works ok, but we have a lot of performance penalties due to this ...
0
votes
0answers
18 views
Table partionning problem
I need your help for a partionning problem. We are using a "log_event" table which log a lot of events sent by our players (subscription, connection, play, share, etc...). We insert 5,000 row / s in ...
3
votes
1answer
90 views
Simple MySQL query randomly takes forever
I'm having an issue on my server with a simple PHP send emails script that runs every minute via a cronjob. The script contains a MySQL query that runs very fast most of the time, but randomly will ...
0
votes
2answers
71 views
Why does using a variable make a difference in performance?
I have a table that constantly doing insert, and I am trying to run a delete script to remove old record.
The delete script looks like this:
DECLARE @StarDate DATETIME = '2013-01-13';
DECLARE ...
0
votes
2answers
62 views
Exploring and optimizing SQL performance of your system (PostgreSQL and Hibernate)?
Imagine you have inherited some project with extensive usage of SQL queries.
Let us assume that Hibernate is used as ORM and PostgreSQL as database, but thats not the point.
A question is: could ...
1
vote
1answer
35 views
Mysql performance for a nullable unique id column in a large table that references a record in another table
We have a large table of contacts (8 million records) that we promote to with mailings. When these people register we store them in a different members table. But we want to go back and update the ...
2
votes
0answers
134 views
MySQL: Improve performance for one row insert into table with unique constraint
I have a table with ~ 40 mil records, with a unique index on the url collumn, of type varchar(255).
Now the insert speed is about 30/s, is this expected? how could I improve it?
I can't use bulk ...
1
vote
3answers
190 views
Good, Bad or Indifferent: WHERE 1=1
Given this question on reddit, I cleaned up the query to point out where the issue was in the query. I use comma first and WHERE 1=1 to make modifying queries easier, so my queries generally end up ...
0
votes
0answers
69 views
What is faster - multiple access of table or using temporary table?
I have created two tables
create table one(ref_no int, name varchar(100), design varchar(100));
create table two(SNo int auto_increment primary key, use_date Date, ref_no int references one(ref_no), ...
0
votes
0answers
39 views
mysql select query optimization [duplicate]
Possible Duplicate:
mysql select query optimization
I have two tables, testa and testb.
CREATE TABLE `testa` (
`id` INT(10) NOT NULL AUTO_INCREMENT,
`name` VARCHAR(50) DEFAULT NULL,
...
-3
votes
0answers
31 views
Doubt :: my sql performance tuning [duplicate]
Possible Duplicate:
MySQL performance tuning
I would like to optimize my MySQL DB and I identified some important points as follows:
enabling query cache,
using memory storage (I know ...
1
vote
0answers
157 views
Finding the bottleneck by analyzing Munin graphs
We’ve been experiencing some issues with our database server during peak hours. In our Nginx error-log we can see that a lot of requests get timed out. The requests are also very slow. We have had ...
4
votes
1answer
128 views
250 billion rows - computing interconnectedness on a really huge scale
I have a table of approximately 700k rows, each identified by a unique itemnumber.
Each row/item can be associated with any of the other rows/items in the table by calculating a single numerical ...
1
vote
2answers
259 views
How to isolate general Oracle 10g issues through SQL
Background:
I've been working on a performance analysis on a system with major performance issues on a Oracle 10g server. Much of the SQL is badly written, or at least not written with performance in ...
6
votes
2answers
260 views
Adding a Clustered index to a HEAP table on someone else's app
We're using a proprietary application based on SQL Server 2005, which has many HEAP based tables (that is, no Clustered index). Over the years, these tables have grown badly fragmented (e.g. 99% ...
1
vote
1answer
431 views
MySQL / InnoDB: Does daily optimization improve performance?
Would performing daily optimizations of tables increase performance for MySQL and InnoDB? I have never did this before, but I have seen this module for Drupal http://drupal.org/project/db_maintenance, ...
9
votes
4answers
768 views
Is it possible to increase query performance on a narrow table with millions of rows?
I have a query that is currently taking an average of 2500ms to complete. My table is very narrow, but there are 44 million rows. What options do I have to improve performance, or is this as good as ...
1
vote
1answer
120 views
Optimizing table and choosing storage engine
Having the follow MyISAM table:
+----------------------+-----------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
...
1
vote
3answers
581 views
How can I speed up “show columns” on MySQL?
My application depends on running "show columns" for certain tables. It takes about 60ms to run, whereas all our other queries take under a ms. Querying information_schema directly is even slower.
...
2
votes
1answer
837 views
PostgreSQL tree structure and recursive CTE optimization
I'm trying to represent a tree structure in PostgreSQL (8.4) to be able to query the path from the root to a given node or to find all the nodes within a sub-branch.
Here is a test table:
CREATE ...
2
votes
2answers
1k views
How to setup mysql on tmpfs?
How to setup mysql on tmpfs ?
I am reading a tutorial in french, where the author do it this way :
1.) Create a tmpfs directory :
mkdir /var/tmpfs
mount -t tmpfs -o size=1G tmpfs /var/tmpfs
chown ...
6
votes
2answers
305 views
What are the pros/cons of splitting date and time into separate fields vs. using the datetime data type and storing the date in a single field?
My database is extremely large and growing at a rate of ~20m rows/day. I have timestamp data that is important but most of the reporting is based on date ranges and week over week or month over month ...
1
vote
2answers
140 views
Explicitly update a table after sp_tableoption “text in row” advices wanted
I have an extremely slow sql server 2000 DB with 8GB, and the cause of this is the 3 ntext columns which are in the more queried table. Table has indexes set and also the full-text ssearch index set ...
2
votes
1answer
415 views
Poor MySQL for Drupal on Shared Hosting
My Drupal site is on a shared host where I cannot modify the my.cnf configurations but the database seems to be performing poorly. Here are some of the flagged issues that I can see...
In ...
2
votes
2answers
479 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 ...
4
votes
2answers
230 views
Huge database logging of event type rows and ways to optimize it
We have a database that stores events. Events are generated at a 1000 per sec rate. We need to keep these events accessible for some years.
Usual use of these events is selecting some of them from the ...
5
votes
2answers
546 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)
...
3
votes
2answers
600 views
How can I optimize performance on a MySQL ndbcluster?
So, this is what I have:
A simple table classes__to_students:
|class |student|
---------------
Math Alice
Math Bob
Math Peter
Math Anne
Music Bob
Music Chis
Music ...
9
votes
2answers
222 views
How many Sproc Parameters is too many?
I've just started writing a Stored Procedure in SQL Server 2008 and have 30+ parameters. I've never written one with more than ~10 parameters, and that got me thinking... At what point are there too ...
2
votes
1answer
279 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 ...
10
votes
3answers
2k views
Does “WHERE 1=1” usually have an impact on query performance?
I recently saw the question "where 1=1 statement"; a SQL construct I have used often in constructing dynamic SQL in an effort to write cleaner code (from the perspective of the host language).
...
5
votes
1answer
590 views
Password hashes: Fixed-length binary fields or single string field?
I'm currently having am amusing debate with a friend, and we simply can't agree on the best method to store salted passwords in a database. The two options on the table are:
Storing the hash and the ...
3
votes
1answer
1k views
Why does MySQL use all of memory and goes into swap when doing lots of delayed inserts?
We have a database server running Centos 5.6 64bit 64Gb of RAM. The server is idle most of the time. However, every hour it gets a lot of DELAYED inserts. Up to 3 mil INSERTs per hour into a MyISAM ...
3
votes
2answers
529 views
Website is too slow when number of records increases?
I have developed a web application called Referral Program, It it developed by using PHP, MySQL. Users can joining the website and when they introduce new members, he/she gets a commission. The system ...
8
votes
4answers
918 views
How can I optimize this MySQL query further?
I have a query that is taking a particularly long time to run (15+ seconds) and it is only getting worse with time as my dataset grows. I have optimized this in the past, and have added indices, ...
0
votes
0answers
456 views
PHp Mysql OPtimization using slow-log-query [closed]
Hi there i'm trying to fix a speed connection problem of my app located at:
sandbox.promls.net
try get access by:
david@vivarealty.com.mx
xxxxxx
you could se the sql statements on there
4
votes
4answers
2k 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 ...
39
votes
6answers
8k 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 ...
