In the context of a database, optimisation refers to the process of the query optimiser selecting the best query plan to execute.
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2answers
336 views
Fastest validation query in PostgreSQL
What is the fastest query in PostgreSQL, which I can use as a validationQuery binding a JNDI resource?
I though that SELECT 1 is the simplest, but in this document it is said that in PostgreSQL we ...
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2answers
2k views
What would be the fastest approach to bulk update this mysql table (Innodb)?
I have a table with 100M rows. I am able update my table like 850 updates / minute. How to speed this up?
I am using following approach:
mysql -uroot < query_file
where query_file contains 1M ...
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1answer
1k views
16 Cores 12 GB RAM server MySql Configuration - my.cnf
The server takes 20+ seconds (wait time/slow IO response time) to response to a HTTP request even with memcached and APC installed. I believe this has something to do with MYSQL since the site as lots ...
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1answer
22 views
How un-clustered is a CLUSTER USING table
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 ...
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1answer
36 views
Will OPTIMIZE TABLE have any impact on my data?
I'm having issues with a database that is getting quite slow. The analyzer in phpMyAdmin recommends that I run OPTIMIZE TABLE on my tables.
But before doing so, I would (of course) like to know if ...
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2answers
76 views
Database and query optimizacion
I have a database containing three tables: tbl_database (main table is the primary), tbl_cmdatabase and tbl_blacklist. The three tables share the same structure but differ in the number of records ...
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1answer
35 views
Message system - delete message, or flag for deletion?
I'm wondering, what is the best approach about message deletion in a mysql based message system.
Plan A:
When the sender sends a message, it will be saved in 2 versions. One for the sender and other ...
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1answer
83 views
Does PostgreSQL optimize queries in transaction?
In my app I need to make big imports from user files, and to achieve that all records are updated/created I do it inside transaction. But before it I need to update massive, already existing in DB, ...
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1answer
90 views
What is the best relationship model for high performance?
I want to model a relationship between Customer and Transaction.
However, because Customer is only described by a unique string and no extra info, I have two possibilities to implement it in the ...
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1answer
120 views
Optimizing table and choosing storage engine
Having the follow MyISAM table:
+----------------------+-----------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
...
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3answers
3k views
I've got 16GB of ram, how should I configure MySQL Server?
I've got a dedicated production server with multiple cpus and 16GB of ram.
I would like to know how can I configure it better to take advantage of the server resources for better performance because ...
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2answers
2k views
Scheduled optimization of tables in MySQL InnoDB
What is the best way to schedule automatic optimization of tables in a MySQL InnoDB database? Can I use events for example? I have recently had a big performance issue (when querying) with one of the ...
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2answers
393 views
In DB2, how can I disable NLJOIN?
I want to indicate to the optimizer, via SET or optimization profiles, that NLJOIN shouldn't be used at all when optimizing a query.
I've been looking for this for a while without any success. I ...
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1answer
94 views
Should I Avoid Repeated References to Aggregate Columns in a View?
So I'm wanting to summarize the balance of the accounts in my business application. My (simplified for our purposes) data model looks like:
--Main account table that holds the single accounts
create ...
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1answer
58 views
Query optimization when no row is returned
I am using explain to figure out what is happening in my query which is:
explain select t from c where u1_id = 1 group by t;
I see "Using where" in the Extra column of the resultset. But this only ...
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1answer
34 views
extra steps after changing storage engine and adding index
Someone told me to look into his website for quick optimization; I'm a programmer and i don't have much experience optimizing databases.
I have a php/MySQL site uses the MyISAM storage engine. It ...
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1answer
36 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 ...
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1answer
107 views
Is there a tuning parameter for MySQL that allows you to set an on-disk gap between non-sequential primary keys?
I understand that one of the primary issues with using a non-sequential primary key is that every disk/memory write that does not come after the last known key causes a re-write of everything from the ...
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1answer
95 views
Proper indexes or anything else to optimize
I need help to optimize the query to avoid using "Using temporary", "Using filesort".
CREATE TABLE `target_bahrain_pepsi` (
`id` int(11) DEFAULT NULL,
`col_value` varchar(50) DEFAULT ...
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2answers
139 views
How do I force a JOIN to use a specific index in MySQL?
I have a query that JOINs 2 tables; lineitem and part,
select
sum(l_extendedprice* (1 - l_discount)) as revenue
from
lineitem force index for join (l_pk),
part
where
(
...
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1answer
99 views
Is there a way to write intelligent queries against a merge table in MySQL that represents a bunch of tables partitioned by date?
I have a set of MySQL tables that are partitioned by date, with a merge table representing all of them. For the query I am writing, the results are joined by date, so rows in table A_2012-12-05 will ...
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1answer
140 views
Is a query with UNIX_TIMESTAMP using indexes in mysql?
If I use
.. WHERE UNIX_TIMESTAMP(`some_timestamp`)>NOW()
in a SELECT, does this query still make use on an index, set on some_timestamp ?
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1answer
685 views
MySQL: how to optimize the stored procedure?
MySQL 5.5.28
Running pt-query-digest on a slow query log, I get something like this:
# 1.2s user time, 10ms system time, 22.30M rss, 114.48M vsz
# Current date: Wed Oct 24 23:44:05 2012
# ...
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1answer
430 views
Slow complex query with group/order
I have a problem with a very important query in my application.
It is very slow when adding group and order to it.
So the full query is:
SELECT
m.id,
m.title,
m.title_text,
...
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1answer
72 views
Optimising query on view that merges similar tables with a clear discriminator
Using PostgreSQL 8.4, I have a number of tables that have a very similar structure, but that belong to different categories:
CREATE TABLE table_a (
id SERIAL PRIMARY KEY,
event_time TIMESTAMP ...
1
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1answer
482 views
Planning simple CMS: How much relation?
I'm currently in the process of designing the database for a rather minimalistic Content Management System I'm working on alone. It should allow scalability while remaining speed, especially on boxes ...
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2answers
141 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 ...
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1answer
130 views
Optimising a sql correlated subquery statement
I am updating a column on tableA with data from tableB like this:
update tableA
set bKey = select bKey from tableB B where B.colB = tableA.colB
bKey has a unique index on tableB.
Which is the ...
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1answer
539 views
At which frequency run CTXSYS.CTX_DDL.OPTIMIZE_INDEX(…) on a fulltext index?
I've been told to run periodically CTXSYS.CTX_DDL.OPTIMIZE_INDEX(...) on some fulltext indexes, with no more information, in particular at which frequency this task should be run.
I guess that it ...
1
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1answer
1k views
Help optimizing MySQL slow query
i'm running a wordpress which needs some mysql optimization, i have a slow query and i would like to get rid of "Using temporary; Using filesort"
query:
EXPLAIN SELECT SQL_CALC_FOUND_ROWS wp_posts.* ...
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0answers
60 views
How can I join one to one to (many to one) without using group_concat
I have a table structure as follows:
--
-- Table structure for table `emails`
--
CREATE TABLE IF NOT EXISTS `emails` (
`ID` int(5) NOT NULL AUTO_INCREMENT,
`email` varchar(255) COLLATE ...
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4answers
107 views
Normalization of DB
I have designed a database using MySQL likewise
My question is what else i can do to normalize the DB, for now i am using InnoDB engine for the table to maintain the relation among different tables.
...
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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 ...
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2answers
244 views
Slow insert with MySQL full-text index
I use a full-text index in a MySQL table, and each insert into this table takes about 3 seconds. It seems that MySQL rebuilds (a part) of the full text index after each insert/update. Is this right?
...
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2answers
309 views
Slow mysql fulltext query
I have a little problem with the performance of a mysql-query which uses a fulltext index.
The following query
SELECT Mention.id
FROM mentions AS Mention
WHERE (MATCH (`Mention`.`title_text`, ...
1
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1answer
587 views
Optimizing MySQL for Read-Only?
We have 14 GB worth of CSV's which total 138 million rows. I imported this into a MySQL table first with InnoDB, and then tried again with MyISAM. In both cases, a simple SELECT on primary key ...
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2answers
82 views
Basic PARTITION question in MySQL
Say I have an application using MySQL and at some point decide that implementing Partitions on certain tables might improve performance.
Would I need to change the applications select statements ...
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0answers
505 views
SQL query optimization in Prestashop e-Commerce solution
I'm working on a layered navigation module within Prestashop e-Commerce solution.
I'm trying to optimize a SQL query which creates a temp table during execution. I think this is creating a ...
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0answers
54 views
Link-table(s) vs Redundant Columns? [duplicate]
Possible Duplicate:
Would it be considered as a bad practice to have multiple nullable FKs on a table in SQL Server
I have two tables, Users and People, both of which share a common ...
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1answer
269 views
Optimization: Delete with Top and minimize the where clause date range
I have a delete statement that get run repetitive until all the data are removed.
Delete TOP (1000) From Log Where CreationDate < '2011-Dec-31' AND pKey NOT IN (...)
I am considering of ...
0
votes
2answers
36 views
Is there a good reason to store big text data outside database?
I was analyzing my MySQL database performance and found that tables containing text fields are just huge, larger than 1Gb.
This data is only used when loading single record (like article or blog ...
0
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2answers
507 views
How can I truly DELETE data from a SQL Server table - still shows up in notepad in backup file?
SQL Server DELETE only marks as DELETED though leaves as data in the data pages.
Data pages are 1024 KB in size and this problem can be eliminated by adding a FILLFACTOR that ensures only 1 record ...
0
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1answer
292 views
Why do aggregate functions alter the way my rows are fetched?
Running this query
SELECT
s0.id,
s0.symbol,
YEARWEEK(p0.datetime) AS label,
p0.id AS point_id,
p0.datetime,
KG_FIRST(p0.open, p0.datetime) AS open,
MAX(p0.high) AS high,
...
0
votes
1answer
47 views
Large INSERTs performance optimization
I have 15 Amazon AWS EC2 t1.micro instances which simultaneously populate Amazon RDS MySQL d2.m2.xlarge database with data using large INSERTs (40000 rows in query).
The queries are send ...
0
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1answer
40 views
Misunderstanding statement in MySQL documentation
I can't understand this statement in Optimizing Data Size:
Declare columns with identical information in different tables with
identical data types, to speed up joins based on the corresponding
...
0
votes
1answer
40 views
What index to add in case of join by two optional fields
I have query similar to the one below, it joins two tables by field which can have NULL value. The result matchs the data if both tables have the same data or consider the condition as optional.
...
0
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2answers
193 views
Slow query with straight_join for small result
I have a performance-problem with a query in my application and I don’t understand the behavior of mysql.
The query consists of different joins, especially the join to the mentioncache-table. If the ...
0
votes
3answers
171 views
Dog slow query, needs optimizing, please help
I found this query in our web app that has been made by hired programmers. It performs like a dog and needs optimization, but I'm no MySQL wizard (yet), unfortunately. Please help, anything is ...
0
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1answer
19 views
Separate table by often changed / not often changed data?
I have a application which querys different gameservers, and stores for example if the server is online, and how many players are connected. But of course there is also data which is changed rarely.
...
0
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1answer
32 views
Need ideas about OPTIMIZE TABLE
Looking at a database with 10 tables and fairly active at by-the-hour changes. On the first of each month, I purge some rows from 3 tables to remove outdated material and keep the size down. All of ...
