MySQL : Open-Source, Relational Database Management System

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2
votes
1answer
51 views

pt-table-checksum says there is a difference but pt-table-sync with --print says nothing

I am using pt-table-checksum to ensure master-slave is synchronized. When I run pt-table-checksum, I see some differences on employee_profile.trigger_log but when I use pt-table-sync with --print, I ...
2
votes
1answer
129 views

My HD crashed and I can't start MySQL

I am on Windows 8, my SSD got corrupted and I installed Windows on a new drive. I had before MySQL 5.6.12, now I installed 5.6.17 and tried to move the entire data dir. The location of the MySQL ...
2
votes
1answer
88 views

how can optimize this sql query for being faster than superman

this my sql query: SELECT * FROM (SELECT * FROM ClassifiedAd WHERE city_id = :city AND currency = :currency AND price > 100) UNION DISTINCT (SELECT c.* ...
2
votes
0answers
72 views

Combined UUID Index + AI PK Insert Performance

I posted this in stackoverflow but realised it probably belongs here instead. Imagine the following table: CREATE TABLE `orders` ( `ORDERID` int(11) unsigned NOT NULL AUTO_INCREMENT, ...
2
votes
1answer
68 views

ibdata1 increases when firing update queries [duplicate]

I have read a lot of posts which explain that the only solution to stop the growth of an ever increasing ibdata1 file is to: Take a dump of all databases Set innodb_file_per_table in the mysqld ...
2
votes
1answer
108 views

View last several innodb deadlocks

I see that I can view the latest deadlock in mysql/innodb, but is there a way to view past deadlocks? We have two deadlock issues, one being important and the other not. The less important deadlock ...
2
votes
3answers
279 views

How can I make MySQL client read password from mylogin.cnf?

I'm trying to make the mysql client connect to a mysql server without requiring the password to be given interactively. Steps taken: 1) First create a mylogin.cnf file $ mysql_config_editor set ...
2
votes
1answer
65 views

MySQL replication for non-standard port (3306)

I want to do MySQL replication using MySQL 5.6.14 under MS Windows 2008 R2, the port for Master and Slave should be 1000 (master database on PC1, slave database installed on PC2 I added the following ...
2
votes
0answers
39 views

How to query for additions and deletions between two sets of rows (mysql)

I have tried several variant queries for finding additions/deletions between two sets of rows. Purely algorithmically, there is a straightforward algorithm that is O(N) for composing a list of ...
2
votes
0answers
49 views

select on table slows done during update on same table [closed]

I have a weird problem with mysql. During a transaction which runs from 10-30s around 270 statements are performed, some of which are updating and inserting a few rows on a table. If a select is ...
2
votes
1answer
76 views

MySQL table indexes change location [closed]

Is it possible to move the MySQL Table indexes to another location rather than "datadir" ? for example a ssd drive or memory partition ?
2
votes
3answers
315 views

Bulk Delete for Large Table in MySQL

I have a Notification table contains about 100 million rows host in Amazon RDS with 1000 IOPS, and I want to delete those rows older than one month. If I do DELETE FROM NOTIFICATION WHERE CreatedAt ...
2
votes
1answer
108 views

MySQL: Why queries with subqueries are much faster than single query?

I made few queries on my db lately First query: SELECT `table`.* FROM (`table`) WHERE table.id in(27172172,[...bunch of ids...],27171770) ORDER BY field (`table`.`id`, ...
2
votes
2answers
625 views

Best practice design when expecting large data in a table

I have come across a way that kind of works for me, and was just wondering if it would have any side effects, or, if I'm just thinking about this the wrong way. I first had this idea when I was ...
2
votes
0answers
73 views

ORA-00937 when calculating a sub-value in an aggregate select statement

The problem described below applies to Oracle 11g databases. I also tested the statements on MySQL and PostgreSQL with no problems of the kind mentioned in this question. I want to use an ...
2
votes
1answer
64 views

Should I use utf8_unicode_ci or utf8_slovak_ci?

I was using utf8_slovak_ci collation until now, but I read that utf8_unicode_ci sorts very wide range of languages. Does it mean, I do not need to use separate collation for every language and I can ...
2
votes
1answer
87 views

What is the best storing device for DB transaction log?

I'm using MySQL with InnoDB storing engine. Transactional log is placed to dedicated HDD. Still as it is HDD atopsar shows big load (>50%) to this HDD because of big amount of small IOs (about 50 ...
2
votes
1answer
36 views

Translate SQL Server update statement to MySQL

I have a development environment with MySQL and a production environment with SQL Server. This update statement works with SQL Server: UPDATE THIS SET <list_of_column_assignments> FROM ...
2
votes
0answers
32 views

longitude lattitude performance [duplicate]

I have to store frequently (at least every min) the position (longitude, latitude) of animals in a DB, and perform for each update a search in order to determinate if ananother animal is near to it. ...
2
votes
0answers
32 views

See indices implicitly created for foreign key constaints in MySQL

When I add a foreign key constraint to my table, SHOW INDEX doesn't show any new indices, but the overall space used by the indices in that table increases. Apparently, the index for the field I put a ...
2
votes
0answers
123 views

Almost identical queries but large time difference in execution

Exhibit A SELECT SUM(value) FROM Credits RIGHT JOIN calendar ON datefield = DATE(FROM_UNIXTIME(created_at)) WHERE confirm = 1 && reason = 1 && country = 'it' && created_at ...
2
votes
0answers
89 views

Performance difference between two MariaDB slaves

I have a pool of MariaDB servers like this : master (5.5.38-MariaDB-log) slave1 (5.5.38-MariaDB-log) slave2 (5.5.38-MariaDB-log) The two slaves servers run on the exact same hardware (Dell ...
2
votes
0answers
50 views

Emulating WITH clause in MySQL/query perfomance review

I have never really worked with MySQL queries till this last week. I was tasked with making a simple tool for my department that tracks contacts. Here are the 2 tables and the type of data they ...
2
votes
0answers
44 views

Sample a Mysql table to increase performance

we are storing all our clients traffic data in a MySQL 5.1.73 database (MyISAM) and then we use it to generate user and internal statistics/graphs, always searchinng for a client id and a date/hour. ...
2
votes
2answers
157 views

Java Spring application Database triggers auditing - how to provide the right user that made the change

We are developing a new web application. one of the most basic requirement is to audit all entities changes into a separate table. We would like to use DB triggers for that purpose. We use MySQL as ...
2
votes
1answer
135 views

Does READ UNCOMMITTED have the same effect as AUTOCOMMIT=1?

AFAIK running transactions as READ UNCOMMITTED means that there is no lock, so every change caused by a transaction is immediately visible to other transactions. Is it correct to assume that this is ...
2
votes
2answers
214 views

ib_logfile opened with O_SYNC when innodb_flush_method=O_DSYNC

mysql will open and flush data/log files as below when innodb_flush_method=O_DSYNC Open log Flush log Open datafile Flush data O_SYNC NONE NONE fsync () ...
2
votes
1answer
127 views

Randomizing the Auto Increment in Mysql

We have a database, where we insert data into table whenever we receive an order from our services. We use auto_increment to generate the ID and assign the order with the same. This is usually same ...
2
votes
1answer
3k views

Error Code: 1133. Can't find any matching row in the user table

Im reading O'Relly "Learning MySQL" and it says that you can create a user in MySQL by doing just this: mysql> GRANT ALL ON *.* TO 'jill'@'%.invyhome.com' IDENTIFIED BY 'the_password'; Query OK, 0 ...
2
votes
1answer
201 views

LOCK=NONE when adding NOT NULL constraint fails with “cannot silently convert NULL values” error despite no NULL values being present

I'm trying to use MySQL's online DDL feature to add a NOT NULL constraint to an InnoDB table without blocking writes to the table. According to manual, this should be possible - the linked table ...
2
votes
2answers
836 views

What is default MySQL binlog retention in AWS RDS?

I tried to retrieve my MySQL RDS binlogs in order to run manual "rollback" for some SQLs. Unfortunately, I noticed that only 2 binlogs for the last 30 minutes are available. "call ...
2
votes
2answers
237 views

Design of an application log database

We are generating logs like following example(this is a table no actual pipes): 2014-06-10 09:00:03.457 | Channel1 | Operation3 | Function15 | 15ms 2014-06-10 09:00:08.245 | Channel2 | Operation5 | ...
2
votes
0answers
67 views

Denormalizing to speed up inserts

I have a MySQL InnoDb table with approximately 40 million rows and the following columns: param1 (int), param2 (int), param3 (int), geo (char2), value1 (bigint), value2 (bigint) I have an ...
2
votes
0answers
21 views

MySQL slow query log not logging all slow queries [duplicate]

I am trying to analyze the hibernate query performance in our application. I tried logging all hibernate queries which take more than 100ms execution time from application side as well as using mysql ...
2
votes
1answer
43 views

Difference of write authorization on file system with mySQL

On my local mySQL (on CentOS 6 VM) database I wanted to export some data from the DB to a file like this: SELECT html FROM mytable WHERE lang = 'en' and id='KEY01' INTO OUTFILE 'key01_en.html' By ...
2
votes
1answer
2k views

Use limit with where clause in in mysql [closed]

I know where clause search and display the records as per criteria comes true, and limit is use to fetch the number of records from a table. But please help me when I am trying to use them both ...
2
votes
1answer
264 views

How can I connect to a network MySQL server using ODBC?

Somewhere on my company's network there's a (Oracle) MySQL server named FOO. I see FOO reference in SAS code written by my team's analysts, who use SAS's PROC SQL command to connect to it using ODBC. ...
2
votes
0answers
333 views

Recover innodb database from ibdata1 and *.frm files only

I have a problem on my server. I had a hard disk error on my server, and I restarted it. After that, I started wamp server software, but mysql services were not started. I checked all mysql data, ...
2
votes
0answers
173 views

Single database won't load MySQL

When I turned off my MySQL server, and turned it back on, it wouldn't read my database anymore. Just a single database, everything else in mySQL was fine. When I try looking at any of the tables it ...
2
votes
1answer
659 views

How to normalize my db schema for a quiz application?

I am putting together a quiz application. (I'm calling each quiz a "challenge") I have a "challenge" table and a "challenge_question" table which is pretty straightforward. challenge table: id ...
2
votes
1answer
138 views

What are possible causes for consistently volatile INSERT performance in MySQL tables?

I have a Java program running on a VM that is sequentially feeding a queue of single row INSERTs through a single connection to a MySQL server on the same VM. The queue execution is not artificially ...
2
votes
1answer
624 views

Why would the size of MySQL MyISAM table indexes (aka MYI file) not match after mysqldump import?

I've been archiving some MySQL (version 5.0.96) MyISAM tables locally and deleting from my server after checking the data. Every time the process has been pretty similar and comes off mostly without a ...
2
votes
1answer
82 views

Moving data from an old table into a newly created table with different field names / number of fields

I've been handed over management of a database, and I have had very little exposure to MySQL (or databases in general) so far. I would like to do two things, both of which are (I expect) fairly ...
2
votes
1answer
279 views

Does MySQL guarantee atomic upgrade from read lock to write lock?

If a client session is currently holding a read lock (to allow concurrent reads while already preventing writes), and then acquires a write lock on the same table(s), does MySQL guarantee that the ...
2
votes
0answers
1k views

How to do While Loops?

How can we use while loops in MySQL? My test script: BEGIN SELECT 0 INTO @n; WHILE @n < 10 DO SELECT @n; SET @n := @n +1; END WHILE; END; But it has syntax errors. I've also ...
2
votes
0answers
24 views

Is it possible for unique key to break master-master replication in mysql?

I have a master-master mysql setup with 2 servers running the exact same application making writes to such a table: CREATE TABLE `metric` ( `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT, ...
2
votes
2answers
187 views

Is there a rule of thumb regarding the size and number of a buffer pool instances?

I know the consensus seems to be approximately 75% of ram should be dedicated to the buffer pool. But, I'm more interested in the optimal number of buffer pool instances. What are some things to ...
2
votes
1answer
1k views

MySQL not releasing memory

MySQL seems to want to keep an entire table in cache (table size = ~20GB) after any large inserts or select statements are performed on it. Right now my innodb buffer pool is 20GB. Total RAM is 32GB. ...
2
votes
0answers
105 views

How to distribute a given database between multiple DBMS on a LAN? [closed]

Given a Database D, i need to distribute it over different DBMS in a LAN. D will be split into tables, and each DBMS will store a given table. Here is a sketch of what i need to do : I also need to ...
2
votes
0answers
2k views

MySQL - high CPU usage (MyISAM tables)

We have a server running LAMP stack on CentOS release 5.6 (Final) MySQL is having high CPU usage constantly which causes server to lag as shown top - 13:50:47 up 80 days, 13:53, 1 user, load ...