MySQL : Open-Source, Relational Database Management System

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4answers
144 views

How do I prove that the act of removing foreign keys doesn't corrupt existing data?

TL;DR: Prove that in practice, the execution of the alter table table_name drop foreign key constraint_name statement does not corrupt existing data. The important consideration is the execution of ...
3
votes
1answer
69 views

Determining what query was called

I want to reverse engineer what exactly happens to the MySQL database when a product is added in Magento. I will have to reproduce the query, because I would like to manually enter new records using a ...
3
votes
1answer
175 views

mysql Wrong bytesec: 0-0-0 at linkstart: 0

I have several MySQL (MyISAM) tables that have been corrupted. Running CHECK TABLE mytable returns: > +-----------------+-------+----------+----------------------------------- | > ...
3
votes
2answers
880 views

Does a MyISAM table locks if I copy it while MySQL is running? (READ DISCLAIMER)

DISCLAIMER: I'm very aware this is not supposed to be done, but time consistency between tables aren't a concert here and Im trying whatever pops in my mind right now to have alternatives for ...
3
votes
1answer
847 views

Why does auto increment jumps by more than the number of rows inserted?

I am very perturbed by this weird behaviour I am seeing in the auto_increment value recorded in the bidID of a Bids table after performing bulk insertion using a stored procedure: INSERT INTO Bids ...
3
votes
1answer
384 views

Tuning key_reads in MySQL

We are trying to tune our MySQL database (Myisam, 5.1.73) which is getting busy. We investigated Key_reads: $ mysqladmin ext -ri10 | grep Key_reads During a normal load we have the following ...
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4answers
3k views

Select rows based on latest date with multiple joins

I have this query (SQLFiddle): SELECT c.name, a.user_id, a.status_id, a.title, a.rtime, u.user_name, s.status_name FROM company c LEFT JOIN action a ON a.company_id=c.id LEFT JOIN user u ON ...
3
votes
2answers
564 views

TokuDB optimize table does not reclaim disk space

Was running an optimize table command against one of my tables about 11Gig in size, surprisingly used disk space grew by 2Gig immediately after optimization process finished. I would expect the ...
3
votes
1answer
582 views

Speeding up a NOT IN subquery

Good evening, I'm currently up to try to improve the performance of some of my queries. As far as I know, statements like "IN" or "NOT IN" are even faster with a large amount of values if a subquery ...
3
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1answer
6k views

MySQL: Row size too large (> 8126)

Here's the issue. I have a table which has 300 columns in it, each up to 255 bytes (there IS a business justification for this). When I try it create it using VARCHAR(255), I go past the limit for ...
3
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2answers
252 views

mysql second slave not syncing while first slave works fine

I have a master (m) - slave (s1) setup using mysql 5.1.45 When I try to add a second slave (s2) the slave lags behind and never catches up on the sync. Even after having synced the s2 with the whole ...
3
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1answer
3k views

Why does that query cause lock wait timeouts?

From time to time, I find a lot of these errors in my PHP error log: MYSQL.1213: Deadlock found when trying to get lock; try restarting transactionSQL The problem persists for about 2 or 3 minutes. ...
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3answers
1k views

Slave SQL thread got hanged

We have a master - slave setup with ROW based replication. We are seeing huge delay's on the salve even though there is no activity running wither on master or slave. When we looked in, we observed ...
3
votes
2answers
5k views

Finding and fixing InnoDB index corruption

I encountered a new issue yesterday with one of my MySQL 5.5 slave DBs that runs on EC2 in AWS. The DB was created from a snapshot of another slave. The data is correct, but for at least one table a ...
3
votes
1answer
10k views

MySQL stored procedure: loop through table, delete rows. Logic problem: won't exit loop because of LIMIT option in query

I've created a procedure to loop through large InnoDB tables and delete a chunk of rows, then pause and repeat until max field value allowed is reached. Binary logging is enabled, but I'm leaving it ...
3
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1answer
382 views

How to categorize rows by SUM of a column in mysql?

I have a table as id num_items folder 1 4 2 33 3 74 4 41 5 24 6 34 7 46 8 55 9 11 I want to assign folder number to rows but limiting the number of items in each folder (e.g. ...
3
votes
3answers
3k views

InnoDB insertion faster

I'm a graduate school student researching OLAP with Mondrian OLAP. So I want to insert data into InnoDB (MySQL 5.5) faster at the initial loading. In this environment, the only user is me, so I think ...
3
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1answer
5k views

how to retrieve rows of different dates using IN clause

My table structure: +-----------------+--------------+------+-----+-------------------+----------------+ | Field | Type | Null | Key | Default | Extra | ...
3
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2answers
5k views

GROUP BY two columns

I want to count two columns, but need to get the results of first column in one row. SELECT country, COUNT(*) FROM table1 GROUP BY country, type This query gives me country type COUNT(*) ...
3
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2answers
2k views

Can I do anything about a very long running KILL command?

I've got a table with 103M+ records in it and takes up 70GB on the disk. I decided to DELETE (in one statement) 70% of the records. As expected, this took an awfully long time to run. I decided to ...
3
votes
3answers
2k views

MySQL optimization - year column grouping - using temporary table, filesort

I have a transactions table which is having 600,000 records, I need to list the count for the dashboard on financial year basis. The table used is MyISAM. I tried adding index for the transaction date ...
3
votes
1answer
225 views

Can underscore be forced as a word splitter without a full-text parser plugin?

Is there any way in MySQL to force underscore to become a word splitter character (like space or dash) without having to use a fulltext parser plugin? If not, does such a plugin already exist or do I ...
3
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1answer
653 views

Does this make my XtraDB Cluster hang?

After seeing the following in the error log on the second node: 121003 7:16:06 [Note] WSREP: Member 0 (joiner) synced with group. 121003 7:16:06 [Note] WSREP: Shifting JOINED -> SYNCED (TO: 0) ...
3
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1answer
2k views

Setting up replication for MyISAM tables?

Before setting up a replication within MySQL, the data first needs to be transferred to the slave. Since MyISAM tables can be copied as files. Would it be okay to copy MyISAM files, .myd .myi .frm, ...
3
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1answer
887 views

User autoincrement ID for username

I want to automatically create user's, which all have a unique ID. Now here's the problem. If two users are created at exactly the same nanosecond, it may not cause problems. Thus, what i do now is: ...
3
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2answers
3k views

pt-table-checksum help required

I am trying to figure out pt-table-checksum, as I am using it for the first time. It look likes the documentation is complex and not easy to understand stuff. I have a complex replication topology ...
3
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2answers
784 views

MySQL insists on trying to use InnoDB even when told not to, please help

We're trying out MySQL 5.5, and have installed it on one of our slave servers as a test run. Our main server is 5.0, and we have zero optimization here for InnoDB, so I want everything to just be ...
3
votes
2answers
336 views

Why ALL PRIVILEGES ON `db`.* gives access to all databases?

I've installed Ubuntu 12.10(quantal) and mysql-server-5.5. When I execute: drop user ''@'localhost'; create database `redmine`; grant all on `redmine`.* to 'redmine'@'localhost'; User ...
3
votes
1answer
333 views

Random write freezes

I have a MySQL 5.5.23 DB that performs about 3k qps, 5% of which are writes. Lately, I've been having a big problem with random write freezes. Everything is going great, and then all of a sudden any ...
3
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1answer
3k views

mysql: deleted performance_schema, is it a problem?

Been following this tutorial http://stackoverflow.com/questions/3927690/howto-clean-a-mysql-innodb-storage-engine/4056261#comment14041132_4056261 in the process I deleted performance_schema along ...
3
votes
1answer
528 views

why is mysql still writing data two hours after all transactions have stopped

I have a mysql server used mostly as data warehouse. It loads about 4-5GB of data per day (actual database size, not the size of the source data). Lately, I noticed something peculiar. After I ...
3
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2answers
4k views

what is bigger than a longblob?

the longblob is the biggest data type of Mysql. If I want to save something bigger than 4gb (longblob) how can I do?. I'm talking about Mysql v-5.+
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1answer
244 views

What's the latest on MySQL Proxy?

Does somebody here know the latest state of the development of MySQL Proxy? Most materials I found on web are outdated.
3
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1answer
1k views

Are many NULL columns harmful in mysql InnoDB?

As I explored the clustered B-tree index system of InnoDB, I think that the presence of many NULL (or small) columns has no significant effect on InnoDB performance. Does the presence of excess ...
3
votes
3answers
1k views

Speed up search across multiple columns

We have a table: user_info (user_id,domain_id,first_name,middle_name,last_name,work_place,.,.,.) Now, we have a user search that search across three columns first_name,last_name and work_place. ...
3
votes
1answer
420 views

How do I prevent updates on an entire table (but allow inserts) in Mysql 5.5?

I want to make the rows in a Mysql table immutable, once they are inserted I don't want it to be possible to change them. How can I do this? This question handles making individual rows immutable, ...
3
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2answers
2k views

MySQL connection count much larger than query count

I'm maintaining a relatively simple LAMP server. It does how ever have a some what high load. What I'm noticing is that in a one hour time span there are roughly 50k connections made to the mysql ...
3
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4answers
6k views

Synchronizing data between MySQL and Oracle databases?

I want to sync data between Oracle & MySQL databases. What is the best possible way to achieve this? Are there any tools/software available? This is not a one-time but an ongoing operation. The ...
3
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2answers
2k views

MySQL replication to slave having VPN connection to Master

I am setting up an environment in which the Master and Slave are on different networks at different physical locations (both run on MySQL 5.5.20). I have set up a VPN connection from slave's network ...
3
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1answer
6k views

MySql - ERROR 1071 Specified key was too long; max key length is 1000 bytes while restoring dump

while trying to restore a MySql Dump, i get the following error: ERROR 1071 (42000) at line 25: Specified key was too long; max key length is 1000 bytes any ideas?
3
votes
1answer
1k views

Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)

I tried restarting the Mysql server but its not working for me. I am sure the server is running and the permissions on the folder /var/lib/mysql/ are correct (777). When i tried to open the file ...
3
votes
1answer
1k views

Master and Slave having same id's

I am working as a remote DBA for some of the production servers. There was replication from Master to Slave. There is something changed in the scenario they have made one of the Slaves as master ...
3
votes
3answers
3k views

indexes, foreign keys and optimization

Not a DBA so pardon my ignorance... I have a table with 20 fields of which 8 are foreign keys. Mysql has by default added an index for each foreign key. Table has about 100k rows. When retrieving ...
3
votes
3answers
763 views

Converting CHAR to BIT

I have a column with char(16) data type and it was mistakenly set to char(16) actually it should be bit(1) because it contains only three distinct values as follows: 16 characters long string 10 ...
3
votes
2answers
589 views

Testing Query Speed

When I'm running a query for the first time, it takes x miliseconds to be executed. When I run it the second time it takes a lot less time. I assume that it is some caching involved in this mechanism, ...
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5answers
3k views

Why is MySQL caching data on our dynamic PHP site?

We are having an annoyance with our PHP/MySQL site in that it seems to cache data from the database and our PHP pages are showing out of date records. In fact, there are pages that link to URLs that ...
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votes
2answers
55 views

Joining two Mysql VIEWs takes a very long time

I have a textbox (for which I used jQuery auto-completion) in my PHP form where user can insert an actor/actress name and then by clicking "Search" button, a new window is opened showing list of ...
2
votes
1answer
253 views

Difference data between adjacent rows

I have a table (called Visits) with ReqTime DATETIME NOT NULL column AND Duration INT UNSIGNED column. Duration should be set to the difference of ReqTime for two adjacent rows. But Duration is not ...
2
votes
3answers
651 views

Can I use PHP function strtotime() in SQL queries?

I have this table, and I need to use a PHP function in the query. id time lastTime 1 08:02 2 08:04 3 08:30 I am using this query with the strtotime(), and it's not working: ...
2
votes
1answer
75 views

Wordpress blog where pages are almost-always served from cache: SSD or more RAM?

I am working on the design of a Wordpress blog which when finished will almost-always serve pages from disk cache and this is because all posts will be published in batch and then cached, with at ...