InnoDB : MySQL's ACID-compliant Storage Engine

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What is effective way to delete duplicate records based on multiple columns in MySQL?

I have a table named users having approx 70 Million records, out of which I guess 10 Million is duplicate. How to remove those 10 Million records keeping one copy of that. Two records are said ...
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2answers
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+250

MySQL Innodb_row_lock_current_waits is 2^64 - 1

I have a MySQL 5.6 server which we monitor using Nagios. Over the weekend, it's started complaining about the Innodb_row_lock_current_waits, which currently has a value of 18446744073709551615, yes, ...
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1answer
13 views

MYSQL TABLESPACE = innodb_file_per_table GIVING ERROR 1030 (HY000): Got error 168 from storage engine

I have tried this statement to place a tables in different disks. Operating system is Linux Oracle 7, I've changed permissions in the directory with chmod -vR 777, to have total access to the disk ...
3
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1answer
867 views

What does “cleaning up” mean in MySQL InnoDB transaction status and how to prevent it?

In our database (MySQL 5.6.22 on RDS) we have a lot of transactions (~500) in a state "cleaning up" under the load: > SHOW ENGINE innodb STATUS; ... ------------ TRANSACTIONS ------------ ... ---...
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2answers
55 views

Converting from InnoDB tables to innodb_file_per_table

I run MySQL and I have 7 schemas, 6 of the 7 schemas are MyISAM. In one of my schemas I have 20 tables that are InnoDB, the rest are MyISAM. I really want to convert those 20 tables over to ...
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1answer
38 views

MySQL insert with sub select slow

We are using Python and LOAD DATA INFILE to load data from CSVs into our staging database. From staging we have sql scripts moving the data into our actual production database. LOAD DATA INFILE is ...
0
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1answer
25 views

MySQL .ibd file is too big

I got a memory issue while in linux. When i checked memory allocation by using df -h i found a path /dev/sda1 and it is used 100%. When i dig more i found that /var/lib/mysql file ate almost all ...
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0answers
29 views

Update on a table on MySQL Innodb seems to hang / lock forerever

When performing an update on a MySQL database for an InnoDB table, the update sentence never finishes. This is the update sentence from the MySQL query log: UPDATE `bb_plan` SET `creation_date` = '...
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1answer
700 views

inno_db_buffer_pool_size and key efficiency

I have the following metrics from mysql workbench After I have set innodb-buffer-pool-size to 6G, according to this answer's query on how to determine the recommended size. While the used buffer ...
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1answer
30 views

Sync two MySQL servers data, while changing the Engine in the slave

I'm running a MySQL server 5.5.44, and I'd need to sync its data to a new server running MySQL 5.7.13 using master-slave. The idea is to bring both DBs synced until we migrate to the second, newer ...
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1answer
159 views

Fastest engine for Mass Updates (only updates done on table)

I have a table of 2 columns and 60 million rows. I want to update the table by incrementing one field by 1 on various different rows (This is the only type of operation that will ever be done on the ...
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1answer
1k views

Cannot Start mySQL Daemon with Error “mysqld from pid file … ended”

I cannot get MySQL to run. It was working just fine hours ago, but upon starting, repeatedly ends without telling me very much. Here are my logs [myusername@location ~/mysql]$ ./bin/mysqld_safe --log-...
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1answer
425 views

MySQL Entity Relationship Problem - 3-way join table?

This is a db relationship question. I have a scenario which I believe I have come up with a solution - however, I can't be sure it's a manageable one, or even correct. The scenario is as follows: ...
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1answer
166 views

Benefits of using prepared statements in stored procedures?

Except from helping avoid SQL injection, what are the benefits - if any - of using prepared statements inside a store procedure (assume query is only executed once in the procedure)? Does the engine ...
0
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1answer
118 views

InnoDB compression: memory usage

InnoDB offers table compression for Barracuda-type tables and the recommendation seems to be to "adjust" buffer_pool_size. The documentation is rather vague about the definite impact of compression on ...
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2answers
70 views

In MySQL, how exactly does data flows from query to disk?

I would like to have clarity on how exactly data flows from the the time of firing a query till it goes to disk. (I have rough idea it will go to buffers, then to redo logs then disk files) but then ...
2
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1answer
309 views

InnoDB internals - checkpoint, LSN, dirty pages

I'm looking into InnoDB internals regarding buffer pool, checkpoint and dirtypage. However there isn't enough information to answer my question. When I run show global status, I can get ...
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0answers
37 views

What exactly is MySQL Spin rounds per wait in SEMAPHORES section?

I am facing slowness issue on MySQL Slave. I am suspecting this due to OS I/O as i compared Spin rounds per wait values with PROD. Slave have higher values. Also slave has less resources compared to ...
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3answers
24k views

How can I change the default storage engine in phpmyadmin?

I use InnoDB almost exclusively in my applications. However, if I'm not careful when setting up the table, I forget to change it and phpmyadmin sticks me with MyISAM. Is there a way to change the ...
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2answers
2k views

Mysql Deadlock on update query on same row

My server is experiencing occasional deadlocks on two update queries on same row both using index (primary key). The conflicting queries are: UPDATE auth_user SET rep_score=185 WHERE (auth_user....
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0answers
41 views

MySQL lost connection during query after specific record

I started getting the usual Error Code 2013 Lost connection to MYSQL server during query at a random moment when working on a PHP script. Some stuffs in the software still works, but the specific ...
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2answers
222 views

How can delete an orphaned temporary table on Mysql Innodb?

I was issuing an Alter table statement and suddenly the server crashed, Now i can not run any alter table to that table because it shows me the error 1050 and it says that a table named #sql1504d ...
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2answers
90 views

Will hacking away ibdata1 destroy databases with only MyISAM tables?

I made a mistake. I have a huge database of MyISAM tables that I was playing with converting [a copy of] to InnoDB. I didn't set innodb_file_per_table=1 before doing so. I know that safely shrinking ...
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2answers
134 views

Does MySQL Workbench lock database during migration process?

I am doing a migration of my database from one server (RDS) to another (localhost) via the MySQL workbench tool. I want to know if during this process my database will be locked for write and read ...
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1answer
486 views

Mysql Tuning for a small server

I have a small Cloud Server running under Ubuntu 2 core, 2GB ram and 2GB swap, with Plesk Panel, Apache, Nginx as reverse proxy and Mysql 5.5. I have about 18 domains hosted here and each domain has ...
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2answers
33 views

guessing unused junk space in table. (innodb mysql/mariadb )

We have in every site (a dozen) one big database with lots of tables and record, using innodb as default and with innodb_file_per_table. from time to time we have space issue on some site and I am ...
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1answer
2k views

MySQL SELECT query hangs - Opening Tables INNODB

On my server I have 6 MySQL databases. They all power Wordpress websites. For some reason, 2 of these databases are not accessible. To my knowledge they use INNODB, but I can't confirm it as even ...
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1answer
482 views

Storing history of full/partial tables

I'm building a web-application with Django and MySQL (InnoDB) and am currently pondering over how to manage historical changes on various tables. I wonder if it's efficient to store a lot of rows ...
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1answer
160 views

Write-lock a whole table during transaction

I need to perform a delicate operation to my table in which I will solely insert, delete and select upon all of my rows and no God may interfere with the table during this operation: the table will be ...
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0answers
24 views

Can InnoDB use a clustered index as a covering index?

The scenario I have in mind is a query like: SELECT id FROM table WHERE id = ? or equivalently, SELECT 1 FROM table WHERE id = ? So here's some background: In a B+ tree (which InnoDB uses as ...
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1answer
334 views

MySQL: Merge Same Database on Several Location into Single Location

I have registration form, which exactly same for several location. Each of them has REG column, which this field is unique for each row. Basically each data input have different REG number for it, ...
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3answers
13k views

Mysql slowly uses memory until it starts to use swap

I am running a 1gb of RAM rackspace database server. For some reason in about 2 days the memory usage goes from using very little swap, to using 100mb. If I don't restart sql it will keep using more ...
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1answer
656 views

Select * from statement execute very slowly, innodb io read speed is low

I have a very simple query " select * from ap_statistic " running in my servers. the servers have the same hardware and software configuration (CPU 8 core, mem :32G, OS: redhat 5.5, mysql version: 5....
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3answers
6k views

Is the overhead of frequent query cache invalidation ever worth it?

I'm currently working on a MySQL database where we are seeing a large number of invalidations from the query cache, primarily because of the high number of INSERT, DELETE and UPDATE statements that ...
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0answers
25 views

InnoDB LSN in the future - how to insert the “required amount” of data?

Please forgive me - I'm not a DBA, I'm a lowly devops whose mysql DBA went on vacation the day before this happened and is gone for 10 days. I'm learning as much as I can about mysql/innodb/LSNs but I'...
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1answer
33 views

How costly are InnoDB rollbacks?

I recently heard a fellow co-worker mention that InnoDB rollbacks are costly and negatively impact performance. How true is this statement? To give a context, we use spring+hibernate and set @...
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1answer
284 views

What's the approach to figure out reason for mysql crash?

The database I'm using crashes a lot recently. And I can't find a decent way to dig into the issue. I looked into mysql error log, but don't know how to start. I know there was a "load data infile" ...
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1answer
190 views

Why do innodb tables get corrupted so easily?

I'm upgrading a legacy system running MySQL 5.1 all the way to MariaDB 10. We're on a brand new Windows server, running XAMPP. I've done plenty of DB migrations in my time but this one has just been ...
2
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1answer
250 views

innodb , mysql Indexes difference when adding index

When I am altering one of my MySQL table to add an index I am getting below error in error log. Table a/b contains 4 indexes inside InnoDB, which is different from the number of indexes 3 defined ...
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Howto defrag a Galera Cluster (5.5.41) with innodb_file_per_table = off? After TRUNCATE a huge table is defrag needed?

First question how to defragment our cluster (see Galera and MariaDB config)? I don't know how Galera replicates the new data files size? Second question, is defrag needed? We truncated a 30 GB table ...
0
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1answer
159 views

Hash index for InnoDB

I saw a database schema that looked like this CREATE TABLE foo ( name_hash bigint, name varachar(500), a varchar(500), b varchar(500), ... PRIMARY KEY (name_hash), KEY ... ...
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2answers
6k views

show table name + number of records for each table in a mysql innodb database

How to list all tables in the current database, together the number of rows of the table. In other words, can you think of a query to come up with something like this in mysql? +---------------------...
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4answers
123k views

How large should be mysql innodb_buffer_pool_size?

I have a busy database with solely InnoDB tables which is about 5GB in size. The database runs on a Debian server using SSD disks and I've set max connections = 800 which sometimes saturate and grind ...
0
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1answer
46 views

MySQL MVCC implementation

The question is about the behavior of simultaneous SELECT and UPDATE in MySQL InnoDB table: We have a relatively large table which we periodically scan reading several fields including a field named, ...
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1answer
210 views

Too much IO to MySQL InnoDB log files

I am using MySQL version: 5.5.38 I have dedicated HDD to InnoDB log files using innodb-log-group-home-dir option. atopsar -d 30 shows big load (>50%) to this HDD The thing is that I have only 75 ...
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How much data is needed to show MySQL Cluster's performance scaling vs. InnoDB

I am evaluating MySQL Cluster as a possible replacement for an InnoDB schema. So far, I have tested it with 10s of MB of data, and found MySQL Cluster slower than InnoDB; however, I have been told ...
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1answer
66 views

MySQL applying second incremental backup causes LSN in the ibdata files to be higher than LSN in the ib_logfiles

Using the backup procedure described below, it gives warnings. These warnings start to appear from the 2nd till 6th (last) incremental backup that is being applied to the base backup. How to solve ...
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1answer
7k views

Configuring MySQL (my.cnf) for MyISAM and InnoDB

I want to convert some (not all) the MyISAM tables to InnoDB. Current my.cnf Show engines output Server has two 6-core Xeon processors (2 threads per core = 24 threads) What would be the best ...
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0answers
35 views

How to improve my big MySQL database with low concurrence?

I have a MySQL database who is been used to storage a large amount of data, it doesn't have a lot of concurrence( its minimum), but every day a big amounts of data is loaded and also a profiling ...
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1answer
1k views

Can't Delete Orphaned MySQL Temp Table

One of my servers had a hick-up yesterday and decided to leave temporary table while (while running alter table add indexes). ls -l sql -rw-rw---- 1 mysql mysql 8570 Mar 13 12:05 #sql-ib32694.frm -...