InnoDB : MySQL's ACID-compliant Storage Engine

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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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27 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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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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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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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 ...
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40 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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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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2answers
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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
54 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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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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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 ...
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27 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
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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24 views

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 ...
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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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20 views

InnoDB: Operating system error number 9

I got error when trying to backup with percona. Backup command [xtrabackup --backup --target-dir=/data/backups/mysql/] was worked and When I try to prepare backup [xtrabackup --prepare --target-dir=/...
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19 views

Innodb Change Buffer merge

I have been testing the performance of my innodb mysql. I ran a script which inserts and selects one after the other for 100000 times. So according to the change buffer concept, the inserted ...
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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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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
33 views

ALTER TABLE engine from MyISAM to InnoDB: why does mysqldump --order-by-primary help me?

I found an interesting mysqldump option in MySQL 5.7 Reference Manual. In internet there are no further details and explanations. --order-by-primary Dump each table's rows sorted by its primary ...
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1answer
71 views

Memory(buffer pool) not populating on mysql start on Percona 5.6.28

We are testing Percona 5.6.28 at the moment, during our testing we found out even though the innodb_buffer_pool_populate is set to ON, it doesn't populate the memory(buffer pool) during mysql start. ...
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1answer
34 views

Mysql repetition of column in Criteria

What happens when I repeat the same column in the criteria part but with different values . For example col1 ='val1' or col1 = 'val2' or col1 = 'val3' . Assume col1 is not indexed. Will mysql ...
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1answer
54 views

How to fix `The table '/tmp/mysql/#sql_xxxxx' is full`?

Ubuntu server 16.04, php7, nginx 1.10, mysql 5.7 in Hyper-V on Windows 10 host How to fix The table '/tmp/mysql/#sql_xxxxx' is full ? In mysql-error.log [ERROR] InnoDB: Tablespace ...
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41 views

MySQL disk scanning algorithm [closed]

How does MySQL (InnoDB engine) read data from disk? What scanning algorithm does it use? Since the rows are stored in data pages will it read the entire data page to get the resulting rows?
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Getting InnoDb internal Errors on every query run

I am having following errors in error.log at the run of each query due to which I am not able to use error.log properly. 2016-05-30 09:39:58 7f7c7e3cb700 InnoDB: Error: Column last_update in table "...
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1answer
62 views

Converting a composite primary key to composite unique, and adding an auto-incremented PK column

Background I have taken over responsibility for a table that, in the long run, will grow monolithic. The table is a very simple link table with 2 columns, call them col1 and col2, both being foreign ...
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20 views

What are the best settings of InnoDB for FULLTEXT queries?

This question has been asked before, but I was unable to find the right answer for my situation. We have a local server with Quad core and 32GB RAM dedicated for a single InnoDB database, which ...
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1answer
33 views

What happens to mysql information_schema after switching to innodb_file_per_table?

We're switching our mysql dev deb instance to innodb_file_per_table and moving the data dir onto another mounted drive so we can free up space on our dev box. We've backed all our dbs up and about to ...
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1answer
49 views

how to purge / shrink .idb tables

I know this has been asked many times but, what is the proper configuration to succesfully purge / shrink .idb tables? I have tried to use optimize table table_name but after the query the .idb ...
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1answer
85 views

howto read/interpret “show engine innodb mutex” output?

We use a 3 node Galera cluster with version 5.5.41-MariaDB-wsrep MariaDB [(none)]> show engine innodb mutex; +--------+---------------------------------+------------------+ | Type | Name ...
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24 views

MySQL innodb_log_file_size change is not being recognized

I am trying to set the innodb_log_file_size option in a MySQL 14.14 (distrib. 5.6.30) installation on Ubuntu 15.10 to solve an issue (importing a database with large BLOB fields) however the log size ...
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1answer
64 views

Composite Primary keys and auto increment?

i'm developing SaaS app with multi-tenancy, and i've decide to use single DB (MySQL Innodb for now) for client's data. I chose to use composite primary keys like PK(client_id, id). I have 2 ways here,...
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60 views

MySQL is using swap memory while I have plenty of free RAM

I have a 6 GB buffer pool size for my database; however, mysqld process is moving to swap while there is plenty of RAM available. I think pool size and pages along with pool of reads and pool of read ...
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1answer
63 views

improving performance of concurrent inserts on innodb with randomized primary

I was looking at my design for primary keys which is based on my own incrementing BIGINT key generator. It is designed to generate batches of 50 numbers for use on that process, but mostly it ends up ...
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Can MyISAM tables affect the backup recovery of innodb tables on Amazon RDS?

I have an Amazon RDS instance containing several databases. All the tables are innnodb except from one, that is MyISAM and currently cannot be converted to innodb. I know that the recovery of MyISAM ...
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1answer
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mysql crashed, innodb fails to recover

On Mysql 5.0 on CentOS 5.11, mysqld service has crashed and fails to start. Adding innodb_force_recovery=3 in /etc/my.cnf, creates the following error, which repeats with all table names of database ...
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Insert and select the row autoincremented id

What I want to do is insert a row and than select its auto incremented id number, In a multhi-threaded enviroment. I know how to do it with a Stored Procedure. Will this line of code work: BEGIN ...
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28 views

How to use FULLTEXT in mysql innoDB?

Sorry, if my question is naive, but it has puzzled me, and cannot benchmark the performance. I want to use the newly introduced feature of innoDB for FULLTEXT index. I wonder what is the difference ...
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1answer
71 views

InnoDB files created even innodb_file_per_table is OFF in mysql-5.7

We have installed mysql 5.7 in ubuntu 16.04 and we got big surprise because databases are being stored individually in each folder even parameter innodb_file_per_table is 0. We decided to change ...
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6 views

1K unused pages in each InnoDB buffer pool instance

I have configured a InnoDB buffer pool of 12 Gb, split into a dozen instances 1 Gb each. The buffer pool hit rate is 1000 / 1000, therefore so far it's looking good. Looking at the stats of the ...
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Completely reset innodb logs and files

So long story short, we've been dealing with a corrupt innodb installation on a MariaDB 10.0 server after a power outage, specifically a log in the future error. Rather than try and fake the log ...
0
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1answer
14 views

Monitor locks over long period of time

I am having some issues with one of my tables in a production server. I know there are many diffrent threads running on this table. I need to put some kind of monitoring tool to see how many locks ...
2
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1answer
65 views

Query with Indexes slower than without Indexes

I'm using MySQL 5.6 and my storage engine is InnoDB. I have a table with 1 million rows containing with the columns: ID (primary key) FirstName LastName foreign_key_id (foreign key, NOT NULL) ...
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48 views

InnoDB: why “non-locking” SELECT still gets locked?

This issue can be related to my first question: InnoDB: very slow random updates, hanging in “updating” state But i think it needs to be clarified in a separate thread. The Problem: a simple read ...
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Is the SQL syntax for InnoDB gauranteed to be the same between MySQL, MariaDB and Percona?

I develop an application that uses MySQL and explicitly uses InnoDB table engine. In a few cases we have clients using this application with MariaDB or Percona. I understand that MariaDB and Percona ...
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InnoDB: very slow random updates, hanging in “updating” state

I've been fighting my problem for the whole last week, studying stackexchange threads with similar issues in the first place. The main problem is that after switching from MyISAM to InnoDB (...
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1answer
66 views

MySQL - NOT IN … vs LEFT JOIN

I am trying to understand in terms of performance which approach is better: Query 1: SELECT * FROM table1 WHERE col1 NOT IN(SELECT col1 FROM table2) Query 2: SELECT * FROM table1 LEFT JOIN table2 ...
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58 views

MySQL queries waiting for other queries to finish

We have 30-40 different projects in Python and PHP that update, insert and select more than 1 million rows of data in MySQL DB every day. Currently we use InnoDB Engine for our tables. The problem: ...
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61 views

MySQL INSERT … SELECT Performance

I know that this query will lock table2: UPDATE table1... SELECT .. FROM table2 How about this query ? INSERT INTO table1... SELECT .. FROM table2 Does this query also create a lock on table2?
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1answer
33 views

How can I disable xb_doublewrite?

Getting error while service restart. [ERROR] InnoDB: A parallel doublewrite file /test/mysql/xb_doublewrite found on startup.