InnoDB : MySQL's ACID-compliant Storage Engine

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Unable to rename table due to metadata lock [on hold]

I am trying to rename a table but it always just hangs with a Waiting for table metadata lock. Here is how I am trying to do it: start transaction; RENAME TABLE `main_territorypricing` TO `...
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1answer
13 views

How can we migrate Data with MySQL 5.1 - MyISAM to another server with MySQL 5.6 - InnoDB

Currently we have a MySQL 5.1 - MyISAM database on a physical server. We need to move it to another server with MySQL 5.6 - InnoDB at another location. DB size is quite large - 210GB Can someone ...
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1answer
21 views

Mysql : Aborted connection …/… (Got an error reading communication packets)

This error message had submitted many times in this forum. I have tried the following without success. Context This is a Symfony1/Doctrine1 web application. The error appear on my computer and on ...
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1answer
28 views

MySQL usage suddenly hitting through the roof

We have a site with MySQL DB running properly for more than 2 years. However, 2 weeks ago we noticed a sudden spike in load. We started the MySQL service and load normalized. We assumed the issue was ...
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1answer
24 views

MySQL 5.6 InnoDB doesn't work

We have been having issues with one of our Windows environments. It uses MySQL and has been running on MyISAM only. We need to create a few InnoDB tables but the engine won't start. We tried changing ...
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21 views

MySQL “stalling” when database grows in size

Having a problem where lots of queries timeout. From innodb engine output it looks like lots of queries are blocked? --Thread 139681112069888 has waited at btr0cur.c line 523 for 0.00 seconds the ...
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1answer
64 views

Optimize mysql database performance

I have a database with some relatively small tables and one big table with about 10 million rows (11 columns) that I would like to optimize its performance. The table looks like this: Id: (int 11, ...
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26 views

Getting values from tables to string, combined one-to-many and many-to-many

I am stuck with one task. I have a database with one-to-many and many-to-many relationship. The whole problem is that I need to take from one table all persons in to a separate strings and count how ...
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2answers
20 views

Innodb_buffer_pool explanation

The title might be a bit misleading, as i am fully aware of the concept of innodb buffer pool, yet want to understand something specific about it's calculation process. According to the mysql docs: ...
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2answers
33 views

MySQL used all drive space running an ALTER and now won't start

I tried to alter a table without paying attention to the size, and MySQL ate up all the free space on the drive. I deleted a million or so old records but the space was still being used. Googling ...
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3answers
20 views

Why is determining existence (or not) of rows matching certain criteria using a 'LIMIT 1' query on indexed columns examining more than 1 row?

Consider a table created like this: CREATE TABLE `someTable` ( `id` bigint(11) unsigned NOT NULL AUTO_INCREMENT, `owner_id` bigint(11) unsigned NOT NULL, `device_id` bigint(11) unsigned NOT ...
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19 views

MySQL - InnoDB deadlock - simple update query

I am facing deadlock issue in one of our production server, details are as follows: Deadlock info: 160711 10:44:45 *** (1) TRANSACTION: TRANSACTION A89CB314, ACTIVE 2 sec fetching rows mysql tables ...
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1answer
13 views

Maximum or suggested number of bound query-parameters in InnoDB (MySQL)?

We have code that adds thousands of parameters to a query as members of an IN (...) criterion. My aesthetics say to bucket it into multiple queries, but I want an objective reason. Does InnoDB have a ...
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51 views

Difference between Mysql table and histats analyzer

Explaining problem immediately. I have partly huge number of transactions (~ 30k per minute) and after putting analyzer system, weird issue comes up. say we have below psudo: Request received ...
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32 views

How similar is using a secondary index in InnoDB to using a second table joining 'into' the PK?

Since InnoDB secondary indexes are separate B-trees with the key as the sort order and the PK as the 'value' stored, I assumed that reading into the main table by the secondary index was a lot like ...
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0answers
37 views

MySQL query much slower after conversion from latin1/myisam to utf-8/innodb

I converted one table from latin1 to utf-8 and changed the engine from MyISAM to InnoDB. After that conversion the same select query is 6x times slower than before. I converted the table with the ...
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0answers
47 views

MySQL server keeps crashing on startup

MySQL keeps crashing on start with the following message. It crashed after I was trying to batch upload data into a table and now it can't start since. This is an already existing database so it ...
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2answers
44 views

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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1answer
27 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 ...
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1answer
46 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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1answer
34 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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2answers
96 views

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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0answers
55 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
80 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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1answer
62 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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1answer
34 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
67 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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1answer
41 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 ...
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32 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
34 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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29 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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1answer
64 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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27 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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20 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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1answer
80 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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2answers
39 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
39 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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3answers
83 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
92 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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1answer
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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1answer
56 views

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
34 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
53 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
94 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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1answer
36 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 ...