why creating view from a left join view is not fast? - mysql

I created views on the tables
each of them had about 46299 rows
I created them successfully in phpMyadmin
after that I created a join of these two views
which itself is a view.
in mysql in a millisecond I got Query OK, 0 rows affected (0.01 sec)
but I couldn't reach my phpMyAdmin
so I decided to drop the view
in mysql it took about 20 minuets for dropping
again I tried my way and now I can't reach phpMyadmin
I don't know that it is under prcessing or not?!
how much I should wait? and why mysql show me fast query ok but phpmyAdmin is still processing if It is really under process
+-----+------+-----------------+-------+---------+------+--------------+--------
------------------------------------+
| Id | User | Host | db | Command | Time | State | Info
|
+-----+------+-----------------+-------+---------+------+--------------+--------
------------------------------------+
| 7 | root | localhost:38993 | week1 | Sleep | 2188 | | NULL
|
| 20 | root | localhost:39223 | week1 | Query | 0 | NULL | SHOW PR
OCESSLIST |
| 104 | root | localhost:39526 | NULL | Query | 800 | Sending data | SELECT
1 FROM `week1`.`alarm` LIMIT 100000 |
| 105 | root | localhost:39527 | week1 | Query | 800 | Sending data | SELECT
1 FROM `week1`.`alarm` LIMIT 100000 |
+-----+------+-----------------+-------+---------+------+--------------+--------
------------------------------------+
4 rows in set (0.00 sec)
mysql>

You can see if something have locked the table by issuing a SHOW PROCESSLIST command.

Related

Can I create MySQL View with SHOW keywords?

I need to create view like
create view GetProcessList
as
show processlist
Is it possible?
Is it possible?
No you can only create a view base on a SELECT statement , not a SHOW statement. But if your question is really how you can access the processlist as if it were a table....then this is already available in the information_schema meta-database:
MariaDB [information_schema]> SELECT * FROM information_schema.PROCESSLIST;
+----+------+-----------+--------------------+---------+------+----------------------+----------------------------------------------+---------+-------+-----------+----------+-------------+---------------+----------+
| ID | USER | HOST | DB | COMMAND | TIME | STATE | INFO | TIME_MS | STAGE | MAX_STAGE | PROGRESS | MEMORY_USED | EXAMINED_ROWS | QUERY_ID |
+----+------+-----------+--------------------+---------+------+----------------------+----------------------------------------------+---------+-------+-----------+----------+-------------+---------------+----------+
| 42 | root | localhost | information_schema | Query | 0 | Filling schema table | SELECT * FROM information_schema.PROCESSLIST | 0.561 | 0 | 0 | 0.000 | 83104 | 0 | 204 |
+----+------+-----------+--------------------+---------+------+----------------------+----------------------------------------------+---------+-------+-----------+----------+-------------+---------------+----------+
1 row in set (0.00 sec)

MySQL "Waiting for table metadata lock" hangs on 1 particular table

I'm trying to add a column to a specific table. Every time I run the migration up or down a SLEEP command pops up and blocks everything. Much like many other people who have run into this problem, I kill the blocking process and everything works as expected.
Ex:MySql alter table hangs
I've tried running the migration against a different table and have no issues. Seems to be something specific with this particular table.
Where or what should I be looking for? Why would this issue occur so consistently?
Thanks.
mysql> show processlist;
+-----+------+-----------------+--------+---------+------+---------------------------------+----------------------------------------------+
| Id | User | Host | db | Command | Time | State | Info |
+-----+------+-----------------+--------+---------+------+---------------------------------+----------------------------------------------+
| 351 | root | localhost:54691 | database | Sleep | 25 | | NULL |
| 352 | root | localhost:54692 | NULL | Sleep | 54 | | NULL |
| 377 | root | localhost | database | Query | 0 | starting | show processlist |
| 381 | root | localhost:54858 | database | Query | 5 | Waiting for table metadata lock | ALTER TABLE company ADD COLUMN active |
| 382 | root | localhost:54860 | database | Sleep | 5 | | NULL |
+-----+------+-----------------+--------+---------+------+---------------------------------+----------------------------------------------+
5 rows in set (0.00 sec)
The offending process in this case was 382.
The answers to many other similar posts say to kill the SLEEP process and then "debug". My problem was related to a circular import issue in Python, not related to MySQL.

Mysql table does not accept any update request

I am using Server version: 5.6.27-log MySQL Community Server (GPL) and I have a problem with a table.
I tried to update some fields with a GUI software, but when I came back to the command line, the lines I tried to update where not updated.
I tried to see if the table was locked using SHOW OPEN TABLES as stated in various other questions. But my table does not appear to be locked:
+--------------------+-------------------------------------------------+--------+-------------+
| Database | Table | In_use | Name_locked |
+--------------------+-------------------------------------------------+--------+-------------+
| arcdev | SCHEDULED_COMMAND | 0 | 0 |
And as soon as I try to make an update like:
UPDATE SCHEDULED_COMMAND SET field = 1;
The server just keeps loading and nothing happen. I tried on other tables and everything worked just fine.
I also tried some DELETE requests and even a DROP TABLE and nothing work so far...
What am I missing?
Thank you for your precious help!
EDIT: Here is the result of the SHOW PROCESSLIST command while a request is hanging:
+--------+----------+---------------------------------------+-----------+---------+------+----------+-------------------------------+
| Id | User | Host | db | Command | Time | State | Info |
+--------+----------+---------------------------------------+-----------+---------+------+----------+-------------------------------+
| 282588 | rdsadmin | localhost:17966 | mysql | Sleep | 2 | | NULL |
| 534575 | arc | XXXXXX:49376 | arcdev | Sleep | 17 | | NULL |
| 534579 | arc | XXXXXX:49443 | arcdev | Query | 0 | init | SHOW PROCESSLIST |
| 534659 | arc | XXXXXX:49836 | arcdev | Query | 14 | updating | DELETE FROM SCHEDULED_COMMAND |
+--------+----------+---------------------------------------+-----------+---------+------+----------+-------------------------------+

MySQL performance_schema not working properly?

I have MySQL 5.6.19 community server running on my Ubuntu 14.04. Lately I have been trying to monitor MySQL server using performance_schema. Previously I used to do this by running SHOW FULL PROCESSLIST query every 5 second using a cronjob.
I configured performance_schema.setup_consumers table as follows.
mysql> use performance_schema;
mysql> select * from setup_consumers;
+--------------------------------+---------+
| NAME | ENABLED |
+--------------------------------+---------+
| events_stages_current | NO |
| events_stages_history | NO |
| events_stages_history_long | NO |
| events_statements_current | YES |
| events_statements_history | NO |
| events_statements_history_long | NO |
| events_waits_current | NO |
| events_waits_history | NO |
| events_waits_history_long | NO |
| global_instrumentation | YES |
| thread_instrumentation | YES |
| statements_digest | YES |
+--------------------------------+---------+
By default the events_statements_history is not enabled. I enabled it as follows.
mysql> update setup_consumers set enabled="YES" where name="events_statements_history";
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from setup_consumers;
+--------------------------------+---------+
| NAME | ENABLED |
+--------------------------------+---------+
| events_stages_current | NO |
| events_stages_history | NO |
| events_stages_history_long | NO |
| events_statements_current | YES |
| events_statements_history | YES |
| events_statements_history_long | NO |
| events_waits_current | NO |
| events_waits_history | NO |
| events_waits_history_long | NO |
| global_instrumentation | YES |
| thread_instrumentation | YES |
| statements_digest | YES |
+--------------------------------+---------+
Now enabled, the events_statements_history table should now be able to capture queries but somehow it is not. Following is the result.
mysql> select count(sql_text) from events_statements_history;
+-----------------+
| count(sql_text) |
+-----------------+
| 0 |
+-----------------+
I do not understand as to why it is not logging in any queries?
The performance schema records data when three conditions are met:
The running thread is instrumented
The instrument currently executed is enabled
The consumers for the data to record are enabled
Threads
By default, every thread (1) is instrumented.
To check if threads are instrumented:
select THREAD_ID, NAME, PROCESSLIST_ID, PROCESSLIST_USER, PROCESSLIST_HOST, INSTRUMENTED from threads;
To change which threads are instrumented by default, use table setup_actors.
Instruments
By default, instruments for statements (aka, queries), are enabled (2).
To see which queries are not instrumented:
select * from setup_instruments where name like "statement/%" and enabled='NO';
To instrument all queries:
update setup_instruments set enabled="YES" where name like "statement/%";
Consumers
By default, only a few consumers are instrumented (3).
To see which consumers are instrumented, or to change this, use select / update on table setup_consumers.
This part seems fine per the question, so check part (1) and (2).
As a side-note, if there is nothing inside the setup_% tables then you might need to enable the performance schema,
https://dev.mysql.com/doc/refman/5.5/en/performance-schema-quick-start.html

MySQL import taking a long time to finish/ never ends

My ~700mb database has been importing for 1hr 27min now, the actual disk activity stopped at around 15min but I just left it running to see if it would finish by itself.
The command I ran:
mysqldump DB1 | pv | mysql DB2
So it's pretty much a straight copy from 1 database to another, with DB2 starting as empty.
I can actually see that the data is already in DB2, but the command refuses to end!
So the question is... Should I let it continue to run? Or can I kill it? :/
Updated:
SHOW PROCESSLIST;
+------+--------------+---------------------+------------+---------+------+--------+------------------------------------------------------------------------------------------------------+
| Id | User | Host | db | Command | Time | State | Info |
+------+--------------+---------------------+------------+---------+------+--------+------------------------------------------------------------------------------------------------------+
| 2762 | user1 | localhost | DB2 | Query | 5298 | Locked | /*!50003 CREATE*/ /*!50020 DEFINER="user2"#"%"*/ /*!50003 FUNCTION "function1" |
| 2763 | user1 | localhost | DB1 | Sleep | 5298 | | NULL |
| 2770 | user2 | localhost | NULL | Query | 3633 | Locked | SELECT COUNT(*) FROM `INFORMATION_SCHEMA`.`ROUTINES` WHERE `ROUTINE_SCHEMA`='DB2' AND `ROUTIN |
| 2775 | user2 | localhost | NULL | Query | 381 | Locked | SELECT COUNT(*) FROM `INFORMATION_SCHEMA`.`ROUTINES` WHERE `ROUTINE_SCHEMA`='DB2' AND `ROUTIN |
| 2776 | user2 | <ipaddress>:<port> | NULL | Query | 0 | NULL | show processlist |
+------+--------------+---------------------+------------+---------+------+--------+------------------------------------------------------------------------------------------------------+
Some settings I have that are non-standard:
innodb_stats_on_metadata=0
innodb_flush_log_at_trx_commit=2