# Ecto MySQL Extras
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This library provides performance insight information on MySQL (and MariaDB) databases.
It's heavily based upon [Ecto PSQL Extras](https://github.com/pawurb/ecto_psql_extras), it reuses most of the design.
This library is an optional dependency of [Phoenix.LiveDashboard](https://hexdocs.pm/phoenix_live_dashboard/Phoenix.LiveDashboard.html).
Currently only `InnoDB` is supported, other engines may work but not all queries will return all or correct data.
The following databases are supported:
* MySQL >= 5.7, <= 8.0
* MariaDB >= 10.2, <= 10.6
Newer version are tested every week to check for any compatibility issues.
## Installation
The package can be installed by adding `:ecto_mysql_extras` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:ecto_mysql_extras, "~> 0.4.0"}
]
end
```
### MySQL/MariaDB configuration
The configured user should have read (SELECT) access on the `mysql`, `information_schema` and `performance_schema` database. Specifically for the following schemas:
* `mysql.innodb_index_stats`
* `performance_schema.table_io_waits_summary_by_index_usage`
An example on how to achieve this can be found in `docker/init/init.sql`.
### Performance schema
The performance schema is enabled by default for MySQL databases but not for MariaDB. To enable this add `performance_schema=ON` to `my.cnf`. A restart is need to take effect.
More information: https://mariadb.com/kb/en/performance-schema-overview/
## Usage
To run a query:
```elixir
EctoMySQLExtras.plugins(MyApp.Repo)
```
This will return a `%MyXQL.Result{}` struct. If you want to display it in a more human readable (ASCII) way:
```elixir
EctoMySQLExtras.plugins(MyApp.Repo, format: :ascii)
```
To view all available queries:
```elixir
EctoMySQLExtras.queries()
```
### `db_settings`
```
EctoMySQLExtras.db_settings(MyApp.Repo, format: :ascii)
+--------------------------------------------+
| MySQL global variables |
+--------------------------------+-----------+
| name | value |
+--------------------------------+-----------+
| INNODB_BUFFER_POOL_INSTANCES | 1 |
| INNODB_BUFFER_POOL_SIZE | 134217728 |
(truncated results for brevity)
```
Shows global variables for selected MySQL settings.
### `db_status`
```
EctoMySQLExtras.db_status(MyApp.Repo, format: :ascii)
+---------------------------------+
| MySQL global status |
+----------------------+----------+
| name | value |
+----------------------+----------+
| Aborted_clients | 100 |
| Aborted_connects | 25 |
(truncated results for brevity)
```
Shows global status for selected MySQL server status.
### `dirty_pages_ratio`
```
EctoMySQLExtras.dirty_pages_ratio(MyApp.Repo, format: :ascii)
+------------------------------------+
| InnoDB Dirty Pages Ratio |
+----------------------+-------------+
| ratio | total_pages |
+----------------------+-------------+
| 0.024798512089274645 | "8065" |
+----------------------+-------------+
```
Shows InnoDB dirty pages ratio.
The ratio of how often InnoDB needs to be flushed. During the write-heavy load, it is normal that this percentage increases.
A good value should be 75% and below.
### `index_size`
```
EctoMySQLExtras.index_size(MyApp.Repo, format: :ascii)
+---------------------------------------------------+
| Size of the indexes, descending by size |
+----------+-------+-------------+-------+----------+
| schema | name | index | pages | size |
+----------+-------+-------------+-------+----------+
| sportsdb | stats | IDX_stats_1 | 97 | 1.5 MB |
| sportsdb | stats | IDX_stats_5 | 23 | 368.0 KB |
(truncated results for brevity)
```
Shows the size of each index in the database, excluding primary keys. Additionally a table can be passed to only get indexes from that table.
```
EctoMySQLExtras.index_size(MyApp.Repo, format: :ascii, args: [table: "my_table"])
```
### `long_running_queries`
```
EctoMySQLExtras.long_running_queries(MyApp.Repo, format: :ascii)
+------------------------------------------------------------------------------+
| All queries longer than the threshold by descending duration |
+----+--------+------+------+----------+-------+-------------+-----------------+
| id | thread | user | host | duration | query | memory_used | max_memory_used |
+----+--------+------+------+----------+-------+-------------+-----------------+
(truncated results for brevity)
```
Shows queries that have been running for longer than 0.5 seconds, descending by duration. The threshold can be configured and is represented in milliseconds, however for MySQL servers this is converted to seconds.
```
EctoMySQLExtras.long_running_queries(MyApp.Repo, format: :ascii, args: [threshold: 1000])
```
### `plugins`
```
EctoMySQLExtras.plugins(MyApp.Repo, format: :ascii)
+--------------------------------------------------------------------------------------------------------------------------------------+
| Available and installed plugins |
+-----------------------+---------+--------+----------------+--------------------------------------------------------------------------+
| name | version | status | type | description |
+-----------------------+---------+--------+----------------+--------------------------------------------------------------------------+
| binlog | 1.0 | ACTIVE | STORAGE ENGINE | This is a pseudo storage engine to represent the binlog in a transaction |
| mysql_native_password | 1.0 | ACTIVE | AUTHENTICATION | Native MySQL authentication |
(truncated results for brevity)
```
Shows all installed plugins, their version and status.
### `records_rank`
```
EctoMySQLExtras.records_rank(MyApp.Repo, format: :ascii)
+-----------------------------------------------------------------------------------------+
| All tables and the number of rows in each table ordered by number of rows descending |
+-------------+------------------------------------------+-----------+--------------------+
| schema | name | engine | estimated_count |
+-------------+------------------------------------------+-----------+--------------------+
| sportsdb | affiliations_events | InnoDB | 13203 |
| sportsdb | participants_events | InnoDB | 8533 |
(truncated results for brevity)
```
Shows an estimated count of rows per table, descending by estimated count. Additionally a table can be passed to only get an estimated count from that table.
```
EctoMySQLExtras.records_rank(MyApp.Repo, format: :ascii, args: [table: "my_table"])
```
### `table_cache`
```
EctoMySQLExtras.table_cache(MyApp.Repo, format: :ascii)
+----------------------------------------+
| Table cache ratio |
+--------------------+-------------------+
| cache_ratio | hit_ratio |
+--------------------+-------------------+
| 10.567458019687319 | 98.08219178082192 |
+--------------------+-------------------+
```
- `cache_ratio`: The ratio of table cache usage for all threads.
A good value should be less than 80%. Increase the table_open_cache variable until the percentage reaches a good value.
- `hit_ratio`: The ratio of table cache hit usage.
A good hit ratio value should be 90% and above. Otherwise, increase the table_open_cache variable until the hit ratio reaches a good value
### `table_indexes_size`
```
EctoMySQLExtras.table_indexes_size(MyApp.Repo, format: :ascii)
+------------------------------------------------------------------------------------------------+
| Total size of all the indexes on each table (excluding PRIMARY indexes), descending by size |
+----------------+---------------------------------------------+--------------+------------------+
| schema | name | engine | index_size |
+----------------+---------------------------------------------+--------------+------------------+
| sportsdb | stats | InnoDB | 3.3 MB |
| sportsdb | participants_events | InnoDB | 880.0 KB |
(truncated results for brevity)
```
Shows the total size of all indexes in a table, descending by size. Primary indexes are not included. This also requires InnoDB as engine. Additionally a table can be passed to only get the total size of all indexes from that table.
```
EctoMySQLExtras.table_indexes_size(MyApp.Repo, format: :ascii, args: [table: "my_table"])
```
### `table_size`
```
EctoMySQLExtras.table_size(MyApp.Repo, format: :ascii)
+----------------------------------------------------------------------+
| Size of the tables (excluding indexes), descending by size |
+----------+---------------------------------------+--------+----------+
| schema | name | engine | size |
+----------+---------------------------------------+--------+----------+
| sportsdb | stats | InnoDB | 1.5 MB |
| sportsdb | participants_events | InnoDB | 496.0 KB |
(truncated results for brevity)
```
Shows the table size of each table in the database excluding indexes, descending by size. Additionally a table can be passed to only get the size from that table.
```
EctoMySQLExtras.table_size(MyApp.Repo, format: :ascii, args: [table: "my_table"])
```
### `total_index_size`
```
EctoMySQLExtras.total_index_size(MyApp.Repo, format: :ascii)
+-------------------------------------------------------------+
| Total size of all indexes (excluding PRIMARY indexes) in MB |
+-------------------------------------------------------------+
| size |
+-------------------------------------------------------------+
| 9.8 MB |
+-------------------------------------------------------------+
```
Shows the total index size of all tables in the database, primary indexes are not included.
### `total_table_size`
```
EctoMySQLExtras.total_table_size(MyApp.Repo, format: :ascii)
+----------------------------------------------------------------------+
| Size of the tables (including indexes), descending by size |
+----------+---------------------------------------+--------+----------+
| schema | name | engine | size |
+----------+---------------------------------------+--------+----------+
| sportsdb | stats | InnoDB | 4.8 MB |
| sportsdb | participants_events | InnoDB | 1.3 MB |
(truncated results for brevity)
```
Shows the total table size of each table in the database including indexes, descending by size. Additionally a table can be passed to only get the total size from that table.
```
EctoMySQLExtras.total_table_size(MyApp.Repo, format: :ascii, args: [table: "my_table"])
```
### `unused_indexes`
```
EctoMySQLExtras.unused_indexes(MyApp.Repo, format: :ascii)
+-----------------------------------------------------------------------------------------------------------------+
| Unused and almost unused indexes |
+----------+--------------------------+-------------------------------------------+-------+----------+------------+
| schema | table | index | pages | size | index_hits |
+----------+--------------------------+-------------------------------------------+-------+----------+------------+
| sportsdb | stats | IDX_stats_1 | 97 | 1.5 MB | 0 |
| sportsdb | events | IDX_FK_eve_pub_id__pub_id | 6 | 96.0 KB | 0 |
(truncated results for brevity)
```
Shows all the indexes that are not used, the database should be running for a while to have the best results since it's based upon IO activity. This also requires InnoDB as engine.
### `waits_for_checkpoint`
```
EctoMySQLExtras.waits_for_checkpoint(MyApp.Repo, format: :ascii)
+--------------------------------------------------------------------------------------------------+
| The ratio of how often InnoDB needs to read or create a page where no clean pages are available |
+---------------------------------------------+----------------------------------------------------+
| ratio | wait_counter |
+---------------------------------------------+----------------------------------------------------+
| 0.0 | "0" |
+---------------------------------------------+----------------------------------------------------+
```
Shows the ratio of how often InnoDB needs to read or create a page where no clean pages are available.
A good ratio value should stay below 1. If `wait_counter` is greater than 0, it is a strong indicator that the InnoDB buffer pool is too small,
and operations had to wait on a checkpoint.
### `waits_for_redolog`
```
EctoMySQLExtras.waits_for_redolog(MyApp.Repo, format: :ascii)
+----------------------------------+
| The ratio of redo log contention |
+-------------+--------------------+
| ratio | wait_counter |
+-------------+--------------------+
| 0.0 | "0" |
+-------------+--------------------+
```
Shows the ratio of redo log contention. A good ratio value should stay below 1.
Check `wait_counter` and if it continues to increase then it is a strong indicator that the InnoDB buffer pool is too small.
It can also mean that the disks are too slow and cannot sustain the disk IO, perhaps due to peak write load.
## Note
Some queries use the `information_schema` table which can cause performance issues when executing on a busy system. Everywhere where possible the `performance_schema` is used instead, but depending on the version and database this might not be available.
## Ecto MySQL Extras differences
Except for the "obvious" difference that `Ecto MySQL Extras` provides information on MySQL (MariaDB) databases and `Ecto PSQL Extras` on PostgreSQL databases, there are some small differences. Below is a list which could be useful if you're already using `Ecto PSQL Extras` and want to try `Ecto MySQL Extras`.
* `:table_rex` is an optional dependency.
* The default format is `:raw` instead of `:ascii`.
## Query sources
- https://severalnines.com/database-blog/monitoring-percona-server-mysql-key-metrics
## Copyright and License
Copyright (c) 2021 Timothy Vanderaerden
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at [https://www.apache.org/licenses/LICENSE-2.0](https://www.apache.org/licenses/LICENSE-2.0).
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
