rust-pg-extras
Rust port of Heroku PG Extras with several additions and improvements. The goal of this project is to provide powerful insights into the PostgreSQL database for Rust apps that are not using the Heroku PostgreSQL plugin.
Queries can be used to obtain information about a Postgres instance, that may be useful when analyzing performance issues. This includes information about locks, index usage, buffer cache hit ratios and vacuum statistics. Rust API enables developers to easily integrate the tool into e.g. automatic monitoring tasks.
You can check out this blog post for detailed step by step tutorial on how to optimize PostgreSQL using PG Extras library.
Alternative versions:
Installation
In your Cargo.toml
pg-extras = "0.3"
calls
and outliers
queries require pg_stat_statements extension.
You can check if it is enabled in your database by running:
use
render_table;
You should see the similar line in the output:
| | | | |
ssl_used
requires sslinfo
extension, and buffercache_usage
/buffercache_usage
queries need pg_buffercache
. You can enable them all by running this SQL:
CREATE EXTENSION IF NOT EXISTS sslinfo;
CREATE EXTENSION IF NOT EXISTS pg_buffercache;
CREATE EXTENSION IF NOT EXISTS pg_stat_statements;
Usage
Package expects the ENV['PG_EXTRAS_DATABASE_URL']
or ENV['DATABASE_URL']
value in the following format:
ENV = "postgresql://postgres:secret@localhost:5432/database_name"
You can run queries using a Rust API to display an ASCCI table with results:
use
render_table;
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Alternatively you can work directly with returned structs:
use
let cache_hit_res: = cache_hit.await?;
println!;
// [CacheHit { name: "index hit rate", ratio: 0.9779... }, CacheHit { name: "table hit rate", ratio: 0.9672... }]
Some methods accept params allowing you to customize queries:
cache_hit.await?;
You can customize the default public
schema by setting ENV['PG_EXTRAS_SCHEMA']
value.
Command line
After running cargo install pg-extras
you can use pg_extras
shell command:
| |
+================+========================+
| | |
| | |
| | |
Available methods
cache_hit
cache_hit | ratio
----------------+------------------------
index hit rate | 0.99957765013541945832
table hit rate | 1.00
This command provides information on the efficiency of the buffer cache, for both index reads (index hit rate
) as well as table reads (table hit rate
). A low buffer cache hit ratio can be a sign that the Postgres instance is too small for the workload.
index_cache_hit
index_cache_hit | name | buffer_hits | block_reads | total_read | ratio |
+-----------------------+-------------+-------------+------------+-------------------+
| teams | 187665 | 109 | 187774 | 0.999419514948821 |
| subscriptions | 5160 | 6 | 5166 | 0.99883855981417 |
| plans | 5718 | 9 | 5727 | 0.998428496595076 |
The same as cache_hit
with each table's indexes cache hit info displayed separately.
table_cache_hit
table_cache_hit | name | buffer_hits | block_reads | total_read | ratio |
+-----------------------+-------------+-------------+------------+-------------------+
| plans | 32123 | 2 | 32125 | 0.999937743190662 |
| subscriptions | 95021 | 8 | 95029 | 0.999915815172211 |
| teams | 171637 | 200 | 171837 | 0.99883610631005 |
The same as cache_hit
with each table's cache hit info displayed seperately.
db_settings
db_settings | setting | unit |
------------------------------+---------+------+
checkpoint_completion_target | 0.7 | |
default_statistics_target | 100 | |
effective_cache_size | 1350000 | 8kB |
effective_io_concurrency | 1 | |
This method displays values for selected PostgreSQL settings. You can compare them with settings recommended by PGTune and tweak values to improve performance.
ssl_used
ssl_used | ssl_is_used |
+---------------------------------+
| t |
Returns boolean indicating if an encrypted SSL is currently used. Connecting to the database via an unencrypted connection is a critical security risk.
index_usage
index_usage | percent_of_times_index_used | rows_in_table
---------------------+-----------------------------+---------------
events | 65 | 1217347
app_infos | 74 | 314057
app_infos_user_info | 0 | 198848
user_info | 5 | 94545
delayed_jobs | 27 | 0
This command provides information on the efficiency of indexes, represented as what percentage of total scans were index scans. A low percentage can indicate under indexing, or wrong data being indexed.
locks
locks | relname | transactionid | granted | query_snippet | mode | age | application |
---------+---------+---------------+---------+-----------------------+------------------------------------------------------
31776 | | | t | <IDLE> in transaction | ExclusiveLock | 00:19:29.837898 | bin/rails
31776 | | 1294 | t | <IDLE> in transaction | RowExclusiveLock | 00:19:29.837898 | bin/rails
31912 | | | t | select * from hello;
3443 | | | t | +| ExclusiveLock | 00:00:00 | bin/sidekiq
| | | | select +| | |
| | | | pg_stat_activi | | |
This command displays queries that have taken out an exclusive lock on a relation. Exclusive locks typically prevent other operations on that relation from taking place, and can be a cause of "hung" queries that are waiting for a lock to be granted.
all_locks
all_locks
This command displays all the current locks, regardless of their type.
outliers
outliers | exec_time | prop_exec_time | ncalls | sync_io_time
-----------------------------------------+------------------+----------------+-------------+--------------
SELECT * FROM archivable_usage_events.. | 154:39:26.431466 | 72.2% | 34,211,877 | 00:00:00
COPY public.archivable_usage_events
This command displays statements, obtained from pg_stat_statements
, ordered by the amount of time to execute in aggregate. This includes the statement itself, the total execution time for that statement, the proportion of total execution time for all statements that statement has taken up, the number of times that statement has been called, and the amount of time that statement spent on synchronous I/O (reading/writing from the file system).
Typically, an efficient query will have an appropriate ratio of calls to total execution time, with as little time spent on I/O as possible. Queries that have a high total execution time but low call count should be investigated to improve their performance. Queries that have a high proportion of execution time being spent on synchronous I/O should also be investigated.
calls
calls | exec_time | prop_exec_time | ncalls | sync_io_time
-----------------------------------------+------------------+----------------+-------------+--------------
SELECT * FROM usage_events WHERE
This command is much like pg:outliers
, but ordered by the number of times a statement has been called.
blocking
blocking | blocking_statement | blocking_duration | blocking_pid | blocked_statement | blocked_duration
-------------+--------------------------+-------------------+--------------+------------------------------------------------------------------------------------+------------------
461 | select count from app | 00:00:03.838314 | 15682 | UPDATE "app" SET "updated_at" = '2013-03-04 15:07:04.746688' WHERE "id" = 12823149 | 00:00:03.821826
This command displays statements that are currently holding locks that other statements are waiting to be released. This can be used in conjunction with pg:locks
to determine which statements need to be terminated in order to resolve lock contention.
total_index_size
total_index_size -------
28194 MB
This command displays the total size of all indexes on the database, in MB. It is calculated by taking the number of pages (reported in relpages
) and multiplying it by the page size (8192 bytes).
index_size
index_size | size | schema |
---------------------------------------------------------------+-------------------
idx_activity_attemptable_and_type_lesson_enrollment | 5196 MB | public |
index_enrollment_attemptables_by_attempt_and_last_in_group | 4045 MB | public |
index_attempts_on_student_id | 2611 MB | custom |
enrollment_activity_attemptables_pkey | 2513 MB | custom |
index_attempts_on_student_id_final_attemptable_type | 2466 MB | custom |
attempts_pkey | 2466 MB | custom |
index_attempts_on_response_id | 2404 MB | public |
index_attempts_on_enrollment_id | 1957 MB | public |
index_enrollment_attemptables_by_enrollment_activity_id | 1789 MB | public |
enrollment_activities_pkey | 458 MB | public |
This command displays the size of each each index in the database, in MB. It is calculated by taking the number of pages (reported in relpages
) and multiplying it by the page size (8192 bytes).
table_size
table_size | size | schema |
---------------------------------------------------------------+-------------------
learning_coaches | 196 MB | public |
states | 145 MB | public |
grade_levels | 111 MB | custom |
charities_customers | 73 MB | public |
charities | 66 MB | public |
This command displays the size of each table and materialized view in the database, in MB. It is calculated by using the system administration function pg_table_size()
, which includes the size of the main data fork, free space map, visibility map and TOAST data.
table_indexes_size
TableIndexesSize table_indexes_size | indexes_size
---------------------------------------------------------------+--------------
learning_coaches | 153 MB
states | 125 MB
charities_customers | 93 MB
charities | 16 MB
grade_levels | 11 MB
This command displays the total size of indexes for each table and materialized view, in MB. It is calculated by using the system administration function pg_indexes_size()
.
total_table_size
total_table_size | size
---------------------------------------------------------------+---------
learning_coaches | 349 MB
states | 270 MB
charities_customers | 166 MB
grade_levels | 122 MB
charities | 82 MB
This command displays the total size of each table and materialized view in the database, in MB. It is calculated by using the system administration function pg_total_relation_size()
, which includes table size, total index size and TOAST data.
unused_indexes
unused_indexes | index | index_size | index_scans
---------------------+--------------------------------------------+------------+-------------
public.grade_levels | index_placement_attempts_on_grade_level_id | 97 MB | 0
public.observations | observations_attrs_grade_resources | 33 MB | 0
public.messages | user_resource_id_idx | 12 MB | 0
This command displays indexes that have < 50 scans recorded against them, and are greater than 5 pages in size, ordered by size relative to the number of index scans. This command is generally useful for eliminating indexes that are unused, which can impact write performance, as well as read performance should they occupy space in memory.
duplicate_indexes
duplicate_indexes | size | idx1 | idx2 | idx3 | idx4 |
+------------+--------------+----------------+----------+-----------+
| 128 k | users_pkey | index_users_id | | |
This command displays multiple indexes that have the same set of columns, same opclass, expression and predicate - which make them equivalent. Usually it's safe to drop one of them.
null_indexes
null_indexes | index | index_size | unique | indexed_column | null_frac | expected_saving
---------+--------------------+------------+--------+----------------+-----------+-----------------
183764 | users_reset_token | 1445 MB | t | reset_token | 97.00% | 1401 MB
88732 | plan_cancelled_at | 539 MB | f | cancelled_at | 8.30% | 44 MB
9827345 | users_email | 18 MB | t | email | 28.67% | 5160 kB
This command displays indexes that contain NULL
values. A high ratio of NULL
values means that using a partial index excluding them will be beneficial in case they are not used for searching.
seq_scans
seq_scans | count
-----------------------------------+----------
learning_coaches | 44820063
states | 36794975
grade_levels | 13972293
charities_customers | 8615277
charities | 4316276
messages | 3922247
contests_customers | 2915972
classroom_goals | 2142014
This command displays the number of sequential scans recorded against all tables, descending by count of sequential scans. Tables that have very high numbers of sequential scans may be under-indexed, and it may be worth investigating queries that read from these tables.
long_running_queries
long_running_queries | duration | query
-------+-----------------+---------------------------------------------------------------------------------------
19578 | 02:29:11.200129 | EXPLAIN SELECT "students".* FROM "students" WHERE "students"."id" = 1450645 LIMIT 1
19465 | 02:26:05.542653 | EXPLAIN SELECT "students".* FROM "students" WHERE "students"."id" = 1889881 LIMIT 1
19632 | 02:24:46.962818 | EXPLAIN SELECT "students".* FROM "students" WHERE "students"."id" = 1581884 LIMIT 1
This command displays currently running queries, that have been running for longer than 5 minutes, descending by duration. Very long running queries can be a source of multiple issues, such as preventing DDL statements completing or vacuum being unable to update relfrozenxid
.
records_rank
records_rank | estimated_count
-----------------------------------+-----------------
tastypie_apiaccess | 568891
notifications_event | 381227
core_todo | 178614
core_comment | 123969
notifications_notification | 102101
django_session | 68078
This command displays an estimated count of rows per table, descending by estimated count. The estimated count is derived from n_live_tup
, which is updated by vacuum operations. Due to the way n_live_tup
is populated, sparse vs. dense pages can result in estimations that are significantly out from the real count of rows.
bloat
bloat | schemaname | object_name | bloat | waste
-------+------------+-------------------------------+-------+----------
table | public | bloated_table | 1.1 | 98 MB
table | public | other_bloated_table | 1.1 | 58 MB
index | public | bloated_index | 3.7 | 34 MB
table | public | clean_table | 0.2 | 3808 kB
table | public | other_clean_table | 0.3 | 1576 kB
This command displays an estimation of table "bloat" – space allocated to a relation that is full of dead tuples, that has yet to be reclaimed. Tables that have a high bloat ratio, typically 10 or greater, should be investigated to see if vacuuming is aggressive enough, and can be a sign of high table churn.
vacuum_stats
vacuum_stats | table | last_vacuum | last_autovacuum | rowcount | dead_rowcount | autovacuum_threshold | expect_autovacuum
--------+-----------------------+-------------+------------------+----------------+----------------+----------------------+-------------------
public | log_table | | 2013-04-26 17:37 | 18,030 | 0 | 3,656 |
public | data_table | | 2013-04-26 13:09 | 79 | 28 | 66 |
public | other_table | | 2013-04-26 11:41 | 41 | 47 | 58 |
public | queue_table | | 2013-04-26 17:39 | 12 | 8,228 | 52 | yes
public | picnic_table | | | 13 | 0 | 53 |
This command displays statistics related to vacuum operations for each table, including an estimation of dead rows, last autovacuum and the current autovacuum threshold. This command can be useful when determining if current vacuum thresholds require adjustments, and to determine when the table was last vacuumed.
buffercache_stats
buffercache_stats
This command shows the relations buffered in database share buffer, ordered by percentage taken. It also shows that how much of the whole relation is buffered.
buffercache_usage
buffercache_usage
This command calculates how many blocks from which table are currently cached.
extensions
extensions
This command lists all the currently installed and available PostgreSQL extensions.
connections
connections +----------------------------------------------------------------+
| Returns the list of all active database connections |
+------------------+--------------------------+------------------+
| username | pid | client_address | application_name |
+------------------+--------------------------+------------------+
| postgres | 15962 | 172.31.69.166/32 | sidekiq |
| postgres | 16810 | 172.31.69.166/32 | bin/rails |
+------------------+--------------------------+------------------+
This command returns the list of all active database connections.
mandelbrot
mandelbrot
This command outputs the Mandelbrot set, calculated through SQL.
Testing