Awesome
pg-extras-rs 
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
cargo install pg-extras
Usage
Package expects the $PG_EXTRAS_DATABASE_URL or $DATABASE_URL env in the following format:
export DATABASE_URL="postgresql://postgres:secret@localhost:5432/database_name"
You can use pgextras shell command:
$ pgextras cache_hit
+----------------+------------------------+
| /* Index and table hit rate */ |
+================+========================+
| name | ratio |
+----------------+------------------------+
| index hit rate | 0.99138647287107053837 |
+----------------+------------------------+
| table hit rate | 0.99984856854492081787 |
+----------------+------------------------+
Diagnose Report
The simplest way to start using pg-extras is to execute a diagnose method. It runs a set of checks and prints out a report highlighting areas that may require additional investigation:
pgextras diagnose
Web UI
Alternatively, you can use the application via the web UI. You have to enable the web feature flag:
cargo install pg-extras --features="web"
Now you can run:
pgextras web
To launch the dashboard on http://localhost:3000 (you can customize the port by setting the PORT ENV).
Keep reading to learn about methods that diagnose uses under the hood.
Rust API
You can also run queries using a Rust API to display an ASCCI table with results:
use pg_extras::{cache_hit, pg_pool, render_table}
let pool = pg_pool().await?;
render_table(cache_hit(None, &pool).await?);
+----------------+------------------------+
| Index and table hit rate |
+----------------+------------------------+
| name | ratio |
+----------------+------------------------+
| index hit rate | 0.97796610169491525424 |
| table hit rate | 0.96724294813466787989 |
+----------------+------------------------+
Alternatively you can work directly with returned structs:
use pg_extras::{cache_hit, pg_pool, render_table}
let pool = pg_pool().await?;
let cache_hit_res = cache_hit(None, &pool).await?;
println!("{:?}", cache_hit_res);
// [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(Some("other_schema".to_string), &pool).await?;
You can also customize the default public schema by setting ENV['PG_EXTRAS_SCHEMA'] value.
Dependencies
calls and outliers queries require pg_stat_statements extension.
You can check if it is enabled in your database by running:
pgextras extensions
You should see the similar line in the output:
| pg_stat_statements | 1.7 | 1.7 | track execution statistics of all SQL statements executed |
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;
Available methods
cache_hit
struct CacheHit {
name: String,
ratio: Decimal,
}
cache_hit(schema: Option<String>, pool: &Pool<Postgres>) -> Result<Vec<CacheHit>, PgExtrasError>
name | ratio
----------------+------------------------
index hit rate | 0.99957765013541945832
table hit rate | 1.00
(2 rows)
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
struct IndexCacheHit {
name: String,
buffer_hits: i64,
block_reads: i64,
total_read: i64,
ratio: String,
}
index_cache_hit(schema: Option<String>, pool: &Pool<Postgres>) -> Result<Vec<IndexCacheHit>, PgExtrasError>
| 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 |
(truncated results for brevity)
The same as cache_hit with each table's indexes cache hit info displayed separately.
table_cache_hit
struct TableCacheHit {
name: String,
buffer_hits: i64,
block_reads: i64,
total_read: i64,
ratio: String,
}
table_cache_hit(pool: &Pool<Postgres>) -> Result<Vec<TableCacheHit>, PgExtrasError>
| 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 |
(truncated results for brevity)
The same as cache_hit with each table's cache hit info displayed seperately.
db_settings
struct DbSettings {
name: String,
setting: String,
unit: String,
short_desc: String,
}
db_settings(pool: &Pool<Postgres>) -> Result<Vec<DbSettings>, PgExtrasError>
name | setting | unit |
------------------------------+---------+------+
checkpoint_completion_target | 0.7 | |
default_statistics_target | 100 | |
effective_cache_size | 1350000 | 8kB |
effective_io_concurrency | 1 | |
(truncated results for brevity)
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
struct SslUsed {
ssl_used: bool,
}
ssl_used(pool: &Pool<Postgres>) -> Result<Vec<SslUsed>, PgExtrasError>
| 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
struct IndexUsage {
relname: String,
percent_of_times_index_used: String,
rows_in_table: i64,
}
index_usage(schema: Option<String>, pool: &Pool<Postgres>) -> Result<Vec<IndexUsage>, PgExtrasError>
relname | 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
(5 rows)
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
struct Locks {
pid: i32,
relname: String,
transactionid: String,
granted: bool,
mode: String,
query_snippet: String,
age: String,
application: String,
}
locks(pool: &Pool<Postgres>) -> Result<Vec<Locks>, PgExtrasError>
procpid | 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; | ExclusiveLock | 00:19:17.94259 | bin/rails
3443 | | | t | +| ExclusiveLock | 00:00:00 | bin/sidekiq
| | | | select +| | |
| | | | pg_stat_activi | | |
(4 rows)
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
struct AllLocks {
pid: String,
relname: String,
transactionid: String,
granted: String,
mode: String,
query_snippet: String,
age: String,
application: String,
}
all_locks(pool: &Pool<Postgres>) -> Result<Vec<AllLocks>, PgExtrasError>
This command displays all the current locks, regardless of their type.
outliers
struct Outliers {
total_exec_time: PgInterval,
prop_exec_time: String,
ncalls: String,
sync_io_time: PgInterval,
query: String,
}
outliers(pool: &Pool<Postgres>) -> Result<Vec<Outliers>, PgExtrasError>
query | 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 (.. | 50:38:33.198418 | 23.6% | 13 | 13:34:21.00108
COPY public.usage_events (id, reporte.. | 02:32:16.335233 | 1.2% | 13 | 00:34:19.784318
INSERT INTO usage_events (id, retaine.. | 01:42:59.436532 | 0.8% | 12,328,187 | 00:00:00
SELECT * FROM usage_events WHERE (alp.. | 01:18:10.754354 | 0.6% | 102,114,301 | 00:00:00
UPDATE usage_events SET reporter_id =.. | 00:52:35.683254 | 0.4% | 23,786,348 | 00:00:00
INSERT INTO usage_events (id, retaine.. | 00:49:24.952561 | 0.4% | 21,988,201 | 00:00:00
(truncated results for brevity)
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
struct Calls {
qry: String,
exec_time: PgInterval,
prop_exec_time: String,
ncalls: String,
sync_io_time: PgInterval,
}
calls(limit: Option<String>, pool: &Pool<Postgres>) -> Result<Vec<Calls>, PgExtrasError>
qry | exec_time | prop_exec_time | ncalls | sync_io_time
-----------------------------------------+------------------+----------------+-------------+--------------
SELECT * FROM usage_events WHERE (alp.. | 01:18:11.073333 | 0.6% | 102,120,780 | 00:00:00
BEGIN | 00:00:51.285988 | 0.0% | 47,288,662 | 00:00:00
COMMIT | 00:00:52.31724 | 0.0% | 47,288,615 | 00:00:00
SELECT * FROM archivable_usage_event.. | 154:39:26.431466 | 72.2% | 34,211,877 | 00:00:00
UPDATE usage_events SET reporter_id =.. | 00:52:35.986167 | 0.4% | 23,788,388 | 00:00:00
INSERT INTO usage_events (id, retaine.. | 00:49:25.260245 | 0.4% | 21,990,326 | 00:00:00
INSERT INTO usage_events (id, retaine.. | 01:42:59.436532 | 0.8% | 12,328,187 | 00:00:00
(truncated results for brevity)
This command is much like pg:outliers, but ordered by the number of times a statement has been called.
blocking
struct Blocking {
blocked_pid: i32,
blocking_statement: String,
blocking_duration: PgInterval,
blocking_pid: i32,
blocked_statement: String,
blocked_duration: PgInterval,
blocked_sql_app: String,
blocking_sql_app: String,
}
blocking(limit: Option<String>, pool: &Pool<Postgres>) -> Result<Vec<Blocking>, PgExtrasError>
blocked_pid | 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
(1 row)
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
struct TotalIndexSize {
size: String,
}
total_index_size(pool: &Pool<Postgres>) -> Result<Vec<TotalIndexSize>, PgExtrasError>
size
-------
28194 MB
(1 row)
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
struct IndexSize {
name: String,
size: String,
schema: String,
}
index_size(pool: &Pool<Postgres>) -> Result<Vec<IndexSize>, PgExtrasError>
name | 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 |
(truncated results for brevity)
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
struct TableSize {
name: String,
size: String,
schema: String,
}
table_size(pool: &Pool<Postgres>) -> Result<Vec<TableSize>, PgExtrasError>
name | 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 |
(truncated results for brevity)
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: String,
index_size: String,
}
table_indexes_size(schema: Option<String>, pool: &Pool<Postgres>) -> Result<Vec<TableIndexesSize>, PgExtrasError>
table | indexes_size
---------------------------------------------------------------+--------------
learning_coaches | 153 MB
states | 125 MB
charities_customers | 93 MB
charities | 16 MB
grade_levels | 11 MB
(truncated results for brevity)
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
struct TotalTableSize {
name: String,
size: String,
}
total_table_size(pool: &Pool<Postgres>) -> Result<Vec<TotalTableSize>, PgExtrasError>
name | size
---------------------------------------------------------------+---------
learning_coaches | 349 MB
states | 270 MB
charities_customers | 166 MB
grade_levels | 122 MB
charities | 82 MB
(truncated results for brevity)
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
struct UnusedIndexes {
table: String,
index: String,
index_size: String,
index_scans: i64,
}
unused_indexes(schema: Option<String>, pool: &Pool<Postgres>) -> Result<Vec<UnusedIndexes>, PgExtrasError>
table | 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
(3 rows)
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
struct DuplicateIndexes {
size: String,
idx1: String,
idx2: String,
idx3: String,
idx4: String,
}
duplicate_indexes(pool: &Pool<Postgres>) -> Result<Vec<DuplicateIndexes>, PgExtrasError>
| 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
struct NullIndexes {
oid: String,
index: String,
index_size: String,
unique: bool,
indexed_column: String,
table: String,
null_frac: String,
expected_saving: String,
schema: String,
}
null_indexes(min_relation_size_mb: Option<String>, pool: &Pool<Postgres>) -> Result<Vec<NullIndexes>, PgExtrasError>
oid | 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
struct SeqScans {
name: String,
count: i64,
}
seq_scans(schema: Option<String>, pool: &Pool<Postgres>) -> Result<Vec<SeqScans>, PgExtrasError>
name | count
-----------------------------------+----------
learning_coaches | 44820063
states | 36794975
grade_levels | 13972293
charities_customers | 8615277
charities | 4316276
messages | 3922247
contests_customers | 2915972
classroom_goals | 2142014
(truncated results for brevity)
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
struct LongRunningQueries {
pid: String,
duration: String,
query: String,
}
long_running_queries(pool: &Pool<Postgres>) -> Result<Vec<LongRunningQueries>, PgExtrasError>
pid | 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
(truncated results for brevity)
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
struct RecordsRank {
name: String,
esiimated_count: i64,
}
records_rank(schema: Option<String>, pool: &Pool<Postgres>) -> Result<Vec<RecordsRank>, PgExtrasError>
name | estimated_count
-----------------------------------+-----------------
tastypie_apiaccess | 568891
notifications_event | 381227
core_todo | 178614
core_comment | 123969
notifications_notification | 102101
django_session | 68078
(truncated results for brevity)
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
struct Bloat {
typefield: String,
schemaname: String,
object_name: String,
bloat: Decimal,
waste: String,
}
bloat(pool: &Pool<Postgres>) -> Result<Vec<Bloat>, PgExtrasError>
type | 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_table::bloated_index | 3.7 | 34 MB
table | public | clean_table | 0.2 | 3808 kB
table | public | other_clean_table | 0.3 | 1576 kB
(truncated results for brevity)
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
struct VacuumStats {
schema: String,
table: String,
last_vacuum: String,
last_autovacuum: String,
rowcount: String,
dead_rowcount: String,
autovacuum_threshold: String,
expect_autovacuum: String,
}
vacuum_stats(pool: &Pool<Postgres>) -> Result<Vec<VacuumStats>, PgExtrasError>
schema | 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 |
(truncated results for brevity)
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
struct BuffercacheStats {
relname: String,
buffered: String,
buffer_percent: Decimal,
percent_of_relation: Decimal,
}
buffercache_stats(pool: &Pool<Postgres>) -> Result<Vec<BuffercacheStats>, PgExtrasError>
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
struct BuffercacheUsage {
relname: String,
buffers: i64,
}
buffercache_usage(pool: &Pool<Postgres>) -> Result<Vec<BuffercacheUsage>, PgExtrasError>
This command calculates how many blocks from which table are currently cached.
extensions
struct Extensions {
name: String,
default_version: String,
installed_version: String,
comment: String,
}
extensions(pool: &Pool<Postgres>) -> Result<Vec<Extensions>, PgExtrasError>
This command lists all the currently installed and available PostgreSQL extensions.
connections
struct Connections {
username: String,
pid: i32,
client_addr: String,
}
connections(pool: &Pool<Postgres>) -> Result<Vec<Connections>, PgExtrasError>
+----------------------------------------------------------------+
| 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
struct Mandelbrot {
array_to_string: String,
}
mandelbrot(pool: &Pool<Postgres>) -> Result<Vec<Mandelbrot>, PgExtrasError>
This command outputs the Mandelbrot set, calculated through SQL.
Testing
cp docker-compose.yml.sample docker-compose.yml
docker compose up -d
cargo test -- --nocapture