Metadata-Version: 2.1
Name: pg-extras
Version: 0.1.2
Summary: Python PostgreSQL database performance insights. Locks, index usage, buffer cache hit ratios, vacuum stats and more.
Home-page: https://github.com/pawurb/python-pg-extras
Author: Pawel Urbanek
Author-email: contact@pawelurbanek.com
License: UNKNOWN
Description: # Python PG Extras [![PyPI version](https://badge.fury.io/py/pg-extras.svg)](https://badge.fury.io/py/pg-extras)
        
        Ruby port of [Heroku PG Extras](https://github.com/heroku/heroku-pg-extras) with several additions and improvements. The goal of this project is to provide powerful insights into the PostgreSQL database for Python 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. Ruby 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](https://pawelurbanek.com/postgresql-fix-performance).
        
        Are you riding on Rails? Check out the [Rails version](https://github.com/pawurb/rails-pg-extras).
        
        JavaScript is your thing? There's [NodeJS version](https://github.com/pawurb/node-postgres-extras) available.
        
        Are you the fan of Elixir and Phoenix? Check out the [ecto_psql_extras](https://github.com/pawurb/ecto_psql_extras).
        
        ## Installation
        
        In `requirements.txt`
        
        ```ruby
        pg-extras
        ```
        
        Some of the queries (e.g., `calls` and `outliers`) require [pg_stat_statements](https://www.postgresql.org/docs/current/pgstatstatements.html) extension enabled.
        
        You can check if it is enabled in your database by running:
        
        ```ruby
        RubyPGExtras.extensions
        ```
        You should see the similar line in the output:
        
        ```bash
        | pg_stat_statements  | 1.7  | 1.7 | track execution statistics of all SQL statements executed |
        ```
        
        ## Usage
        
        Gem expects the `ENV['DATABASE_URL']` value in the following format:
        
        ```ruby
        ENV["DATABASE_URL"] = "postgresql://postgres:secret@localhost:5432/database_name"
        ```
        
        Alternatively you can set it using the module class method:
        
        ```ruby
        RubyPGExtras.database_url = "postgresql://postgres:secret@localhost:5432/database_name"
        ```
        
        You can run queries using a simple Ruby API:
        
        ```ruby
        RubyPGExtras.cache_hit
        ```
        ```bash
        +----------------+------------------------+
        |        Index and table hit rate         |
        +----------------+------------------------+
        | name           | ratio                  |
        +----------------+------------------------+
        | index hit rate | 0.97796610169491525424 |
        | table hit rate | 0.96724294813466787989 |
        +----------------+------------------------+
        ```
        
        By default the ASCII table is displayed, to change to format you need to specify the `in_format` parameter (`[:display_table, :hash, :array, :raw]` options are available):
        
        ```ruby
        RubyPGExtras.cache_hit(in_format: :hash) =>
        
         [{"name"=>"index hit rate", "ratio"=>"0.97796610169491525424"}, {"name"=>"table hit rate", "ratio"=>"0.96724294813466787989"}]
        
        RubyPGExtras.cache_hit(in_format: :array) =>
        
         [["index hit rate", "0.97796610169491525424"], ["table hit rate", "0.96724294813466787989"]]
        
        RubyPGExtras.cache_hit(in_format: :raw) =>
        
         #<PG::Result:0x00007f75777f7328 status=PGRES_TUPLES_OK ntuples=2 nfields=2 cmd_tuples=2>
        ```
        
        ## Available methods
        
        ### `cache_hit`
        
        ```ruby
        
        RubyPGExtras.cache_hit
        
              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`
        
        ```ruby
        
        RubyPGExtras.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 |
        (truncated results for brevity)
        ```
        
        The same as `cache_hit` with each table's indexes cache hit info displayed seperately.
        
        ### `table_cache_hit`
        
        ```ruby
        
        RubyPGExtras.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  |
        (truncated results for brevity)
        ```
        
        The same as `cache_hit` with each table's cache hit info displayed seperately.
        
        ### `index_usage`
        
        ```ruby
        
        RubyPGExtras.index_usage
        
               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`
        
        ```ruby
        
        RubyPGExtras.locks
        
         procpid | relname | transactionid | granted |     query_snippet     | mode             |       age
        ---------+---------+---------------+---------+-----------------------+-------------------------------------
           31776 |         |               | t       | <IDLE> in transaction | ExclusiveLock    |  00:19:29.837898
           31776 |         |          1294 | t       | <IDLE> in transaction | RowExclusiveLock |  00:19:29.837898
           31912 |         |               | t       | select * from hello;  | ExclusiveLock    |  00:19:17.94259
            3443 |         |               | t       |                      +| ExclusiveLock    |  00:00:00
                 |         |               |         |    select            +|                  |
                 |         |               |         |      pg_stat_activi   |                  |
        (4 rows)
        ```
        
        This command displays queries that have taken out an exlusive 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`
        
        ```ruby
        
        RubyPGExtras.all_locks
        
        ```
        
        This command displays all the current locks, regardless of their type.
        
        ### `outliers`
        
        ```ruby
        
        RubyPGExtras.outliers
        
                           qry                   |    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 filesystem).
        
        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`
        
        ```ruby
        
        RubyPGExtras.calls
        
                           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`
        
        ```ruby
        
        RubyPGExtras.blocking
        
         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`
        
        ```ruby
        
        RubyPGExtras.total_index_size
        
          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`
        
        ```ruby
        
        RubyPGExtras.index_size
        
                                     name                              |  size
        ---------------------------------------------------------------+---------
         idx_activity_attemptable_and_type_lesson_enrollment           | 5196 MB
         index_enrollment_attemptables_by_attempt_and_last_in_group    | 4045 MB
         index_attempts_on_student_id                                  | 2611 MB
         enrollment_activity_attemptables_pkey                         | 2513 MB
         index_attempts_on_student_id_final_attemptable_type           | 2466 MB
         attempts_pkey                                                 | 2466 MB
         index_attempts_on_response_id                                 | 2404 MB
         index_attempts_on_enrollment_id                               | 1957 MB
         index_enrollment_attemptables_by_enrollment_activity_id       | 1789 MB
         enrollment_activities_pkey                                    |  458 MB
        (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`
        
        ```ruby
        
        RubyPGExtras.table_size
        
                                     name                              |  size
        ---------------------------------------------------------------+---------
         learning_coaches                                              |  196 MB
         states                                                        |  145 MB
         grade_levels                                                  |  111 MB
         charities_customers                                           |   73 MB
         charities                                                     |   66 MB
        (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`
        
        ```ruby
        
        RubyPGExtras.table_indexes_size
        
                                     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 calcualtes by using the system administration function `pg_indexes_size()`.
        
        ### `total_table_size`
        
        ```ruby
        
        RubyPGExtras.total_table_size
        
                                     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`
        
        ```ruby
        
        RubyPGExtras.unused_indexes
        
                  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.
        
        ### `seq_scans`
        
        ```ruby
        
        RubyPGExtras.seq_scans
        
        
                       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 underindexed, and it may be worth investigating queries that read from these tables.
        
        ### `long_running_queries`
        
        ```ruby
        
        RubyPGExtras.long_running_queries
        
        
          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`
        
        ```ruby
        
        RubyPGExtras.records_rank
        
                       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`
        
        ```ruby
        
        RubyPGExtras.bloat
        
        
         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`
        
        ```ruby
        
        RubyPGExtras.vacuum_stats
        
         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 estiamtion 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.
        
        ### `kill_all`
        
        ```ruby
        
        RubyPGExtras.kill_all
        
        ```
        
        This commands kills all the currently active connections to the database. It can be useful as a last resort when your database is stuck in a deadlock.
        
        ### `extensions`
        
        ```ruby
        
        RubyPGExtras.extensions
        
        ```
        
        This command lists all the currently installed and available PostgreSQL extensions.
        
        ### `mandelbrot`
        
        ```ruby
        
        RubyPGExtras.mandelbrot
        
        ```
        
        This command outputs the Mandelbrot set, calculated through SQL.
        
        ## FAQ
        
        * Does is not violate the Heroku PG Extras license?
        
        The original plugin is MIT based so it means that copying and redistribution in any format is permitted.
        
Platform: UNKNOWN
Classifier: Programming Language :: Python :: 3
Classifier: License :: OSI Approved :: MIT License
Classifier: Operating System :: OS Independent
Classifier: Topic :: Software Development :: Libraries :: Python Modules
Classifier: Topic :: Database
Requires-Python: >=3.6
Description-Content-Type: text/markdown
