# 54.1. Overview

[Table 54.1](https://www.postgresql.org/docs/current/views-overview.html#VIEW-TABLE) lists the system views. More detailed documentation of each catalog follows below. Except where noted, all the views described here are read-only.

#### **Table 54.1. System Views**

| View Name                                                                                                              | Purpose                                                               |
| ---------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------- |
| [`pg_available_extensions`](https://www.postgresql.org/docs/current/view-pg-available-extensions.html)                 | available extensions                                                  |
| [`pg_available_extension_versions`](https://www.postgresql.org/docs/current/view-pg-available-extension-versions.html) | available versions of extensions                                      |
| [`pg_backend_memory_contexts`](https://www.postgresql.org/docs/current/view-pg-backend-memory-contexts.html)           | backend memory contexts                                               |
| [`pg_config`](https://www.postgresql.org/docs/current/view-pg-config.html)                                             | compile-time configuration parameters                                 |
| [`pg_cursors`](https://www.postgresql.org/docs/current/view-pg-cursors.html)                                           | open cursors                                                          |
| [`pg_file_settings`](https://www.postgresql.org/docs/current/view-pg-file-settings.html)                               | summary of configuration file contents                                |
| [`pg_group`](https://www.postgresql.org/docs/current/view-pg-group.html)                                               | groups of database users                                              |
| [`pg_hba_file_rules`](https://www.postgresql.org/docs/current/view-pg-hba-file-rules.html)                             | summary of client authentication configuration file contents          |
| [`pg_ident_file_mappings`](https://www.postgresql.org/docs/current/view-pg-ident-file-mappings.html)                   | summary of client user name mapping configuration file contents       |
| [`pg_indexes`](https://www.postgresql.org/docs/current/view-pg-indexes.html)                                           | indexes                                                               |
| [`pg_locks`](https://www.postgresql.org/docs/current/view-pg-locks.html)                                               | locks currently held or awaited                                       |
| [`pg_matviews`](https://www.postgresql.org/docs/current/view-pg-matviews.html)                                         | materialized views                                                    |
| [`pg_policies`](https://www.postgresql.org/docs/current/view-pg-policies.html)                                         | policies                                                              |
| [`pg_prepared_statements`](https://www.postgresql.org/docs/current/view-pg-prepared-statements.html)                   | prepared statements                                                   |
| [`pg_prepared_xacts`](https://www.postgresql.org/docs/current/view-pg-prepared-xacts.html)                             | prepared transactions                                                 |
| [`pg_publication_tables`](https://www.postgresql.org/docs/current/view-pg-publication-tables.html)                     | publications and information of their associated tables               |
| [`pg_replication_origin_status`](https://www.postgresql.org/docs/current/view-pg-replication-origin-status.html)       | information about replication origins, including replication progress |
| [`pg_replication_slots`](https://www.postgresql.org/docs/current/view-pg-replication-slots.html)                       | replication slot information                                          |
| [`pg_roles`](https://www.postgresql.org/docs/current/view-pg-roles.html)                                               | database roles                                                        |
| [`pg_rules`](https://www.postgresql.org/docs/current/view-pg-rules.html)                                               | rules                                                                 |
| [`pg_seclabels`](https://www.postgresql.org/docs/current/view-pg-seclabels.html)                                       | security labels                                                       |
| [`pg_sequences`](https://www.postgresql.org/docs/current/view-pg-sequences.html)                                       | sequences                                                             |
| [`pg_settings`](https://www.postgresql.org/docs/current/view-pg-settings.html)                                         | parameter settings                                                    |
| [`pg_shadow`](https://www.postgresql.org/docs/current/view-pg-shadow.html)                                             | database users                                                        |
| [`pg_shmem_allocations`](https://www.postgresql.org/docs/current/view-pg-shmem-allocations.html)                       | shared memory allocations                                             |
| [`pg_stats`](https://www.postgresql.org/docs/current/view-pg-stats.html)                                               | planner statistics                                                    |
| [`pg_stats_ext`](https://www.postgresql.org/docs/current/view-pg-stats-ext.html)                                       | extended planner statistics                                           |
| [`pg_stats_ext_exprs`](https://www.postgresql.org/docs/current/view-pg-stats-ext-exprs.html)                           | extended planner statistics for expressions                           |
| [`pg_tables`](https://www.postgresql.org/docs/current/view-pg-tables.html)                                             | tables                                                                |
| [`pg_timezone_abbrevs`](https://www.postgresql.org/docs/current/view-pg-timezone-abbrevs.html)                         | time zone abbreviations                                               |
| [`pg_timezone_names`](https://www.postgresql.org/docs/current/view-pg-timezone-names.html)                             | time zone names                                                       |
| [`pg_user`](https://www.postgresql.org/docs/current/view-pg-user.html)                                                 | database users                                                        |
| [`pg_user_mappings`](https://www.postgresql.org/docs/current/view-pg-user-mappings.html)                               | user mappings                                                         |
| [`pg_views`](https://www.postgresql.org/docs/current/view-pg-views.html)                                               | views                                                                 |


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.postgresql.tw/15/internals/54.-system-views/overview.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.