PostgreSQL is a program that belongs to the class of database management systems.
| Process Name | Role Description |
|---|---|
Postmaster (postgres) |
Main PostgreSQL server process, coordinating other processes, handling client connections. |
Checkpointer (postgres: checkpointer) |
Writes dirty pages from shared buffer pool to disk periodically to minimize crash recovery work. |
Background Writer (postgres: background writer) |
Writes dirty pages from shared buffer pool to disk in the background to free buffer space. |
WAL Writer (postgres: walwriter) |
Writes WAL (Write-Ahead Logging) data from WAL buffers to disk to ensure transaction durability. |
Autovacuum Launcher (postgres: autovacuum launcher) |
Manages the autovacuum process, cleaning up dead tuples to reclaim storage and maintain performance. |
Stats Collector (postgres: stats collector) |
Collects and maintains statistical data for query planning and performance tuning. |
Logical Replication Launcher (postgres: logical replication launcher) |
Manages logical replication, streaming changes from one database to another in real-time. |
| Name | Description |
|---|---|
base |
Directory containing subdirectories for each database in the cluster, each containing the actual table data. |
global |
Directory containing cluster-wide tables such as user and database tables. |
pg_commit_ts |
Directory storing commit timestamp data for transactions. |
pg_dynshmem |
Directory used for dynamic shared memory management. |
pg_hba.conf |
Configuration file for client authentication (Host-Based Authentication). |
pg_ident.conf |
Configuration file for user name mapping. |
pg_logical |
Directory containing logical replication information. |
pg_multixact |
Directory storing multi-transaction status data. |
pg_notify |
Directory used for storing NOTIFY/LISTEN information. |
pg_replslot |
Directory containing replication slot data for streaming replication. |
pg_serial |
Directory storing information about serialized transactions. |
pg_snapshots |
Directory containing exported snapshot information. |
pg_stat |
Directory containing statistics data. |
pg_stat_tmp |
Directory for temporary statistics data. |
pg_subtrans |
Directory storing subtransaction status data. |
pg_tblspc |
Directory containing symbolic links to tablespaces. |
pg_twophase |
Directory storing data for two-phase commits. |
pg_wal |
Directory containing Write-Ahead Log (WAL) files. |
pg_xact |
Directory storing transaction status data. |
PG_VERSION |
File containing the PostgreSQL version of the database cluster. |
postgresql.auto.conf |
Configuration file for settings applied with ALTER SYSTEM command. |
postgresql.conf |
Main configuration file for PostgreSQL server settings. |
postmaster.opts |
File containing the command-line options passed to the postmaster process. |
postmaster.pid |
File containing the process ID (PID) of the running postmaster process. |
Schema are namespace that store all objects of a database.
public is the default schema for user objects unless other settings are specified.
pg_catalog is used for system catalog tables.
information_schema providesanalternativeviewforthesystemcatalogasdefined by the standard.
pg_toast is used for objects related to.
pg_temp comprises temporary tables. Although different users create temporary tables in different schemas called pg_temp_N, everyone refers to their objects using the pg_temp alias.
<aside> <img src="/icons/fireworks_blue.svg" alt="/icons/fireworks_blue.svg" width="40px" /> Each schema is confined to a particular database, and all database objects belong to this or that schema.
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A tablespace is a storage location where the data files containing database objects (such as tables and indexes) are stored. Tablespaces allow database administrators to control the physical storage of data by assigning different parts of a database to different storage locations.