A separate server process is spawned for each client connection to the database.

A separate server process is started for each database within the database cluster.

Several processes are running, including the WAL writer, autovacuum launcher, and statistics collector; all are created from the same "postgres" executable.

When no clients are connected, typically only the "postmaster" process is running.

A single "postmaster" process is running for each database cluster.

The "global" directory contains tables that are shared across the entire database cluster.

The "pg_tblspc" directory contains tables managed by tablespaces.

The "pg_xact" directory contains data related to transaction commit statuses.

The "pg_wal" directory contains WAL files.

The "pg_stat_tmp" directory contains temporary files used by the statistics collector to exchange information with backend processes.

If sorted data is loaded in ascending order, the optimal query plan is created without running ANALYZE.

The autovacuum daemon may perform ANALYZE operations.

Increasing the value of default_statistics_target will reduce the time required for ANALYZE, but may degrade the quality of the planner's estimates.

A SHARE UPDATE EXCLUSIVE lock is acquired on the target table.

The PostgreSQL ANALYZE statement is compliant with the SQL standard.

 If the user executing VACUUM does not have the necessary privileges to perform VACUUM on the target table, an error will occur.

VACUUM operations performed within a transaction block can be rolled back using ROLLBACK. 

A standard VACUUM, even without specifying any options, might return unused space to the operating system.

VACUUM ANALYZE should be executed after a significant number of rows have been added or deleted.

Online backups will no longer be available.

Unused space cannot be recovered by VACUUM.

Connection to the database will be disabled.

New transaction cannot be started.

A table is locked for a long time, and DDL operations on the table cannot be completed.

Adding the FULL option reclaims unused space in the entire database.

Adding the VERBOSE option allows you to obtain detailed information about the VACUUM process.

Adding the AUTO option performs VACUUM using the autovacuum settings.

Adding the ANALYZE option also updates statistics.

You can specify multiple tables in a single VACUUM command.

You can obtain a base backup of a PostgreSQL database cluster running on a separate server.

The pg_start_backup command must be executed before the pg_basebackup command is executed.

In the case of fetch method, the max_wal_senders parameter should be set to at least 1.

WAL is included in the backup if the command is executed without explicitly specifying options.

If an additional tablespace is created, the data within the tablespace is not included in the backup.

The CLUSTER command physically reorganizes the table data and may improve read performance.

Reads on tables for which the CLUSTER command is running will be held back.

The CLUSTER command cannot be executed on a table for which a PRIMARY KEY does not exist.

Increasing the value of maintenance_work_mem may improve the performance of the CLUSTER command.

CLUSTER command may reduce table and index size.

 log_min_error_statement

log_rotation_age

log_directory

log_truncate_on_rotation

log_connections

VACUUM mytable;

VACUUM FULL mytable;

VACUUM VERBOSE mytable;

VACUUM FULL;

VACUUM -f mytable;

Encrypts data by specifying a symmetric key

Calculates a binary hash of the data

Performs password hashing

Computes the hashed MAC of the data

Creates a new random salt string to be used when hashing passwords