## 2. Difference between Postgres Pro Enterprise and PostgreSQL

Postgres Pro provides the most actual PostgreSQL version with some additional patches applied and extensions added. It includes new features developed by Postgres Professional, as well as third-party patches already accepted by the PostgreSQL community for the upcoming PostgreSQL versions. Postgres Pro Enterprise users thus have early access to important features and fixes.

Postgres Pro Enterprise provides the following enhancements over PostgreSQL:

- 64-bit transaction IDs that are not subject to wraparound. (See Section 24.1.5.)
- Page-level compression. (See Chapter 33.)
- Support for autonomous transactions. (See Chapter 16.)
- K-nearest neighbors (k-NN) algorithm for B-tree, GiST, and SP-GiST index types. (See Section 11.13.)
- Reduced WAL size on `CREATE INDEX` operation for GiST, GIN, SP-GiST.
- Reduced B-tree index size, which is achieved by storing duplicate keys only once, with item pointers located in posting lists.
- Lazy placement of temporary tables on disk. Disk space for temporary tables is allocated only when they exceed the temp_buffers size and have to be spilled to disk. Since disk space for temporary tables is not reserved in advance anymore, it allows to significantly reduce disk usage when working with multiple small temporary tables.
- Resource prioritization experimental feature, which allows to allocate more resources to high-priority sessions. (See Section 18.4.6.)
- Automatic page repair via streaming replication from standby in case of data corruption. (See Section 26.2.5.3.)
- NUL byte replacement with the specified ASCII code while loading data using the `COPY FROM` command. (See nul_byte_replacement_on_import parameter description.)
- Fair lightweight lock scheduling after the specified number of shared locks is acquired. (See lwlock_shared_limit parameter description.)
- Controlling the amount of cache used by prepared statements. With plan_cache_lru_size configuration parameter enabled, query trees and generic plans of the least recently used statements are evicted from cache once the specified limit is reached.
- Improved prioritization of sequential and index scans. (See seq_scan_startup_cost_first_row parameter description.)
- Improved multi-host connection handling and failover by libpq. (See hostorder and failover_timeout parameter descriptions.)
- Timeout for idle sessions on the server side. (See idle_session_timeout parameter description.)
- Enabling libpq to forget the entered password, which allows to prevent reconnections when required by a security policy. (See reusepass parameter description.)
- Support for client/server connections using remote direct memory access (RDMA) technology. (See Section 18.11.)
- Support for timestamp output in pg_waldump.
- Support for relaxed synchronous replication restrictions, which allows the primary server to continue running while some of the standbys are temporarily unavailable. (See synchronous_standby_gap parameter description.)

- Experimental built-in connection pooler that can limit the number of backends when working with multiple clients, without imposing restrictions on using session configuration parameters, prepared statements, or temporary tables.

- The autoprepare mode that allows to implicitly prepare frequently used statements, thus eliminating the cost of their compilation and planning on each subsequent execution. (See Section 14.6.)

- Support for changing configuration of other sessions. For example, you can use this feature to switch on debug messages to trace sessions with unexpected behavior. (See Section 9.26.1.)

- Support for replacing a constraint index without dropping this constraint using the `ALTER CONSTRAINT ... USING INDEX` clause of the ALTER TABLE command.

- Periodic verification of client-server connection during query execution, which allows to detect broken connections earlier and free server resources upon disconnection. (See client_connection_check_interval parameter description.)
- An improved version of pgbench that handles transactions with serialization or deadlock errors, as well as supports compound commands.
- Improved deadlock detection mechanism that does not cause performance degradation.
- ICU collation support on all platforms to provide platform-independent sort for various locales. By default, the `icu` collation provider is used for all locales except `C` and `POSIX`. (See Section 23.2.2.)
- PTRACK implementation, which enables pg_probackup to track page changes on the fly when creating incremental backups.
- Enhanced support for command-line editing using `WinEditLine` in the Windows version of psql.

- `pg_recovery_settings` view that displays the current recovery settings stored in the `recovery.conf` file.

- Consistent reads on standby servers. (See WAITLSN.)

- Unified structure of binary installation packages across all Linux distributions, which facilitates migration between them and allows to install different PostgreSQL-based products side by side, without any conflicts. (See Chapter 17.)

Postgres Pro Enterprise also includes the following additional modules:

- aqo extension for adaptive query optimization.
- dump_stat module that allows to save and restore database statistics when dumping/restoring the database.
- fasttrun module that provides transaction-unsafe function to truncate temporary tables without growing `pg_class` size.
- fulleq module that provides additional equivalence operator for compatibility with Microsoft SQL Server.
- hunspell-dict module that provides dictionaries for several languages.
- in_memory module that enables you to store data in Postgres Pro shared memory.
- jsquery module that provides a specific language for effective index-supported querying of JSONB data.
- mamonsu monitoring service, which is implemented as a Zabbix agent.
- mchar module that provides additional data type for compatibility with Microsoft SQL Server.
- multimaster extension that turns Postgres Pro Enterprise into a synchronous shared-nothing cluster to provide Online Transaction Processing (OLTP) scalability for read transactions and high availability with automatic disaster recovery.
- online_analyze module that provides a set of changes to immediately update statistics after `INSERT`, `UPDATE`, `DELETE` or `SELECT INTO` operations applied for affected tables.
- pgbouncer connection pooler.
- pg_hint_plan module that controls the execution plan by providing hints to the planner.
- pg_pathman module that provides optimized partitioning mechanism and functions to manage partitions, as well as declarative syntax.
- pg_probackup, a backup and recovery manager.
- pgpro_scheduler module that provides background workers for task scheduling.
- pg_query_state module that enables you to get the current state of query execution for a backend.
- pg_repack utility for reorganizing tables.
- pg_transfer module that provides support for relocatable tables.
- pg_variables module that provides functions for working with variables of various types.
- pg_tsparser module, which is an alternative text search parser.
- pg_shardman experimental module that enables sharding, aiming for scalability and fault tolerance with transaction support. It provides best results for OLTP workloads.
- pg_wait_sampling extension for sampling-based statistics of wait events. With this extension, you can get an insight into the server activity, including the current wait events for all processes and background workers.
- rum module that provides RUM index based on GIN.
- plantuner module that provides hints for the planner to disable or enable indexes for query execution.
- shared_ispell module that enables storing dictionaries in shared memory.
- sr_plan module that allows to save and restore query plans.
- vops experimental module that provides a vertical data model for Postgres Pro Enterprise. It can speed up OLAP queries with filtering and aggregation by times.

Postgres Pro Enterprise releases follow PostgreSQL releases, though sometimes occur more frequently. The Postgres Pro Enterprise versioning scheme is based on the PostgreSQL one and has an additional decimal place.