E.6. Release 15
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## E.6. Release 15

Release date: 2022-10-13

### E.6.1. Overview

PostgreSQL 15 contains many new features and enhancements, including:

- Support for the SQL `MERGE` command.

- Selective publication of tables' contents within logical replication publications, through the ability to specify column lists and row filter conditions.

- More options for compression, including support for Zstandard (zstd) compression. This includes support for performing compression on the server side during pg_basebackup.

- Support for structured server log output using the JSON format.

- Performance improvements, particularly for in-memory and on-disk sorting.

The above items and other new features of PostgreSQL 15 are explained in more detail in the sections below.

### E.6.2. Migration to Version 15

A dump/restore using pg_dumpall or use of pg_upgrade or logical replication is required for those wishing to migrate data from any previous release. See Section 19.6 for general information on migrating to new major releases.

Version 15 contains a number of changes that may affect compatibility with previous releases. Observe the following incompatibilities:

- Remove `PUBLIC` creation permission on the `public` schema (Noah Misch)

  The new default is one of the secure schema usage patterns that Section 5.9.6 has recommended since the security release for CVE-2018-1058. The change applies to new database clusters and to newly-created databases in existing clusters. Upgrading a cluster or restoring a database dump will preserve `public`'s existing permissions.

  For existing databases, especially those having multiple users, consider revoking `CREATE` permission on the `public` schema to adopt this new default. For new databases having no need to defend against insider threats, granting `CREATE` permission will yield the behavior of prior releases.

- Change the owner of the `public` schema to be the new `pg_database_owner` role (Noah Misch)

  This allows each database's owner to have ownership privileges on the `public` schema within their database. Previously it was owned by the bootstrap superuser, so that non-superuser database owners could not do anything with it.

  This change applies to new database clusters and to newly-created databases in existing clusters. Upgrading a cluster or restoring a database dump will preserve `public`'s existing ownership specification.

- Remove long-deprecated exclusive backup mode (David Steele, Nathan Bossart)

  If the database server stops abruptly while in this mode, the server could fail to start. The non-exclusive backup mode is considered superior for all purposes. Functions `pg_start_backup()`/`pg_stop_backup()` have been renamed to `pg_backup_start()`/`pg_backup_stop()`, and the functions `pg_backup_start_time()` and `pg_is_in_backup()` have been removed.

- Increase `hash_mem_multiplier` default to 2.0 (Peter Geoghegan)

  This allows query hash operations to use more `work_mem` memory than other operations.

- Remove server-side language `plpython2u` and generic Python language `plpythonu` (Andres Freund)

  Python 2.x is no longer supported. While the original intent of `plpythonu` was that it could eventually refer to `plpython3u`, changing it now seems more likely to cause problems than solve them, so it's just been removed.

- Generate an error if `array_to_tsvector()` is passed an empty-string array element (Jean-Christophe Arnu)

  This is prohibited because lexemes should never be empty. Users of previous Postgres releases should verify that no empty lexemes are stored because they can lead to dump/restore failures and inconsistent results.

- Generate an error when `chr()` is supplied with a negative argument (Peter Eisentraut)

- Prevent `CREATE OR REPLACE VIEW` from changing the collation of an output column (Tom Lane)

- Disallow zero-length Unicode identifiers, e.g., `U&""` (Peter Eisentraut)

  Non-Unicode zero-length identifiers were already disallowed.

- Prevent numeric literals from having non-numeric trailing characters (Peter Eisentraut)

  Previously, query text like `123abc` would be interpreted as `123` followed by a separate token `abc`.

- Adjust JSON numeric literal processing to match the SQL/JSON-standard (Peter Eisentraut)

  This accepts numeric formats like `.1` and `1.`, and disallows trailing junk after numeric literals, like `1.type()`.

- When `interval` input provides a fractional value for a unit greater than months, round to the nearest month (Bruce Momjian)

  For example, convert `1.99 years` to `2 years`, not `1 year 11 months` as before.

- Improve consistency of `interval` parsing with trailing periods (Tom Lane)

  Numbers with trailing periods were rejected on some platforms.

- Mark the `interval` output function as stable, not immutable, since it depends on `IntervalStyle` (Tom Lane)

  This will, for example, cause creation of indexes relying on the text output of `interval` values to fail.

- Detect integer overflow in interval justification functions (Joe Koshakow)

  The affected functions are `justify_interval()`, `justify_hours()`, and `justify_days()`.

- Change the I/O format of type `"char"` for non-ASCII characters (Tom Lane)

  Bytes with the high bit set are now output as a backslash and three octal digits, to avoid encoding issues.

- Remove the default `ADMIN OPTION` privilege a login role has on its own role membership (Robert Haas)

  Previously, a login role could add/remove members of its own role, even without `ADMIN OPTION` privilege.

- Allow logical replication to run as the owner of the subscription (Mark Dilger)

  Because row-level security policies are not checked, only superusers, roles with `bypassrls`, and table owners can replicate into tables with row-level security policies.

- Prevent `UPDATE` and `DELETE` logical replication operations on tables where the subscription owner does not have `SELECT` permission on the table (Jeff Davis)

  `UPDATE` and `DELETE` commands typically involve reading the table as well, so require the subscription owner to have table `SELECT` permission.

- When `EXPLAIN` references the session's temporary object schema, refer to it as `pg_temp` (Amul Sul)

  Previously the actual schema name was reported, leading to inconsistencies across sessions.

- Fix `pg_statio_all_tables` to sum values for the rare case of TOAST tables with multiple indexes (Andrei Zubkov)

  Previously such cases would show one row for each index.

- Disallow setting custom options that match the name of an installed extension, but are not one of the extension's declared variables (Florin Irion, Tom Lane)

  This change causes any such pre-existing variables to be deleted during extension load, and then prevents new ones from being created later in the session. The intent is to prevent confusion about whether a variable is associated with an extension or not.

- Remove obsolete server variable `stats_temp_directory` (Andres Freund, Kyotaro Horiguchi)

- Improve the algorithm used to compute `random()` (Fabien Coelho)

  This will cause `random()`'s results to differ from what was emitted by prior versions, even for the same seed value.

- libpq's `PQsendQuery()` function is no longer supported in pipeline mode (Álvaro Herrera)

  Applications that are using that combination will need to be modified to use `PQsendQueryParams()` instead.

- On non-Windows platforms, consult the `HOME` environment variable to find the user's home directory (Anders Kaseorg)

  If `HOME` is empty or unset, fall back to the previous method of checking the `<pwd.h>` database. This change affects libpq (for example, while looking up `~/.pgpass`) as well as various client application programs.

- Remove pg_dump's `--no-synchronized-snapshots` option (Tom Lane)

  All still-supported server versions support synchronized snapshots, so there's no longer a need for this option.

- After an error is detected in psql's `--single-transaction` mode, change the final `COMMIT` command to `ROLLBACK` only if `ON_ERROR_STOP` is set (Michael Paquier)

- Avoid unnecessary casting of constants in queries sent by postgres_fdw (Dian Fay)

  When column types are intentionally different between local and remote databases, such casts could cause errors.

- Remove xml2's `xml_is_well_formed()` function (Tom Lane)

  This function has been implemented in the core backend since Postgres 9.1.

- Allow custom scan providers to indicate if they support projections (Sven Klemm)

  The default is now that custom scan providers are assumed to not support projections; those that do will need to be updated for this release.

### E.6.3. Changes

Below you will find a detailed account of the changes between PostgreSQL 15 and the previous major release.

#### E.6.3.1. Server

- Record and check the collation version of each database (Peter Eisentraut)

  This feature is designed to detect collation version changes to avoid index corruption. Function `pg_database_collation_actual_version()` reports the underlying operating system collation version, and `ALTER DATABASE ... REFRESH` sets the recorded database collation version to match the operating system collation version.

- Allow ICU collations to be set as the default for clusters and databases (Peter Eisentraut)

  Previously, only libc-based collations could be selected at the cluster and database levels. ICU collations could only be used via explicit `COLLATE` clauses.

- Add system view `pg_ident_file_mappings` to report `pg_ident.conf` information (Julien Rouhaud)

##### E.6.3.1.1. Partitioning

- Improve planning time for queries referencing partitioned tables (David Rowley)

  This change helps when only a few of many partitions are relevant.

- Allow ordered scans of partitions to avoid sorting in more cases (David Rowley)

  Previously, a partitioned table with a `DEFAULT` partition or a `LIST` partition containing multiple values could not be used for ordered partition scans. Now they can be used if such partitions are pruned during planning.

- Improve foreign key behavior of updates on partitioned tables that move rows between partitions (Amit Langote)

  Previously, such updates ran a delete action on the source partition and an insert action on the target partition. PostgreSQL will now run an update action on the partition root, providing cleaner semantics.

- Allow `CLUSTER` on partitioned tables (Justin Pryzby)

- Fix `ALTER TRIGGER RENAME` on partitioned tables to properly rename triggers on all partitions (Arne Roland, Álvaro Herrera)

  Also prohibit cloned triggers from being renamed.

##### E.6.3.1.2. Indexes

- Allow btree indexes on system and TOAST tables to efficiently store duplicates (Peter Geoghegan)

  Previously de-duplication was disabled for these types of indexes.

- Improve lookup performance of GiST indexes that were built using sorting (Aliaksandr Kalenik, Sergei Shoulbakov, Andrey Borodin)

- Allow unique constraints and indexes to treat `NULL` values as not distinct (Peter Eisentraut)

  Previously `NULL` entries were always treated as distinct values, but this can now be changed by creating constraints and indexes using `UNIQUE NULLS NOT DISTINCT`.

- Allow the `^@` starts-with operator and the `starts_with()` function to use btree indexes if using the C collation (Tom Lane)

  Previously these could only use SP-GiST indexes.

##### E.6.3.1.3. Optimizer

- Allow extended statistics to record statistics for a parent with all its children (Tomas Vondra, Justin Pryzby)

  Regular statistics already tracked parent and parent-plus-all-children statistics separately.

- Add server variable `recursive_worktable_factor` to allow the user to specify the expected size of the working table of a recursive query (Simon Riggs)

##### E.6.3.1.4. General Performance

- Allow hash lookup for `NOT IN` clauses with many constants (David Rowley, James Coleman)

  Previously the code always sequentially scanned the list of values.

- Allow `SELECT DISTINCT` to be parallelized (David Rowley)

- Speed up encoding validation of UTF-8 text by processing 16 bytes at a time (John Naylor, Heikki Linnakangas)

  This will improve text-heavy operations like `COPY FROM`.

- Improve performance for sorts that exceed `work_mem` (Heikki Linnakangas)

  When the sort data no longer fits in `work_mem`, switch to a batch sorting algorithm that uses more output streams than before.

- Improve performance and reduce memory consumption of in-memory sorts (Ronan Dunklau, David Rowley, Thomas Munro, John Naylor)

- Allow WAL full page writes to use LZ4 and Zstandard compression (Andrey Borodin, Justin Pryzby)

  This is controlled by the `wal_compression` server setting.

- Add support for writing WAL using direct I/O on macOS (Thomas Munro)

  This only works if `max_wal_senders = 0` and `wal_level = minimal`.

- Allow vacuum to be more aggressive in setting the oldest frozen and multi transaction id (Peter Geoghegan)

- Allow a query referencing multiple foreign tables to perform parallel foreign table scans in more cases (Andrey Lepikhov, Etsuro Fujita)

- Improve the performance of window functions that use `row_number()`, `rank()`, `dense_rank()` and `count()` (David Rowley)

- Improve the performance of spinlocks on high-core-count ARM64 systems (Geoffrey Blake)

##### E.6.3.1.5. Monitoring

- Enable default logging of checkpoints and slow autovacuum operations (Bharath Rupireddy)

  This changes the default of `log_checkpoints` to `on` and that of `log_autovacuum_min_duration` to 10 minutes. This will cause even an idle server to generate some log output, which might cause problems on resource-constrained servers without log file rotation. These defaults should be changed in such cases.

- Generate progress messages in the server log during slow server starts (Nitin Jadhav, Robert Haas)

  The messages report the cause of the delay. The time interval for notification is controlled by the new server variable `log_startup_progress_interval`.

- Store cumulative statistics system data in shared memory (Kyotaro Horiguchi, Andres Freund, Melanie Plageman)

  Previously this data was sent to a statistics collector process via UDP packets, and could only be read by sessions after transferring it via the file system. There is no longer a separate statistics collector process.

- Add additional information to `VACUUM VERBOSE` and autovacuum logging messages (Peter Geoghegan)

- Add `EXPLAIN (BUFFERS)` output for temporary file block I/O (Masahiko Sawada)

- Allow log output in JSON format (Sehrope Sarkuni, Michael Paquier)

  The new setting is `log_destination = jsonlog`.

- Allow `pg_stat_reset_single_table_counters()` to reset the counters of relations shared across all databases (Sadhuprasad Patro)

- Add wait events for local shell commands (Fujii Masao)

  The new wait events are used when calling `archive_command`, `archive_cleanup_command`, `restore_command` and `recovery_end_command`.

##### E.6.3.1.6. Privileges

- Allow table accesses done by a view to optionally be controlled by privileges of the view's caller (Christoph Heiss)

  Previously, view accesses were always treated as being done by the view's owner. That's still the default.

- Allow members of the `pg_write_server_files` predefined role to perform server-side base backups (Dagfinn Ilmari Mannsåker)

  Previously only superusers could perform such backups.

- Allow `GRANT` to grant permissions to change individual server variables via `SET` and `ALTER SYSTEM` (Mark Dilger)

  The new function `has_parameter_privilege()` reports on this privilege.

- Add predefined role `pg_checkpoint` that allows members to run `CHECKPOINT` (Jeff Davis)

  Previously checkpoints could only be run by superusers.

- Allow members of the `pg_read_all_stats` predefined role to access the views `pg_backend_memory_contexts` and `pg_shmem_allocations` (Bharath Rupireddy)

  Previously these views could only be accessed by superusers.

- Allow `GRANT` to grant permissions on `pg_log_backend_memory_contexts()` (Jeff Davis)

  Previously this function could only be run by superusers.

##### E.6.3.1.7. Server Configuration

- Add server variable `shared_memory_size` to report the size of allocated shared memory (Nathan Bossart)

- Add server variable `shared_memory_size_in_huge_pages` to report the number of huge memory pages required (Nathan Bossart)

  This is only supported on Linux.

- Honor server variable `shared_preload_libraries` in single-user mode (Jeff Davis)

  This change supports use of `shared_preload_libraries` to load custom access methods and WAL resource managers, which would be essential for database access even in single-user mode.

- On Solaris, make the default setting of `dynamic_shared_memory_type` be `sysv` (Thomas Munro)

  The previous default choice, `posix`, can result in spurious failures on this platform.

- Allow `postgres -C` to properly report runtime-computed values (Nathan Bossart)

  Previously runtime-computed values `data_checksums`, `wal_segment_size`, and `data_directory_mode` would report values that would not be accurate on the running server. However, this does not work on a running server.

#### E.6.3.2. Streaming Replication and Recovery

- Add support for LZ4 and Zstandard compression of server-side base backups (Jeevan Ladhe, Robert Haas)

- Run the checkpointer and bgwriter processes during crash recovery (Thomas Munro)

  This helps to speed up long crash recoveries.

- Allow WAL processing to pre-fetch needed file contents (Thomas Munro)

  This is controlled by the server variable `recovery_prefetch`.

- Allow archiving via loadable modules (Nathan Bossart)

  Previously, archiving was only done by calling shell commands. The new server variable `archive_library` can be set to specify a library to be called for archiving.

- No longer require `IDENTIFY_SYSTEM` to be run before `START_REPLICATION` (Jeff Davis)

##### E.6.3.2.1. Logical Replication

- Allow publication of all tables in a schema (Vignesh C, Hou Zhijie, Amit Kapila)

  For example, this syntax is now supported: `CREATE PUBLICATION pub1 FOR TABLES IN SCHEMA s1,s2`. `ALTER PUBLICATION` supports a similar syntax. Tables added later to the listed schemas will also be replicated.

- Allow publication content to be filtered using a `WHERE` clause (Hou Zhijie, Euler Taveira, Peter Smith, Ajin Cherian, Tomas Vondra, Amit Kapila)

  Rows not satisfying the `WHERE` clause are not published.

- Allow publication content to be restricted to specific columns (Tomas Vondra, Álvaro Herrera, Rahila Syed)

- Allow skipping of transactions on a subscriber using `ALTER SUBSCRIPTION ... SKIP` (Masahiko Sawada)

- Add support for prepared (two-phase) transactions to logical replication (Peter Smith, Ajin Cherian, Amit Kapila, Nikhil Sontakke, Stas Kelvich)

  The new `CREATE_REPLICATION_SLOT` option is called `TWO_PHASE`. pg_recvlogical now supports a new `--two-phase` option during slot creation.

- Prevent logical replication of empty transactions (Ajin Cherian, Hou Zhijie, Euler Taveira)

  Previously, publishers would send empty transactions to subscribers if subscribed tables were not modified.

- Add SQL functions to monitor the directory contents of logical replication slots (Bharath Rupireddy)

  The new functions are `pg_ls_logicalsnapdir()`, `pg_ls_logicalmapdir()`, and `pg_ls_replslotdir()`. They can be run by members of the predefined `pg_monitor` role.

- Allow subscribers to stop the application of logical replication changes on error (Osumi Takamichi, Mark Dilger)

  This is enabled with the subscriber option `disable_on_error` and avoids possible infinite error loops during stream application.

- Adjust subscriber server variables to match the publisher so datetime and float8 values are interpreted consistently (Japin Li)

  Some publishers might be relying on inconsistent behavior.

- Add system view `pg_stat_subscription_stats` to report on subscriber activity (Masahiko Sawada)

  The new function `pg_stat_reset_subscription_stats()` allows resetting these statistics counters.

- Suppress duplicate entries in the `pg_publication_tables` system view (Hou Zhijie)

  In some cases a partition could appear more than once.

#### E.6.3.3. Utility Commands

- Add SQL `MERGE` command to adjust one table to match another (Simon Riggs, Pavan Deolasee, Álvaro Herrera, Amit Langote)

  This is similar to `INSERT ... ON CONFLICT` but more batch-oriented.

- Add support for `HEADER` option in `COPY` text format (Rémi Lapeyre)

  The new option causes the column names to be output, and optionally verified on input.

- Add new WAL-logged method for database creation (Dilip Kumar)

  This is the new default method for copying the template database, as it avoids the need for checkpoints during database creation. However, it might be slow if the template database is large, so the old method is still available.

- Allow `CREATE DATABASE` to set the database OID (Shruthi Gowda, Antonin Houska)

- Prevent `DROP DATABASE`, `DROP TABLESPACE`, and `ALTER DATABASE SET TABLESPACE` from occasionally failing during concurrent use on Windows (Thomas Munro)

- Allow foreign key `ON DELETE SET` actions to affect only specified columns (Paul Martinez)

  Previously, all of the columns in the foreign key were always affected.

- Allow `ALTER TABLE` to modify a table's `ACCESS METHOD` (Justin Pryzby, Jeff Davis)

- Properly call object access hooks when `ALTER TABLE` causes table rewrites (Michael Paquier)

- Allow creation of unlogged sequences (Peter Eisentraut)

- Track dependencies on individual columns in the results of functions returning composite types (Tom Lane)

  Previously, if a view or rule contained a reference to a specific column within the result of a composite-returning function, that was not noted as a dependency; the view or rule was only considered to depend on the composite type as a whole. This meant that dropping the individual column would be allowed, causing problems in later use of the view or rule. The column-level dependency is now also noted, so that dropping such a column will be rejected unless the view is changed or dropped.

#### E.6.3.4. Data Types

- Allow the scale of a `numeric` value to be negative, or greater than its precision (Dean Rasheed, Tom Lane)

  This allows rounding of values to the left of the decimal point, e.g., `'1234'::numeric(4, -2)` returns 1200.

- Improve overflow detection when casting values to interval (Joe Koshakow)

- Change the I/O format of type `"char"` for non-ASCII characters (Tom Lane)

- Update the display width information of modern Unicode characters, like emojis (Jacob Champion)

  Also update from Unicode 5.0 to 14.0.0. There is now an automated way to keep Postgres updated with Unicode releases.

#### E.6.3.5. Functions

- Add multirange input to `range_agg()` (Paul Jungwirth)

- Add `MIN()` and `MAX()` aggregates for the `xid8` data type (Ken Kato)

- Add regular expression functions for compatibility with other relational systems (Gilles Darold, Tom Lane)

  The new functions are `regexp_count()`, `regexp_instr()`, `regexp_like()`, and `regexp_substr()`. Some new optional arguments were also added to `regexp_replace()`.

- Add the ability to compute the distance between `polygons` (Tom Lane)

- Add `to_char()` format codes `of`, `tzh`, and `tzm` (Nitin Jadhav)

  The upper-case equivalents of these were already supported.

- When applying `AT TIME ZONE` to a `time with time zone` value, use the transaction start time rather than wall clock time to determine whether DST applies (Aleksander Alekseev, Tom Lane)

  This allows the conversion to be considered stable rather than volatile, and it saves a kernel call per invocation.

- Ignore NULL array elements in `ts_delete()` and `setweight()` functions with array arguments (Jean-Christophe Arnu)

  These functions effectively ignore empty-string array elements (since those could never match a valid lexeme). It seems consistent to let them ignore NULL elements too, instead of failing.

- Add support for petabyte units to `pg_size_pretty()` and `pg_size_bytes()` (David Christensen)

- Change `pg_event_trigger_ddl_commands()` to output references to other sessions' temporary schemas using the actual schema name (Tom Lane)

  Previously this function reported all temporary schemas as `pg_temp`, but it's misleading to use that for any but the current session's temporary schema.

#### E.6.3.6. PL/pgSQL

- Fix enforcement of PL/pgSQL variable `CONSTANT` markings (Tom Lane)

  Previously, a variable could be used as a `CALL` output parameter or refcursor `OPEN` variable despite being marked `CONSTANT`.

#### E.6.3.7. libpq

- Allow IP address matching against a server certificate's Subject Alternative Name (Jacob Champion)

- Allow `PQsslAttribute()` to report the SSL library type without requiring a libpq connection (Jacob Champion)

- Change query cancellations sent by the client to use the same TCP settings as normal client connections (Jelte Fennema)

  This allows configured TCP timeouts to apply to query cancel connections.

- Prevent libpq event callback failures from forcing an error result (Tom Lane)

#### E.6.3.8. Client Applications

- Allow pgbench to retry after serialization and deadlock failures (Yugo Nagata, Marina Polyakova)

##### E.6.3.8.1. psql

- Improve performance of psql's `\copy` command, by sending data in larger chunks (Heikki Linnakangas)

- Add `\dconfig` command to report server variables (Mark Dilger, Tom Lane)

  This is similar to the server-side `SHOW` command, but it can process patterns to show multiple variables conveniently.

- Add `\getenv` command to assign the value of an environment variable to a psql variable (Tom Lane)

- Add `+` option to the `\lo_list` and `\dl` commands to show large-object privileges (Pavel Luzanov)

- Add a pager option for the `\watch` command (Pavel Stehule, Thomas Munro)

  This is only supported on Unix and is controlled by the `PSQL_WATCH_PAGER` environment variable.

- Make psql include intra-query double-hyphen comments in queries sent to the server (Tom Lane, Greg Nancarrow)

  Previously such comments were removed from the query before being sent. Double-hyphen comments that are before any query text are not sent, and are not recorded as separate psql history entries.

- Adjust psql so that Readline's meta-`#` command will insert a double-hyphen comment marker (Tom Lane)

  Previously a pound marker was inserted, unless the user had taken the trouble to configure a non-default comment marker.

- Make psql output all results when multiple queries are passed to the server at once (Fabien Coelho)

  Previously, only the last query result was displayed. The old behavior can be restored by setting the `SHOW_ALL_RESULTS` psql variable to `off`.

- After an error is detected in `--single-transaction` mode, change the final `COMMIT` command to `ROLLBACK` only if `ON_ERROR_STOP` is set (Michael Paquier)

  Previously, detection of an error in a `-c` command or `-f` script file would lead to issuing `ROLLBACK` at the end, regardless of the value of `ON_ERROR_STOP`.

- Improve psql's tab completion (Shinya Kato, Dagfinn Ilmari Mannsåker, Peter Smith, Koyu Tanigawa, Ken Kato, David Fetter, Haiying Tang, Peter Eisentraut, Álvaro Herrera, Tom Lane, Masahiko Sawada)

- Limit support of psql's backslash commands to servers running PostgreSQL 9.2 or later (Tom Lane)

  Remove code that was only used when running with an older server. Commands that do not require any version-specific adjustments compared to 9.2 will still work.

##### E.6.3.8.2. pg_dump

- Make pg_dump dump `public` schema ownership changes and security labels (Noah Misch)

- Improve performance of dumping databases with many objects (Tom Lane)

  This will also improve the performance of pg_upgrade.

- Improve parallel pg_dump's performance for tables with large TOAST tables (Tom Lane)

- Add dump/restore option `--no-table-access-method` to force restore to only use the default table access method (Justin Pryzby)

- Limit support of pg_dump and pg_dumpall to servers running PostgreSQL 9.2 or later (Tom Lane)

#### E.6.3.9. Server Applications

- Add new pg_basebackup option `--target` to control the base backup location (Robert Haas)

  The new options are `server` to write the backup locally and `blackhole` to discard the backup (for testing).

- Allow pg_basebackup to do server-side gzip, LZ4, and Zstandard compression and client-side LZ4 and Zstandard compression of base backup files (Dipesh Pandit, Jeevan Ladhe)

  Client-side `gzip` compression was already supported.

- Allow pg_basebackup to compress on the server side and decompress on the client side before storage (Dipesh Pandit)

  This is accomplished by specifying compression on the server side and plain output format.

- Allow pg_basebackup's `--compress` option to control the compression location (server or client), compression method, and compression options (Michael Paquier, Robert Haas)

- Add the LZ4 compression method to pg_receivewal (Georgios Kokolatos)

  This is enabled via `--compress=lz4` and requires binaries to be built using `--with-lz4`.

- Add additional capabilities to pg_receivewal's `--compress` option (Georgios Kokolatos)

- Improve pg_receivewal's ability to restart at the proper WAL location (Ronan Dunklau)

  Previously, pg_receivewal would start based on the WAL file stored in the local archive directory, or at the sending server's current WAL flush location. With this change, if the sending server is running Postgres 15 or later, the local archive directory is empty, and a replication slot is specified, the replication slot's restart point will be used.

- Add pg_rewind option `--config-file` to simplify use when server configuration files are stored outside the data directory (Gunnar Bluth)

##### E.6.3.9.1. pg_upgrade

- Store pg_upgrade's log and temporary files in a subdirectory of the new cluster called `pg_upgrade_output.d` (Justin Pryzby)

  Previously such files were left in the current directory, requiring manual cleanup. Now they are automatically removed on successful completion of pg_upgrade.

- Disable default status reporting during pg_upgrade operation if the output is not a terminal (Andres Freund)

  The status reporting output can be enabled for non-tty usage by using `--verbose`.

- Make pg_upgrade report all databases with invalid connection settings (Jeevan Ladhe)

  Previously only the first database with an invalid connection setting was reported.

- Make pg_upgrade preserve tablespace and database OIDs, as well as relation relfilenode numbers (Shruthi Gowda, Antonin Houska)

- Add a `--no-sync` option to pg_upgrade (Michael Paquier)

  This is recommended only for testing.

- Limit support of pg_upgrade to old servers running PostgreSQL 9.2 or later (Tom Lane)

##### E.6.3.9.2. pg_waldump

- Allow pg_waldump output to be filtered by relation file node, block number, fork number, and full page images (David Christensen, Thomas Munro)

- Make pg_waldump report statistics before an interrupted exit (Bharath Rupireddy)

  For example, issuing a control-C in a terminal running `pg_waldump --stats --follow` will report the current statistics before exiting. This does not work on Windows.

- Improve descriptions of some transaction WAL records reported by pg_waldump (Masahiko Sawada, Michael Paquier)

- Allow pg_waldump to dump information about multiple resource managers (Heikki Linnakangas)

  This is enabled by specifying the `--rmgr` option multiple times.

#### E.6.3.10. Documentation

- Add documentation for `pg_encoding_to_char()` and `pg_char_to_encoding()` (Ian Lawrence Barwick)

- Document the `^@` starts-with operator (Tom Lane)

#### E.6.3.11. Source Code

- Add support for continuous integration testing using cirrus-ci (Andres Freund, Thomas Munro, Melanie Plageman)

- Add configure option `--with-zstd` to enable Zstandard builds (Jeevan Ladhe, Robert Haas, Michael Paquier)

- Add an ABI identifier field to the magic block in loadable libraries, allowing non-community PostgreSQL distributions to identify libraries that are not compatible with other builds (Peter Eisentraut)

  An ABI field mismatch will generate an error at load time.

- Create a new `pg_type.typcategory` value for `"char"` (Tom Lane)

  Some other internal-use-only types have also been assigned to this category.

- Add new protocol message `TARGET` to specify a new `COPY` method to be used for base backups (Robert Haas)

  pg_basebackup now uses this method.

- Add new protocol message `COMPRESSION` and `COMPRESSION_DETAIL` to specify the compression method and options (Robert Haas)

- Remove server support for old `BASE_BACKUP` command syntax and base backup protocol (Robert Haas)

- Add support for extensions to set custom backup targets (Robert Haas)

- Allow extensions to define custom WAL resource managers (Jeff Davis)

- Add function `pg_settings_get_flags()` to get the flags of server variables (Justin Pryzby)

- On Windows, export all the server's global variables using `PGDLLIMPORT` markers (Robert Haas)

  Previously, only specific variables were accessible to extensions on Windows.

- Require GNU make version 3.81 or later to build PostgreSQL (Tom Lane)

- Require OpenSSL to build the pgcrypto extension (Peter Eisentraut)

- Require Perl version 5.8.3 or later (Dagfinn Ilmari Mannsåker)

- Require Python version 3.2 or later (Andres Freund)

#### E.6.3.12. Additional Modules

- Allow amcheck to check sequences (Mark Dilger)

- Improve amcheck sanity checks for TOAST tables (Mark Dilger)

- Add new module basebackup_to_shell as an example of a custom backup target (Robert Haas)

- Add new module basic_archive as an example of performing archiving via a library (Nathan Bossart)

- Allow btree_gist indexes on boolean columns (Emre Hasegeli)

  These can be used for exclusion constraints.

- Fix pageinspect's `page_header()` to handle 32-kilobyte page sizes (Quan Zongliang)

  Previously, improper negative values could be returned in certain cases.

- Add counters for temporary file block I/O to pg_stat_statements (Masahiko Sawada)

- Add JIT counters to pg_stat_statements (Magnus Hagander)

- Add new module pg_walinspect (Bharath Rupireddy)

  This gives SQL-level output similar to pg_waldump.

- Indicate the permissive/enforcing state in sepgsql log messages (Dave Page)

##### E.6.3.12.1. postgres_fdw

- Allow postgres_fdw to push down `CASE` expressions (Alexander Pyhalov)

- Add server variable `postgres_fdw.application_name` to control the application name of postgres_fdw connections (Hayato Kuroda)

  Previously the remote session's `application_name` could only be set on the remote server or via a postgres_fdw connection specification. `postgres_fdw.application_name` supports some escape sequences for customization, making it easier to tell such connections apart on the remote server.

- Allow parallel commit on postgres_fdw servers (Etsuro Fujita)

  This is enabled with the `CREATE SERVER` option `parallel_commit`.

### E.6.4. Acknowledgments

The following individuals (in alphabetical order) have contributed to this release as patch authors, committers, reviewers, testers, or reporters of issues.

Abhijit Menon-Sen
Adam Brusselback
Adam Mackler
Adrian Ho
Ahsan Hadi
Ajin Cherian
Alastair McKinley
Aleksander Alekseev
Ales Zeleny
Alex Kingsborough
Alex Kozhemyakin
Alexander Korotkov
Alexander Kukushkin
Alexander Lakhin
Alexander Nawratil
Alexander Pyhalov
Alexey Borzov
Alexey Ermakov
Aliaksandr Kalenik
Álvaro Herrera
Amit Kapila
Amit Khandekar
Amit Langote
Amul Sul
Anastasia Lubennikova
Anders Kaseorg
Andreas Dijkman
Andreas Grob
Andreas Seltenreich
Andrei Zubkov
Andres Freund
Andrew Alsup
Andrew Bille
Andrew Dunstan
Andrew Gierth
Andrew Kesper
Andrey Borodin
Andrey Lepikhov
Andrey Sokolov
Andy Fan
Anton Melnikov
Anton Voloshin
Antonin Houska
Arjan van de Ven
Arne Roland
Arthur Zakirov
Ashutosh Bapat
Ashutosh Sharma
Ashwin Agrawal
Asif Rehman
Asim Praveen
Atsushi Torikoshi
Aya Iwata
Bauyrzhan Sakhariyev
Benoit Lobréau
Bernd Dorn
Bertrand Drouvot
Bharath Rupireddy
Björn Harrtell
Boris Kolpackov
Boris Korzun
Brad Nicholson
Brar Piening
Bruce Momjian
Bruno da Silva
Bryn Llewellyn
Carl Sopchak
Cary Huang
Chapman Flack
Chen Jiaoqian
Chris Bandy
Chris Lowder
Christian Quest
Christoph Berg
Christoph Heiss
Christophe Pettus
Christopher Painter-Wakefield
Claudio Freire
Clemens Zeidler
Corey Huinker
Dag Lem
Dagfinn Ilmari Mannsåker
Dan Kubb
Daniel Cherniy
Daniel Gustafsson
Daniel Polski
Daniel Vérité
Daniel Westermann
Daniele Varrazzo
Daniil Anisimov
Danny Shemesh
Darafei Praliaskouski
Daria Lepikhova
Dave Cramer
Dave Page
David Christensen
David Fetter
David G. Johnston
David Rowley
David Steele
David Zhang
Dean Rasheed
Dian Fay
Dilip Kumar
Dipesh Pandit
Dmitry Dolgov
Dmitry Koval
Dmitry Marakasov
Dominique Devienne
Dong Wook
Drew DeVault
Eduard Català
Egor Chindyaskin
Egor Rogov
Ekaterina Kiryanova
Elena Indrupskaya
Elvis Pranskevichus
Emmanuel Quincerot
Emre Hasegeli
Eric Mutta
Erica Zhang
Erik Rijkers
Erki Eessaar
Etsuro Fujita
Euler Taveira
Fabien Coelho
Fabrice Chapuis
Fabrice Fontaine
Fabrízio de Royes Mello
Feike Steenbergen
Filip Gospodinov
Florin Irion
Floris Van Nee
Frédéric Yhuel
Gabriela Serventi
Gaurab Dey
Geoff Winkless
Geoffrey Blake
Georgios Kokolatos
Gilles Darold
Greg Nancarrow
Greg Rychlewski
Greg Sabino Mullane
Greg Stark
Gregory Smith
Guillaume Lelarge
Gunnar Bluth
Gurjeet Singh
Haiyang Wang
Haiying Tang
Hannu Krosing
Hans Buschmann
Hayato Kuroda
Heath Lord
Heikki Linnakangas
Herwig Goemans
Himanshu Upadhyaya
Holly Roberts
Hou Zhijie
Hubert Lubaczewski
Ian Barwick
Ian Campbell
Ibrar Ahmed
Ildus Kurbangaliev
Ilya Anfimov
Itamar Gafni
Jacob Champion
Jaime Casanova
Jakub Wartak
James Coleman
James Hilliard
James Inform
Jan Piotrowski
Japin Li
Jason Harvey
Jason Kim
Jean-Christophe Arnu
Jeevan Ladhe
Jeff Davis
Jeff Janes
Jehan-Guillaume de Rorthais
Jelte Fennema
Jeremy Evans
Jeremy Schneider
Jian Guo
Jian He
Jimmy Yih
Jiri Fejfar
Jitka Plesníková
Joe Conway
Joe Wildish
Joel Jacobson
Joey Bodoia
John Naylor
Jonathan Katz
Josef Simanek
Joseph Koshakow
Josh Soref
Joshua Brindle
Juan José Santamaría Flecha
Julien Rouhaud
Julien Roze
Junwang Zhao
Jürgen Purtz
Justin Pryzby
Ken Kato
Kevin Burke
Kevin Grittner
Kevin Humphreys
Kevin McKibbin
Kevin Sweet
Kevin Zheng
Klaudie Willis
Konstantin Knizhnik
Konstantina Skovola
Kosei Masumura
Kotaro Kawamoto
Koyu Tanigawa
Kuntal Ghosh
Kyotaro Horiguchi
Lars Kanis
Lauren Fliksteen
Laurent Hasson
Laurenz Albe
Leslie Lemaire
Liam Bowen
Lingjie Qiang
Liu Huailing
Louis Jachiet
Lukas Fittl
Ma Liangzhu
Maciek Sakrejda
Magnus Hagander
Mahendra Singh Thalor
Maksim Milyutin
Marc Bachmann
Marcin Krupowicz
Marcus Gartner
Marek Szuba
Marina Polyakova
Mario Emmenlauer
Mark Dilger
Mark Murawski
Mark Wong
Markus Wanner
Markus Winand
Martijn van Oosterhout
Martin Jurca
Martin Kalcher
Martín Marqués
Masahiko Sawada
Masahiro Ikeda
Masao Fujii
Masaya Kawamoto
Masayuki Hirose
Matthias van de Meent
Matthijs van der Vleuten
Maxim Orlov
Maxim Yablokov
Melanie Plageman
Michael Banck
Michael Harris
Michael J. Sullivan
Michael Meskes
Michael Mühlbeyer
Michael Paquier
Michael Powers
Mike Fiedler
Mike Oh
Mikhail Kulagin
Miles Delahunty
Naoki Okano
Nathan Bossart
Nathan Long
Nazir Bilal Yavuz
Neha Sharma
Neil Chen
Nicola Contu
Nicolas Lutic
Nikhil Benesch
Nikhil Shetty
Nikhil Sontakke
Nikita Glukhov
Nikolai Berkoff
Nikolay Samokhvalov
Nikolay Shaplov
Nitin Jadhav
Noah Misch
Noboru Saito
Noriyoshi Shinoda
Olaf Bohlen
Olly Betts
Onder Kalaci
Oskar Stenberg
Otto Kekalainen
Paul Guo
Paul Jungwirth
Paul Martinez
Pavan Deolasee
Pavel Borisov
Pavel Luzanov
Pavel Stehule
Peter Eisentraut
Peter Geoghegan
Peter Slavov
Peter Smith
Petr Jelínek
Phil Florent
Phil Krylov
Pierre-Aurélien Georges
Prabhat Sahu
Quan Zongliang
Rachel Heaton
Rahila Syed
Rajakavitha Kodhandapani
Rajkumar Raghuwanshi
Ranier Vilela
Rei Kamigishi
Reid Thompson
Rémi Lapeyre
Renan Soares Lopes
Richard Guo
Richard Wesley
RKN Sai Krishna
Robert Haas
Robert Treat
Roberto Mello
Robins Tharakan
Roger Mason
Roman Zharkov
Ronan Dunklau
Rui Zhao
Ryan Kelly
Ryo Matsumura
Ryohei Takahashi
Sadhuprasad Patro
Sait Talha Nisanci
Sami Imseih
Sandeep Thakkar
Sebastian Kemper
Sehrope Sarkuni
Sergei Kornilov
Sergei Shoulbakov
Sergey Shinderuk
Shay Rojansky
Shenhao Wang
Shi Yu
Shinya Kato
Shruthi Gowda
Simon Perepelitsa
Simon Riggs
Sirisha Chamarthi
Soumyadeep Chakraborty
Stan Hu
Stas Kelvich
Stefen Hillman
Stephen Frost
Steve Chavez
Sumanta Mukherjee
Suraj Khamkar
Suraj Kharage
Sven Klemm
Takamichi Osumi
Takayuki Tsunakawa
Takeshi Ideriha
Tatsuhiro Nakamori
Tatsuhito Kasahara
Tatsuo Ishii
Tatsuro Yamada
Teja Mupparti
Teodor Sigaev
Thibaud Walkowiak
Thom Brown
Thomas McKay
Thomas Munro
Tim McNamara
Timo Stolz
Timur Khanjanov
Tom Lane
Tomas Barton
Tomas Vondra
Tony Reix
Troy Frericks
Tushar Ahuja
Victor Wagner
Victor Yegorov
Vignesh C
Vik Fearing
Vincas Dargis
Vitaly Burovoy
Vitaly Voronov
Vladimir Sitnikov
Wang Ke
Wei Sun
Wei Wang
Whale Song
Will Mortensen
Wolfgang Walther
Yanliang Lei
Yaoguang Chen
Yogendra Suralkar
YoungHwan Joo
Yugo Nagata
Yukun Wang
Yura Sokolov
Yusuke Egashira
Yuzuko Hosoya
Zhang Mingli
Zhang Wenjie
Zhihong Yu
Zhiyong Wu

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