E.1. Release 14
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## E.1. Release 14

Release date: 2021-??-?? (AS OF 2021-06-20)

### E.1.1. Overview

PostgreSQL 14 contains many new features and enhancements, including:

The above items and other new features of PostgreSQL 14 are explained in more detail in the sections below.

### E.1.2. Migration to Version 14

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

- Prevent the containment operators (`<@` and `@>`) for intarray from using GiST indexes (Tom Lane)

  Previously a full GiST index scan was required, so just avoid that and scan the heap, which is faster. Indexes created for this purpose should be removed.

- Remove deprecated containment operators `@` and `~` for built-in geometric data types and contrib modules cube, hstore, intarray, and seg (Justin Pryzby)

  The more consistent <@ and @> have been recommended for many years.

- Fix `to_tsquery()` and `websearch_to_tsquery()` to properly parse query text containing discarded tokens (Alexander Korotkov)

  Certain discarded tokens, like underscore, caused the output of these functions to produce incorrect tsquery output, e.g., both `websearch_to_tsquery('"pg_class pg"')` and `to_tsquery('pg_class <-> pg')` used to output `( 'pg' & 'class' ) <-> 'pg'`, but now both output `'pg' <-> 'class' <-> 'pg'`.

- Fix `websearch_to_tsquery()` to properly parse multiple adjacent discarded tokens in quotes (Alexander Korotkov)

  Previously, quoted text that contained multiple adjacent discarded tokens were treated as multiple tokens, causing incorrect tsquery output, e.g., `websearch_to_tsquery('"aaa: bbb"')` used to output `'aaa' <2> 'bbb'`, but now outputs `'aaa' <-> 'bbb'`.

- Change the default of the password_encryption server parameter to `scram-sha-256` (Peter Eisentraut)

  Previously it was `md5`. All new passwords will be stored as SHA256 unless this server variable is changed or the password is specified in md5 format. Also, the legacy (and undocumented) Boolean-like values which were previously synonyms for `md5` are no longer accepted.

- Overhaul the specification of `clientcert` in `pg_hba.conf` (Kyotaro Horiguchi)

  Values `1`/`0`/`no-verify` are no longer supported; only the strings `verify-ca` and `verify-full` can be used. Also, disallow `verify-ca` if cert authentication is enabled since cert requires `verify-full` checking.

- Remove support for SSL compression (Daniel Gustafsson, Michael Paquier)

  This was already disabled by default in previous PostgreSQL releases, and most modern OpenSSL and TLS versions no longer support it.

- Remove server and libpq support for the version 2 wire protocol (Heikki Linnakangas)

  This was last used as the default in PostgreSQL 7.3 (year 2002).

- Change `EXTRACT` to return the `NUMERIC` data type (Peter Eisentraut)

  `EXTRACT(date)` now throws an error for units that are not part of the `date` data type.

- Fix handling of infinite window function ranges (Tom Lane)

  Previously window frame clauses like `'inf' PRECEDING AND 'inf' FOLLOWING` returned incorrect results.

- Prevent tablefunc's function `normal_rand()` from accepting negative values (Ashutosh Bapat)

  Negative values produced undesirable results.

- Change `var_samp()` and `stddev_samp()` with numeric parameters to return NULL for a single NaN value (Tom Lane)

  Previously `NaN` was returned.

- User-defined objects that reference some built-in array functions along with their argument types must be recreated (Tom Lane)

  Specifically, `array_append()`, `array_prepend()`, `array_cat()`, `array_position()`, `array_positions()`, `array_remove()`, `array_replace()`, or `width_bucket()` used to take `anyarray` arguments but now take `anycompatiblearray`. Therefore, user-defined objects like aggregates and operators that reference old array function signatures must be dropped before upgrading and recreated once the upgrade completes.

- Remove factorial operators `!` and `!!` (Mark Dilger)

  The `factorial()` function is still supported. Also remove function `numeric_fac()`.

- Disallow `factorial()` of negative numbers (Peter Eisentraut)

  Previously such cases returned 1.

- Remove support for postfix (right-unary) operators (Mark Dilger)

  pg_dump and pg_upgrade will warn if postfix operators are being dumped.

- Allow `\D` and `\W` shorthands to match newlines in regular expression newline-sensitive mode (Tom Lane)

  Previously they did not match; `[^[:digit:]]` or `[^[:word:]]` can be used to get the old behavior.

- Improve handling of regular expression back-references (Tom Lane)

  For example, disregard `^` in its expansion in `\1` in `(^\d+).*\1`.

- Disallow `\w` as range start/end in character classes (Tom Lane)

  This previously was allowed but produced incorrect results.

- Require custom server variable names to use only characters which are valid for unquoted SQL identifiers (Tom Lane)

- Remove server variable `vacuum_cleanup_index_scale_factor` (Peter Geoghegan)

  This setting was ignored starting in PostgreSQL version 13.3.

- Return false for `has_column_privilege()` checks on non-existent or dropped columns when using attribute numbers (Joe Conway)

  Previously such attribute numbers returned an invalid column error.

- Pass doubled quote marks in ecpg SQL command strings literally (Tom Lane)

  Previously `'abc''def'` was passed to the server as `'abc'def'`, and `"abc""def"` was passed as `"abc"def"`.

- Disallow single-quoting of the language name in the `CREATE/DROP LANGUAGE` command (Peter Eisentraut)

- Remove contrib program pg_standby (Justin Pryzby)

- Remove composite types for sequences or toast tables (Tom Lane)

- Remove `operator_precedence_warning` setting (Tom Lane)

  This was needed for warning applications about PostgreSQL 9.5 changes.

### E.1.3. Changes

Below you will find a detailed account of the changes between PostgreSQL 14 and the previous major release.

#### E.1.3.1. Server

- Add predefined roles `pg_read_all_data` and `pg_write_all_data` (Stephen Frost)

  These non-login roles can be used to give read or write permission to all tables, views, and sequences.

- Add a predefined role to match the database owner (Noah Misch)

  It is called `pg_database_owner`; this is useful in template databases.

- Remove temporary files after backend crashes (Euler Taveira)

  These files were previously retained for debugging purposes; deletion can be disabled with remove_temp_files_after_crash.

- Allow long-running queries to be canceled if the client disconnects (Sergey Cherkashin, Thomas Munro)

  The server variable client_connection_check_interval allows some supported operating systems to automatically cancel queries by disconnected clients.

- Add an optional timeout parameter to `pg_terminate_backend()`

- Allow wide tuples to be always added to almost-empty heap pages (John Naylor, Floris van Nee)

  Previously tuples whose insertion would have exceeded the page's fill factor were instead added to new pages.

- Add Server Name Indication (SNI) for SSL connection packets (Peter Eisentraut)

  This can be disabled by turning off client option `sslsni`.

##### E.1.3.1.1. Vacuuming

- Allow vacuum to skip index vacuuming when the number of removable index entries is insignificant (Masahiko Sawada, Peter Geoghegan)

  The vacuum parameter `INDEX_CLEANUP` has a new default of `auto` to enable this optimization.

- Allow vacuum to more eagerly add deleted btree pages to the free space map (Peter Geoghegan)

  Previously vacuum could only add pages to the free space map that were marked as deleted by previous vacuums.

- Allow vacuum to reclaim space used by unused trailing heap line pointers (Matthias van de Meent, Peter Geoghegan)

- Allow vacuum to be more aggressive in removing dead rows during minimal-locking index operations (Álvaro Herrera)

  Specifically, `CREATE INDEX CONCURRENTLY` and `REINDEX CONCURRENTLY` no longer limit the dead row removal of other relations.

- Speed up vacuuming of databases with many relations (Tatsuhito Kasahara)

- Reduce the default value of vacuum_cost_page_miss to better reflect current hardware capabilities (Peter Geoghegan)

- Add ability to skip vacuuming of TOAST tables (Nathan Bossart)

  `VACUUM` now has a `PROCESS_TOAST` option which can be set to false to disable TOAST processing, and vacuumdb has a `--no-process-toast` option.

- Have `COPY FREEZE` appropriately update page visibility bits (Anastasia Lubennikova, Pavan Deolasee, Jeff Janes)

- Cause vacuum operations to be more aggressive if the table is near xid or multixact wraparound (Masahiko Sawada, Peter Geoghegan)

  This is controlled by vacuum_failsafe_age and vacuum_multixact_failsafe_age.

- Increase warning time and hard limit before transaction id and multi-transaction wraparound (Noah Misch)

  This should reduce the possibility of failures that occur without having issued warnings about wraparound.

- Autovacuum now analyzes partitioned tables (Yuzuko Hosoya, Álvaro Herrera)

  Insert, update, and delete tuple counts from partitions are now propagated to their parent tables so autovacuum knows when to process them.

- Add per-index information to autovacuum logging output (Masahiko Sawada)

##### E.1.3.1.2. Partitioning

- Improve the performance of updates/deletes on partitioned tables when only a few partitions are affected (Amit Langote, Tom Lane)

  This also allows updates/deletes on partitioned tables to use execution-time partition pruning.

- Allow partitions to be detached in a non-blocking manner (Álvaro Herrera)

  The syntax is `ALTER TABLE ... DETACH PARTITION ... CONCURRENTLY`, and `FINALIZE`.

- Allow arbitrary collations of partition boundary values (Tom Lane)

  Previously it had to match the collation of the partition key.

##### E.1.3.1.3. Indexes

- Allow btree index additions to remove expired index entries to prevent page splits (Peter Geoghegan)

  This is particularly helpful for reducing index bloat on tables whose indexed columns are frequently updated.

- Allow BRIN indexes to record multiple min/max values per range (Tomas Vondra)

  This is useful if there are groups of values in each page range.

- Allow BRIN indexes to use bloom filters (Tomas Vondra)

  This allows BRIN indexes to be used effectively with data that is not physically localized in the heap.

- Allow some GiST indexes to be built by presorting the data (Andrey Borodin)

  Presorting happens automatically and allows for faster index creation and smaller indexes.

- Allow SP-GiST to use `INCLUDE`'d columns (Pavel Borisov)

##### E.1.3.1.4. Optimizer

- Allow hash lookup of `IN` clause with many constants (James Coleman, David Rowley)

  Previously the only option was to sequentially scan the list of constants.

- Increase the number of places extended statistics can be used for `OR` clause estimation (Tomas Vondra, Dean Rasheed)

- Allow extended statistics on expressions (Tomas Vondra)

  This allows statistics on a group of expressions and columns, rather than only columns like previously. System view `pg_stats_ext_exprs` reports such statistics. `ALTER TABLE ... ALTER COLUMN ... TYPE RESETS STASTISTICS`?

- Allow efficient heap scanning of a range of `TIDs` (Edmund Horner, David Rowley)

  Previously a sequential scan was required for non-equality `TID` specifications.

- Fix `EXPLAIN CREATE TABLE AS` and `EXPLAIN CREATE MATERIALIZED VIEW` to honor `IF NOT EXISTS` (Bharath Rupireddy)

  Previously, if the object already existed, `EXPLAIN` would fail.

##### E.1.3.1.5. General Performance

- Improve the speed of computing MVCC visibility snapshots on systems with many CPUs and high session counts (Andres Freund)

  This also improves performance when there are many idle sessions.

- Add executor method to cache results from the inner-side of nested loop joins (David Rowley)

  This is useful if only a small percentage of rows is checked on the inner side and is controlled by enable_memoize.

- Allow window functions to perform incremental sorts (David Rowley)

- Improve the I/O performance of parallel sequential scans (Thomas Munro, David Rowley)

  This was done by allocating blocks in groups to parallel workers.

- Allow a query referencing multiple foreign tables to perform foreign table scans in parallel (Robert Haas, Kyotaro Horiguchi, Thomas Munro, Etsuro Fujita)

  postgres_fdw supports this type of scan if `async_capable` is set.

- Allow analyze to do page prefetching (Stephen Frost)

  This is controlled by maintenance_io_concurrency.

- Improve the performance of regular expression comparisons (Tom Lane)

- Dramatically improve Unicode normalization (John Naylor)

  This speeds `normalize()` and `IS NORMALIZED`.

- Add ability to use LZ4 compression on TOAST data (Dilip Kumar)

  This can be set at the column level, or set as a default via server setting default_toast_compression. The server must be compiled with `--with-lz4` to support this feature; the default is still pglz.

##### E.1.3.1.6. Monitoring

- If server variable compute_query_id is enabled, display the query id in `pg_stat_activity`, `EXPLAIN VERBOSE`, csvlog, and optionally in log_line_prefix (Julien Rouhaud)

  A query id computed by an extension will also be displayed.

- Improve logging of auto-vacuum and auto-analyze (Stephen Frost, Jakub Wartak)

  This reports I/O timings for auto-vacuum and auto-analyze if track_io_timing is enabled. Also, report buffer read and dirty rates for auto-analyze.

- Add information about the original user name supplied by the client to the output of log_connections (Jacob Champion)

##### E.1.3.1.7. System Views

- Add system view `pg_stat_progress_copy` to report `COPY` progress (Josef Šimánek, Matthias van de Meent)

- Add system view `pg_stat_wal`, which reports WAL activity (Masahiro Ikeda)

- Add system view `pg_stat_replication_slots` to report replication slot activity (Sawada Masahiko, Amit Kapila, Vignesh C)

  The function `pg_stat_reset_replication_slot()` resets slot statistics.

- Add system view `pg_backend_memory_contexts` to report session memory usage (Atsushi Torikoshi, Fujii Masao)

- Add function `pg_log_backend_memory_contexts()` to output the memory contexts of arbitrary backends (Atsushi Torikoshi)

- Add session statistics to the `pg_stat_database` system view (Laurenz Albe)

- Add columns to `pg_prepared_statements` to report generic and custom plan counts (Atsushi Torikoshi, Kyotaro Horiguchi)

- Add lock wait start time to `pg_locks` (Atsushi Torikoshi)

- Make the archiver process visible in `pg_stat_activity` (Kyotaro Horiguchi)

- Add wait event `WalReceiverExit` to report WAL receiver exit wait time (Fujii Masao)

- Implement information schema view `routine_column_usage` to track columns referenced by function and procedure default expressions (Peter Eisentraut)

##### E.1.3.1.8. Authentication

- Allow the certificate's distinguished name (DN) to be matched for client certificate authentication (Andrew Dunstan)

  The new `pg_hba.conf` keyword `clientname=DN` allows comparison with certificate attributes beyond the `CN` and can be combined with ident maps.

- Allow `pg_hba.conf` and `pg_ident.conf` records to span multiple lines (Fabien Coelho)

  A backslash at the end of a line allows record contents to be continued on the next line.

- Allow the specification of a certificate revocation list (CRL) directory (Kyotaro Horiguchi)

  This is controlled by server variable ssl_crl_dir and libpq connection option sslcrldir. Previously only CRL files could be specified.

- Allow passwords of an arbitrary length (Tom Lane, Nathan Bossart)

##### E.1.3.1.9. Server Configuration

- Add server setting idle_session_timeout to close idle sessions (Li Japin)

  This is similar to idle_in_transaction_session_timeout.

- Change checkpoint_completion_target default to 0.9 (Stephen Frost)

  The previous default was 0.5.

- Allow %P in log_line_prefix to report the parallel group leader (Justin Pryzby)

- Allow unix_socket_directories to specify paths as individual, comma-separated quoted strings (Ian Lawrence Barwick)

  Previously all the paths had to be in a single quoted string.

- Allow startup allocation of dynamic shared memory (Thomas Munro)

  This is controlled by min_dynamic_shared_memory. This allows more use of huge pages.

- Add setting huge_page_size to control the size of huge pages used on Linux (Odin Ugedal)

#### E.1.3.2. Streaming Replication and Recovery

- Allow standby servers to be rewound via pg_rewind (Heikki Linnakangas)

- Allow restore_command setting to be changed during a server reload (Sergei Kornilov)

  You can also set `restore_command` to an empty string and reload to force recovery to only read from the `pg_wal` directory.

- Add server variable log_recovery_conflict_waits to report long recovery conflict wait times (Bertrand Drouvot, Masahiko Sawada)

- Pause recovery if the primary changes its parameters in a way that prevents replay on the hot standby (Peter Eisentraut)

  Previously the standby would shut down immediately.

- Add function `pg_get_wal_replay_pause_state()` to report the recovery state (Dilip Kumar)

  It gives more detailed information than `pg_is_wal_replay_paused()`, which still exists.

- Add new server-side variable in_hot_standby (Haribabu Kommi, Greg Nancarrow, Tom Lane)

- Speed truncation of small tables during recovery on clusters with a large number of shared buffers (Kirk Jamison)

- Allow file system sync at the start of crash recovery on Linux (Thomas Munro)

  By default, PostgreSQL opens and fsyncs every data file at the start of crash recovery. This new setting, recovery_init_sync_method `=syncfs`, instead syncs each filesystem used by the database cluster. This allows for faster recovery on systems with many database files.

- Add function `pg_xact_commit_timestamp_origin()` to return the commit timestamp and replication origin of the specified transaction (Movead Li)

- Add the replication origin to the record returned by `pg_last_committed_xact()` (Movead Li)

- Allow replication origin functions to be controlled using standard function permission controls (Martín Marqués)

  Previously these functions could only be executed by superusers, and this is still the default.

##### E.1.3.2.1. Logical Replication

- Allow logical replication to stream long in-progress transactions to subscribers (Dilip Kumar, Amit Kapila, Ajin Cherian, Tomas Vondra, Nikhil Sontakke, Stas Kelvich)

  Previously transactions that exceeded logical_decoding_work_mem were written to disk until the transaction completed.

- Enhance the logical replication API to allow streaming large in-progress transactions (Tomas Vondra, Dilip Kumar, Amit Kapila)

  The output functions begin with `stream`. test_decoding also supports these.

- Allow multiple transactions during table sync in logical replication (Peter Smith, Amit Kapila, and Takamichi Osumi)

- Immediately WAL-log subtransaction and top-level `XID` association (Tomas Vondra, Dilip Kumar, Amit Kapila)

  This is useful for logical decoding.

- Enhance logical decoding APIs to handle two-phase commits (Ajin Cherian, Amit Kapila, Nikhil Sontakke, Stas Kelvich)

  This is controlled via `pg_create_logical_replication_slot()`.

- Generate WAL invalidation messages during command completion when using logical replication (Dilip Kumar, Tomas Vondra, Amit Kapila)

  When logical replication is disabled, WAL invalidation messages are generated at transaction completion. This allows logical streaming of in-progress transactions.

- Allow logical decoding to more efficiently process cache invalidation messages (Dilip Kumar)

  This allows logical decoding to work efficiently in presence of a large amount of DDL.

- Allow control over whether logical decoding messages are sent to the replication stream (David Pirotte, Euler Taveira)

- Allow logical replication subscriptions to use binary transfer mode (Dave Cramer)

  This is faster than text mode, but slightly less robust.

- Allow logical decoding to be filtered by xid (Markus Wanner)

#### E.1.3.3. `SELECT`, `INSERT`

- Reduce the number of keywords that can't be used as column labels without `AS` (Mark Dilger)

  There are now 90% fewer restricted keywords.

- Allow an alias to be specified for `JOIN`'s `USING` clause (Peter Eisentraut)

  The alias is created by using `AS` after the `USING` clause and represents an alias for the `USING` columns.

- Allow `DISTINCT` to be added to `GROUP BY` to remove duplicate `GROUPING SET` combinations (Vik Fearing)

  For example, `GROUP BY CUBE (a,b), CUBE (b,c)` will generate duplicate grouping combinations without `DISTINCT`.

- Properly handle `DEFAULT` values for columns in multi-column inserts (Dean Rasheed)

  This used to throw an error.

- Add SQL-standard `SEARCH` and `CYCLE` clauses for common table expressions (Peter Eisentraut)

  This could be accomplished previously using existing syntax.

- Allow the `WHERE` clause of `ON CONFLICT` to be table-qualified (Tom Lane)

  Only the target table can be referenced.

#### E.1.3.4. Utility Commands

- Allow `REFRESH MATERIALIZED VIEW` to use parallelism (Bharath Rupireddy)

- Allow `REINDEX` to change the tablespace of the new index (Alexey Kondratov, Michael Paquier, Justin Pryzby)

  This is done by specifying a `TABLESPACE` clause. A `--tablespace` option was also added to reindexdb to control this.

- Allow `REINDEX` to process all child tables or indexes of a partitioned relation (Justin Pryzby, Michael Paquier)

- Allow index commands using `CONCURRENTLY` to avoid waiting for the completion of other operations using `CONCURRENTLY` (Álvaro Herrera)

- Improve the performance of `COPY FROM` in binary mode (Bharath Rupireddy, Amit Langote)

- Preserve SQL standard syntax in view definitions, if possible (Tom Lane)

  Previously non-function call SQL standard syntax, e.g. `EXTRACT`, were converted to non-SQL standard function calls.

- Add the SQL-standard clause `GRANTED BY` to `GRANT` and `REVOKE` (Peter Eisentraut)

- Add `OR REPLACE` for `CREATE TRIGGER` (Takamichi Osumi)

  This allows pre-existing triggers to be conditionally replaced.

- Allow `TRUNCATE` to operate on foreign tables (Kazutaka Onishi, Kohei KaiGai)

  The postgres_fdw module also now supports this.

- Allow publications to be more easily added and removed (Japin Li)

  The new syntax is `ALTER SUBSCRIPTION ... ADD/DROP PUBLICATION`. This avoids having to specify all publications to add/remove entries.

- Add primary keys, unique constraints, and foreign keys to system catalogs (Peter Eisentraut)

  This helps GUI tools analyze the system tables. The constraints are visible using pg_get_catalog_foreign_keys().

- Allow `CURRENT_ROLE` every place `CURRENT_USER` is accepted (Peter Eisentraut)

#### E.1.3.5. Data Types

- Allow extensions and built-in data types to implement subscripting (Dmitry Dolgov)

  Previously subscript handling was hard-coded into the server, so that subscripting could only be applied to array types. This change allows subscript notation to be used to extract or assign portions of a value of any type for which the concept makes sense.

- Allow subscripting of `JSONB` (Dmitry Dolgov)

  `JSONB` subscripting can be used to extract and assign to portions of `JSONB` documents.

- Add support for multirange data types (Paul Jungwirth, Alexander Korotkov)

  These are like range data types, but they allow the specification of multiple, ordered, non-overlapping ranges. All existing range types now also support multirange versions.

- Add point operators `<<|` and `|>>` to be strictly above/below geometry (Emre Hasegeli)

  Previously `>^` and `<^` were marked as performing this test, but non-point geometric operators used these operators for non-strict comparisons, leading to confusion. The old operators still exist but will be eventually removed. ACCURATE?

- Add support for the stemming of languages Armenian, Basque, Catalan, Hindi, Serbian, and Yiddish (Peter Eisentraut)

- Allow tsearch data files to have unlimited line lengths (Tom Lane)

  The previous limit was 4k bytes. Also remove function `t_readline()`.

- Add support for `infinity` and `-infinity` values to the numeric data type (Tom Lane)

  Floating-point data types already supported these.

- Improve the accuracy of floating-point computations involving infinity (Tom Lane)

- Have non-zero float values divided by infinity return zero (Kyotaro Horiguchi)

  Previously such operations produced underflow errors.

- Cause floating-point division of NaN by zero to return NaN (Tom Lane)

  Previously this returned an error. Division with Numerics always returned NaN.

- Add operators to add and subtract `LSN` and numeric (byte) values (Fujii Masao)

- Allow binary data transfer to be more forgiving of array and record `OID` mismatches (Tom Lane)

- Create composite array types for most system relations (Wenjing Zeng)

#### E.1.3.6. Functions

- Allow SQL-language functions and procedures to use SQL-standard function bodies (Peter Eisentraut)

  Previously only single-quoted or $$-quoted function bodies were supported.

- Allow procedures to have `OUT` parameters (Peter Eisentraut)

- Allow some array functions to operate on a mix of compatible data types (Tom Lane)

  The functions are `array_append()`, `array_prepend()`, `array_cat()`, `array_position()`, `array_positions()`, `array_remove()`, `array_replace()`, and `width_bucket()`. Previously only identical data types could be used.

- Add SQL-standard `trim_array()` function (Vik Fearing)

  This can already be done with array slices.

- Add bytea equivalents of `ltrim()` and `rtrim()` (Joel Jacobson)

- Support negative indexes in `split_part()` (Nikhil Benesch)

  Negative values start from the last field and count backward.

- Add `string_to_table()` function to split a string on delimiters (Pavel Stehule)

  This is similar to the `regexp_split_to_table()` function.

- Add `unistr()` function to allow Unicode characters to be specified as backslash-hex escapes in strings (Pavel Stehule)

  This is similar to how Unicode can be specified in literal strings.

- Add `bit_xor()` XOR aggregate function (Alexey Bashtanov)

- Add function `bit_count()` to return the number of bits set in a bit or byte string (David Fetter)

- Add `date_bin()` function (John Naylor)

  The function `date_bin()` "bins" the input timestamp into a specified interval aligned with a specified origin.

- Allow `make_timestamp()`/`make_timestamptz()` to accept negative years (Peter Eisentraut)

  They are interpreted as `BC` years.

- Add newer regular expression `substring()` syntax (Peter Eisentraut)

  The new syntax is `SUBSTRING(text SIMILAR pattern ESCAPE escapechar)`. The previous standard syntax was `SUBSTRING(text FROM pattern FOR escapechar)`, and is still supported by PostgreSQL.

- Allow complemented character class escapes \D, `\S`, and `\W` within regex brackets (Tom Lane)

- Add `[[:word:]]` as a character class to match `\w` (Tom Lane)

- Allow more flexible data types for default values of `lead()` and `lag()` window functions (Vik Fearing)

- Cause `exp()` and `power()` for negative-infinity exponents to return zero (Tom Lane)

  Previously they often returned underflow errors.

- Mark built-in type coercion functions as leakproof where possible (Tom Lane)

  This allows more use of functions that require type conversion in security-sensitive situations.

- Mark `pg_stat_get_subscription()` as returning a set (Tom Lane)

  While it worked in previous releases, it didn't report proper optimizer statistics and couldn't be used in the target list. FUNCTION NOT DOCUMENTED.

- Prevent `inet_server_addr()` and `inet_server_port()` from being run by parallel workers (Masahiko Sawada)

- Change `pg_describe_object()`, `pg_identify_object()`, and `pg_identify_object_as_address()` to always report helpful error messages for non-existent objects (Michael Paquier)

#### E.1.3.7. PL/pgSQL

- Improve PL/pgSQL's expression and assignment parsing (Tom Lane)

  This adds nested record and array slicing support.

- Allow plpgsql's `RETURN QUERY` to execute its query using parallelism (Tom Lane)

- Improve performance of repeated CALLs within plpgsql procedures (Pavel Stehule, Tom Lane)

#### E.1.3.8. Client Interfaces

- Add pipeline mode to libpq (Craig Ringer, Matthieu Garrigues, Álvaro Herrera)

  This allows multiple queries to be sent and only wait for completion when a specific synchronization message is sent.

- Enhance libpq's `target_session_attrs` parameter options (Haribabu Kommi, Greg Nancarrow, Vignesh C, Tom Lane)

  The new options are `read-only`, `primary`, `standby`, and `prefer-standby`.

- Improve the output format of libpq's `PQtrace()` (Aya Iwata, Álvaro Herrera)

- Allow an ECPG SQL identifier to be linked to a specific connection (Hayato Kuroda)

  This is done via `DECLARE ... STATEMENT`.

#### E.1.3.9. Client Applications

- Allow vacuumdb to skip index cleanup and truncation (Nathan Bossart)

  The options are `--no-index-cleanup` and `--no-truncate`.

- Allow pg_dump to dump only certain extensions (Guillaume Lelarge)

  This is controlled by option `--extension`.

- Add pgbench `permute()` function to randomly shuffle values (Fabien Coelho, Hironobu Suzuki, Dean Rasheed)

- Allow multiple verbose option specifications (`-v`) to increase the logging verbosity (Tom Lane)

  This is now supported by pg_dump, pg_dumpall, and pg_restore.

##### E.1.3.9.1. psql

- Allow psql's `\df` and `\do` commands to specify function and operator argument types (Greg Sabino Mullane, Tom Lane)

  This helps reduce the number of matches for overloaded entries.

- Add an access method column to psql's \d[i|m|t]+ output (Georgios Kokolatos)

- Allow psql's `\dt` and `\di` to show TOAST tables and their indexes (Justin Pryzby)

- Add psql command `\dX` to list extended statistics objects (Tatsuro Yamada)

- Fix psql's `\dT` to understand array syntax and backend grammar aliases, like "int" for "integer" (Greg Sabino Mullane, Tom Lane)

- When editing the previous query or a file with psql's `\e`, or using `\ef` and `\ev`, ignore the contents if the editor exits without saving (Laurenz Albe)

  Previously, such edits would still execute the editor contents.

- Improve psql's handling of `\connect` with `-reuse-previous` (Tom Lane)

  Specifically, properly reuse the password previously specified, and prompt for a new password if the previous one failed.

- Improve tab completion (Vignesh C, Michael Paquier, Justin Pryzby, Georgios Kokolatos, Julien Rouhaud, ADD NAMES)

#### E.1.3.10. Server Applications

- Add command-line utility pg_amcheck to simplify running contrib/amcheck operations on many relations (Mark Dilger)

- Add `--no-instructions` option to initdb (Magnus Hagander)

  This removes the server start instructions that are normally output.

- Stop pg_upgrade from creating `analyze_new_cluster` script (Magnus Hagander)

  Instead, give comparable vacuumdb instructions.

- Remove support for the postmaster `-o` option (Magnus Hagander)

  This option was unnecessary since all passed options could already be specified directly.

#### E.1.3.11. Documentation

- Rename "Default Roles" to "Predefined Roles" (Bruce Momjian, Stephen Frost)

- Add documentation for the `factorial()` function (Peter Eisentraut)

  With the removal of the ! operator in this release, `factorial()` is the only built-in way to compute a factorial.

#### E.1.3.12. Source Code

- Add configure option `--with-ssl={openssl}` to behave like `--with-openssl` (Daniel Gustafsson, Michael Paquier)

  The option `--with-openssl` is kept for compatibility.

- Add support for abstract Unix-domain sockets (Peter Eisentraut)

  This is currently supported on Linux and Windows.

- Allow Windows to properly handle files larger than four gigabytes (Juan José Santamaría Flecha)

  For example this allows `COPY,` WAL files, and relation segment files to be larger than four gigabytes.

- Add debug_discard_caches to control cache flushing for test purposes (Craig Ringer)

  Previously this behavior could only be set at compile time.

- Various improvements in valgrind detection (Álvaro Herrera, Peter Geoghegan)

- Add a test module for the regular expression package (Tom Lane)

- Add support for LLVM version 12 (Andres Freund)

- Change SHA1, SHA2, and MD5 hash computations to use the OpenSSL EVP API (Michael Paquier)

  This is more modern and supports FIPS mode.

- Remove build control over the random library used (Daniel Gustafsson)

- Add direct conversion routines between EUC_TW and Big5 (Heikki Linnakangas)

- Add collation versions for FreeBSD (Thomas Munro)

- Add `amadjustmembers` to the index access method API (Tom Lane)

  REMOVE?

#### E.1.3.13. Additional Modules

- Allow subscripting of hstore values (Tom Lane, Dmitry Dolgov)

- Allow GiST/GIN pg_trgm indexes to do equality lookups (Julien Rouhaud)

  This is similar to `LIKE` except no wildcards are honored.

- Allow the cube data type to be transferred in binary mode (KaiGai Kohei)

- Allow `pgstattuple_approx()` to report on TOAST tables (Peter Eisentraut)

- Add contrib module pg_surgery which allows changes to row visibility (Ashutosh Sharma)

  This is useful for correcting database corruption.

- Add contrib module old_snapshot to report the `XID`/time mapping used by an active old_snapshot_threshold (Robert Haas)

- Allow amcheck to also check heap pages (Mark Dilger)

  Previously it only checked B-Tree index pages.

- Allow pageinspect to inspect GiST indexes (Andrey Borodin, Heikki Linnakangas)

- Change pageinspect block numbers to be `bigints` (Peter Eisentraut)

- Mark btree_gist functions as parallel safe (Steven Winfield)

##### E.1.3.13.1. pg_stat_statements

- Move query hash computation from pg_stat_statements to the core server (Julien Rouhaud)

  The new server variable compute_query_id's default of `auto` will automatically enable query id computation when this extension is loaded.

- Allow pg_stat_statements to track top and nested statements independently (Julien Rohaud)

  Previously, when tracking all statements, identical top and nested statements were tracked together.

- Add row counts for utility commands to `pg_stat_statements` (Fujii Masao, Katsuragi Yuta, Seino Yuki)

- Add `pg_stat_statements_info` system view to show `pg_stat_statements` activity (Katsuragi Yuta, Yuki Seino, Naoki Nakamichi)

##### E.1.3.13.2. postgres_fdw

- Allow postgres_fdw to `INSERT` rows in bulk (Takayuki Tsunakawa, Tomas Vondra, Amit Langote)

- Allow postgres_fdw to import table partitions if specified by `IMPORT FOREIGN SCHEMA ... LIMIT TO` (Matthias van de Meent)

  By default, only the root of partitioned tables is imported.

- Add postgres_fdw function `postgres_fdw_get_connections()` to report open foreign server connections (Bharath Rupireddy)

- Allow control over whether foreign servers keep connections open after transaction completion (Bharath Rupireddy)

  This is controlled by `keep_connections` and defaults to on.

- Allow postgres_fdw to reestablish foreign server connections if necessary (Bharath Rupireddy)

  Previously foreign server restarts could cause foreign table access errors.

- Add postgres_fdw functions to discard cached connections (Bharath Rupireddy)

### E.1.4. Acknowledgments

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

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