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E.23. Release 12

E.23. Release 12
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E.23.1. Overview
E.23.2. Migration to Version 12
E.23.3. Changes
E.23.4. Acknowledgments

Release date: 2019-10-03

E.23.1. Overview

Major enhancements in PostgreSQL 12 include:

  • General performance improvements, including:

    • Optimizations to space utilization and read/write performance for B-tree indexes

    • Partitioning performance enhancements, including improved query performance on tables with thousands of partitions, improved insertion performance with INSERT and COPY , and the ability to execute ALTER TABLE ATTACH PARTITION without blocking queries

    • Automatic (but overridable) inlining of common table expressions ( CTEs )

    • Reduction of WAL overhead for creation of GiST , GIN , and SP-GiST indexes

    • Support for covering GiST indexes, via the INCLUDE clause

    • Multi-column most-common-value (MCV) statistics can be defined via CREATE STATISTICS , to support better plans for queries that test several non-uniformly-distributed columns

  • Enhancements to administrative functionality, including:

  • Support for the SQL/JSON path language

  • Stored generated columns

  • Nondeterministic ICU collations, enabling case-insensitive and accent-insensitive grouping and ordering

  • New authentication features, including:

    • Encryption of TCP/IP connections when using GSSAPI authentication

    • Discovery of LDAP servers using DNS SRV records

    • Multi-factor authentication, using the clientcert=verify-full option combined with an additional authentication method in pg_hba.conf

The above items are explained in more detail in the sections below.

E.23.2. Migration to Version 12

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 18.6 for general information on migrating to new major releases.

Version 12 contains a number of changes that may affect compatibility with previous releases. Observe the following incompatibilities:

  • Remove the special behavior of oid columns (Andres Freund, John Naylor) §

    Previously, a normally-invisible oid column could be specified during table creation using WITH OIDS ; that ability has been removed. Columns can still be explicitly declared as type oid . Operations on tables that have columns created using WITH OIDS will need adjustment.

    The system catalogs that previously had hidden oid columns now have ordinary oid columns. Hence, SELECT * will now output those columns, whereas previously they would be displayed only if selected explicitly.

  • Remove data types abstime , reltime , and tinterval (Andres Freund) §

    These are obsoleted by SQL-standard types such as timestamp .

  • Remove the timetravel extension (Andres Freund) §

  • Move recovery.conf settings into postgresql.conf (Masao Fujii, Simon Riggs, Abhijit Menon-Sen, Sergei Kornilov) §

    recovery.conf is no longer used, and the server will not start if that file exists. recovery.signal and standby.signal files are now used to switch into non-primary mode. The trigger_file setting has been renamed to promote_trigger_file . The standby_mode setting has been removed.

  • Do not allow multiple conflicting recovery_target * specifications (Peter Eisentraut) §

    Specifically, only allow one of recovery_target , recovery_target_lsn , recovery_target_name , recovery_target_time , and recovery_target_xid . Previously, multiple different instances of these parameters could be specified, and the last one was honored. Now, only one can be specified, though the same one can be specified multiple times and the last specification is honored.

  • Cause recovery to advance to the latest timeline by default (Peter Eisentraut) §

    Specifically, recovery_target_timeline now defaults to latest . Previously, it defaulted to current .

  • Refactor code for geometric functions and operators (Emre Hasegeli) § § §

    This could lead to more accurate, but slightly different, results compared to previous releases. Notably, cases involving NaN, underflow, overflow, and division by zero are handled more consistently than before.

  • Improve performance by using a new algorithm for output of real and double precision values (Andrew Gierth) § §

    Previously, displayed floating-point values were rounded to 6 (for real ) or 15 (for double precision ) digits by default, adjusted by the value of extra_float_digits . Now, whenever extra_float_digits is more than zero (as it now is by default), only the minimum number of digits required to preserve the exact binary value are output. The behavior is the same as before when extra_float_digits is set to zero or less.

    Also, formatting of floating-point exponents is now uniform across platforms: two digits are used unless three are necessary. In previous releases, Windows builds always printed three digits.

  • random() and setseed() now behave uniformly across platforms (Tom Lane) § §

    The sequence of random() values generated following a setseed() call with a particular seed value is likely to be different now than before. However, it will also be repeatable, which was not previously guaranteed because of interference from other uses of random numbers inside the server. The SQL random() function now has its own private per-session state to forestall that.

  • Change SQL-style substring() to have standard-compliant greediness behavior (Tom Lane) §

    In cases where the pattern can be matched in more than one way, the initial sub-pattern is now treated as matching the least possible amount of text rather than the greatest; for example, a pattern such as %#"aa*#"% now selects the first group of a 's from the input, not the last group.

  • Do not pretty-print the result of xpath() or the XMLTABLE construct (Tom Lane) §

    In some cases, these functions would insert extra whitespace (newlines and/or spaces) in nodeset values. This is undesirable since depending on usage, the whitespace might be considered semantically significant.

  • Rename command-line tool pg_verify_checksums to pg_checksums (Michaël Paquier) §

  • In pg_restore , require specification of -f - to send the dump contents to standard output (Euler Taveira) §

    Previously, this happened by default if no destination was specified, but that was deemed to be unfriendly.

  • Disallow non-unique abbreviations in psql 's \pset format command (Daniel Vérité) § §

    Previously, for example, \pset format a chose aligned ; it will now fail since that could equally well mean asciidoc .

  • In new btree indexes, the maximum index entry length is reduced by eight bytes, to improve handling of duplicate entries (Peter Geoghegan) §

    This means that a REINDEX operation on an index pg_upgrade 'd from a previous release could potentially fail.

  • Cause DROP IF EXISTS FUNCTION / PROCEDURE / AGGREGATE / ROUTINE to generate an error if no argument list is supplied and there are multiple matching objects (David Rowley) §

    Also improve the error message in such cases.

  • Split the pg_statistic_ext catalog into two catalogs, and add the pg_stats_ext view of it (Dean Rasheed, Tomas Vondra) § §

    This change supports hiding potentially-sensitive statistics data from unprivileged users.

  • Remove obsolete pg_constraint . consrc column (Peter Eisentraut) §

    This column has been deprecated for a long time, because it did not update in response to other catalog changes (such as column renamings). The recommended way to get a text version of a check constraint's expression from pg_constraint is pg_get_expr(conbin, conrelid) . pg_get_constraintdef() is also a useful alternative.

  • Remove obsolete pg_attrdef . adsrc column (Peter Eisentraut) §

    This column has been deprecated for a long time, because it did not update in response to other catalog changes (such as column renamings). The recommended way to get a text version of a default-value expression from pg_attrdef is pg_get_expr(adbin, adrelid) .

  • Mark table columns of type name as having " C " collation by default (Tom Lane, Daniel Vérité) § §

    The comparison operators for data type name can now use any collation, rather than always using " C " collation. To preserve the previous semantics of queries, columns of type name are now explicitly marked as having " C " collation. A side effect of this is that regular-expression operators on name columns will now use the " C " collation by default, not the database collation, to determine the behavior of locale-dependent regular expression patterns (such as \w ). If you want non-C behavior for a regular expression on a name column, attach an explicit COLLATE clause. (For user-defined name columns, another possibility is to specify a different collation at table creation time; but that just moves the non-backwards-compatibility to the comparison operators.)

  • Treat object-name columns in the information_schema views as being of type name , not varchar (Tom Lane) § § §

    Per the SQL standard, object-name columns in the information_schema views are declared as being of domain type sql_identifier . In PostgreSQL , the underlying catalog columns are really of type name . This change makes sql_identifier be a domain over name , rather than varchar as before. This eliminates a semantic mismatch in comparison and sorting behavior, which can greatly improve the performance of queries on information_schema views that restrict an object-name column. Note however that inequality restrictions, for example 

    SELECT ... FROM information_schema.tables WHERE table_name < 'foo';

    will now use " C " -locale comparison semantics by default, rather than the database's default collation as before. Sorting on these columns will also follow " C " ordering rules. The previous behavior (and inefficiency) can be enforced by adding a COLLATE "default" clause.

  • Remove the ability to disable dynamic shared memory (Kyotaro Horiguchi) §

    Specifically, dynamic_shared_memory_type can no longer be set to none .

  • Parse libpq integer connection parameters more strictly (Fabien Coelho) §

    In previous releases, using an incorrect integer value for connection parameters connect_timeout , keepalives , keepalives_count , keepalives_idle , keepalives_interval and port resulted in libpq either ignoring those values or failing with incorrect error messages.

E.23.3. Changes

Below you will find a detailed account of the changes between PostgreSQL 12 and the previous major release.

E.23.3.1. Server

E.23.3.1.1. Partitioning

  • Improve performance of many operations on partitioned tables (Amit Langote, David Rowley, Tom Lane, Álvaro Herrera) § § § § §

    Allow tables with thousands of child partitions to be processed efficiently by operations that only affect a small number of partitions.

  • Allow foreign keys to reference partitioned tables (Álvaro Herrera) §

  • Improve speed of COPY into partitioned tables (David Rowley) §

  • Allow partition bounds to be any expression (Kyotaro Horiguchi, Tom Lane, Amit Langote) §

    Such expressions are evaluated at partitioned-table creation time. Previously, only simple constants were allowed as partition bounds.

  • Allow CREATE TABLE 's tablespace specification for a partitioned table to affect the tablespace of its children (David Rowley, Álvaro Herrera) §

  • Avoid sorting when partitions are already being scanned in the necessary order (David Rowley) §

  • ALTER TABLE ATTACH PARTITION is now performed with reduced locking requirements (Robert Haas) §

  • Add partition introspection functions (Michaël Paquier, Álvaro Herrera, Amit Langote) § § §

    The new function pg_partition_root() returns the top-most parent of a partition tree, pg_partition_ancestors() reports all ancestors of a partition, and pg_partition_tree() displays information about partitions.

  • Include partitioned indexes in the system view pg_indexes (Suraj Kharage) §

  • Add psql command \dP to list partitioned tables and indexes (Pavel Stehule) §

  • Improve psql \d and \z display of partitioned tables (Pavel Stehule, Michaël Paquier, Álvaro Herrera) § § §

  • Fix bugs that could cause ALTER TABLE DETACH PARTITION to leave behind incorrect dependency state, allowing subsequent operations to misbehave, for example by not dropping a former partition child index when its table is dropped (Tom Lane) §

E.23.3.1.2. Indexes

  • Improve performance and space utilization of btree indexes with many duplicates (Peter Geoghegan, Heikki Linnakangas) § § §

    Previously, duplicate index entries were stored unordered within their duplicate groups. This caused overhead during index inserts, wasted space due to excessive page splits, and it reduced VACUUM 's ability to recycle entire pages. Duplicate index entries are now sorted in heap-storage order.

    Indexes pg_upgrade 'd from previous releases will not have these benefits.

  • Allow multi-column btree indexes to be smaller (Peter Geoghegan, Heikki Linnakangas)

    Internal pages and min/max leaf page indicators now only store index keys until the change key, rather than all indexed keys. This also improves the locality of index access.

    Indexes pg_upgrade 'd from previous releases will not have these benefits.

  • Improve speed of btree index insertions by reducing locking overhead (Alexander Korotkov) §

  • Support INCLUDE columns in GiST indexes (Andrey Borodin) §

  • Add support for nearest-neighbor ( KNN ) searches of SP-GiST indexes (Nikita Glukhov, Alexander Korotkov, Vlad Sterzhanov) §

  • Reduce the WAL write overhead of GiST , GIN , and SP-GiST index creation (Anastasia Lubennikova, Andrey V. Lepikhov) §

  • Allow index-only scans to be more efficient on indexes with many columns (Konstantin Knizhnik) §

  • Improve the performance of vacuum scans of GiST indexes (Andrey Borodin, Konstantin Kuznetsov, Heikki Linnakangas) §

  • Delete empty leaf pages during GiST VACUUM (Andrey Borodin) §

  • Reduce locking requirements for index renaming (Peter Eisentraut) §

E.23.3.1.3. Optimizer

  • Allow CREATE STATISTICS to create most-common-value statistics for multiple columns (Tomas Vondra) § §

    This improves optimization for queries that test several columns, requiring an estimate of the combined effect of several WHERE clauses. If the columns are correlated and have non-uniform distributions then multi-column statistics will allow much better estimates.

  • Allow common table expressions ( CTEs ) to be inlined into the outer query (Andreas Karlsson, Andrew Gierth, David Fetter, Tom Lane) § §

    Specifically, CTE s are automatically inlined if they have no side-effects, are not recursive, and are referenced only once in the query. Inlining can be prevented by specifying MATERIALIZED , or forced for multiply-referenced CTE s by specifying NOT MATERIALIZED . Previously, CTE s were never inlined and were always evaluated before the rest of the query.

  • Allow control over when generic plans are used for prepared statements (Pavel Stehule) §

    This is controlled by the plan_cache_mode server parameter.

  • Improve optimization of partition and UNION ALL queries that have only a single child (David Rowley) §

  • Improve processing of domains that have no check constraints (Tom Lane) §

    Domains that are being used purely as type aliases no longer cause optimization difficulties.

  • Pre-evaluate calls of LEAST and GREATEST when their arguments are constants (Vik Fearing) §

  • Improve optimizer's ability to verify that partial indexes with IS NOT NULL conditions are usable in queries (Tom Lane, James Coleman) § §

    Usability can now be recognized in more cases where the calling query involves casts or large x IN ( array ) clauses.

  • Compute ANALYZE statistics using the collation defined for each column (Tom Lane) §

    Previously, the database's default collation was used for all statistics. This potentially gives better optimizer behavior for columns with non-default collations.

  • Improve selectivity estimates for inequality comparisons on ctid columns (Edmund Horner) §

  • Improve optimization of joins on columns of type tid (Tom Lane) § §

    These changes primarily improve the efficiency of self-joins on ctid columns.

  • Fix the leakproofness designations of some btree comparison operators and support functions (Tom Lane) § §

    This allows some optimizations that previously would not have been applied in the presence of security barrier views or row-level security.

E.23.3.1.4. General Performance

  • Enable Just-in-Time ( JIT ) compilation by default, if the server has been built with support for it (Andres Freund) §

    Note that this support is not built by default, but has to be selected explicitly while configuring the build.

  • Speed up keyword lookup (John Naylor, Joerg Sonnenberger, Tom Lane) § §

  • Improve search performance for multi-byte characters in position() and related functions (Heikki Linnakangas) §

  • Allow toasted values to be minimally decompressed (Paul Ramsey) §

    This is useful for routines that only need to examine the initial portion of a toasted field.

  • Allow ALTER TABLE ... SET NOT NULL to avoid unnecessary table scans (Sergei Kornilov) §

    This can be optimized when the table's column constraints can be recognized as disallowing nulls.

  • Allow ALTER TABLE ... SET DATA TYPE changing between timestamp and timestamptz to avoid a table rewrite when the session time zone is UTC (Noah Misch) §

    In the UTC time zone, these two data types are binary compatible.

  • Improve speed in converting strings to int2 or int4 integers (Andres Freund) §

  • Allow parallelized queries when in SERIALIZABLE isolation mode (Thomas Munro) §

    Previously, parallelism was disabled when in this mode.

  • Use pread() and pwrite() for random I/O (Oskari Saarenmaa, Thomas Munro) § §

    This reduces the number of system calls required for I/O.

  • Improve the speed of setting the process title on FreeBSD (Thomas Munro) §

E.23.3.1.5. Monitoring

  • Allow logging of statements from only a percentage of transactions (Adrien Nayrat) §

    The parameter log_transaction_sample_rate controls this.

  • Add progress reporting to CREATE INDEX and REINDEX operations (Álvaro Herrera, Peter Eisentraut) § §

    Progress is reported in the pg_stat_progress_create_index system view.

  • Add progress reporting to CLUSTER and VACUUM FULL (Tatsuro Yamada) §

    Progress is reported in the pg_stat_progress_cluster system view.

  • Add progress reporting to pg_checksums (Michael Banck, Bernd Helmle) §

    This is enabled with the option --progress .

  • Add counter of checksum failures to pg_stat_database (Magnus Hagander) §

  • Add tracking of global objects in system view pg_stat_database (Julien Rouhaud) §

    Global objects are shown with a pg_stat_database . datid value of zero.

  • Add the ability to list the contents of the archive directory (Christoph Moench-Tegeder) §

    The function is pg_ls_archive_statusdir() .

  • Add the ability to list the contents of temporary directories (Nathan Bossart) §

    The function, pg_ls_tmpdir() , optionally allows specification of a tablespace.

  • Add information about the client certificate to the system view pg_stat_ssl (Peter Eisentraut) §

    The new columns are client_serial and issuer_dn . Column clientdn has been renamed to client_dn for clarity.

  • Restrict visibility of rows in pg_stat_ssl for unprivileged users (Peter Eisentraut) §

  • At server start, emit a log message including the server version number (Christoph Berg) §

  • Prevent logging " incomplete startup packet " if a new connection is immediately closed (Tom Lane) §

    This avoids log spam from certain forms of monitoring.

  • Include the application_name , if set, in log_connections log messages (Don Seiler) §

  • Make the walreceiver set its application name to the cluster name, if set (Peter Eisentraut) §

  • Add the timestamp of the last received standby message to pg_stat_replication (Lim Myungkyu) §

  • Add a wait event for fsync of WAL segments (Konstantin Knizhnik) §

E.23.3.1.6. Authentication

  • Add GSSAPI encryption support (Robbie Harwood, Stephen Frost) §

    This feature allows TCP/IP connections to be encrypted when using GSSAPI authentication, without having to set up a separate encryption facility such as SSL. In support of this, add hostgssenc and hostnogssenc record types in pg_hba.conf for selecting connections that do or do not use GSSAPI encryption, corresponding to the existing hostssl and hostnossl record types. There is also a new gssencmode libpq option, and a pg_stat_gssapi system view.

  • Allow the clientcert pg_hba.conf option to check that the database user name matches the client certificate's common name (Julian Markwort, Marius Timmer) §

    This new check is enabled with clientcert=verify-full .

  • Allow discovery of an LDAP server using DNS SRV records (Thomas Munro) §

    This avoids the requirement of specifying ldapserver . It is only supported if PostgreSQL is compiled with OpenLDAP .

E.23.3.1.7. Server Configuration

  • Add ability to enable/disable cluster checksums using pg_checksums (Michael Banck, Michaël Paquier) §

    The cluster must be shut down for these operations.

  • Reduce the default value of autovacuum_vacuum_cost_delay to 2ms (Tom Lane) §

    This allows autovacuum operations to proceed faster by default.

  • Allow vacuum_cost_delay to specify sub-millisecond delays, by accepting fractional values (Tom Lane) §

  • Allow time-based server parameters to use units of microseconds ( us ) (Tom Lane) §

  • Allow fractional input for integer server parameters (Tom Lane) §

    For example, SET work_mem = '30.1GB' is now allowed, even though work_mem is an integer parameter. The value will be rounded to an integer after any required units conversion.

  • Allow units to be defined for floating-point server parameters (Tom Lane) §

  • Add wal_recycle and wal_init_zero server parameters to control WAL file recycling (Jerry Jelinek) §

    Avoiding file recycling can be beneficial on copy-on-write file systems like ZFS .

  • Add server parameter tcp_user_timeout to control the server's TCP timeout (Ryohei Nagaura) §

  • Allow control of the minimum and maximum SSL protocol versions (Peter Eisentraut) §

    The server parameters are ssl_min_protocol_version and ssl_max_protocol_version .

  • Add server parameter ssl_library to report the SSL library version used by the server (Peter Eisentraut) §

  • Add server parameter shared_memory_type to control the type of shared memory to use (Andres Freund) §

    This allows selection of System V shared memory, if desired.

E.23.3.2. Streaming Replication and Recovery

E.23.3.3. Utility Commands

  • Add REINDEX CONCURRENTLY option to allow reindexing without locking out writes (Michaël Paquier, Andreas Karlsson, Peter Eisentraut) §

    This is also controlled by the reindexdb application's --concurrently option.

  • Add support for generated columns (Peter Eisentraut) §

    The content of generated columns are computed from expressions (including references to other columns in the same table) rather than being specified by INSERT or UPDATE commands.

  • Add a WHERE clause to COPY FROM to control which rows are accepted (Surafel Temesgen) §

    This provides a simple way to filter incoming data.

  • Allow enumerated values to be added more flexibly (Andrew Dunstan, Tom Lane, Thomas Munro) §

    Previously, ALTER TYPE ... ADD VALUE could not be called in a transaction block, unless it was part of the same transaction that created the enumerated type. Now it can be called in a later transaction, so long as the new enumerated value is not referenced until after it is committed.

  • Add commands to end a transaction and start a new one (Peter Eisentraut) §

    The commands are COMMIT AND CHAIN and ROLLBACK AND CHAIN .

  • Add VACUUM and CREATE TABLE options to prevent VACUUM from truncating trailing empty pages (Takayuki Tsunakawa) § §

    These options are vacuum_truncate and toast.vacuum_truncate . Use of these options reduces VACUUM 's locking requirements, but prevents returning disk space to the operating system.

  • Allow VACUUM to skip index cleanup (Masahiko Sawada) § §

    This change adds a VACUUM command option INDEX_CLEANUP as well as a table storage option vacuum_index_cleanup . Use of this option reduces the ability to reclaim space and can lead to index bloat, but it is helpful when the main goal is to freeze old tuples.

  • Add the ability to skip VACUUM and ANALYZE operations on tables that cannot be locked immediately (Nathan Bossart) §

    This option is called SKIP_LOCKED .

  • Allow VACUUM and ANALYZE to take optional Boolean argument specifications (Masahiko Sawada) §

  • Prevent TRUNCATE , VACUUM and ANALYZE from requesting a lock on tables for which the user lacks permission (Michaël Paquier) § §

    This prevents unauthorized locking, which could interfere with user queries.

  • Add EXPLAIN option SETTINGS to output non-default optimizer settings (Tomas Vondra) §

    This output can also be obtained when using auto_explain by setting auto_explain.log_settings .

  • Add OR REPLACE option to CREATE AGGREGATE (Andrew Gierth) §

  • Allow modifications of system catalogs' options using ALTER TABLE (Peter Eisentraut) §

    Modifications of catalogs' reloptions and autovacuum settings are now supported. (Setting allow_system_table_mods is still required.)

  • Use all key columns' names when selecting default constraint names for foreign keys (Peter Eisentraut) §

    Previously, only the first column name was included in the constraint name, resulting in ambiguity for multi-column foreign keys.

E.23.3.4. Data Types

  • Update assorted knowledge about Unicode to match Unicode 12.1.0 (Peter Eisentraut) § §

    This fixes, for example, cases where psql would misformat output involving combining characters.

  • Update Snowball stemmer dictionaries with support for new languages (Arthur Zakirov) §

    This adds word stemming support for Arabic, Indonesian, Irish, Lithuanian, Nepali, and Tamil to full text search .

  • Allow creation of collations that report string equality for strings that are not bit-wise equal (Peter Eisentraut) §

    This feature supports " nondeterministic " collations that can define case- and accent-agnostic equality comparisons. Thus, for example, a case-insensitive uniqueness constraint on a text column can be made more easily than before. This is only supported for ICU collations.

  • Add support for ICU collation attributes on older ICU versions (Peter Eisentraut) §

    This allows customization of the collation rules in a consistent way across all ICU versions.

  • Allow data type name to more seamlessly be compared to other text types (Tom Lane) §

    Type name now behaves much like a domain over type text that has default collation " C " . This allows cross-type comparisons to be processed more efficiently.

E.23.3.5. Functions

  • Add support for the SQL/JSON path language (Nikita Glukhov, Teodor Sigaev, Alexander Korotkov, Oleg Bartunov, Liudmila Mantrova) § § §

    This allows execution of complex queries on JSON values using an SQL -standard language.

  • Add support for hyperbolic functions (Lætitia Avrot) §

    Also add log10() as an alias for log() , for standards compliance.

  • Improve the accuracy of statistical aggregates like variance() by using more precise algorithms (Dean Rasheed) §

  • Allow date_trunc() to have an additional argument to control the time zone (Vik Fearing, Tom Lane) §

    This is faster and simpler than using the AT TIME ZONE clause.

  • Adjust to_timestamp() / to_date() functions to be more forgiving of template mismatches (Artur Zakirov, Alexander Korotkov, Liudmila Mantrova) §

    This new behavior more closely matches the Oracle functions of the same name.

  • Fix assorted bugs in XML functions (Pavel Stehule, Markus Winand, Chapman Flack) §

    Specifically, in XMLTABLE , xpath() , and xmlexists() , fix some cases where nothing was output for a node, or an unexpected error was thrown, or necessary escaping of XML special characters was omitted.

  • Allow the BY VALUE clause in XMLEXISTS and XMLTABLE (Chapman Flack) §

    This SQL-standard clause has no effect in PostgreSQL 's implementation, but it was unnecessarily being rejected.

  • Prevent current_schema() and current_schemas() from being run by parallel workers, as they are not parallel-safe (Michaël Paquier) §

  • Allow RECORD and RECORD[] to be used as column types in a query's column definition list for a table function that is declared to return RECORD (Elvis Pranskevichus) §

E.23.3.6. PL/pgSQL

  • Allow SQL commands and variables with the same names as those commands to be used in the same PL/pgSQL function (Tom Lane) §

    For example, allow a variable called comment to exist in a function that calls the COMMENT SQL command. Previously this combination caused a parse error.

  • Add new optional warning and error checks to PL/pgSQL (Pavel Stehule) §

    The new checks allow for run-time validation of INTO column counts and single-row results.

E.23.3.7. Client Interfaces

  • Add connection parameter tcp_user_timeout to control libpq 's TCP timeout (Ryohei Nagaura) §

  • Allow libpq (and thus psql ) to report only the SQLSTATE value in error messages (Didier Gautheron) §

  • Add libpq function PQresultMemorySize() to report the memory used by a query result (Lars Kanis, Tom Lane) §

  • Remove the no-display/debug flag from libpq 's options connection parameter (Peter Eisentraut) §

    This allows this parameter to be set by postgres_fdw .

  • Allow ecpg to create variables of data type bytea (Ryo Matsumura) §

    This allows ECPG clients to interact with bytea data directly, rather than using an encoded form.

  • Add PREPARE AS support to ECPG (Ryo Matsumura) §

E.23.3.8. Client Applications

  • Allow vacuumdb to select tables for vacuum based on their wraparound horizon (Nathan Bossart) §

    The options are --min-xid-age and --min-mxid-age .

  • Allow vacuumdb to disable waiting for locks or skipping all-visible pages (Nathan Bossart) §

    The options are --skip-locked and --disable-page-skipping .

  • Add colorization to the output of command-line utilities (Peter Eisentraut) §

    This is enabled by setting the environment variable PG_COLOR to always or auto . The specific colors used can be adjusted by setting the environment variable PG_COLORS , using ANSI escape codes for colors. For example, the default behavior is equivalent to PG_COLORS="error=01;31:warning=01;35:locus=01" .

E.23.3.8.1. psql

  • Add CSV table output mode in psql (Daniel Vérité) §

    This is controlled by \pset format csv or the command-line --csv option.

  • Show the manual page URL in psql 's \help output for a SQL command (Peter Eisentraut) §

  • Display the IP address in psql 's \conninfo (Fabien Coelho) § §

  • Improve tab completion of CREATE TABLE , CREATE TRIGGER , CREATE EVENT TRIGGER , ANALYZE , EXPLAIN , VACUUM , ALTER TABLE , ALTER INDEX , ALTER DATABASE , and ALTER INDEX ALTER COLUMN (Dagfinn Ilmari Mannsåker, Tatsuro Yamada, Michaël Paquier, Tom Lane, Justin Pryzby) § § § § § § § § §

E.23.3.8.2. pgbench

  • Allow values produced by queries to be assigned to pgbench variables (Fabien Coelho, Álvaro Herrera) § §

    The command for this is \gset .

  • Improve precision of pgbench 's --rate option (Tom Lane) §

  • Improve pgbench 's error reporting with clearer messages and return codes (Peter Eisentraut) §

E.23.3.9. Server Applications

  • Allow control of log file rotation via pg_ctl (Kyotaro Horiguchi, Alexander Kuzmenkov, Alexander Korotkov) §

    Previously, this was only possible via an SQL function or a process signal.

  • Properly detach the new server process during pg_ctl start (Paul Guo) §

    This prevents the server from being shut down if the shell script that invoked pg_ctl is interrupted later.

  • Allow pg_upgrade to use the file system's cloning feature, if there is one (Peter Eisentraut) §

    The --clone option has the advantages of --link , while preventing the old cluster from being changed after the new cluster has started.

  • Allow specification of the socket directory to use in pg_upgrade (Daniel Gustafsson) §

    This is controlled by --socketdir ; the default is the current directory.

  • Allow pg_checksums to disable fsync operations (Michaël Paquier) §

    This is controlled by the --no-sync option.

  • Allow pg_rewind to disable fsync operations (Michaël Paquier) §

  • Fix pg_test_fsync to report accurate open_datasync durations on Windows (Laurenz Albe) § §

  • When pg_dump emits data with INSERT commands rather than COPY , allow more than one data row to be included in each INSERT (Surafel Temesgen, David Rowley) § §

    The option controlling this is --rows-per-insert .

  • Allow pg_dump to emit INSERT ... ON CONFLICT DO NOTHING (Surafel Temesgen) §

    This avoids conflict failures during restore. The option is --on-conflict-do-nothing .

  • Decouple the order of operations in a parallel pg_dump from the order used by a subsequent parallel pg_restore (Tom Lane) §

    This allows pg_restore to perform more-fully-parallelized parallel restores, especially in cases where the original dump was not done in parallel. Scheduling of a parallel pg_dump is also somewhat improved.

  • Allow the extra_float_digits setting to be specified for pg_dump and pg_dumpall (Andrew Dunstan) §

    This is primarily useful for making dumps that are exactly comparable across different source server versions. It is not recommended for normal use, as it may result in loss of precision when the dump is restored.

  • Add --exclude-database option to pg_dumpall (Andrew Dunstan) §

E.23.3.10. Source Code

  • Add CREATE ACCESS METHOD command to create new table types (Andres Freund, Haribabu Kommi, Álvaro Herrera, Alexander Korotkov, Dmitry Dolgov) § § § § § § § § §

    This enables the development of new table access methods , which can optimize storage for different use cases. The existing heap access method remains the default.

  • Add planner support function interfaces to improve optimizer estimates, inlining, and indexing for functions (Tom Lane) § § §

    This allows extensions to create planner support functions that can provide function-specific selectivity, cost, and row-count estimates that can depend on the function's arguments. Support functions can also supply simplified representations and index conditions, greatly expanding optimization possibilities.

  • Simplify renumbering manually-assigned OIDs, and establish a new project policy for management of such OIDs (John Naylor, Tom Lane) § §

    Patches that manually assign OIDs for new built-in objects (such as new functions) should now randomly choose OIDs in the range 8000-9999. At the end of a development cycle, the OIDs used by committed patches will be renumbered down to lower numbers, currently somewhere in the 4 xxx range, using the new renumber_oids.pl script. This approach should greatly reduce the odds of OID collisions between different in-process patches.

    While there is no specific policy reserving any OIDs for external use, it is recommended that forks and other projects needing private manually-assigned OIDs use numbers in the high 7 xxx range. This will avoid conflicts with recently-merged patches, and it should be a long time before the core project reaches that range.

  • Build Cygwin binaries using dynamic instead of static libraries (Marco Atzeri) §

  • Remove configure switch --disable-strong-random (Michaël Paquier) §

    A strong random-number source is now required.

  • printf -family functions, as well as strerror and strerror_r , now behave uniformly across platforms within Postgres code (Tom Lane) § § § §

    Notably, printf understands %m everywhere; on Windows, strerror copes with Winsock error codes (it used to do so in backend but not frontend code); and strerror_r always follows the GNU return convention.

  • Require a C99-compliant compiler, and MSVC 2013 or later on Windows (Andres Freund) §

  • Use pandoc , not lynx , for generating plain-text documentation output files (Peter Eisentraut) § §

    This affects only the INSTALL file generated during make dist and the seldom-used plain-text postgres.txt output file. Pandoc produces better output than lynx and avoids some locale/encoding issues. Pandoc version 1.13 or later is required.

  • Support use of images in the PostgreSQL documentation (Jürgen Purtz) §

E.23.3.11. Additional Modules

  • Allow ORDER BY sorts and LIMIT clauses to be pushed to postgres_fdw foreign servers in more cases (Etsuro Fujita) § §

  • Improve optimizer cost accounting for postgres_fdw queries (Etsuro Fujita) § § §

  • Properly honor WITH CHECK OPTION on views that reference postgres_fdw tables (Etsuro Fujita) §

    While CHECK OPTION s on postgres_fdw tables are ignored (because the reference is foreign), views on such tables are considered local, so this change enforces CHECK OPTION s on them. Previously, only INSERT s and UPDATE s with RETURNING clauses that returned CHECK OPTION values were validated.

  • Allow pg_stat_statements_reset() to be more granular (Haribabu Kommi, Amit Kapila) §

    The function now allows reset of statistics for specific databases, users, and queries.

  • Allow control of the auto_explain log level (Tom Dunstan, Andrew Dunstan) §

    The default is LOG .

  • Update unaccent rules with new punctuation and symbols (Hugh Ranalli, Michaël Paquier) §

  • Allow unaccent to handle some accents encoded as combining characters (Hugh Ranalli) §

  • Allow unaccent to remove accents from Greek characters (Tasos Maschalidis) §

  • Add a parameter to amcheck 's bt_index_parent_check() function to check each index tuple from the root of the tree (Peter Geoghegan) §

  • Improve oid2name and vacuumlo option handling to match other commands (Tatsuro Yamada) § §

E.23.4. 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
Achilleas Mantzios
Adam Berlin
Adam Bielanski
Aditya Toshniwal
Adrien Nayrat
Alan Jackson
Albert Schabhuetl
Aleksander Alekseev
Alex Aktsipetrov
Alex Kliukin
Alex Macy
Alexander Korotkov
Alexander Kukushkin
Alexander Kuzmenkov
Alexander Lakhin
Alexandra Ryzhevich
Alexey Bashtanov
Alexey Ermakov
Alexey Kondratov
Alexey Kryuchkov
Alexey Stepanov
Allison Kaptur
Álvaro Herrera
Alyssa Ross
Amit Kapila
Amit Khandekar
Amit Langote
Amul Sul
Anastasia Lubennikova
André Hänsel
Andrea Gelmini
Andreas Joseph Krogh
Andreas Karlsson
Andreas Kunert
Andreas Scherbaum
Andreas Seltenreich
Andrei Yahorau
Andres Freund
Andrew Dunstan
Andrew Fletcher
Andrew Gierth
Andrew Krasichkov
Andrey Borodin
Andrey Klychkov
Andrey Lepikhov
Andy Abelisto
Anthony Greene
Anthony Skorski
Antonin Houska
Arne Roland
Arseny Sher
Arthur Zakirov
Ash Marath
Ashutosh Bapat
Ashutosh Sharma
Ashwin Agrawal
Aya Iwata
Bartosz Polnik
Basil Bourque
Bernd Helmle
Brad DeJong
Brigitte Blanc-Lafay
Bruce Klein
Bruce Momjian
Bruno Wolff
Chapman Flack
Chen Huajun
Chris Travers
Chris Wilson
Christian Hofstaedtler
Christoph Berg
Christoph Moench-Tegeder
Clemens Ladisch
Colm McHugh
Corey Huinker
Craig Ringer
Dagfinn Ilmari Mannsåker
Daisuke Higuchi
Daniel Fiori
Daniel Gustafsson
Daniel Vérité
Daniel Westermann
Daniel Wilches
Darafei Praliaskouski
Daryl Waycott
Dave Cramer
David Binderman
David Fetter
David G. Johnston
David Rowley
David Steele
Davy Machado
Dean Rasheed
Derek Hans
Derek Nelson
Devrim Gündüz
Dian Fay
Didier Gautheron
Dilip Kumar
Dmitry Dolgov
Dmitry Marakasov
Dmitry Molotkov
Dmitry Shalashov
Don Seiler
Donald Dong
Doug Rady
Edmund Horner
Eduards Bezverhijs
Elvis Pranskevichus
Emanuel Araújo
Emre Hasegeli
Eric Cyr
Erik Rijkers
Ertugrul Kahveci
Etsuro Fujita
Eugen Konkov
Euler Taveira
Fabien Coelho
Fabrízio de Royes Mello
Feike Steenbergen
Filip Rembialkowski
Gaby Schilders
Geert Lobbestael
George Tarasov
Georgios Kokolatos
Gianni Ciolli
Gilles Darold
Greg Stark
Grigory Smolkin
Guillaume Lelarge
Gunnlaugur Thor Briem
Gurjeet Singh
Hadi Moshayedi
Hailong Li
Hans Buschmann
Haribabu Kommi
Haruka Takatsuka
Hayato Kuroda
Heikki Linnakangas
Hironobu Suzuki
Hubert Lubaczewski
Hugh Ranalli
Ian Barwick
Ibrar Ahmed
Ildar Musin
Insung Moon
Ioseph Kim
Isaac Morland
Ivan Panchenko
Jack Kelly
Jacob Champion
Jaime Casanova
Jakob Egger
Jakub Glapa
Jakub Janecek
James Coleman
James Inform
James Robinson
James Sewell
James Tomson
Jan Chochol
Jaroslav Sivy
Jean-Christophe Arnu
Jean-Marc Voillequin
Jean-Pierre Pelletier
Jeevan Chalke
Jeevan Ladhe
Jeff Davis
Jeff Janes
Jeremy Evans
Jeremy Schneider
Jeremy Smith
Jerry Jelinek
Jesper Pedersen
Jianing Yang
Jie Zhang
Jim Nasby
Jimmy Yih
Joe Conway
Joe Wildish
Joerg Sonnenberger
John Klann
John Naylor
Jonah Harris
Jonathan S. Katz
Jorge Gustavo Rocha
José Arthur Benetasso Villanova
Joshua D. Drake
Juan José Santamaría Flecha
Julian Hsiao
Julian Markwort
Julian Schauder
Julien Rouhaud
Jürgen Purtz
Jürgen Strobel
Justin Pryzby
Kaiting Chen
Karen Huddleston
Karl Czajkowski
Karl O. Pinc
Keiichi Hirobe
Keith Fiske
Ken Tanzer
Kenji Uno
Kevin Grittner
Kevin Hale Boyes
Kieran McCusker
Kirk Jamison
Kohei KaiGai
Konstantin Knizhnik
Konstantin Kuznetsov
Kristjan Tammekivi
Kuntal Ghosh
Kyle Samson
Kyotaro Horiguchi
Lætitia Avrot
Lars Kanis
Laurenz Albe
Lim Myungkyu
Liu Huailing
Liudmila Mantrova
Lloyd Albin
Luca Ferrari
Luis M. Carril
Lukas Eder
Lukas Fittl
Madelaine Thibaut
Madeleine Thompson
Magnus Hagander
Mahendra Singh
Mai Peng
Maksim Milyutin
Maksym Boguk
Malthe Borch
Manuel Rigger
Marco Atzeri
Marco Slot
Marina Polyakova
Mario De Frutos Dieguez
Marius Timmer
Mark Chambers
Mark Dilger
Marko Tiikkaja
Markus Winand
Martín Marqués
Masahiko Sawada
Masao Fujii
Mateusz Guzik
Mathias Brossard
Matt Williams
Matthias Otterbach
Matvey Arye
Melanie Plageman
Mi Tar
Michael Banck
Michael Davidson
Michael Meskes
Michael Paquier
Michael Vitale
Michel Pelletier
Mikalai Keida
Mike Palmiotto
Mithun Cy
Morgan Owens
Murat Kabilov
Nathan Bossart
Nawaz Ahmed
Neeraj Kumar
Nick Barnes
Nico Williams
Nikita Glukhov
Nikolay Shaplov
Ning Yu
Nishant Fnu
Noah Misch
Norbert Benkocs
Noriyoshi Shinoda
Oleg Bartunov
Oleg Samoilov
Oleksii Kliukin
Ondrej Bouda
Oskari Saarenmaa
Pan Bian
Patrick Francelle
Patrick McHardy
Paul A. Jungwirth
Paul Bonaud
Paul Guo
Paul Martinez
Paul Ramsey
Paul Schaap
Paul van der Linden
Pavan Deolasee
Pavel Oskin
Pavel Raiskup
Pavel Stehule
Peifeng Qiu
Peter Billen
Peter Eisentraut
Peter Geoghegan
Peter Neave
Petr Fedorov
Petr Jelínek
Petr Slavov
Petru-Florin Mihancea
Phil Bayer
Phil Florent
Philip Dubé
Pierre Ducroquet
Piotr Gabriel Kosinski
Piotr Stefaniak
Piotr Wlodarczyk
Prabhat Sahu
Quentin Rameau
Rafael Castro
Rafia Sabih
Rahila Syed
Rajkumar Raghuwanshi
Rares Salcudean
Raúl Marín Rodríguez
Regina Obe
Renaud Navarro
Richard Guo
Rick Otten
Rikard Falkeborn
RK Korlapati
Robbie Harwood
Robert Haas
Robert Treat
Robert Vollmert
Roger Curley
Roman Zharkov
Ronan Dunklau
Rui Hai Jiang
Rushabh Lathia
Ryan Lambert
Ryo Matsumura
Ryohei Nagaura
Ryohei Takahashi
Samuel Williams
Sand Stone
Sanyo Capobiango
Satoru Koizumi
Sean Johnston
Serge Latyntsev
Sergei Kornilov
Sergey Pashkov
Sergio Conde Gómez
Shawn Debnath
Shay Rojansky
Sho Kato
Shohei Mochizuki
Shouyu Luo
Simon Riggs
Sivasubramanian Ramasubramanian
Slawomir Chodnicki
Stas Kelvish
Stefan Kadow
Stepan Yankevych
Stephen Amell
Stephen Frost
Steve Rogerson
Steve Singer
Steven Winfield
Surafel Temesgen
Suraj Kharage
Suresh Kumar R
Takayuki Tsunakawa
Takeshi Ideriha
Takuma Hoshiai
Tasos Maschalidis
Tatsuo Ishii
Tatsuro Yamada
Teodor Sigaev
Thom Brown
Thomas Munro
Thomas Poty
Tillmann Schulz
Tim Möhlmann
Timur Birsh
Tobias Bussmann
Tom Cassidy
Tom Dunstan
Tom Gottfried
Tom Lane
Tomas Vondra
Tushar Ahuja
Ulf Adams
Vaishnavi Prabakaran
Victor Petrovykh
Victor Wagner
Victor Yegorov
Vijaykumar Jain
Vik Fearing
Vlad Sterzhanov
Vladimir Baranoff
Vladimir Kriukov
Wu Fei
Yaroslav Schekin
Yi Huang
Yoshikazu Imai
Yugo Nagata
Yulian Khodorkovskiy
Yuming Wang
YunQiang Su
Yuri Kurenkov
Yusuke Egashira
Yuzuko Hosoya
Zhou Digoal
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