PostgreSQL

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.

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

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.

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.

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

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.

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.

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.

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.

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.

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

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

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

Also improve the error message in such cases.

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

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.

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).

The comparison operators for data type name can now use any collation, rather than always using “[.quote]#C”# collation. To preserve the previous semantics of queries, columns of type name are now explicitly marked as having “[.quote]#C”# collation. A side effect of this is that regular-expression operators on name columns will now use the “[.quote]#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.)

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

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

Specifically, dynamic_shared_memory_type can no longer be set to none.

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.

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

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

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.

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.

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.

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.

Specifically, CTEs 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 CTEs by specifying NOT MATERIALIZED. Previously, CTEs were never inlined and were always evaluated before the rest of the query.

This is controlled by the plan_cache_mode server parameter.

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

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

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

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

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

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

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

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

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

Previously, parallelism was disabled when in this mode.

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

The parameter log_transaction_sample_rate controls this.

Progress is reported in the pg_stat_progress_create_index system view.

Progress is reported in the pg_stat_progress_cluster system view.

This is enabled with the option --progress.

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

The function is pg_ls_archive_statusdir().

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

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

This avoids log spam from certain forms of monitoring.

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.

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

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

The cluster must be shut down for these operations.

This allows autovacuum operations to proceed faster by default.

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.

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

The server parameters are ssl_min_protocol_version and ssl_max_protocol_version.

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

These parameters are archive_cleanup_command, promote_trigger_file, recovery_end_command, and recovery_min_apply_delay.

Previously, this could only be set cluster-wide.

Previously, this operation was only possible by using pg_ctl or creating a trigger file.

The functions for this are pg_copy_physical_replication_slot() and pg_copy_logical_replication_slot().

Previously, a warning was logged and recovery continued, allowing the transaction to be lost.

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

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.

This provides a simple way to filter incoming data.

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.

The commands are COMMIT AND CHAIN and ROLLBACK AND CHAIN.

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.

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.

This option is called SKIP_LOCKED.

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

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

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

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

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

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

This feature supports “[.quote]#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.

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

Type name now behaves much like a domain over type text that has default collation “[.quote]#C”#. This allows cross-type comparisons to be processed more efficiently.

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

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

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

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

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.

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

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.

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

This allows this parameter to be set by postgres_fdw.

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

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

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

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".

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

The command for this is \gset.

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

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

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

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

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

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

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

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.

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.

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.

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.

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.

A strong random-number source is now required.

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.

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.

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.

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

The default is LOG.