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E.45.1. Overview

E.45.2. Migration to Version 9.5

E.45.3. Changes

• AddBlock Range Indexes (BRIN) (Álvaro Herrera)

  BRIN indexes store only summary data (such as minimum and maximum values) for ranges of heap blocks. They are therefore very compact and cheap to update; but if the data is naturally clustered, they can still provide substantial speedup of searches.

• Allow queries to perform accurate distance filtering of bounding-box-indexed objects (polygons, circles) usingGiST indexes (Alexander Korotkov, Heikki Linnakangas)

  Previously, to exploit such an index a subquery had to be used to select a large number of rows ordered by bounding-box distance, and the result then had to be filtered further with a more accurate distance calculation.

• AllowGiST indexes to perform index-only scans (Anastasia Lubennikova, Heikki Linnakangas, Andreas Karlsson)

• Add configuration parametergin_pending_list_limit to control the size ofGIN pending lists (Fujii Masao)

  This value can also be set on a per-index basis as an index storage parameter. Previously the pending-list size was controlled bywork_mem, which was awkward because appropriate values forwork_mem are often much too large for this purpose.

• Issue a warning during the creation ofhash indexes because they are not crash-safe (Bruce Momjian)

• Improve the speed of sorting ofvarchar,text, andnumeric fields via“abbreviated” keys (Peter Geoghegan, Andrew Gierth, Robert Haas)

• Extend the infrastructure that allows sorting to be performed by inlined, non-SQL-callable comparison functions to coverCREATE INDEX,REINDEX, andCLUSTER (Peter Geoghegan)

• Improve performance of hash joins (Tomas Vondra, Robert Haas)

• Improve concurrency of shared buffer replacement (Robert Haas, Amit Kapila, Andres Freund)

• Reduce the number of page locks and pins during index scans (Kevin Grittner)

  The primary benefit of this is to allow index vacuums to be blocked less often.

• Make per-backend tracking of buffer pins more memory-efficient (Andres Freund)

• Improve lock scalability (Andres Freund)

  This particularly addresses scalability problems when running on systems with multipleCPU sockets.

• Allow the optimizer to remove unnecessary references to left-joined subqueries (David Rowley)

• Allow pushdown of query restrictions into subqueries withwindow functions, where appropriate (David Rowley)

• Allow a non-leakproof function to be pushed down into a security barrier view if the function does not receive any view output columns (Dean Rasheed)

• Teach the planner to use statistics obtained from an expression index on a boolean-returning function, when a matching function call appears inWHERE (Tom Lane)

• MakeANALYZE compute basic statistics (null fraction and average column width) even for columns whose data type lacks an equality function (Oleksandr Shulgin)

• Speed upCRC (cyclic redundancy check) computations and switch to CRC-32C (Abhijit Menon-Sen, Heikki Linnakangas)

• Improve bitmap index scan performance (Teodor Sigaev, Tom Lane)

• Speed upCREATE INDEX by avoiding unnecessary memory copies (Robert Haas)

• Increase the number of buffer mapping partitions (Amit Kapila, Andres Freund, Robert Haas)

  This improves performance for highly concurrent workloads.

• Add per-table autovacuum logging control via newlog_autovacuum_min_duration storage parameter (Michael Paquier)

• Add new configuration parametercluster_name (Thomas Munro)

  This string, typically set inpostgresql.conf, allows clients to identify the cluster. This name also appears in the process title of all server processes, allowing for easier identification of processes belonging to the same cluster.

• Prevent non-superusers from changinglog_disconnections on connection startup (Fujii Masao)

• Check“Subject Alternative Names” inSSL server certificates, if present (Alexey Klyukin)

  When they are present, this replaces checks against the certificate's“Common Name”.

• Add system viewpg_stat_ssl to reportSSL connection information (Magnus Hagander)

• Addlibpq functions to returnSSL information in an implementation-independent way (Heikki Linnakangas)

  WhilePQgetssl() can still be used to callOpenSSL functions, it is now considered deprecated because future versions oflibpq might support otherSSL implementations. When possible, use the new functionsPQsslAttribute(),PQsslAttributeNames(), andPQsslInUse() to obtainSSL information in anSSL-implementation-independent way.

• Makelibpq honor anyOpenSSL thread callbacks (Jan Urbanski)

  Previously they were overwritten.

• Replace configuration parametercheckpoint_segments withmin_wal_size andmax_wal_size (Heikki Linnakangas)

  This change allows the allocation of a large number ofWAL files without keeping them after they are no longer needed. Therefore the default formax_wal_size has been set to1GB, much larger than the old default forcheckpoint_segments. Also note that standby servers perform restartpoints to try to limit their WAL space consumption tomax_wal_size; previously they did not pay any attention tocheckpoint_segments.

• Control the LinuxOOM killer via new environment variablesPG_OOM_ADJUST_FILE andPG_OOM_ADJUST_VALUE (Gurjeet Singh)

  The previousOOM control infrastructure involved compile-time optionsLINUX_OOM_SCORE_ADJ andLINUX_OOM_ADJ, which are no longer supported. The new behavior is available in all builds.

• Allow recording of transaction commit time stamps when configuration parametertrack_commit_timestamp is enabled (Álvaro Herrera, Petr Jelínek)

  Time stamp information can be accessed using functionspg_xact_commit_timestamp() andpg_last_committed_xact().

• Allowlocal_preload_libraries to be set byALTER ROLE SET (Peter Eisentraut, Kyotaro Horiguchi)

• Allowautovacuum workers to respond to configuration parameter changes during a run (Michael Paquier)

• Make configuration parameterdebug_assertions read-only (Andres Freund)

  This means that assertions can no longer be turned off if they were enabled at compile time, allowing for more efficient code optimization. This change also removes thepostgres-A option.

• Allow settingeffective_io_concurrency on systems where it has no effect (Peter Eisentraut)

• Add system viewpg_file_settings to show the contents of the server's configuration files (Sawada Masahiko)

• Addpending_restart to the system viewpg_settings to indicate a change has been made but will not take effect until a database restart (Peter Eisentraut)

• AllowALTER SYSTEM values to be reset withALTER SYSTEM RESET (Vik Fearing)

  This command removes the specified setting frompostgresql.auto.conf.

• AllowREINDEX to reindex an entire schema using theSCHEMA option (Sawada Masahiko)

• AddVERBOSE option toREINDEX (Sawada Masahiko)

• PreventREINDEX DATABASE andSCHEMA from outputting object names, unlessVERBOSE is used (Simon Riggs)

• Remove obsoleteFORCE option fromREINDEX (Fujii Masao)

• Add support forIMPORT FOREIGN SCHEMA (Ronan Dunklau, Michael Paquier, Tom Lane)

  This command allows automatic creation of local foreign tables that match the structure of existing tables on a remote server.

• AllowCHECK constraints to be placed on foreign tables (Shigeru Hanada, Etsuro Fujita)

  Such constraints are assumed to be enforced on the remote server, and are not enforced locally. However, they are assumed to hold for purposes of query optimization, such asconstraint exclusion.

• Allow foreign tables to participate in inheritance (Shigeru Hanada, Etsuro Fujita)

  To let this work naturally, foreign tables are now allowed to have check constraints marked as not valid, and to set storage andOID characteristics, even though these operations are effectively no-ops for a foreign table.

• Allow foreign data wrappers and custom scans to implement join pushdown (KaiGai Kohei)

• Whenever addl_command_end event trigger is installed, capture details ofDDL activity for it to inspect (Álvaro Herrera)

  This information is available through a set-returning functionpg_event_trigger_ddl_commands(), or by inspection of C data structures if that function doesn't provide enough detail.

• Allow event triggers on table rewrites caused byALTER TABLE (Dimitri Fontaine)

• Add event trigger support for database-levelCOMMENT,SECURITY LABEL, andGRANT/REVOKE (Álvaro Herrera)

• Add columns to the output ofpg_event_trigger_dropped_objects (Álvaro Herrera)

  This allows simpler processing of delete operations.

• Addjsonb functionsjsonb_set() andjsonb_pretty() (Dmitry Dolgov, Andrew Dunstan, Petr Jelínek)

• Addjsonb generator functionsto_jsonb(),jsonb_object(),jsonb_build_object(),jsonb_build_array(),jsonb_agg(), andjsonb_object_agg() (Andrew Dunstan)

  Equivalent functions already existed for typejson.

• Reduce casting requirements to/fromjson andjsonb (Tom Lane)

• Allowtext,text array, andinteger values to besubtracted fromjsonb documents (Dmitry Dolgov, Andrew Dunstan)

• Addjsonb|| operator (Dmitry Dolgov, Andrew Dunstan)

• Addjson_strip_nulls() andjsonb_strip_nulls() functions to remove JSON null values from documents (Andrew Dunstan)

• Add functionpg_get_object_address() to returnOIDs that uniquely identify an object, and functionpg_identify_object_as_address() to return object information based onOIDs (Álvaro Herrera)

• Loosen security checks for viewing queries inpg_stat_activity, executingpg_cancel_backend(), and executingpg_terminate_backend() (Stephen Frost)

  Previously, only the specific role owning the target session could perform these operations; now membership in that role is sufficient.

• Addpg_stat_get_snapshot_timestamp() to output the time stamp of the statistics snapshot (Matt Kelly)

  This represents the last time the snapshot file was written to the file system.

• Addmxid_age() to compute multi-xid age (Bruce Momjian)

• Addmin()/max() aggregates forinet/cidr data types (Haribabu Kommi)

• Use 128-bit integers, where supported, as accumulators for some aggregate functions (Andreas Karlsson)

• ImprovePL/pgSQL array performance (Tom Lane)

• Add anASSERT statement inPL/pgSQL (Pavel Stehule)

• Allow morePL/pgSQL keywords to be used as identifiers (Tom Lane)

• Allowpsql to produce AsciiDoc output (Szymon Guz)

• Add anerrors mode that displays only failed commands topsql'sECHO variable (Pavel Stehule)

  This behavior can also be selected withpsql's-b option.

• Provide separate column, header, and border linestyle control inpsql's unicode linestyle (Pavel Stehule)

  Single or double lines are supported; the default issingle.

• Add new option%l inpsql'sPROMPT variables to display the current multiline statement line number (Sawada Masahiko)

• Add\pset optionpager_min_lines to control pager invocation (Andrew Dunstan)

• Improvepsql line counting used when deciding to invoke the pager (Andrew Dunstan)

• psql now fails if the file specified by an--output or--log-file switch cannot be written (Tom Lane, Daniel Vérité)

  Previously, it effectively ignored the switch in such cases.

• Addpsql tab completion when setting thesearch_path variable (Jeff Janes)

  Currently only the first schema can be tab-completed.

• Improvepsql's tab completion for triggers and rules (Andreas Karlsson)

• Allowpg_dump to share a snapshot taken by another session using--snapshot (Simon Riggs, Michael Paquier)

  The remote snapshot must have been exported bypg_export_snapshot() or logical replication slot creation. This can be used to share a consistent snapshot across multiplepg_dump processes.

• Support table sizes exceeding 8GB in tar archive format (Tom Lane)

  The POSIX standard for tar format does not allow elements of a tar archive to exceed 8GB, but most modern implementations of tar support an extension that does allow it. Use the extension format when necessary, rather than failing.

• Makepg_dump always print the server andpg_dump versions (Jing Wang)

  Previously, version information was only printed in--verbose mode.

• Remove the long-ignored-i/--ignore-version option frompg_dump,pg_dumpall, andpg_restore (Fujii Masao)

• Support multiplepg_ctl-o options, concatenating their values (Bruce Momjian)

• Allow control ofpg_ctl's event source logging onMS Windows (MauMau)

  This only controlspg_ctl, not the server, which has separate settings inpostgresql.conf.

• If the server's listen address is set to a wildcard value (0.0.0.0 in IPv4 or:: in IPv6), connect via the loopback address rather than trying to use the wildcard address literally (Kondo Yuta)

  This fix primarily affects Windows, since on other platformspg_ctl will prefer to use a Unix-domain socket.

• Movepg_upgrade fromcontrib tosrc/bin (Peter Eisentraut)

  In connection with this change, the functionality previously provided by thepg_upgrade_support module has been moved into the core server.

• Support multiplepg_upgrade-o/-O options, concatenating their values (Bruce Momjian)

• Improve database collation comparisons inpg_upgrade (Heikki Linnakangas)

• Remove support for upgrading from 8.3 clusters (Bruce Momjian)

• Move pgbench fromcontrib tosrc/bin (Peter Eisentraut)

• Fix calculation of TPS number“excluding connections establishing” (Tatsuo Ishii, Fabien Coelho)

  The overhead for connection establishment was miscalculated whenever the number of pgbench threads was less than the number of client connections. Although this is clearly a bug, we won't back-patch it into pre-9.5 branches since it makes TPS numbers not comparable to previous results.

• Allow counting of pgbench transactions that take over a specified amount of time (Fabien Coelho)

  This is controlled by a new--latency-limit option.

• Allow pgbench to generate Gaussian/exponential distributions using\setrandom (Kondo Mitsumasa, Fabien Coelho)

• Allowpgbench's\set command to handle arithmetic expressions containing more than one operator, and add% (modulo) to the set of operators it supports (Robert Haas, Fabien Coelho)

• Allow higher-precision time stamp resolution onWindows 8,Windows Server 2012, and later Windows systems (Craig Ringer)

• Install shared libraries tobin inMS Windows (Peter Eisentraut, Michael Paquier)

• Installsrc/test/modules together withcontrib onMSVC builds (Michael Paquier)

• Allowconfigure's--with-extra-version option to be honored by theMSVC build (Michael Paquier)

• PassPGFILEDESC intoMSVC contrib builds (Michael Paquier)

• Add icons to allMSVC-built binaries and version information to allMS Windows binaries (Noah Misch)

  MinGW already had such icons.

• Add optional-argument support to the internalgetopt_long() implementation (Michael Paquier, Andres Freund)

  This is used by theMSVC build.