PostgreSQL 是什麼，跟 MySQL 有什麼差別

What's new in this version:

- Preserve the indisclustered setting of indexes rewritten by ALTER TABLE
- Previously, ALTER TABLE lost track of which index had been used for CLUSTER.
- Preserve the replica identity properties of indexes rewritten by ALTER TABLE
- Lock objects sooner during DROP OWNED BY
- This avoids failures in race-condition cases where another session is deleting some of the same objects.
- Fix error-case processing for CREATE ROLE ... IN ROL
- Some error cases would be reported as "unexpected node type" or the like, instead of the intended message.
- Fix full text search to handle NOT above a phrase search correctly
- Queries such as !(foo<->bar) failed to find matching rows when implemented as a GiST or GIN index search.
- Fix full text search for cases where a phrase search includes an item with both prefix matching and a weight restriction
- Fix ts_headline() to make better headline selections when working with phrase queries
- Fix bugs in gin_fuzzy_search_limit processing
- A small value of gin_fuzzy_search_limit could result in unexpected slowness due to unintentionally rescanning the same index page many times. Another code path failed to apply the intended filtering at all, possibly returning too many values.
- Allow input of type circle to accept the format "(x,y),r" as the documentation says it does (David Zhang)
- Make the get_bit() and set_bit() functions cope with bytea strings longer than 256MB (Movead Li)
- Since the bit number argument is only int4, it's impossible to use these functions to access bits beyond the first 256MB of a long bytea. We'll widen the argument to int8 in v13, but in the meantime, allow these functions to work on the initial substring of a long bytea.
- Avoid possibly leaking an open-file descriptor for a directory in pg_ls_dir(), pg_timezone_names(), pg_tablespace_databases(), and allied functions
- Fix polymorphic-function type resolution to correctly infer the actual type of an anyarray output when given only an anyrange input
- Avoid unlikely crash when REINDEX is terminated by a session-shutdown signal
- Prevent printout of possibly-incorrect hash join table statistics in EXPLAIN
- Fix reporting of elapsed time for heap truncation steps in VACUUM VERBOSE
- Avoid possibly showing "waiting" twice in a process's PS status
- Avoid premature recycling of WAL segments during crash recovery
- WAL segments that become ready to be archived during crash recovery were potentially recycled without being archived.
- Avoid scanning irrelevant timelines during archive recovery
- This can eliminate many attempts to fetch non-existent WAL files from archive storage, which is helpful if archive access is slow.
- Remove bogus "subtransaction logged without previous top-level txn record" error check in logical decoding
- This condition is legitimately reachable in various scenarios, so remove the check.
- Ensure that a replication slot's io_in_progress_lock is released in failure code paths
- This could result in a walsender later becoming stuck waiting for the lock.
- Fix race conditions in synchronous standby management
- During a change in the synchronous_standby_names setting, there was a window in which wrong decisions could be made about whether it is OK to release transactions that are waiting for synchronous commit. Another hazard for similarly wrong decisions existed if a walsender process exited and was immediately replaced by another.
- Ensure nextXid can't go backwards on a standby server
- This race condition could allow incorrect hot standby feedback messages to be sent back to the primary server, potentially allowing VACUUM to run too soon on the primary.
- Add missing SQLSTATE values to a few error reports
- Fix PL/pgSQL to reliably refuse to execute an event trigger function as a plain function
- Fix memory leak in libpq when using sslmode=verify-full
- Certificate verification during connection startup could leak some memory. This would become an issue if a client process opened many database connections during its lifetime.
- Fix ecpg to treat an argument of just "-" as meaning "read from stdin" on all platforms
- Add pg_dump support for ALTER ... DEPENDS ON EXTENSION
- pg_dump previously ignored dependencies added this way, causing them to be forgotten during dump/restore or pg_upgrade.
- Fix pg_dump to dump comments on RLS policy objects
- In pg_dump, postpone restore of event triggers till the end
- This minimizes the risk that an event trigger could interfere with the restoration of other objects.
- Fix quoting of --encoding, --lc-ctype and --lc-collate values in createdb utility
- contrib/lo's lo_manage() function crashed if called directly rather than as a trigger
- In contrib/ltree, protect against overflow of ltree and lquery length fields
- Fix cache reference leak in contrib/sepgsql
- Avoid failures when dealing with Unix-style locale names on Windows
- In MSVC builds, cope with spaces in the path name for Python
- In MSVC builds, fix detection of Visual Studio version to work with more language settings
- In MSVC builds, use -Wno-deprecated with bison versions newer than 3.0, as non-Windows builds already do
- Update time zone data files to tzdata release 2020a for DST law changes in Morocco and the Canadian Yukon, plus historical corrections for Shanghai.
- The America/Godthab zone has been renamed to America/Nuuk to reflect current English usage; however, the old name remains available as a compatibility link.
- Also, update initdb's list of known Windows time zone names to include recent additions, improving the odds that it will correctly translate the system time zone setting on that platform.