PostgreSQL 是什麼，跟 MySQL 有什麼差別

What's new in this version:

- Restrict visibility of pg_user_mappings.umoptions, to protect passwords stored as user mapping options
- Prevent exposure of statistical information via leaky operators
- Restore libpq's recognition of the PGREQUIRESSL environment variable
- Fix possibly-invalid initial snapshot during logical decoding
- Fix possible corruption of "init forks" of unlogged indexes
- Fix incorrect reconstruction of pg_subtrans entries when a standby server replays a prepared but uncommitted two-phase transaction
- Avoid possible crash in walsender due to failure to initialize a string buffer
- Fix possible crash when rescanning a nearest-neighbor index-only scan on a GiST index
- Prevent delays in postmaster's launching of multiple parallel worker processes
- Fix postmaster's handling of fork() failure for a background worker process
- Fix possible "no relation entry for relid 0" error when planning nested set operations
- Fix assorted minor issues in planning of parallel queries
- Avoid applying "physical targetlist" optimization to custom scans
- Use the correct sub-expression when applying a FOR ALL row-level-security policy
- Ensure parsing of queries in extension scripts sees the results of immediately-preceding DDL
- Skip tablespace privilege checks when ALTER TABLE ... ALTER COLUMN TYPE rebuilds an existing index
- Fix ALTER TABLE ... VALIDATE CONSTRAINT to not recurse to child tables when the constraint is marked NO INHERIT
- Avoid dangling pointer in COPY ... TO when row-level security is active for the source table
- Avoid accessing an already-closed relcache entry in CLUSTER and VACUUM FULL
- Fix VACUUM to account properly for pages that could not be scanned due to conflicting page pins
- Ensure that bulk-tuple-transfer loops within a hash join are interruptible by query cancel requests
- Fix incorrect support for certain box operators in SP-GiST
- Fix integer-overflow problems in interval comparison
- Fix cursor_to_xml() to produce valid output with tableforest = false
- Fix roundoff problems in float8_timestamptz() and make_interval()
- These functions truncated, rather than rounded, when converting a floating-point value to integer microseconds; that could cause unexpectedly off-by-one results.
- Fix pg_get_object_address() to handle members of operator families correctly
- Fix cancelling of pg_stop_backup() when attempting to stop a non-exclusive backup
- If pg_stop_backup() was cancelled while waiting for a non-exclusive backup to end, related state was left inconsistent; a new exclusive backup could not be started, and there were other minor problems.
- Improve performance of pg_timezone_names view
- Reduce memory management overhead for contexts containing many large blocks
- Fix sloppy handling of corner-case errors from lseek() and close()
- Neither of these system calls are likely to fail in typical situations, but if they did, fd.c could get quite confused.
- Fix incorrect check for whether postmaster is running as a Windows service
- This could result in attempting to write to the event log when that isn't accessible, so that no logging happens at all.
- Fix ecpg to support COMMIT PREPARED and ROLLBACK PREPARED
- Fix a double-free error when processing dollar-quoted string literals in ecpg
- Fix pgbench to handle the combination of --connect and --rate options correctly
- Fix pgbench to honor the long-form option spelling --builtin, as per its documentation
- Fix pg_dump/pg_restore to correctly handle privileges for the public schema when using --clean option
- Other schemas start out with no privileges granted, but public does not; this requires special-case treatment when it is dropped and restored due to the --clean option.
- In pg_dump, fix incorrect schema and owner marking for comments and security labels of some types of database objects
- In simple cases this caused no ill effects; but for example, a schema-selective restore might omit comments it should include, because they were not marked as belonging to the schema of their associated object.
- Fix typo in pg_dump's query for initial privileges of a procedural language
- This resulted in pg_dump always believing that the language had no initial privileges. Since that's true for most procedural languages, ill effects from this bug are probably rare.
- Avoid emitting an invalid list file in pg_restore -l when SQL object names contain newlines
- Replace newlines by spaces, which is sufficient to make the output valid for pg_restore -L's purposes
- Fix pg_upgrade to transfer comments and security labels attached to "large objects" (blobs)
- Previously, blobs were correctly transferred to the new database, but any comments or security labels attached to them were lost
- Improve error handling in contrib/adminpack's pg_file_write() function
- Notably, it failed to detect errors reported by fclose().
- In contrib/dblink, avoid leaking the previous unnamed connection when establishing a new unnamed connection
- Fix contrib/pg_trgm's extraction of trigrams from regular expressions
- In some cases it would produce a broken data structure that could never match anything, leading to GIN or GiST indexscans that use a trigram index not finding any matches to the regular expression.
- In contrib/postgres_fdw, allow join conditions that contain shippable extension-provided functions to be pushed to the remote server
- Support Tcl 8.6 in MSVC builds
- Sync our copy of the timezone library with IANA release tzcode2017b
- This fixes a bug affecting some DST transitions in January 2038.
- Update time zone data files to tzdata release 2017b for DST law changes in Chile, Haiti, and Mongolia, plus historical corrections for Ecuador, Kazakhstan, Liberia, and Spain. Switch to numeric abbreviations for numerous time zones in South America, the Pacific and Indian oceans, and some Asian and Middle Eastern countries.
- The IANA time zone database previously provided textual abbreviations for all time zones, sometimes making up abbreviations that have little or no currency among the local population. They are in process of reversing that policy in favor of using numeric UTC offsets in zones where there is no evidence of real-world use of an English abbreviation. At least for the time being, PostgreSQL will continue to accept such removed abbreviations for timestamp input. But they will not be shown in the pg_timezone_names view nor used for output.
- Use correct daylight-savings rules for POSIX-style time zone names in MSVC builds
- The Microsoft MSVC build scripts neglected to install the posixrules file in the timezone directory tree. This resulted in the timezone code falling back to its built-in rule about what DST behavior to assume for a POSIX-style time zone name. For historical reasons that still corresponds to the DST rules the USA was using before 2007 (i.e., change on first Sunday in April and last Sunday in October). With this fix, a POSIX-style zone name will use the current and historical DST transition dates of the US/Eastern zone. If you don't want that, remove the posixrules file, or replace it with a copy of some other zone file (see Section 8.5.3). Note that due to caching, you may need to restart the server to get such changes to take effect.