diff --git a/doc/src/sgml/release-9.6.sgml b/doc/src/sgml/release-9.6.sgml
index 0c28dce3662..21d7f2df0d8 100644
--- a/doc/src/sgml/release-9.6.sgml
+++ b/doc/src/sgml/release-9.6.sgml
@@ -1,6 +1,916 @@
+
+ Release 9.6.21
+
+
+ Release date:
+ 2021-02-11
+
+
+
+ This release contains a variety of fixes from 9.6.20.
+ For information about new features in the 9.6 major release, see
+ .
+
+
+
+ The PostgreSQL community will stop
+ releasing updates for the 9.6.X release series in November 2021.
+ Users are encouraged to update to a newer release branch soon.
+
+
+
+ Migration to Version 9.6.21
+
+
+ A dump/restore is not required for those running 9.6.X.
+
+
+
+ However, see the first changelog item below,
+ which describes cases in which reindexing indexes after the upgrade
+ may be advisable.
+
+
+
+ Also, if you are upgrading from a version earlier than 9.6.16,
+ see .
+
+
+
+
+ Changes
+
+
+
+
+
+
+ Fix CREATE INDEX CONCURRENTLY to wait for
+ concurrent prepared transactions (Andrey Borodin)
+
+
+
+ At the point where CREATE INDEX CONCURRENTLY
+ waits for all concurrent transactions to complete so that it can see
+ rows they inserted, it must also wait for all prepared transactions
+ to complete, for the same reason. Its failure to do so meant that
+ rows inserted by prepared transactions might be omitted from the new
+ index, causing queries relying on the index to miss such rows.
+ In installations that have enabled prepared transactions
+ (max_prepared_transactions > 0),
+ it's recommended to reindex any concurrently-built indexes in
+ case this problem occurred when they were built.
+
+
+
+
+
+
+ Avoid incorrect results when WHERE CURRENT OF is
+ applied to a cursor whose plan contains a MergeAppend node (Tom
+ Lane)
+
+
+
+ This case is unsupported (in general, a cursor using ORDER
+ BY is not guaranteed to be simply updatable); but the code
+ previously did not reject it, and could silently give false matches.
+
+
+
+
+
+
+ Fix crash when WHERE CURRENT OF is applied to a
+ cursor whose plan contains a custom scan node (David Geier)
+
+
+
+
+
+
+ Fix planner's handling of a placeholder that is computed at some
+ join level and used only at that same level (Tom Lane)
+
+
+
+ This oversight could lead to failed to build
+ any N-way joins planner errors.
+
+
+
+
+
+
+ Be more careful about whether index AMs support mark/restore
+ (Andrew Gierth)
+
+
+
+ This prevents errors about missing support functions in rare edge
+ cases.
+
+
+
+
+
+
+ Fix ALTER DEFAULT PRIVILEGES to handle duplicated
+ arguments safely (Michael Paquier)
+
+
+
+ Duplicate role or schema names within the same command could lead
+ to tuple already updated by self errors or
+ unique-constraint violations.
+
+
+
+
+
+
+ Flush ACL-related caches when pg_authid
+ changes (Noah Misch)
+
+
+
+ This change ensures that permissions-related decisions will promptly
+ reflect the results of ALTER ROLE ... [NO] INHERIT.
+
+
+
+
+
+
+ Prevent misprocessing of ambiguous CREATE TABLE
+ LIKE clauses (Tom Lane)
+
+
+
+ A LIKE clause is re-examined after initial
+ creation of the new table, to handle importation of indexes and
+ such. It was possible for this re-examination to find a different
+ table of the same name, causing unexpected behavior; one example is
+ where the new table is a temporary table of the same name as
+ the LIKE target.
+
+
+
+
+
+
+ Rearrange order of operations in CREATE TABLE
+ LIKE so that indexes are cloned before building foreign
+ key constraints (Tom Lane)
+
+
+
+ This fixes the case where a self-referential foreign key constraint
+ declared in the outer CREATE TABLE depends on an
+ index that's coming from the LIKE clause.
+
+
+
+
+
+
+ Disallow converting an inheritance child table to a view
+ (Tom Lane)
+
+
+
+
+
+
+ Ensure that disk space allocated for a dropped relation is released
+ promptly at commit (Thomas Munro)
+
+
+
+ Previously, if the dropped relation spanned multiple 1GB segments,
+ only the first segment was truncated immediately. Other segments
+ were simply unlinked, which doesn't authorize the kernel to release
+ the storage so long as any other backends still have the files open.
+
+
+
+
+
+
+ Fix handling of backslash-escaped multibyte characters
+ in COPY FROM (Heikki Linnakangas)
+
+
+
+ A backslash followed by a multibyte character was not handled
+ correctly. In some client character encodings, this could lead to
+ misinterpreting part of a multibyte character as a field separator
+ or end-of-copy-data marker.
+
+
+
+
+
+
+ Avoid preallocating executor hash tables
+ in EXPLAIN without ANALYZE
+ (Alexey Bashtanov)
+
+
+
+
+
+
+ Fix recently-introduced race conditions
+ in LISTEN/NOTIFY queue
+ handling (Tom Lane)
+
+
+
+ A newly-listening backend could attempt to read SLRU pages that
+ were in process of being truncated, possibly causing an error.
+
+
+
+ The queue tail pointer could become
+ set to a value that's not equal to the queue position of any
+ backend, resulting in effective disabling of the queue truncation
+ logic. Continued use of NOTIFY then led to
+ queue-fill warnings, and eventually to inability to send any more
+ notifies until the server is restarted.
+
+
+
+
+
+
+ Allow the jsonb concatenation operator to handle all
+ combinations of JSON data types (Tom Lane)
+
+
+
+ We can concatenate two JSON objects or two JSON arrays. Handle
+ other cases by wrapping non-array inputs in one-element arrays,
+ then performing an array concatenation. Previously, some
+ combinations of inputs followed this rule but others arbitrarily
+ threw an error.
+
+
+
+
+
+
+ Fix use of uninitialized value while parsing a *
+ quantifier in a BRE-mode regular expression (Tom Lane)
+
+
+
+ This error could cause the quantifier to act non-greedy, that is
+ behave like a *? quantifier would do in full
+ regular expressions.
+
+
+
+
+
+
+ Fix numeric power() for the case where the
+ exponent is exactly INT_MIN (-2147483648)
+ (Dean Rasheed)
+
+
+
+ Previously, a result with no significant digits was produced.
+
+
+
+
+
+
+ Prevent possible data loss from incorrect detection of the
+ wraparound point of an SLRU log
+ (Noah Misch)
+
+
+
+ The wraparound point typically falls in the middle of a page, which
+ must be rounded off to a page boundary, and that was not done
+ correctly. No issue could arise unless an installation had gotten
+ to within one page of SLRU overflow, which is unlikely in a
+ properly-functioning system. If this did happen, it would manifest
+ in later apparent wraparound or could not
+ access status of transaction errors.
+
+
+
+
+
+
+ Fix memory leak in walsender processes while sending new snapshots
+ for logical decoding (Amit Kapila)
+
+
+
+
+
+
+ Fix walsender to accept additional commands after
+ terminating replication (Jeff Davis)
+
+
+
+
+
+
+ Ensure detection of deadlocks between hot standby backends and the
+ startup (WAL-application) process (Fujii Masao)
+
+
+
+ The startup process did not run the deadlock detection code, so that
+ in situations where the startup process is last to join a circular
+ wait situation, the deadlock might never be recognized.
+
+
+
+
+
+
+ Fix portability problem in parsing
+ of recovery_target_xid values (Michael Paquier)
+
+
+
+ The target XID is potentially 64 bits wide, but it was parsed
+ with strtoul(), causing misbehavior on
+ platforms where long is 32 bits (such as Windows).
+
+
+
+
+
+
+ Avoid assertion failure in pg_get_functiondef()
+ when examining a function with a TRANSFORM option
+ (Tom Lane)
+
+
+
+
+
+
+ In psql, re-allow including a password
+ in a connection_string argument of a
+ \connect command (Tom Lane)
+
+
+
+ This used to work, but a recent bug fix caused the password to be
+ ignored (resulting in prompting for a password).
+
+
+
+
+
+
+ Fix assorted bugs
+ in psql's \help
+ command (Kyotaro Horiguchi, Tom Lane)
+
+
+
+ \help with two argument words failed to find a
+ command description using only the first word, for
+ example \help reset all should show the help
+ for RESET but did not.
+ Also, \help often failed to invoke the pager when
+ it should. It also leaked memory.
+
+
+
+
+
+
+ Fix pg_dump to handle WITH
+ GRANT OPTION in an extension's initial privileges
+ (Noah Misch)
+
+
+
+ If an extension's script creates an object and grants privileges
+ on it with grant option, then later the user revokes such
+ privileges, pg_dump would generate
+ incorrect SQL for reproducing the situation. (Few if any extensions
+ do this today.)
+
+
+
+
+
+
+ In pg_rewind, ensure that all WAL is
+ accounted for when rewinding a standby server
+ (Ian Barwick, Heikki Linnakangas)
+
+
+
+
+
+
+ Report the correct database name in connection failure error
+ messages from some client programs (Álvaro Herrera)
+
+
+
+ If the database name was defaulted rather than given on the command
+ line, pg_dumpall,
+ pgbench, oid2name,
+ and vacuumlo would produce misleading
+ error messages after a connection failure.
+
+
+
+
+
+
+ Fix memory leak in contrib/auto_explain
+ (Japin Li)
+
+
+
+ Memory consumed while producing the EXPLAIN
+ output was not freed until the end of the current transaction (for a
+ top-level statement) or the end of the surrounding statement (for a
+ nested statement). This was particularly a problem
+ with log_nested_statements enabled.
+
+
+
+
+
+
+ In contrib/postgres_fdw, avoid leaking open
+ connections to remote servers when a user mapping or foreign server
+ object is dropped (Bharath Rupireddy)
+
+
+
+ Open connections that depend on a dropped user mapping or foreign
+ server can no longer be referenced, but formerly they were kept
+ around anyway for the duration of the local session.
+
+
+
+
+
+
+ In contrib/pgcrypto, check for error returns
+ from OpenSSL's EVP functions (Michael Paquier)
+
+
+
+ We do not really expect errors here, but this change silences
+ warnings from static analysis tools.
+
+
+
+
+
+
+ In contrib/pg_trgm's GiST index support, avoid
+ crash in the rare case that picksplit is called on exactly two index
+ items (Andrew Gierth, Alexander Korotkov)
+
+
+
+
+
+
+ Fix miscalculation of timeouts
+ in contrib/pg_prewarm
+ and contrib/postgres_fdw
+ (Alexey Kondratov, Tom Lane)
+
+
+
+ The main loop in contrib/pg_prewarm's
+ autoprewarm parent process underestimated its desired sleep time by
+ a factor of 1000, causing it to consume much more CPU than intended.
+ When waiting for a result from a remote
+ server, contrib/postgres_fdw overestimated the
+ desired timeout by a factor of 1000 (though this error had been
+ mitigated by imposing a clamp to 60 seconds).
+
+
+
+ Both of these errors stemmed from incorrectly converting
+ seconds-and-microseconds to milliseconds. Introduce a new
+ API TimestampDifferenceMilliseconds()
+ to make it easier to get this right in the future.
+
+
+
+
+
+
+ Improve configure's heuristics for
+ selecting PG_SYSROOT on macOS (Tom Lane)
+
+
+
+ The new method is more likely to produce desirable results when
+ Xcode is newer than the underlying operating system. Choosing
+ a sysroot that does not match the OS version may result in
+ nonfunctional executables.
+
+
+
+
+
+
+ While building on macOS, specify in
+ link steps as well as compile steps (James Hilliard)
+
+
+
+ This likewise improves the results when Xcode is out of sync with
+ the operating system.
+
+
+
+
+
+
+ Update time zone data files to tzdata
+ release 2021a for DST law changes in Russia (Volgograd zone) and
+ South Sudan, plus historical corrections for Australia, Bahamas,
+ Belize, Bermuda, Ghana, Israel, Kenya, Nigeria, Palestine,
+ Seychelles, and Vanuatu.
+
+
+
+ Notably, the Australia/Currie zone has been corrected to the point
+ where it is identical to Australia/Hobart.
+
+
+
+
+
+
+
+
Release 9.6.20