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<sect1 id="release-9-0-20">

<title>Release 9.0.20</title>

<note>

<title>Release Date</title>

<simpara>2015-05-21</simpara>

</note>

<para>

This release contains a variety of fixes from 9.0.19.

For information about new features in the 9.0 major release, see

<xref linkend="release-9-0">.

</para>

<para>

The <productname>PostgreSQL</> community will stop releasing updates

for the 9.0.X release series in September 2015.

Users are encouraged to update to a newer release branch soon.

</para>

<sect2>

<title>Migration to Version 9.0.20</title>

<para>

A dump/restore is not required for those running 9.0.X.

</para>

<para>

However, if you are upgrading from a version earlier than 9.0.18,

see <xref linkend="release-9-0-18">.

</para>

</sect2>

<sect2>

<title>Changes</title>

<itemizedlist>

<listitem>

<para>

Fix incorrect checking of deferred exclusion constraints after a HOT

update (Tom Lane)

</para>

<para>

If a new row that potentially violates a deferred exclusion constraint

is HOT-updated (that is, no indexed columns change and the row can be

stored back onto the same table page) later in the same transaction,

the exclusion constraint would be reported as violated when the check

finally occurred, even if the row(s) the new row originally conflicted

with had been deleted.

</para>

</listitem>

<listitem>

<para>

Prevent improper reordering of antijoins (NOT EXISTS joins) versus

other outer joins (Tom Lane)

</para>

<para>

This oversight in the planner has been observed to cause <quote>could

not find RelOptInfo for given relids</> errors, but it seems possible

that sometimes an incorrect query plan might get past that consistency

check and result in silently-wrong query output.

</para>

</listitem>

<listitem>

<para>

Fix incorrect matching of subexpressions in outer-join plan nodes

(Tom Lane)

</para>

<para>

Previously, if textually identical non-strict subexpressions were used

both above and below an outer join, the planner might try to re-use

the value computed below the join, which would be incorrect because the

executor would force the value to NULL in case of an unmatched outer row.

</para>

</listitem>

<listitem>

<para>

Fix GEQO planner to cope with failure of its join order heuristic

(Tom Lane)

</para>

<para>

This oversight has been seen to lead to <quote>failed to join all

relations together</> errors in queries involving <literal>LATERAL</>,

and that might happen in other cases as well.

</para>

</listitem>

<listitem>

<para>

Fix possible deadlock at startup

when <literal>max_prepared_transactions</> is too small

(Heikki Linnakangas)

</para>

</listitem>

<listitem>

<para>

Don't archive useless preallocated WAL files after a timeline switch

(Heikki Linnakangas)

</para>

</listitem>

<listitem>

<para>

Recursively <function>fsync()</> the data directory after a crash

(Abhijit Menon-Sen, Robert Haas)

</para>

<para>

This ensures consistency if another crash occurs shortly later. (The

second crash would have to be a system-level crash, not just a database

crash, for there to be a problem.)

</para>

</listitem>

<listitem>

<para>

Fix autovacuum launcher's possible failure to shut down, if an error

occurs after it receives SIGTERM (&Aacute;lvaro Herrera)

</para>

</listitem>

<listitem>

<para>

Cope with unexpected signals in <function>LockBufferForCleanup()</>

(Andres Freund)

</para>

<para>

This oversight could result in spurious errors about <quote>multiple

backends attempting to wait for pincount 1</>.

</para>

</listitem>

<listitem>

<para>

Avoid waiting for WAL flush or synchronous replication during commit of

a transaction that was read-only so far as the user is concerned

(Andres Freund)

</para>

<para>

Previously, a delay could occur at commit in transactions that had

written WAL due to HOT page pruning, leading to undesirable effects

such as sessions getting stuck at startup if all synchronous replicas

are down. Sessions have also been observed to get stuck in catchup

interrupt processing when using synchronous replication; this will fix

that problem as well.

</para>

</listitem>

<listitem>

<para>

Fix crash when manipulating hash indexes on temporary tables

(Heikki Linnakangas)

</para>

</listitem>

<listitem>

<para>

Fix possible failure during hash index bucket split, if other processes

are modifying the index concurrently (Tom Lane)

</para>

</listitem>

<listitem>

<para>

Check for interrupts while analyzing index expressions (Jeff Janes)

</para>

<para>

<command>ANALYZE</> executes index expressions many times; if there are

slow functions in such an expression, it's desirable to be able to

cancel the <command>ANALYZE</> before that loop finishes.

</para>

</listitem>

<listitem>

<para>

Add the name of the target server to object description strings for

foreign-server user mappings (&Aacute;lvaro Herrera)

</para>

</listitem>

<listitem>

<para>

Recommend setting <literal>include_realm</> to 1 when using

Kerberos/GSSAPI/SSPI authentication (Stephen Frost)

</para>

<para>

Without this, identically-named users from different realms cannot be

distinguished. For the moment this is only a documentation change, but

it will become the default setting in <productname>PostgreSQL</> 9.5.

</para>

</listitem>

<listitem>

<para>

Remove code for matching IPv4 <filename>pg_hba.conf</> entries to

IPv4-in-IPv6 addresses (Tom Lane)

</para>

<para>

This hack was added in 2003 in response to a report that some Linux

kernels of the time would report IPv4 connections as having

IPv4-in-IPv6 addresses. However, the logic was accidentally broken in

9.0. The lack of any field complaints since then shows that it's not

needed anymore. Now we have reports that the broken code causes

crashes on some systems, so let's just remove it rather than fix it.

(Had we chosen to fix it, that would make for a subtle and potentially

security-sensitive change in the effective meaning of

IPv4 <filename>pg_hba.conf</> entries, which does not seem like a good

thing to do in minor releases.)

</para>

</listitem>

<listitem>

<para>

While shutting down service on Windows, periodically send status

updates to the Service Control Manager to prevent it from killing the

service too soon; and ensure that <application>pg_ctl</> will wait for

shutdown (Krystian Bigaj)

</para>

</listitem>

<listitem>

<para>

Reduce risk of network deadlock when using <application>libpq</>'s

non-blocking mode (Heikki Linnakangas)

</para>

<para>

When sending large volumes of data, it's important to drain the input

buffer every so often, in case the server has sent enough response data

to cause it to block on output. (A typical scenario is that the server

is sending a stream of NOTICE messages during <literal>COPY FROM

STDIN</>.) This worked properly in the normal blocking mode, but not

so much in non-blocking mode. We've modified <application>libpq</>

to opportunistically drain input when it can, but a full defense

against this problem requires application cooperation: the application

should watch for socket read-ready as well as write-ready conditions,

and be sure to call <function>PQconsumeInput()</> upon read-ready.

</para>

</listitem>

<listitem>

<para>

Fix array handling in <application>ecpg</> (Michael Meskes)

</para>

</listitem>

<listitem>

<para>

Fix <application>psql</> to sanely handle URIs and conninfo strings as

the first parameter to <command>\connect</>

(David Fetter, Andrew Dunstan, &Aacute;lvaro Herrera)

</para>

<para>

This syntax has been accepted (but undocumented) for a long time, but

previously some parameters might be taken from the old connection

instead of the given string, which was agreed to be undesirable.

</para>

</listitem>

<listitem>

<para>

Suppress incorrect complaints from <application>psql</> on some

platforms that it failed to write <filename>~/.psql_history</> at exit

(Tom Lane)

</para>

<para>

This misbehavior was caused by a workaround for a bug in very old

(pre-2006) versions of <application>libedit</>. We fixed it by

removing the workaround, which will cause a similar failure to appear

for anyone still using such versions of <application>libedit</>.

Recommendation: upgrade that library, or use <application>libreadline</>.

</para>

</listitem>

<listitem>

<para>

Fix <application>pg_dump</>'s rule for deciding which casts are

system-provided casts that should not be dumped (Tom Lane)

</para>

</listitem>

<listitem>

<para>

Fix dumping of views that are just <literal>VALUES(...)</> but have

column aliases (Tom Lane)

</para>

</listitem>

<listitem>

<para>

In <application>pg_upgrade</>, force timeline 1 in the new cluster

(Bruce Momjian)

</para>

<para>

This change prevents upgrade failures caused by bogus complaints about

missing WAL history files.

</para>

</listitem>

<listitem>

<para>

In <application>pg_upgrade</>, check for improperly non-connectable

databases before proceeding

(Bruce Momjian)

</para>

</listitem>

<listitem>

<para>

In <application>pg_upgrade</>, quote directory paths

properly in the generated <literal>delete_old_cluster</> script

(Bruce Momjian)

</para>

</listitem>

<listitem>

<para>

In <application>pg_upgrade</>, preserve database-level freezing info

properly

(Bruce Momjian)

</para>

<para>

This oversight could cause missing-clog-file errors for tables within

the <literal>postgres</> and <literal>template1</> databases.

</para>

</listitem>

<listitem>

<para>

Run <application>pg_upgrade</> and <application>pg_resetxlog</> with

restricted privileges on Windows, so that they don't fail when run by

an administrator (Muhammad Asif Naeem)

</para>

</listitem>

<listitem>

<para>

Fix slow sorting algorithm in <filename>contrib/intarray</> (Tom Lane)

</para>

</listitem>

<listitem>

<para>

Fix compile failure on Sparc V8 machines (Rob Rowan)

</para>

</listitem>

<listitem>

<para>

Update time zone data files to <application>tzdata</> release 2015d

for DST law changes in Egypt, Mongolia, and Palestine, plus historical

changes in Canada and Chile. Also adopt revised zone abbreviations for

the America/Adak zone (HST/HDT not HAST/HADT).

</para>

</listitem>

</itemizedlist>

</sect2>

</sect1>

<sect1 id="release-9-0-19">

<title>Release 9.0.19</title>