This improves reporting, as the error string now includes the actual
Python exception. As a side effect, this no longer sets the errcode to
ERRCODE_DATA_EXCEPTION, which might be considered a feature, as it's
not documented and not clear why iterator errors should be treated
differently.

Jan Urbański

Per a suggestion from Thom Brown, though this is not his proposed patch.

Per suggestions from Thom Brown and Robert Haas.

periodically rescan the archive for new timelines, while waiting for new WAL
segments to arrive. This allows you to set up a standby server that follows
the TLI change if another standby server is promoted to master. Before this,
you had to restart the standby server to make it notice the new timeline.

This patch only scans the archive for TLI changes, it won't follow a TLI
change in streaming replication. That is much needed too, but it would be a
much bigger patch than I dare to sneak in this late in the release cycle.

There was discussion on improving the sanity checking of the WAL segments so
that the system would notice more reliably if the new timeline isn't an
ancestor of the current one, but that is not included in this patch.

Reviewed by Fujii Masao.

Per Josh Berkus; some additional explanatory text by me.

Thom Brown

This fixes an oversight in commit 946045f0
of 2010-08-21, as reported by Itagaki Takahiro.  Also a couple of minor
cosmetic adjustments.

Kevin Grittner

assertions.

Seen with an older gcc version.  I'm not sure these represent any real
risk factor, but still a bit scary.  Anyway we have lots of other
volatile-marked variables in this code, so a couple more won't hurt.

Per testing with a compiler that doesn't like that.

Mixing them together alphabetically won't be nice.  Per my gripe of
2011-02-12.

If a standby is broadcasting reply messages and we have named
one or more standbys in synchronous_standby_names then allow
users who set synchronous_replication to wait for commit, which
then provides strict data integrity guarantees. Design avoids
sending and receiving transaction state information so minimises
bookkeeping overheads. We synchronize with the highest priority
standby that is connected and ready to synchronize. Other standbys
can be defined to takeover in case of standby failure.

This version has very strict behaviour; more relaxed options
may be added at a later date.

Simon Riggs and Fujii Masao, with reviews by Yeb Havinga, Jaime
Casanova, Heikki Linnakangas and Robert Haas, plus the assistance
of many other design reviewers.

Since this field is after a variable-length field, it can't simply be
accessed via the C struct for pg_index.  Fortunately, the relcache already
did the dirty work of pulling the information out to where it can be
accessed easily, so this is a one-line fix.

Andres Freund

toast file names to match the new relfilenode.

failures.

error.

It's more likely that pg_pltemplate will go away in the future than
that we'll add additional specialized infrastructure for it.

The original scheme for this was to symlink plpython.$DLSUFFIX to
plpython2.$DLSUFFIX, but that doesn't work on Windows, and only
accidentally failed to fail because of the way that CREATE LANGUAGE created
or didn't create new C functions.  My changes of yesterday exposed the
weakness of that approach.  To fix, get rid of the symlink and make
pg_pltemplate show what's really going on.

In createlang this is a one-line change.  In droplang there's a whole
lot of cruft that can be discarded since the extension mechanism now
manages removal of the language's support functions.

Also, add deprecation notices to these two programs' reference pages,
since per discussion we may toss them overboard altogether in a release
or two.

Noted by Andy Colson

In preparation for 9.1alpha4 release notes, where only the 9.1alpha4
features will be emphasized.

Recommend use of CREATE EXTENSION rather than plain CREATE LANGUAGE
where relevant.  Encourage PL authors to provide extension wrappers
for their PLs.

This mostly just involves creating control, install, and
update-from-unpackaged scripts for them.  However, I had to adjust plperl
and plpython to not share the same support functions between variants,
because we can't put the same function into multiple extensions.

catversion bump forced due to new contents of pg_pltemplate, and because
initdb now installs plpgsql as an extension not a bare language.

Add support for regression testing these as extensions not bare
languages.

Fix a couple of other issues that popped up while testing this: my initial
hack at pg_dump binary-upgrade support didn't work right, and we don't want
an extra schema permissions test after all.

Documentation changes still to come, but I'm committing now to see
whether the MSVC build scripts need work (likely they do).

This avoids duplicate (and not-quite-matching) code, and makes the logic
for SECURITY LABEL match COMMENT and ALTER EXTENSION ADD/DROP.

It is possible that an expression ends up with a collatable type but
without a collation.  CREATE TABLE AS could then create a table based
on that.  But such a column cannot be dumped with valid SQL syntax, so
we disallow creating such a column.

per test report from Noah Misch

Remove the unconditional superuser permissions check in CREATE EXTENSION,
and instead define a "superuser" extension property, which when false
(not the default) skips the superuser permissions check.  In this case
the calling user only needs enough permissions to execute the commands
in the extension's installation script.  The superuser property is also
enforced in the same way for ALTER EXTENSION UPDATE cases.

In other ALTER EXTENSION cases and DROP EXTENSION, test ownership of
the extension rather than superuserness.  ALTER EXTENSION ADD/DROP needs
to insist on ownership of the target object as well; to do that without
duplicating code, refactor comment.c's big switch for permissions checks
into a separate function in objectaddress.c.

I also removed the superuserness checks in pg_available_extensions and
related functions; there's no strong reason why everybody shouldn't
be able to see that info.

Also invent an IF NOT EXISTS variant of CREATE EXTENSION, and use that
in pg_dump, so that dumps won't fail for installed-by-default extensions.
We don't have any of those yet, but we will soon.

This is all per discussion of wrapping the standard procedural languages
into extensions.  I'll make those changes in a separate commit; this is
just putting the core infrastructure in place.