Allow background workers to be started dynamically.

There is a new API, RegisterDynamicBackgroundWorker, which allows
an ordinary user backend to register a new background writer during
normal running.  This means that it's no longer necessary for all
background workers to be registered during processing of
shared_preload_libraries, although the option of registering workers
at that time remains available.

When a background worker exits and will not be restarted, the
slot previously used by that background worker is automatically
released and becomes available for reuse.  Slots used by background
workers that are configured for automatic restart can't (yet) be
released without shutting down the system.

This commit adds a new source file, bgworker.c, and moves some
of the existing control logic for background workers there.
Previously, there was little enough logic that it made sense to
keep everything in postmaster.c, but not any more.

This commit also makes the worker_spi contrib module into an
extension and adds a new function, worker_spi_launch, which can
be used to demonstrate the new facility.
Add support for REFRESH MATERIALIZED VIEW CONCURRENTLY.

This allows reads to continue without any blocking while a REFRESH
runs.  The new data appears atomically as part of transaction
commit.

Review questioned the Assert that a matview was not a system
relation.  This will be addressed separately.

Reviewed by Hitoshi Harada, Robert Haas, Andres Freund.
Merged after review with security patch f3ab5d4.
Add --progress option to show progress report

Patch contributed by Fabien COELHO, reviewed by KONDO Mitsumasa.
Comment on why planagg.c punts "MIN(x ORDER BY y)".
Implement the FILTER clause for aggregate function calls.

This is SQL-standard with a few extensions, namely support for
subqueries and outer references in clause expressions.

catversion bump due to change in Aggref and WindowFunc.

David Fetter, reviewed by Dean Rasheed.
Fix systable_recheck_tuple() for MVCC scan snapshots.

Since this function assumed non-MVCC snapshots, it broke when commit
568d4138c646cd7cd8a837ac244ef2caf27c6bb8 switched its one caller from
SnapshotNow scans to MVCC-snapshot scans.

Reviewed by Robert Haas, Tom Lane and Andres Freund.
Use correct parameter name for view_option_value

The documentation for ALTER VIEW had a minor copy-and-paste error in
defining the parameters.  Noticed when reviewing the WITH CHECK OPTION
patch.

Backpatch to 9.2 where this was first introduced.
Fix typo in previous pgbench --progress patch.
Fix end-of-loop optimization in pglz_find_match() function.

After the recent pglz optimization patch, the next/prev pointers in the
hash table are never NULL, INVALID_ENTRY_PTR is used to represent invalid
entries instead. The end-of-loop check in pglz_find_match() function didn't
get the memo. The result was the same from a correctness point of view, but
because the NULL-check would never fail, the tiny optimization turned into
a pessimization.

Reported by Stephen Frost, using Coverity scanner.
Fix assert failure at end of recovery, broken by XLogInsert scaling patch.

Initialization of the first XLOG buffer at end-of-recovery was broken for
the case that the last read WAL record ended at a page boundary. Instead of
trying to copy the last full xlog page to the buffer cache in that case,
just set shared state so that the next page is initialized when the first
WAL record after startup is inserted. (that's what we did in earlier
version, too)

To make the shared state required for that case less surprising, replace the
XLogCtl->curridx variable, which was the index of the latest initialized
buffer, with an XLogRecPtr of how far the buffers have been initialized.
That also allows us to get rid of the XLogRecEndPtrToBufIdx macro.

While we're at it, make a similar change for XLogCtl->Write.curridx, getting
rid of that variable and calculating the next buffer to write from
XLogCtl->LogwrtResult instead.
Fix variable names mentioned in comment to match the code.

Also, in another comment, explain why holding an insertion slot is a
critical section.

Per review by Amit Kapila.
Fix a few problems in barrier.h.

On HPPA, implement pg_memory_barrier() as pg_compiler_barrier(), which
should be correct since this arch doesn't do memory access reordering,
and is anyway better than the completely-nonfunctional-on-this-arch
dummy_spinlock code.  (But note this patch only fixes things for gcc,
not for builds with HP's compiler.)

Also, fix incorrect default definition of pg_memory_barrier as a macro
requiring an argument.

Also, fix incorrect spelling of "#elif" as "#else if" in icc code path
(spotted by pgindent).

This doesn't come close to fixing all of the functional and stylistic
deficiencies in barrier.h, but at least it un-breaks my personal build.
Now that we're actually using barriers in the code, this file is going
to need some serious attention.
doc: Remove tab from SGML file
Fix direct access to Relation->rd_indpred.

Should use RelationGetIndexPredicate(), since rd_indpred is just a cache
that is not computed until/unless demanded.  Per buildfarm failure on
CLOBBER_CACHE_ALWAYS animals; diagnosis and fix by Hitoshi Harada.
Move checking an explicit VARIADIC "any" argument into the parser.

This is more efficient and simpler . It does mean that an untyped NULL
can no longer be used in such cases, which should be mentioned in
Release Notes, but doesn't seem a terrible loss. The workaround is to
cast the NULL to some array type.

Pavel Stehule, reviewed by Jeevan Chalke.
Fix pgstattuple functions to use regclass-type as the argument.

This allows us to specify the target relation with several expressions,
'relname', 'schemaname.relname' and OID in all pgstattuple functions.
pgstatindex() and pg_relpages() could not accept OID as the argument
so far.

Per discussion on -hackers, we decided to keep two types of interfaces,
with regclass-type and TEXT-type argument, for each pgstattuple
function because of the backward-compatibility issue. The functions
which have TEXT-type argument will be deprecated in the future release.

Patch by Satoshi Nagayasu, reviewed by Rushabh Lathia and Fujii Masao.
Fix typo in update scripts for some contrib modules.
WITH CHECK OPTION support for auto-updatable VIEWs

For simple views which are automatically updatable, this patch allows
the user to specify what level of checking should be done on records
being inserted or updated.  For 'LOCAL CHECK', new tuples are validated
against the conditionals of the view they are being inserted into, while
for 'CASCADED CHECK' the new tuples are validated against the
conditionals for all views involved (from the top down).

This option is part of the SQL specification.

Dean Rasheed, reviewed by Pavel Stehule
Fix regex match failures for backrefs combined with non-greedy quantifiers.

An ancient logic error in cfindloop() could cause the regex engine to fail
to find matches that begin later than the start of the string.  This
function is only used when the regex pattern contains a back reference,
and so far as we can tell the error is only reachable if the pattern is
non-greedy (i.e. its first quantifier uses the ? modifier).  Furthermore,
the actual match must begin after some potential match that satisfies the
DFA but then fails the back-reference's match test.

Reported and fixed by Jeevan Chalke, with cosmetic adjustments by me.
Add checks for valid multibyte character length in UtfToLocal, LocalToUtf.

This is mainly to suppress "uninitialized variable" warnings from very
recent versions of gcc.  But it seems like a good robustness thing anyway,
not to mention that we might someday decide to support 6-byte UTF8.

Per report from Karol Trzcionka.  No back-patch since there's no reason
at the moment to think this is more than cosmetic.