In combination with 569174f1, which
taught the btree AM how to perform parallel index scans, this allows
parallel index scan plans on btree indexes.  This infrastructure
should be general enough to support parallel index scans for other
index AMs as well, if someone updates them to support parallel
scans.

Amit Kapila, reviewed and tested by Anastasia Lubennikova, Tushar
Ahuja, and Haribabu Kommi, and me.

Commit f82ec32a renamed the pg_xlog
directory to pg_wal.  To make things consistent, and because "xlog" is
terrible terminology for either "transaction log" or "write-ahead log"
rename all SQL-callable functions that contain "xlog" in the name to
instead contain "wal".  (Note that this may pose an upgrade hazard for
some users.)

Similarly, rename the xlog_position argument of the functions that
create slots to be called wal_position.

Discussion: https://www.postgresql.org/message-id/CA+Tgmob=YmA=H3DbW1YuOXnFVgBheRmyDkWcD9M8f=5bGWYEoQ@mail.gmail.com

It's always been possible for index AMs to cache data across successive
amgettuple calls within a single SQL command: the IndexScanDesc.opaque
field is meant for precisely that.  However, no comparable facility
exists for amortizing setup work across successive aminsert calls.
This patch adds such a feature and teaches GIN, GIST, and BRIN to use it
to amortize catalog lookups they'd previously been doing on every call.
(The other standard index AMs keep everything they need in the relcache,
so there's little to improve there.)

For GIN, the overall improvement in a statement that inserts many rows
can be as much as 10%, though it seems a bit less for the other two.
In addition, this makes a really significant difference in runtime
for CLOBBER_CACHE_ALWAYS tests, since in those builds the repeated
catalog lookups are vastly more expensive.

The reason this has been hard up to now is that the aminsert function is
not passed any useful place to cache per-statement data.  What I chose to
do is to add suitable fields to struct IndexInfo and pass that to aminsert.
That's not widening the index AM API very much because IndexInfo is already
within the ken of ambuild; in fact, by passing the same info to aminsert
as to ambuild, this is really removing an inconsistency in the AM API.

Discussion: https://postgr.es/m/27568.1486508680@sss.pgh.pa.us

Backpatch to all supported versions, where applicable, to make backpatching
of future fixes go more smoothly.

Josh Soref

Discussion: https://www.postgresql.org/message-id/CACZqfqCf+5qRztLPgmmosr-B0Ye4srWzzw_mo4c_8_B_mtjmJQ@mail.gmail.com

This patch doesn't actually make any index AM parallel-aware, but it
provides the necessary functions at the AM layer to do so.

Rahila Syed, Amit Kapila, Robert Haas

This avoids that builtins.h has to include additional header files.

Previously, it was thought that this only needed to be done for the
benefit of possible standbys, so wal_level = minimal skipped it.
But that's not safe, because during crash recovery we might replay
XLOG_DBASE_CREATE or XLOG_TBLSPC_CREATE record which recursively
removes the directory that contains the new init fork.  So log it
always.

The user-visible effect of this bug is that if you create a database
or tablespace, then create an unlogged table, then crash without
checkpointing, then restart, accessing the table will fail, because
the it won't have been properly reset.  This commit fixes that.

Michael Paquier, per a report from Konstantin Knizhnik.  Wording of
the comments per a suggestion from me.

Prototypes for functions implementing V1-callable functions are no
longer necessary.

Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Thomas Munro <thomas.munro@enterprisedb.com>

Using offsetof() with a run-time computed argument is not allowed in
either C or C++.  Apparently, gcc allows it, but g++ doesn't.

Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Thomas Munro <thomas.munro@enterprisedb.com>

I found that half a dozen (nearly 5%) of our AllocSetContextCreate calls
had typos in the context-sizing parameters.  While none of these led to
especially significant problems, they did create minor inefficiencies,
and it's now clear that expecting people to copy-and-paste those calls
accurately is not a great idea.  Let's reduce the risk of future errors
by introducing single macros that encapsulate the common use-cases.
Three such macros are enough to cover all but two special-purpose contexts;
those two calls can be left as-is, I think.

While this patch doesn't in itself improve matters for third-party
extensions, it doesn't break anything for them either, and they can
gradually adopt the simplified notation over time.

In passing, change TopMemoryContext to use the default allocation
parameters.  Formerly it could only be extended 8K at a time.  That was
probably reasonable when this code was written; but nowadays we create
many more contexts than we did then, so that it's not unusual to have a
couple hundred K in TopMemoryContext, even without considering various
dubious code that sticks other things there.  There seems no good reason
not to let it use growing blocks like most other contexts.

Back-patch to 9.6, mostly because that's still close enough to HEAD that
it's easy to do so, and keeping the branches in sync can be expected to
avoid some future back-patching pain.  The bugs fixed by these changes
don't seem to be significant enough to justify fixing them further back.

Discussion: <21072.1472321324@sss.pgh.pa.us>

In blinsert(), cope with the possibility that a page we pull from the
notFullPage list is marked BLOOM_DELETED.  This could happen if VACUUM
recently marked it deleted but hasn't (yet) updated the metapage.
We can re-use such a page safely, but we *must* reinitialize it so that
it's no longer marked deleted.

Fix blvacuum() so that it updates the notFullPage list even if it's
going to update it to empty.  The previous "optimization" of skipping
the update seems pretty dubious, since it means that the next blinsert()
will uselessly visit whatever pages we left in the list.

Uniformly treat PageIsNew pages the same as deleted pages.  This should
allow proper recovery if a crash occurs just after relation extension.

Properly use vacuum_delay_point, not assorted ad-hoc CHECK_FOR_INTERRUPTS
calls, in the blvacuum() main loop.

Fix broken tuple-counting logic: blvacuum.c counted the number of live
index tuples over again in each scan, leading to VACUUM VERBOSE reporting
some multiple of the actual number of surviving index tuples after any
vacuum that removed any tuples (since they'd be counted in blvacuum, maybe
more than once, and then again in blvacuumcleanup, without ever zeroing the
counter).  It's sufficient to count them in blvacuumcleanup.

stats->estimated_count is a boolean, not a counter, and we don't want
to set it true, so don't add tuple counts to it.

Add a couple of Asserts that we don't overrun available space on a bloom
page.  I don't think there's any bug there today, but the way the
FreeBlockNumberArray size calculation is set up is scarily fragile, and
BloomPageGetFreeSpace isn't much better.  The Asserts should help catch
any future mistakes.

Per investigation of a report from Jeff Janes.  I think the first item
above may explain his report; the other changes were things I noticed
while casting about for an explanation.

Report: <CAMkU=1xEUuBphDwDmB1WjN4+td4kpnEniFaTBxnk1xzHCw8_OQ@mail.gmail.com>

Per discussion, we should provide such functions to replace the lost
ability to discover AM properties by inspecting pg_am (cf commit
65c5fcd3).  The added functionality is also meant to displace any code
that was looking directly at pg_index.indoption, since we'd rather not
believe that the bit meanings in that field are part of any client API
contract.

As future-proofing, define the SQL API to not assume that properties that
are currently AM-wide or index-wide will remain so unless they logically
must be; instead, expose them only when inquiring about a specific index
or even specific index column.  Also provide the ability for an index
AM to override the behavior.

In passing, document pg_am.amtype, overlooked in commit 473b9328.

Andrew Gierth, with kibitzing by me and others

Discussion: <87mvl5on7n.fsf@news-spur.riddles.org.uk>

Don't spell "InvalidOid" as "0".  Initialize method fields in the same
order as amapi.h declares them (and every other AM handler initializes
them).

Extension scripts should never use CREATE OR REPLACE for initial object
creation.  If there is a collision with a pre-existing (probably
user-created) object, we want extension installation to fail, not silently
overwrite the user's object.  Bloom and sslinfo both violated this precept.

Also fix a number of scripts that had no standard header (the file name
comment and the \echo...\quit guard).  Probably the \echo...\quit hack
is less important now than it was in 9.1 days, but that doesn't mean
that individual extensions get to choose whether to use it or not.

And fix a couple of evident copy-and-pasteos in file name comments.

No need for back-patch: the REPLACE bugs are both new in 9.6, and the
rest of this is pretty much cosmetic.

Andreas Karlsson and Tom Lane

COMMENT ON ACCESS METHOD was missing; add it, along psql tab-completion
support for it.

psql was also missing a way to list existing access methods; the new \dA
command does that.

Also add tab-completion support for DROP ACCESS METHOD.

Author: Michael Paquier
Discussion: https://www.postgresql.org/message-id/CAB7nPqTzdZdu8J7EF8SXr_R2U5bSUUYNOT3oAWBZdEoggnwhGA@mail.gmail.com

Per discussion, this is a more understandable and future-proof way of
exposing the setting to users.  On-disk, we can still store it in words,
so as to not break on-disk compatibility with beta1.

Along the way, clean up the code associated with Bloom reloptions.
Provide explicit macros for default and maximum lengths rather than
having magic numbers buried in multiple places in the code.  Drop
the adjustBloomOptions() code altogether: it was useless in view of
the fact that reloptions.c already performed default-substitution and
range checking for the options.  Rename a couple of macros and types
for more clarity.

Discussion: <23767.1464926580@sss.pgh.pa.us>

blbuildempty did not do even approximately the right thing: it tried
to add a metapage to the relation's regular data fork, which already
has one at that point.  It should look like the ambuildempty methods
for all the standard index types, ie, initialize a metapage image in
some transient storage and then write it directly to the init fork.
To support that, refactor BloomInitMetapage into two functions.

In passing, fix BloomInitMetapage so it doesn't leave the rd_options
field of the index's relcache entry pointing at transient storage.
I'm not sure this had any visible consequence, since nothing much
else is likely to look at a bloom index's rd_options, but it's
certainly poor practice.

Per bug #14155 from Zhou Digoal.

Report: <20160524144146.22598.42558@wrigleys.postgresql.org>

It's possible to begin and end an indexscan without ever calling
amrescan.  contrib/bloom, unlike every other index AM, allocated
its "scan->opaque" storage at amrescan time, and thus would crash
in amendscan if amrescan hadn't been called.  We could fix this
by putting in a null-pointer check in blendscan, but I see no very
good reason why contrib/bloom should march to its own drummer in
this respect.  Let's move that initialization to blbeginscan
instead.  Per report from Jeff Janes.

Use macroses for definition amstrategies/amsupport fields instead of
hardcoded values.

Author: Nikolay Shaplov with addition for contrib/bloom

Revert commit 7cb1db1d, which represented
a misunderstanding of the problem (if snapmgr.h weren't already included
in bufmgr.h, things wouldn't compile anywhere).  Instead install what
I think is the real fix.

Windows builds on buildfarm are failing because
old_snapshot_threshold is not found in the bloom filter contrib
module.

The reverted changes were intended to force a choice of whether any
newly-added BufferGetPage() calls needed to be accompanied by a
test of the snapshot age, to support the "snapshot too old"
feature.  Such an accompanying test is needed in about 7% of the
cases, where the page is being used as part of a scan rather than
positioning for other purposes (such as DML or vacuuming).  The
additional effort required for back-patching, and the doubt whether
the intended benefit would really be there, have indicated it is
best just to rely on developers to do the right thing based on
comments and existing usage, as we do with many other conventions.

This change should have little or no effect on generated executable
code.

Motivated by the back-patching pain of Tom Lane and Robert Haas

Rename this function to GenericXLogRegisterBuffer() to make it clearer
what it does, and leave room for other sorts of "register" actions in
future.  Also, replace its "bool isNew" argument with an integer flags
argument, so as to allow adding more flags in future without an API
break.

Alexander Korotkov, adjusted slightly by me

Added to ensure that bloom index pages can be distinguished from other pages
by pg_filedump. Because there wasn't any public/production versions before,
it doesn't pay attention to any compatibility issues.

Per notice from Tom Lane

Originally, this test created a 100000-row test table, which made it
run rather slowly compared to other contrib tests.  Investigation with
gcov showed that we got no further improvement in code coverage after
the first 700 or so rows, making the large table 99% a waste of time.
Cut it back to 2000 rows to fix the runtime problem and still leave
some headroom for testing behaviors that may appear later.

A closer look at the gcov results showed that the main coverage
omissions in contrib/bloom occurred because the test never filled more
than one entry in the notFullPage array; which is unsurprising because
it exercised index cleanup only in the scenario of complete table
deletion, allowing every page in the index to become deleted rather
than not-full.  Add testing that allows the not-full path to be
exercised as well.

Also, test the amvalidate function, because blvalidate.c had zero
coverage without that, and besides it's a good idea to check for
mistakes in the bloom opclass definitions.

That routine is dangerous, and unnecessary once we get rid of this
one caller.

In passing, fix failure to clean up temp memory context, or switch
back to caller's context, during slowest exit path.

This feature is controlled by a new old_snapshot_threshold GUC.  A
value of -1 disables the feature, and that is the default.  The
value of 0 is just intended for testing.  Above that it is the
number of minutes a snapshot can reach before pruning and vacuum
are allowed to remove dead tuples which the snapshot would
otherwise protect.  The xmin associated with a transaction ID does
still protect dead tuples.  A connection which is using an "old"
snapshot does not get an error unless it accesses a page modified
recently enough that it might not be able to produce accurate
results.

This is similar to the Oracle feature, and we use the same SQLSTATE
and error message for compatibility.

This patch is a no-op patch which is intended to reduce the chances
of failures of omission once the functional part of the "snapshot
too old" patch goes in.  It adds parameters for snapshot, relation,
and an enum to specify whether the snapshot age check needs to be
done for the page at this point.  This initial patch passes NULL
for the first two new parameters and BGP_NO_SNAPSHOT_TEST for the
third.  The follow-on patch will change the places where the test
needs to be made.

Michael Paquier

The code was supposing that rd_amcache wouldn't disappear from under it
during a scan; which is wrong.  Copy the data out of the relcache rather
than trying to reference it there.

Coverity complained about implicit sign-extension in the
BloomPageGetFreeSpace macro, probably because sizeOfBloomTuple isn't wide
enough for size calculations.  No overflow is really possible as long as
maxoff and sizeOfBloomTuple are small enough to represent a realistic
situation, but it seems like a good idea to declare sizeOfBloomTuple as
Size not int32.

Add missing check on BloomPageAddItem() result, again from Coverity.

Avoid core dump due to not allocating so->sign array when
scan->numberOfKeys is zero.  Also thanks to Coverity.

Use FLEXIBLE_ARRAY_MEMBER rather than declaring an array as size 1
when it isn't necessarily.

Very minor beautification of related code.

Unfortunately, none of the Coverity-detected mistakes look like they
could account for the remaining buildfarm unhappiness with this
module.  It's barely possible that the FLEXIBLE_ARRAY_MEMBER mistake
does account for that, if it's enabling bogus compiler optimizations;
but I'm not terribly optimistic.  We probably still have bugs to
find here.

Per buildfarm member pademelon.

Comment is right, but if - not.

Vacuum might put page into list of pages with some free space and mark as
deleted at the same time.

Looking at result of buildfarm member jaguarundi it seems to me that
BloomOptions isn't inited sometime, but I don't see yet how it's possible.
Nevertheless, check of signature length's is missed, so, add
a limit of it. Also add missed GenericXLogAbort() in case of already
deleted page in vacuum + minor code refactoring.

- macroses llike (var & FLAG) are changed to ((var & FLAG) != 0)
- do not copy uninitialized part of notFullPage array to page

Module provides new access method. It is actually a simple Bloom filter
implemented as pgsql's index. It could give some benefits on search
with large number of columns.

Module is a single way to test generic WAL interface committed earlier.

Author: Teodor Sigaev, Alexander Korotkov
Reviewers: Aleksander Alekseev, Michael Paquier, Jim Nasby