As we merge with upstream and by that keep refining the Postgres
planner, legacy planner is no longer a suitable name. This changes
all variations of the spelling (legacy planner, legacy optimizer,
legacy query optimizer etc) to say "Postgres" rather than "legacy".
Reviewed-by: NVenkatesh Raghavan <vraghavan@pivotal.io>
Reviewed-by: NDavid Yozie <dyozie@pivotal.io>
Reviewed-by: NGeorgios Kokolatos <gkokolatos@pivotal.io>

The Greenplum specific error handling via ereport()/elog() calls was
in need of a unification effort as some parts of the code was using a
different messaging style to others (and to upstream). This aims at
bringing many of the GPDB error calls in line with the upstream error
message writing guidelines and thus make the user experience of
Greenplum more consistent.

The main contributions of this patch are:

* errmsg() messages shall start with a lowercase letter, and not end
  with a period. errhint() and errdetail() shall be complete sentences
  starting with capital letter and ending with a period. This attempts
  to fix this on as many ereport() calls as possible, with too detailed
  errmsg() content broken up into details and hints where possible.

* Reindent ereport() calls to be more consistent with the common style
  used in upstream and most parts of Greenplum:

	ereport(ERROR,
			(errcode(<CODE>),
			 errmsg("short message describing error"),
			 errhint("Longer message as a complete sentence.")));

* Avoid breaking messages due to long lines since it makes grepping
  for error messages harder when debugging. This is also the de facto
  standard in upstream code.

* Convert a few internal error ereport() calls to elog(). There are
  no doubt more that can be converted, but the low hanging fruit has
  been dealt with. Also convert a few elog() calls which are user
  facing to ereport().

* Update the testfiles to match the new messages.

Spelling and wording is mostly left for a follow-up commit, as this was
getting big enough as it was. The most obvious cases have been handled
but there is work left to be done here.

Discussion: https://github.com/greenplum-db/gpdb/pull/6378Reviewed-by: NAshwin Agrawal <aagrawal@pivotal.io>
Reviewed-by: NHeikki Linnakangas <hlinnakangas@pivotal.io>

In a case where we have multiple relation-scan nodes in a cursor plan,
such as a scan of an inheritance tree, it's possible to fetch from a
given scan node, then rewind the cursor and fetch some row from an
earlier scan node.  In such a case, execCurrent.c mistakenly thought
that the later scan node was still active, because ExecReScan hadn't
done anything to make it look not-active.  We'd get some sort of
failure in the case of a SeqScan node, because the node's scan tuple
slot would be pointing at a HeapTuple whose t_self gets reset to
invalid by heapam.c.  But it seems possible that for other relation
scan node types we'd actually return a valid tuple TID to the caller,
resulting in updating or deleting a tuple that shouldn't have been
considered current.  To fix, forcibly clear the ScanTupleSlot in
ExecScanReScan.

Another issue here, which seems only latent at the moment but could
easily become a live bug in future, is that rewinding a cursor does
not necessarily lead to *immediately* applying ExecReScan to every
scan-level node in the plan tree.  Upper-level nodes will think that
they can postpone that call if their child node is already marked
with chgParam flags.  I don't see a way for that to happen today in
a plan tree that's simple enough for execCurrent.c's search_plan_tree
to understand, but that's one heck of a fragile assumption.  So, add
some logic in search_plan_tree to detect chgParam flags being set on
nodes that it descended to/through, and assume that that means we
should consider lower scan nodes to be logically reset even if their
ReScan call hasn't actually happened yet.

Per bug #15395 from Matvey Arye.  This has been broken for a long time,
so back-patch to all supported branches.

Discussion: https://postgr.es/m/153764171023.14986.280404050547008575@wrigleys.postgresql.org

"UPDATE/DELETE WHERE CURRENT OF cursor_name" failed, with an error message
like "cannot extract system attribute from virtual tuple", if the cursor
was using a index-only scan for the target table.  Fix it by digging the
current TID out of the indexscan state.

It seems likely that the same failure could occur for CustomScan plans
and perhaps some FDW plan types, so that leaving this to be treated as an
internal error with an obscure message isn't as good an idea as it first
seemed.  Hence, add a bit of heaptuple.c infrastructure to let us deliver
a more on-topic message.  I chose to make the message match what you get
for the case where execCurrentOf can't identify the target scan node at
all, "cursor "foo" is not a simply updatable scan of table "bar"".
Perhaps it should be different, but we can always adjust that later.

In the future, it might be nice to provide hooks that would let custom
scan providers and/or FDWs deal with this in other ways; but that's
not a suitable topic for a back-patchable bug fix.

It's been like this all along, so back-patch to all supported branches.

Yugo Nagata and Tom Lane

Discussion: https://postgr.es/m/20180201013349.937dfc5f.nagata@sraoss.co.jp

Looks right.

These were added in GPDB a long time ago, probably before gpdiff.pl was
introduced to mask row order differences in regression test output. But
now that gpdiff.pl can do that, these are unnecessary. Revert to match
the upstream more closely.

This includes updates to the 'rules' and 'inherit' tests, although they
are disabled and still doesn't pass after these changes.

* Enable analyzing root partitions
* Ensure that the name of the guc is clear
* Remove double negation (where possible)
* Update comments
* Co-locate gucs that have similar purpose
* Remove dead gucs
* Classify them correctly so that they are no longer hidden

isSimplyUpdatableRelation may get an invalid input from statements like
"DECLARE XX CURSOR FOR SELECT * FROM LOWER('HH')" where a function is selected.

ActiveSnapshot needs to be set when we call ExecutorRewind because some
plan node types may execute user-defined functions during their ReScan
calls (nodeLimit.c does so, at least).  The wisdom of that is somewhat
debatable, perhaps, but for now the simplest fix is to make sure the
required context is valid.  Failure to do this typically led to a
null-pointer-dereference core dump, though it's possible that in more
complex cases a function could be executed with the wrong snapshot
leading to very subtle misbehavior.

Per report from Leif Jensen.  It's been broken for a long time, so
back-patch to all active branches.

My tweak of these error messages in commit c359a1b0 contained the
thinko that a query would always have rowMarks set for a query
containing a locking clause.  Not so: when declaring a cursor, for
instance, rowMarks isn't set at the point we're checking, so we'd be
dereferencing a NULL pointer.

The fix is to pass the lock strength to the function raising the error,
instead of trying to reverse-engineer it.  The result not only is more
robust, but it also seems cleaner overall.

Per report from Robert Haas.

The old coding was using a regular snapshot, referenced elsewhere, that was
subject to having its command counter updated.  Fix by creating a private copy
of the snapshot exclusively for the cursor.

Backpatch to 8.4, which is when the bug was introduced during the snapshot
management rewrite.

Bernd Helmle

locate the target row, if the cursor was declared with FOR UPDATE or FOR
SHARE.  This approach is more flexible and reliable than digging through the
plan tree; for instance it can cope with join cursors.  But we still provide
the old code for use with non-FOR-UPDATE cursors.  Per gripe from Robert Haas.

return the tableoid as well as the ctid for any FOR UPDATE targets that
have child tables.  All child tables are listed in the ExecRowMark list,
but the executor just skips the ones that didn't produce the current row.

Curiously, this longstanding restriction doesn't seem to have been documented
anywhere; so no doc changes.

data.  This makes for a significant speedup at the cost that the results
now vary between little-endian and big-endian machines; which forces us
to add explicit ORDER BYs in a couple of regression tests to preserve
machine-independent comparison results.  Also, force initdb by bumping
catversion, since the contents of hash indexes will change (at least on
big-endian machines).

Kenneth Marshall and Tom Lane, based on work from Bob Jenkins.  This commit
does not adopt Bob's new faster mix() algorithm, however, since we still need
to convince ourselves that that doesn't degrade the quality of the hashing.

in corner cases such as re-fetching a just-deleted row.  We may be able to
relax this someday, but let's find out how many people really care before
we invest a lot of work in it.  Per report from Heikki and subsequent
discussion.

While in the neighborhood, make the combination of INSENSITIVE and FOR UPDATE
throw an error, since they are semantically incompatible.  (Up to now we've
accepted but just ignored the INSENSITIVE option of DECLARE CURSOR.)

then-delete on the current cursor row.  The basic fix is that nodeTidscan.c
has to apply heap_get_latest_tid() to the current-scan-TID obtained from the
cursor query; this ensures we get the latest row version to work with.
However, since that only works if the query plan is a TID scan, we also have
to hack the planner to make sure only that type of plan will be selected.
(Formerly, the planner might decide to apply a seqscan if the table is very
small.  This change is probably a Good Thing anyway, since it's hard to see
how a seqscan could really win.)  That means the execQual.c code to support
CurrentOfExpr as a regular expression type is dead code, so replace it with
just an elog().  Also, add regression tests covering these cases.  Note
that the added tests expose the fact that re-fetching an updated row
misbehaves if the cursor used FOR UPDATE.  That's an independent bug that
should be fixed later.  Per report from Dharmendra Goyal.

Along the way, allow FOR UPDATE in non-WITH-HOLD cursors; there may once
have been a reason to disallow that, but it seems to work now, and it's
really rather necessary if you want to select a row via a cursor and then
update it in a concurrent-safe fashion.

Original patch by Arul Shaji, rather heavily editorialized by Tom Lane.

results due to syncscan patch, when shared_buffers is small enough.  Per
buildfarm reports and some local testing with shared_buffers set to the
lowest value considered by initdb.

reviewed by Neil Conway. This patch adds the following DDL command
variants: RESET SESSION, RESET TEMP, RESET PLANS, CLOSE ALL, and
DEALLOCATE ALL. RESET SESSION is intended for use by connection
pool software and the like, in order to reset a client session
to something close to its initial state.

Note that while most of these command variants can be executed
inside a transaction block (but are not transaction-aware!),
RESET SESSION cannot. While this is inconsistent, it is intended
to catch programmer mistakes: RESET SESSION in an open transaction
block is probably unintended.

particular get rid of single quotes around language names and old WITH ()
construct.

cursors. Patch from Joachim Wieland, review and ediorialization by Neil
Conway. The view lists cursors defined by DECLARE CURSOR, using SPI, or
via the Bind message of the frontend/backend protocol. This means the
view does not list the unnamed portal or the portal created to implement
EXECUTE. Because we do list SPI portals, there might be more rows in
this view than you might expect if you are using SPI implicitly (e.g.
via a procedural language).

Per recent discussion on -hackers, the query string included in the
view for cursors defined by DECLARE CURSOR is based on
debug_query_string. That means it is not accurate if multiple queries
separated by semicolons are submitted as one query string. However,
there doesn't seem a trivial fix for that: debug_query_string
is better than nothing. I also changed SPI_cursor_open() to include
the source text for the portal it creates: AFAICS there is no reason
not to do this.

Update the documentation and regression tests, bump the catversion.

deferred triggers: either one can create more work for the other,
so we have to loop till it's all gone.  Per example from andrew@supernews.
Add a regression test to help spot trouble in this area in future.

executed.  Previously, the DECLARE would succeed but subsequent FETCHes
would fail since the parameter values supplied to DECLARE were not
propagated to the portal created for the cursor.
In support of this, add type Oids to ParamListInfo entries, which seems
like a good idea anyway since code that extracts a value can double-check
that it got the type of value it was expecting.
Oliver Jowett, with minor editorialization by Tom Lane.

Along the way, fix some logic problems in pgstat_initstats, notably the
bogus assumption that malloc returns zeroed memory.

context sloppiness, some other things.  Includes Neil's mopup patch
of 22-Apr.

(materialization into a tuple store) discussed on pgsql-hackers earlier.
I've updated the documentation and the regression tests.

Notes on the implementation:

- I needed to change the tuple store API slightly -- it assumes that it
won't be used to hold data across transaction boundaries, so the temp
files that it uses for on-disk storage are automatically reclaimed at
end-of-transaction. I added a flag to tuplestore_begin_heap() to control
this behavior. Is changing the tuple store API in this fashion OK?

- in order to store executor results in a tuple store, I added a new
CommandDest. This works well for the most part, with one exception: the
current DestFunction API doesn't provide enough information to allow the
Executor to store results into an arbitrary tuple store (where the
particular tuple store to use is chosen by the call site of
ExecutorRun). To workaround this, I've temporarily hacked up a solution
that works, but is not ideal: since the receiveTuple DestFunction is
passed the portal name, we can use that to lookup the Portal data
structure for the cursor and then use that to get at the tuple store the
Portal is using. This unnecessarily ties the Portal code with the
tupleReceiver code, but it works...

The proper fix for this is probably to change the DestFunction API --
Tom suggested passing the full QueryDesc to the receiveTuple function.
In that case, callers of ExecutorRun could "subclass" QueryDesc to add
any additional fields that their particular CommandDest needed to get
access to. This approach would work, but I'd like to think about it for
a little bit longer before deciding which route to go. In the mean time,
the code works fine, so I don't think a fix is urgent.

- (semi-related) I added a NO SCROLL keyword to DECLARE CURSOR, and
adjusted the behavior of SCROLL in accordance with the discussion on
-hackers.

- (unrelated) Cleaned up some SGML markup in sql.sgml, copy.sgml

Neil Conway

which is broken in some weird way that I don't understand.  I think it
may be exposing a bug in the new psql --- for one thing, I get different
results when I run psql by hand than the regress script gets.  What
the heck???

Modified a few tests to match results on RedHat Linux/gcc for v6.1beta.