Commit Graph

41971 Commits

Author SHA1 Message Date
Simon Riggs 9401883a7a Update ddl.sgml for declarative partitioning syntax
Add a section titled "Partitioned Tables" to describe what are
partitioned tables, partition, their similarities with inheritance.
The existing section on inheritance is retained for clarity.

Then add examples to the partitioning chapter that show syntax for
partitioned tables.  In fact they implement the same partitioning
scheme that is currently shown using inheritance.

Amit Langote, with additional details and explanatory text by me
2017-02-10 10:03:28 +00:00
Simon Riggs 61c9a9dac4 Add keywords for partitioning
Amit Langote
2017-02-10 09:07:18 +00:00
Simon Riggs c1369fe2ea Improve CREATE TABLE documentation of partitioning
Amit Langote, with corrections by me
2017-02-10 08:59:37 +00:00
Robert Haas 62e8b38751 Rename command line options for ongoing xlog -> wal conversion.
initdb and pg_basebackup now have a --waldir option rather --xlogdir,
and pg_basebackup now has --wal-method rather than --xlog-method.
2017-02-09 16:42:51 -05:00
Robert Haas 3f01fd4ca0 Rename dtrace probes for ongoing xlog -> wal conversion.
xlog-switch becomes wal-switch, and xlog-insert becomes wal-insert.
2017-02-09 16:40:19 -05:00
Robert Haas 85c11324ca Rename user-facing tools with "xlog" in the name to say "wal".
This means pg_receivexlog because pg_receivewal, pg_resetxlog
becomes pg_resetwal, and pg_xlogdump becomes pg_waldump.
2017-02-09 16:23:46 -05:00
Tom Lane 5d2adf0f81 Blind try to fix portability issue in commit 8f93bd851 et al.
The S/390 members of the buildfarm are showing failures indicating
that they're having trouble with the rint() calls I added yesterday.
There's no good reason for that, and I wonder if it is a compiler bug
similar to the one we worked around in d9476b838.  Try to fix it using
the same method as before, namely to store the result of rint() back
into a "double" variable rather than immediately converting to int64.
(This isn't entirely waving a dead chicken, since on machines with
wider-than-double float registers, the extra store forces a width
conversion.  I don't know if S/390 is like that, but it seems worth
trying.)

In passing, merge duplicate ereport() calls in float8_timestamptz().

Per buildfarm.
2017-02-09 15:50:16 -05:00
Robert Haas 806091c96f Remove all references to "xlog" from SQL-callable functions in pg_proc.
Commit f82ec32ac3 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
2017-02-09 15:10:09 -05:00
Robert Haas 72257f9578 simplehash: Additional tweaks to make specifying an allocator work.
Even if we don't emit definitions for SH_ALLOCATE and SH_FREE, we
still need prototypes.  The user can't define them before including
simplehash.h because SH_TYPE isn't available yet.

For the allocator to be able to access private_data, it needs to
become an argument to SH_CREATE.  Previously we relied on callers
to set that after returning from SH_CREATE, but SH_CREATE calls
SH_ALLOCATE before returning.

Dilip Kumar, reviewed by me.
2017-02-09 14:59:57 -05:00
Robert Haas 3f3d60d3bb Fix race condition in ConditionVariablePrepareToSleep.
Thomas Munro
2017-02-09 14:42:32 -05:00
Robert Haas fc8219dc54 pageinspect: Fix hash_bitmap_info not to read the underlying page.
It did that to verify that the page was an overflow page rather than
anything else, but that means that checking the status of all the
overflow bits requires reading the entire index.  So don't do that.
The new code validates that the page is not a primary bucket page
or bitmap page by looking at the metapage, so that using this on
large numbers of pages can be reasonably efficient.

Ashutosh Sharma, per a complaint from me, and with further
modifications by me.
2017-02-09 14:34:34 -05:00
Tom Lane 86d911ec0f Allow index AMs to cache data across aminsert calls within a SQL command.
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
2017-02-09 11:52:12 -05:00
Andres Freund 7c5d8c16e1 Add explicit ORDER BY to a few tests that exercise hash-join code.
A proposed patch, also by Thomas and in the same thread, would change
the output order of these.  Independent of the follow-up patches
getting committed, nailing down the order in these specific tests at
worst seems harmless.

Author: Thomas Munro
Discussion: https://postgr.es/m/CAEepm=1D4-tP7j7UAgT_j4ZX2j4Ehe1qgZQWFKBMb8F76UW5Rg@mail.gmail.com
2017-02-08 16:58:21 -08:00
Tom Lane 8f93bd8512 Fix roundoff problems in float8_timestamptz() and make_interval().
When converting a float value to integer microseconds, we should be careful
to round the value to the nearest integer, typically with rint(); simply
assigning to an int64 variable will truncate, causing apparently off-by-one
values in cases that should work.  Most places in the datetime code got
this right, but not these two.

float8_timestamptz() is new as of commit e511d878f (9.6).  Previous
versions effectively depended on interval_mul() to do roundoff correctly,
which it does, so this fixes an accuracy regression in 9.6.

The problem in make_interval() dates to its introduction in 9.4.  Aside
from being careful to round not truncate, let's incorporate the hours and
minutes inputs into the result with exact integer arithmetic, rather than
risk introducing roundoff error where there need not have been any.

float8_timestamptz() problem reported by Erik Nordström, though this is
not his proposed patch.  make_interval() problem found by me.

Discussion: https://postgr.es/m/CAHuQZDS76jTYk3LydPbKpNfw9KbACmD=49dC4BrzHcfPv6yA1A@mail.gmail.com
2017-02-08 18:04:59 -05:00
Robert Haas a507b86900 Add WAL consistency checking facility.
When the new GUC wal_consistency_checking is set to a non-empty value,
it triggers recording of additional full-page images, which are
compared on the standby against the results of applying the WAL record
(without regard to those full-page images).  Allowable differences
such as hints are masked out, and the resulting pages are compared;
any difference results in a FATAL error on the standby.

Kuntal Ghosh, based on earlier patches by Michael Paquier and Heikki
Linnakangas.  Extensively reviewed and revised by Michael Paquier and
by me, with additional reviews and comments from Amit Kapila, Álvaro
Herrera, Simon Riggs, and Peter Eisentraut.
2017-02-08 15:45:30 -05:00
Peter Eisentraut 115cb31597 Fix relcache leaks in get_object_address_publication_rel() 2017-02-07 22:09:53 -05:00
Peter Eisentraut e35bbea7dd doc: Some improvements in CREATE SUBSCRIPTION ref page
Add link to description of libpq connection strings.  Add link to
explanation of replication access control.  This currently points to the
description of streaming replication access control, which is currently
the same as for logical replication, but that might be refined later.
Also remove plain-text passwords from the examples, to not encourage
that dubious practice.

based on suggestions from Simon Riggs
2017-02-07 21:26:50 -05:00
Robert Haas c3c4f6e174 Revise the way the element allocator for a simplehash is specified.
This method is more elegant and more efficient.

Per a suggestion from Andres Freund, who also briefly reviewed
the patch.
2017-02-07 17:10:08 -05:00
Tom Lane 242066cc8e Speed up "brin" regression test a little bit.
In the large DO block, collect row TIDs into array variables instead of
creating and dropping a pile of temporary tables.  In a normal build,
this reduces the brin test script's runtime from about 1.1 sec to 0.4 sec
on my workstation.  That's not all that exciting perhaps, but in a
CLOBBER_CACHE_ALWAYS test build, the runtime drops from 20 min to 17 min,
which is a little more useful.  In combination with some other changes
I plan to propose, this will help provide a noticeable reduction in
cycle time for CLOBBER_CACHE_ALWAYS buildfarm critters.
2017-02-07 16:34:37 -05:00
Robert Haas ac8eb972f2 Avoid redefining simplehash_allocate/simplehash_free.
There's no generic guard against multiple inclusion in this file,
for good reason.  But these typedefs need one, as per a report
from Jeff Janes.
2017-02-07 16:20:05 -05:00
Robert Haas 565903af47 Allow the element allocator for a simplehash to be specified.
This is infrastructure for a pending patch to allow parallel bitmap
heap scans.

Dilip Kumar, reviewed (in earlier versions) by Andres Freund and
(more recently) by me.  Some further renaming by me, also.
2017-02-07 16:01:44 -05:00
Robert Haas 94708c0e8c Fix compiler warning.
Mithun Cy, per a report by Erik Rijkers
2017-02-07 15:09:14 -05:00
Robert Haas 293e24e507 Cache hash index's metapage in rel->rd_amcache.
This avoids a very significant amount of buffer manager traffic and
contention when scanning hash indexes, because it's no longer
necessary to lock and pin the metapage for every scan.  We do need
some way of figuring out when the cache is too stale to use any more,
so that when we lock the primary bucket page to which the cached
metapage points us, we can tell whether a split has occurred since we
cached the metapage data.  To do that, we use the hash_prevblkno field
in the primary bucket page, which would otherwise always be set to
InvalidBuffer.

This patch contains code so that it will continue working (although
less efficiently) with hash indexes built before this change, but
perhaps we should consider bumping the hash version and ripping out
the compatibility code.  That decision can be made later, though.

Mithun Cy, reviewed by Jesper Pedersen, Amit Kapila, and by me.
Before committing, I made a number of cosmetic changes to the last
posted version of the patch, adjusted _hash_getcachedmetap to be more
careful about order of operation, and made some necessary updates to
the pageinspect documentation and regression tests.
2017-02-07 12:35:45 -05:00
Tom Lane 39c3ca5161 Correct thinko in last-minute release note item.
The CREATE INDEX CONCURRENTLY bug can only be triggered by row updates,
not inserts, since the problem would arise from an update incorrectly
being made HOT.  Noted by Alvaro.
2017-02-07 10:24:24 -05:00
Tom Lane 64ee636a5b Release notes for 9.6.2, 9.5.6, 9.4.11, 9.3.16, 9.2.20. 2017-02-06 15:30:42 -05:00
Peter Eisentraut 696af9ab0a doc: Document sequence function privileges better
Document the privileges required for each of the sequence functions.
This was already in the GRANT reference page, but also add it to the
function description for easier reference.
2017-02-06 15:27:01 -05:00
Peter Eisentraut ab82340a43 Avoid permission failure in pg_sequences.last_value
Before, reading pg_sequences.last_value would fail unless the user had
appropriate sequence permissions, which would make the pg_sequences view
cumbersome to use.  Instead, return null instead of the real value when
there are no permissions.

From: Michael Paquier <michael.paquier@gmail.com>
Reported-by: Shinoda, Noriyoshi <noriyoshi.shinoda@hpe.com>
2017-02-06 15:27:01 -05:00
Tom Lane ad6af3fc42 Release note updates.
Add item for last-minute CREATE INDEX CONCURRENTLY fix.
Repair a couple of misspellings of patch authors' names.

Back-branch updates will follow shortly, but I thought I'd
commit this separately just to make it more visible.
2017-02-06 14:19:23 -05:00
Tom Lane 2aaec65464 Avoid returning stale attribute bitmaps in RelationGetIndexAttrBitmap().
The problem with the original coding here is that we might receive (and
clear) a relcache invalidation signal for the target relation down inside
one of the index_open calls we're doing.  Since the target is open, we
would not drop the relcache entry, just reset its rd_indexvalid and
rd_indexlist fields.  But RelationGetIndexAttrBitmap() kept going, and
would eventually cache and return potentially-obsolete attribute bitmaps.

The case where this matters is where the inval signal was from a CREATE
INDEX CONCURRENTLY telling us about a new index on a formerly-unindexed
column.  (In all other cases, the lock we hold on the target rel should
prevent any concurrent change in index state.)  Even just returning the
stale attribute bitmap is not such a problem, because it shouldn't matter
during the transaction in which we receive the signal.  What hurts is
caching the stale data, because it can survive into later transactions,
breaking CREATE INDEX CONCURRENTLY's expectation that later transactions
will not create new broken HOT chains.  The upshot is that there's a window
for building corrupted indexes during CREATE INDEX CONCURRENTLY.

This patch fixes the problem by rechecking that the set of index OIDs
is still the same at the end of RelationGetIndexAttrBitmap() as it was
at the start.  If not, we loop back and try again.  That's a little
more than is strictly necessary to fix the bug --- in principle, we
could return the stale data but not cache it --- but it seems like a
bad idea on general principles for relcache to return data it knows
is stale.

There might be more hazards of the same ilk, or there might be a better
way to fix this one, but this patch definitely improves matters and seems
unlikely to make anything worse.  So let's push it into today's releases
even as we continue to study the problem.

Pavan Deolasee and myself

Discussion: https://postgr.es/m/CABOikdM2MUq9cyZJi1KyLmmkCereyGp5JQ4fuwKoyKEde_mzkQ@mail.gmail.com
2017-02-06 13:20:19 -05:00
Peter Eisentraut 549f74733f doc: Update CREATE DATABASE examples
The example of using CREATE DATABASE with the ENCODING option did not
work anymore (except in special circumstances) and did not represent a
good general-purpose example, so write some new examples.

Reported-by: marc+pgsql@milestonerdl.com
2017-02-06 11:55:39 -05:00
Tom Lane a59318346e Update comment in relcache.c.
Commit 665d1fad9 introduced rd_pkindex, and made RelationGetIndexList
responsible for updating it, but didn't bother to fix
RelationGetIndexList's header comment to say so.
2017-02-06 11:31:23 -05:00
Peter Eisentraut afcb0c97ef Add missing newline to error messages
Also improve the message style a bit while we're here.
2017-02-06 09:47:39 -05:00
Heikki Linnakangas d93b7535a6 Fix typo also in expected output.
Commit 181bdb90ba fixed the typo in the .sql file, but forgot to update the
expected output.
2017-02-06 12:04:04 +02:00
Heikki Linnakangas d02d985349 Fix typo in variable name.
Masahiko Sawada
2017-02-06 11:45:08 +02:00
Heikki Linnakangas 181bdb90ba Fix typos in comments.
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
2017-02-06 11:33:58 +02:00
Tom Lane 9863017b87 First-draft release notes for 9.6.2.
As usual, the release notes for other branches will be made by cutting
these down, but put them up for community review first.
2017-02-04 12:51:33 -05:00
Robert Haas 6f4b4ceefa Remove redundant comment.
Rafia Sabih
2017-02-03 19:05:49 -05:00
Robert Haas 38c363adf4 Improve grammar of message about two-phase state files.
When there's only one two-phase state file, there's also only one
long-running prepared transaction.  Adjust the message text
accordingly.

Nikhil Sontakke

Discussion: http://postgr.es/m/CAMGcDxcmR_DWZXXndGoPzVQx=B17A5=RviEA1qNaF=FWLy5Whw@mail.gmail.com
2017-02-03 17:16:54 -05:00
Robert Haas 871ec0e336 pageinspect: More type-sanity surgery on the new hash index code.
Uniformly expose unsigned quantities using the next-wider signed
integer type (since we have no unsigned types at the SQL level).
At the SQL level, this results a change to report itemoffset as
int4 rather than int2.  Also at the SQL level, report one value
that is an OID as type oid.  Under the hood, uniformly use macros
that match the SQL output type as to both width and signedness.
2017-02-03 16:28:13 -05:00
Robert Haas e759854a09 pgstattuple: Add pgstathashindex.
Since pgstattuple v1.5 hasn't been released yet, no need for a new
extension version.  The new function exposes statistics about hash
indexes similar to what other pgstatindex functions return for other
index types.

Ashutosh Sharma, reviewed by Kuntal Ghosh.  Substantial further
revisions by me.
2017-02-03 14:37:16 -05:00
Fujii Masao 39b8cc991f Be sure to release LogicalRepLauncherLock in DROP SUBSCRIPTION command.
Previously DROP SUBSCRIPTION command forgot to release the lock at all.

Original patches by Kyotaro Horiguchi and Michael Paquier,
but I didn't use them.
Discussion: http://postgr.es/m/20170201.173623.66249355.horiguchi.kyotaro@lab.ntt.co.jp
2017-02-04 03:18:13 +09:00
Tom Lane 14e9b18fed In pageinspect/hashfuncs.c, avoid crashes on alignment-picky machines.
On machines with MAXALIGN = 8, the payload of a bytea is not maxaligned,
since it will start 4 bytes into a palloc'd value.  On alignment-picky
hardware, this will cause failures in accesses to 8-byte-wide values
within the page.  We already encountered this problem when we introduced
GIN index inspection functions, and fixed it in commit 84ad68d64.  Make
use of the same function for hash indexes.

A small difficulty is that up to now contrib/pageinspect has not shared
any functions at all across files.  To support that, introduce a common
header file "pageinspect.h" for the module.

Also, move get_page_from_raw() out of ginfuncs.c, where it didn't
especially belong, and put it in rawpage.c which seems a more natural home.

Per buildfarm.

Discussion: https://postgr.es/m/17311.1486134714@sss.pgh.pa.us
2017-02-03 11:34:47 -05:00
Robert Haas 29e312bc13 pageinspect: Remove platform-dependent values from hash tests.
Per a report from Tom Lane, the ffactor reported by hash_metapage_info
and the free_size reported by hash_page_stats vary by platform.

Ashutosh Sharma and Robert Haas
2017-02-03 11:06:41 -05:00
Tom Lane c6eeb67dcc Fix a bunch more portability bugs in commit 08bf6e529.
It seems like somebody used a dartboard while choosing integer widths
for the various values taken and returned by these functions ... and
then threw a fresh set of darts while writing the SQL declarations.

This patch brings the C code into line with what the SQL declarations
say, which is enough to make it not dump core on the particular 32-bit
machine I'm testing on.  But I think we could do with another round
of looking at what the datum widths *should* be.  For instance, it's
not all that sensible that hash_bitmap_info decided to use int64 to
represent a BlockNumber input when get_raw_page doesn't do it that way.

There's also a remaining problem that the expected outputs from the
test script are platform-dependent, but I'll leave that issue for
somebody else.

Per buildfarm.
2017-02-02 23:11:08 -05:00
Robert Haas ed807fda6d pageinspect: Try to fix some bugs in previous commit.
Commit 08bf6e5295 seems not to have
used the correct *GetDatum and PG_GETARG_* macros for the SQL types
in some cases, and some of the SQL types seem to have been poorly
chosen, too.  Try to fix it.  I'm not sure if this is the reason
why the buildfarm is currently unhappy with this code, but it
seems like a good place to start.

Buildfarm unhappiness reported by Tom Lane.
2017-02-02 22:32:06 -05:00
Tom Lane fd6cd69803 Clean up psql's behavior for a few more control variables.
Modify FETCH_COUNT to always have a defined value, like other control
variables, mainly so it will always appear in "\set" output.

Add hooks to force HISTSIZE to be defined and require it to have an
integer value.  (I don't see any point in allowing it to be set to
non-integral values.)

Add hooks to force IGNOREEOF to be defined and require it to have an
integer value.  Unlike the other cases, here we're trying to be
bug-compatible with a rather bogus externally-defined behavior, so I think
we need to continue to allow "\set IGNOREEOF whatever".  Fix it so that
the substitution hook silently replace non-numeric values with "10",
so that the stored value always reflects what we're really doing.

Add a dummy assign hook for HISTFILE, just so it's always in
variables.c's list.  We can't require it to be defined always, because
that would break the interaction with the PSQL_HISTORY environment
variable, so there isn't any change in visible behavior here.

Remove tab-complete.c's private list of known variable names, since that's
really a maintenance nuisance.  Given the preceding changes, there are no
control variables it won't show anyway.  This does mean that if for some
reason you've unset one of the status variables (DBNAME, HOST, etc), that
variable would not appear in tab completion for \set.  But I think that's
fine, for at least two reasons: we shouldn't be encouraging people to use
those variables as regular variables, and if someone does do so anyway,
why shouldn't it act just like a regular variable?

Remove ugly and no-longer-used-anywhere GetVariableNum().  In general,
future additions of integer-valued control variables should follow the
paradigm of adding an assign hook using ParseVariableNum(), so there's
no reason to expect we'd need this again later.

Discussion: https://postgr.es/m/17516.1485973973@sss.pgh.pa.us
2017-02-02 20:16:17 -05:00
Tom Lane 8ac0365c22 Avoid improbable null pointer dereference in pgpassfileWarning().
Coverity complained that we might pass a null pointer to strcmp()
if PQresultErrorField were to return NULL.  That shouldn't be possible,
since the server is supposed to always provide some SQLSTATE or other
in an error message.  But we usually defend against such hazards, and
it only takes a little more code to do so here.

There's no good reason to think this is a live bug, so no back-patch.
2017-02-02 19:49:15 -05:00
Tom Lane 555494d1bc Fix placement of initPlans when forcibly materializing a subplan.
If we forcibly place a Material node atop a finished subplan, we need
to move any initPlans attached to the subplan up to the Material node,
in order to keep SS_finalize_plan() happy.  I'd figured this out in
commit 7b67a0a49 for the case of materializing a cursor plan, but out of
an abundance of caution, I put the initPlan movement hack at the call
site for that case, rather than inside materialize_finished_plan().
That was the wrong thing, because it turns out to also be necessary for
the only other caller of materialize_finished_plan(), ie subselect.c.
We lacked any test cases that exposed the mistake, but bug#14524 from
Wei Congrui shows that it's possible to get an initPlan reference into
the top tlist in that case too, and then SS_finalize_plan() complains.
Hence, move the hack into materialize_finished_plan().

In HEAD, also relocate some recently-added tests in subselect.sql, which
I'd unthinkingly dropped into the middle of a sequence of related tests.

Report: https://postgr.es/m/20170202060020.1400.89021@wrigleys.postgresql.org
2017-02-02 19:11:32 -05:00
Peter Eisentraut aa09b9dcd5 doc: Add missing include in example code
It's not broken because the header file is included via other headers,
but for better style we should be more explicit.

Reported-by: mthrockmorton@hme.com
2017-02-02 16:50:28 -05:00
Tom Lane c82d4e658e Fix mishandling of tSRFs at different nesting levels.
Given a targetlist like "srf(x), f(srf(x))", split_pathtarget_at_srfs()
decided that it needed two levels of ProjectSet nodes, failing to notice
that the two SRF calls are textually equal().  Because of that, setrefs.c
would convert the upper ProjectSet's tlist to "Var1, f(Var1)" (where Var1
represents a reference to the srf(x) output of the lower ProjectSet).
This triggered an assertion in nodeProjectSet.c complaining that it found
no SRFs to evaluate, as reported by Erik Rijkers.

What we want in such a case is to evaluate srf(x) only once and use a plain
Result node to compute "Var1, f(Var1)"; that gives results similar to what
previous versions produced, whereas allowing srf(x) to be evaluated again
in an upper ProjectSet would square the number of rows emitted.

Furthermore, even if the SRF calls aren't textually identical, we want them
to be evaluated in lockstep, because that's what happened in the old
implementation.  But split_pathtarget_at_srfs() got this completely wrong,
using two levels of ProjectSet for a case like "srf(x), f(srf(y))".

Hence, rewrite split_pathtarget_at_srfs() from the ground up so that it
groups SRFs according to the depth of nesting of SRFs in their arguments.
This is pretty much how we envisioned that working originally, but I blew
it when it came to implementation.

In passing, optimize the case of target == input_target, which I noticed
is not only possible but quite common.

Discussion: https://postgr.es/m/dcbd2853c05d22088766553d60dc78c6@xs4all.nl
2017-02-02 16:38:18 -05:00