Tom Lane [Tue, 3 Jan 2017 17:33:29 +0000 (12:33 -0500)]
Disable prompting for passphrase while (re)loading SSL config files.
OpenSSL's default behavior when loading a passphrase-protected key file
is to open /dev/tty and demand the password from there. It was kinda
sorta okay to allow that to happen at server start, but really that was
never workable in standard daemon environments. And it was a complete
fail on Windows, where the same thing would happen at every backend launch.
Yesterday's commit de41869b6 put the final nail in the coffin by causing
that to happen at every SIGHUP; even if you've still got a terminal acting
as the server's TTY, having the postmaster freeze until you enter the
passphrase again isn't acceptable.
Hence, override the default behavior with a callback that returns an empty
string, ensuring failure. Change the documentation to say that you can't
have a passphrase-protected server key, period.
If we can think of a production-grade way of collecting a passphrase from
somewhere, we might do that once at server startup and use this callback
to feed it to OpenSSL, but it's far from clear that anyone cares enough
to invest that much work in the feature. The lack of complaints about
the existing fractionally-baked behavior suggests nobody's using it anyway.
Remove bogus notice that older clients might not work with MD5 passwords.
That was written when we still had "crypt" authentication, and it was
referring to the fact that an older client might support "crypt"
authentication but not "md5". But we haven't supported "crypt" for years.
(As soon as we add a new authentication mechanism that doesn't work with
MD5 hashes, we'll need a similar notice again. But this text as it's worded
now is just wrong.)
Tom Lane [Tue, 3 Jan 2017 02:37:12 +0000 (21:37 -0500)]
Allow SSL configuration to be updated at SIGHUP.
It is no longer necessary to restart the server to enable, disable,
or reconfigure SSL. Instead, we just create a new SSL_CTX struct
(by re-reading all relevant files) whenever we get SIGHUP. Testing
shows that this is fast enough that it shouldn't be a problem.
In conjunction with that, downgrade the logic that complains about
pg_hba.conf "hostssl" lines when SSL isn't active: now that's just
a warning condition not an error.
An issue that still needs to be addressed is what shall we do with
passphrase-protected server keys? As this stands, the server would
demand the passphrase again on every SIGHUP, which is certainly
impractical. But the case was only barely supported before, so that
does not seem a sufficient reason to hold up committing this patch.
Andreas Karlsson, reviewed by Michael Banck and Michael Paquier
Tom Lane [Mon, 2 Jan 2017 18:41:51 +0000 (13:41 -0500)]
Use clock_gettime(), if available, in instr_time measurements.
The advantage of clock_gettime() is that the API allows the result to
be precise to nanoseconds, not just microseconds as in gettimeofday().
Now that it's routinely possible to do tens of plan node executions
in 1us, we really need more precision than gettimeofday() can offer
for EXPLAIN ANALYZE to accumulate statistics with.
Some research shows that clock_gettime() is available on pretty nearly
every modern Unix-ish platform, and as far as I have been able to test,
it has about the same execution time as gettimeofday(), so there's no
loss in switching over. (By the same token, this doesn't do anything
to fix the fact that we really wish clock readings were faster. But
there's enough win here to justify changing anyway.)
A small side benefit is that on most platforms, we can use CLOCK_MONOTONIC
instead of CLOCK_REALTIME and thereby render EXPLAIN impervious to
concurrent resets of the system clock. (This means that code must not
assume that the contents of struct instr_time have any well-defined
interpretation as timestamps, but really that was true before.)
Some platforms offer nonstandard clock IDs that might be of interest.
This patch knows we should use CLOCK_MONOTONIC_RAW on macOS, because it
provides more precision and is faster to read than their CLOCK_MONOTONIC.
If there turn out to be many more cases where we need special rules, it
might be appropriate to handle the selection of clock ID in configure,
but for the moment that doesn't seem worth the trouble.
Tom Lane [Mon, 2 Jan 2017 17:26:03 +0000 (12:26 -0500)]
In pgbench logging, avoid assuming that instr_times match Unix timestamps.
For aggregated logging, pg_bench supposed that printing the integer part of
INSTR_TIME_GET_DOUBLE() would produce a Unix timestamp. That was already
broken on Windows, and it's about to get broken on most other platforms as
well. As in commit 74baa1e3b, we can remove the entanglement at the price
of one extra syscall per transaction; though here it seems more convenient
to use time(NULL) instead of gettimeofday(), since we only need
integral-second precision.
I took the time to do some wordsmithing on the documentation about
pgbench's logging features, too.
Tom Lane [Sun, 1 Jan 2017 20:17:08 +0000 (15:17 -0500)]
Avoid assuming that instr_time == struct timeval in pgbench logging.
This code was presuming undue familiarity with the contents of the
instr_time struct. That was already broken on Windows, and it's about
to get broken on most other platforms as well. The simplest solution
that preserves the current output definition is to just do our own
gettimeofday() call here. Realistically, the extra cost is probably
negligible in comparison to everything else that's going on in a
pgbench transaction, so it's not worth sweating over.
On Windows, the precision delivered by gettimeofday() is lower than
one could wish, but this is still a big improvement over printing
zeroes, as the code did before.
Tom Lane [Sat, 31 Dec 2016 23:39:08 +0000 (18:39 -0500)]
Fix unstable regression test results.
Commit 2ac3ef7a0 added a query with an underdetermined output row order;
it has failed multiple times in the buildfarm since then. Add an ORDER BY
to fix. Also, don't rely on a DROP CASCADE to drop in a well-determined
order; that hasn't failed yet but I don't trust it much, and we're not
saving any typing by using CASCADE anyway.
Tom Lane [Thu, 29 Dec 2016 21:57:41 +0000 (16:57 -0500)]
Remove manual breaks in NodeTag assignments to fix duplicate tag numbers.
Commit f0e44751d added new node tags at a place in the tag numbering
where there was no daylight left before the next hard-coded number,
resulting in some duplicate tag assignments. This doesn't seem to have
caused any big problem so far, but it's surely trouble waiting to happen.
We could adjust the manually assigned breakpoints to make more room,
but that just leaves the same hazard waiting to strike again in future.
What seems like a better idea is to get rid of the manual assignments
and leave NodeTags to be automatically assigned, consecutively from one
on up. This means that any change in the tag list forces a backend-wide
recompile, but realistically that's usually needed anyway.
Peter Eisentraut [Wed, 28 Dec 2016 17:00:00 +0000 (12:00 -0500)]
Make more use of RoleSpec struct
Most code was casting this through a generic Node. By declaring
everything as RoleSpec appropriately, we can remove a bunch of casts and
ad-hoc node type checking.
Tom Lane [Tue, 27 Dec 2016 20:43:54 +0000 (15:43 -0500)]
Fix interval_transform so it doesn't throw away non-no-op casts.
interval_transform() contained two separate bugs that caused it to
sometimes mistakenly decide that a cast from interval to restricted
interval is a no-op and throw it away.
First, it was wrong to rely on dt.h's field type macros to have an
ordering consistent with the field's significance; in one case they do
not. This led to mistakenly treating YEAR as less significant than MONTH,
so that a cast from INTERVAL MONTH to INTERVAL YEAR was incorrectly
discarded.
Second, fls(1<<k) produces k+1 not k, so comparing its output directly
to SECOND was wrong. This led to supposing that a cast to INTERVAL
MINUTE was really a cast to INTERVAL SECOND and so could be discarded.
To fix, get rid of the use of fls(), and make a function based on
intervaltypmodout to produce a field ID code adapted to the need here.
Per bug #14479 from Piotr Stefaniak. Back-patch to 9.2 where transform
functions were introduced, because this code was born broken.
Andrew Dunstan [Tue, 27 Dec 2016 16:23:46 +0000 (11:23 -0500)]
Explain unaccounted for space in pgstattuple.
In addition to space accounted for by tuple_len, dead_tuple_len and
free_space, the table_len includes page overhead, the item pointers
table and padding bytes.
Magnus Hagander [Tue, 27 Dec 2016 09:37:11 +0000 (10:37 +0100)]
Don't rename .partial files in pg_receivexlog if an error occured
In 56c7d8d the behavior to keep .partial segments around
(considered corrupt) in case an connection failure occurs was
accidentally removed. This would lead to an incomplete segment
being considered complete.
Tom Lane [Mon, 26 Dec 2016 19:58:02 +0000 (14:58 -0500)]
Remove triggerable Assert in hashname().
hashname() asserted that the key string it is given is shorter than
NAMEDATALEN. That should surely always be true if the input is in fact a
regular value of type "name". However, for reasons of coding convenience,
we allow plain old C strings to be treated as "name" values in many places.
Some SQL functions accept arbitrary "text" inputs, convert them to C
strings, and pass them otherwise-untransformed to syscache lookups for name
columns, allowing an overlength input value to trigger hashname's Assert.
This would be a DOS problem, except that it only happens in assert-enabled
builds which aren't recommended for production. In a production build,
you'll just get a name lookup error, since regardless of the hash value
computed by hashname, the later equality comparison checks can't match.
Likewise, if the catalog lookup is done by seqscan or indexscan searches,
there will just be a lookup error, since the name comparison functions
don't contain any similar length checks, and will see an overlength input
as unequal to any stored entry.
After discussion we concluded that we should simply remove this Assert.
It's inessential to hashname's own functionality, and having such an
assertion in only some paths for name lookup is more of a foot-gun than
a useful check. There may or may not be a case for the affected callers
to do something other than let the name lookup fail, but we'll consider
that separately; in any case we probably don't want to change such
behavior in the back branches.
Per report from Tushar Ahuja. Back-patch to all supported branches.
Tom Lane [Sun, 25 Dec 2016 21:04:31 +0000 (16:04 -0500)]
Fix incorrect error reporting for duplicate data in \crosstabview.
\crosstabview's complaint about multiple entries for the same crosstab
cell quoted the wrong row and/or column values. It would accidentally
appear to work if the data had been in strcmp() order to start with,
which probably explains how we missed noticing this during development.
This could be fixed in more than one way, but the way I chose was to
hang onto both result pointers from bsearch() and use those to get at
the value names.
In passing, avoid casting away const in the bsearch comparison functions.
No bug there, just poor style.
Per bug #14476 from Tomonari Katsumata. Back-patch to 9.6 where
\crosstabview was introduced.
Stephen Frost [Sat, 24 Dec 2016 06:41:59 +0000 (01:41 -0500)]
pg_dumpall: Include --verbose option in --help output
The -v/--verbose option was not included in the output from --help for
pg_dumpall even though it's in the pg_dumpall documentation and has
apparently been around since pg_dumpall was reimplemented in C in 2002.
Stephen Frost [Sat, 24 Dec 2016 02:01:29 +0000 (21:01 -0500)]
Fix tab completion in psql for ALTER DEFAULT PRIVILEGES
When providing tab completion for ALTER DEFAULT PRIVILEGES, we are
including the list of roles as possible options for completion after the
GRANT or REVOKE. Further, we accept FOR ROLE/IN SCHEMA at the same time
and in either order, but the tab completion was only working for one or
the other. Lastly, we weren't using the actual list of allowed kinds of
objects for default privileges for completion after the 'GRANT X ON' but
instead were completeing to what 'GRANT X ON' supports, which isn't the
ssame at all.
Address these issues by improving the forward tab-completion for ALTER
DEFAULT PRIVILEGES and then constrain and correct how the tail
completion is done when it is for ALTER DEFAULT PRIVILEGES.
Back-patch the forward/tail tab-completion to 9.6, where we made it easy
to handle such cases.
For 9.5 and earlier, correct the initial tab-completion to at least be
correct as far as it goes and then add a check for GRANT/REVOKE to only
tab-complete when the GRANT/REVOKE is the start of the command, so we
don't try to do tab-completion after we get to the GRANT/REVOKE part of
the ALTER DEFAULT PRIVILEGES command, which is better than providing
incorrect completions.
Initial patch for master and 9.6 by Gilles Darold, though I cleaned it
up and added a few comments. All bugs in the 9.5 and earlier patch are
mine.
Tom Lane [Fri, 23 Dec 2016 18:35:11 +0000 (13:35 -0500)]
Replace enum InhOption with simple boolean.
Now that it has only INH_NO and INH_YES values, it's just weird that
it's not a plain bool, so make it that way.
Also rename RangeVar.inhOpt to "inh", to be like RangeTblEntry.inh.
My recollection is that we gave it a different name specifically because
it had a different representation than the derived bool value, but it
no longer does. And this is a good forcing function to be sure we
catch any places that are affected by the change.
Bump catversion because of possible effect on stored RangeVar nodes.
I'm not exactly convinced that we ever store RangeVar on disk, but
we have a readfuncs function for it, so be cautious. (If we do do so,
then commit e13486eba was in error not to bump catversion.)
Tom Lane [Fri, 23 Dec 2016 17:53:09 +0000 (12:53 -0500)]
Doc: improve index entry for "median".
We had an index entry for "median" attached to the percentile_cont function
entry, which was pretty useless because a person following the link would
never realize that that function was the one they were being hinted to use.
Instead, make the index entry point at the example in syntax-aggregates,
and add a <seealso> link to "percentile".
Also, since that example explicitly claims to be calculating the median,
make it use percentile_cont not percentile_disc. This makes no difference
in terms of the larger goals of that section, but so far as I can find,
nearly everyone thinks that "median" means the continuous not discrete
calculation.
Per gripe from Steven Winfield. Back-patch to 9.4 where we introduced
percentile_cont.
Tom Lane [Fri, 23 Dec 2016 16:53:35 +0000 (11:53 -0500)]
Spellcheck: s/descendent/descendant/g
I got a little annoyed by reading documentation paragraphs containing
both spellings within a few lines of each other. My dictionary says
"descendant" is the preferred spelling, and it's certainly the majority
usage in our tree, so standardize on that.
For one usage in parallel.sgml, I thought it better to rewrite to avoid
the term altogether.
Peter Eisentraut [Fri, 23 Dec 2016 17:00:00 +0000 (12:00 -0500)]
pg_dump: Remove obsolete handling of sequence names
There was code that attempted to check whether the sequence name stored
inside the sequence was the same as the name in pg_class. But that code
was already ifdef'ed out, and now that the sequence no longer stores its
own name, it's altogether obsolete, so remove it.
Robert Haas [Fri, 23 Dec 2016 12:14:37 +0000 (07:14 -0500)]
Remove _hash_chgbufaccess().
This is basically for the same reasons I got rid of _hash_wrtbuf()
in commit 25216c98938495fd741bf585dcbef45b3a9ffd40: it's not
convenient to have a function which encapsulates MarkBufferDirty(),
especially as we move towards having hash indexes be WAL-logged.
Patch by me, reviewed (but not entirely endorsed) by Amit Kapila.
Joe Conway [Fri, 23 Dec 2016 01:56:50 +0000 (17:56 -0800)]
Improve RLS documentation with respect to COPY
Documentation for pg_restore said COPY TO does not support row security
when in fact it should say COPY FROM. Fix that.
While at it, make it clear that "COPY FROM" does not allow RLS to be
enabled and INSERT should be used instead. Also that SELECT policies
will apply to COPY TO statements.
Back-patch to 9.5 where RLS first appeared.
Author: Joe Conway Reviewed-By: Dean Rasheed and Robert Haas
Discussion: https://postgr.es/m/5744FA24.3030008%40joeconway.com
Robert Haas [Thu, 22 Dec 2016 22:31:52 +0000 (17:31 -0500)]
Fix tuple routing in cases where tuple descriptors don't match.
The previous coding failed to work correctly when we have a
multi-level partitioned hierarchy where tables at successive levels
have different attribute numbers for the partition key attributes. To
fix, have each PartitionDispatch object store a standalone
TupleTableSlot initialized with the TupleDesc of the corresponding
partitioned table, along with a TupleConversionMap to map tuples from
the its parent's rowtype to own rowtype. After tuple routing chooses
a leaf partition, we must use the leaf partition's tuple descriptor,
not the root table's. To that end, a dedicated TupleTableSlot for
tuple routing is now allocated in EState.
Stephen Frost [Thu, 22 Dec 2016 22:08:43 +0000 (17:08 -0500)]
Use TSConfigRelationId in AlterTSConfiguration()
When we are altering a text search configuration, we are getting the
tuple from pg_ts_config and using its OID, so use TSConfigRelationId
when invoking any post-alter hooks and setting the object address.
Further, in the functions called from AlterTSConfiguration(), we're
saving information about the command via
EventTriggerCollectAlterTSConfig(), so we should be setting
commandCollected to true. Also add a regression test to
test_ddl_deparse for ALTER TEXT SEARCH CONFIGURATION.
Author: Artur Zakirov, a few additional comments by me
Discussion: https://www.postgresql.org/message-id/57a71eba-f2c7-e7fd-6fc0-2126ec0b39bd%40postgrespro.ru
Back-patch the fix for the InvokeObjectPostAlterHook() call to 9.3 where
it was introduced, and the fix for the ObjectAddressSet() call and
setting commandCollected to true to 9.5 where those changes to
ProcessUtilitySlow() were introduced.
Tom Lane [Thu, 22 Dec 2016 21:23:33 +0000 (16:23 -0500)]
Fix CREATE TABLE ... LIKE ... WITH OIDS.
Having a WITH OIDS specification should result in the creation of an OID
column, but commit b943f502b broke that in the case that there were LIKE
tables without OIDS. Commentary in that patch makes it look like this was
intentional, but if so it was based on a faulty reading of what inheritance
does: the parent tables can add an OID column, but they can't subtract one.
AFAICS, the behavior ought to be that you get an OID column if any of the
inherited tables, LIKE tables, or WITH clause ask for one.
Also, revert that patch's unnecessary split of transformCreateStmt's loop
over the tableElts list into two passes. That seems to have been based on
a misunderstanding as well: we already have two-pass processing here,
we don't need three passes.
Per bug #14474 from Jeff Dafoe. Back-patch to 9.6 where the misbehavior
was introduced.
Tom Lane [Thu, 22 Dec 2016 20:01:27 +0000 (15:01 -0500)]
Fix handling of expanded objects in CoerceToDomain and CASE execution.
When the input value to a CoerceToDomain expression node is a read-write
expanded datum, we should pass a read-only pointer to any domain CHECK
expressions and then return the original read-write pointer as the
expression result. Previously we were blindly passing the same pointer to
all the consumers of the value, making it possible for a function in CHECK
to modify or even delete the expanded value. (Since a plpgsql function
will absorb a passed-in read-write expanded array as a local variable
value, it will in fact delete the value on exit.)
A similar hazard of passing the same read-write pointer to multiple
consumers exists in domain_check() and in ExecEvalCase, so fix those too.
The fix requires adding MakeExpandedObjectReadOnly calls at the appropriate
places, which is simple enough except that we need to get the data type's
typlen from somewhere. For the domain cases, solve this by redefining
DomainConstraintRef.tcache as okay for callers to access; there wasn't any
reason for the original convention against that, other than not wanting the
API of typcache.c to be any wider than it had to be. For CASE, there's
no good solution except to add a syscache lookup during executor start.
Per bug #14472 from Marcos Castedo. Back-patch to 9.5 where expanded
values were introduced.
Andres Freund [Thu, 22 Dec 2016 19:31:50 +0000 (11:31 -0800)]
Skip checkpoints, archiving on idle systems.
Some background activity (like checkpoints, archive timeout, standby
snapshots) is not supposed to happen on an idle system. Unfortunately
so far it was not easy to determine when a system is idle, which
defeated some of the attempts to avoid redundant activity on an idle
system.
To make that easier, allow to make individual WAL insertions as not
being "important". By checking whether any important activity happened
since the last time an activity was performed, it now is easy to check
whether some action needs to be repeated.
Use the new facility for checkpoints, archive timeout and standby
snapshots.
The lack of a facility causes some issues in older releases, but in my
opinion the consequences (superflous checkpoints / archived segments)
aren't grave enough to warrant backpatching.
Author: Michael Paquier, editorialized by Andres Freund Reviewed-By: Andres Freund, David Steele, Amit Kapila, Kyotaro HORIGUCHI
Bug: #13685
Discussion:
https://www.postgresql.org/message-id/20151016203031.3019.72930@wrigleys.postgresql.org
https://www.postgresql.org/message-id/CAB7nPqQcPqxEM3S735Bd2RzApNqSNJVietAC=6kfkYv_45dKwA@mail.gmail.com
Backpatch: -
Robert Haas [Thu, 22 Dec 2016 18:54:40 +0000 (13:54 -0500)]
Fix broken error check in _hash_doinsert.
You can't just cast a HashMetaPage to a Page, because the meta page
data is stored after the page header, not at offset 0. Fortunately,
this didn't break anything because it happens to find hashm_bsize
at the offset at which it expects to find pd_pagesize_version, and
the values are close enough to the same that this works out.
Still, it's a bug, so back-patch to all supported versions.
Joe Conway [Thu, 22 Dec 2016 17:48:05 +0000 (09:48 -0800)]
Make dblink try harder to form useful error messages
When libpq encounters a connection-level error, e.g. runs out of memory
while forming a result, there will be no error associated with PGresult,
but a message will be placed into PGconn's error buffer. postgres_fdw
takes care to use the PGconn error message when PGresult does not have
one, but dblink has been negligent in that regard. Modify dblink to mirror
what postgres_fdw has been doing.
Back-patch to all supported branches.
Author: Joe Conway Reviewed-By: Tom Lane
Discussion: https://postgr.es/m/02fa2d90-2efd-00bc-fefc-c23c00eb671e%40joeconway.com
Joe Conway [Thu, 22 Dec 2016 17:19:44 +0000 (09:19 -0800)]
Protect dblink from invalid options when using postgres_fdw server
When dblink uses a postgres_fdw server name for its connection, it
is possible for the connection to have options that are invalid
with dblink (e.g. "updatable"). The recommended way to avoid this
problem is to use dblink_fdw servers instead. However there are use
cases for using postgres_fdw, and possibly other FDWs, for dblink
connection options, therefore protect against trying to use any
options that do not apply by using is_valid_dblink_option() when
building the connection string from the options.
Back-patch to 9.3. Although 9.2 supports FDWs for connection info,
is_valid_dblink_option() did not yet exist, and neither did
postgres_fdw, at least in the postgres source tree. Given the lack
of previous complaints, fixing that seems too invasive/not worth it.
Author: Corey Huinker Reviewed-By: Joe Conway
Discussion: https://postgr.es/m/CADkLM%3DfWyXVEyYcqbcRnxcHutkP45UHU9WD7XpdZaMfe7S%3DRwA%40mail.gmail.com
No more indirect blocks. The blocks form a linked list instead.
This saves some memory, because we don't need to have a buffer in memory to
hold the indirect block (or blocks). To reflect that, TAPE_BUFFER_OVERHEAD
is reduced from 3 to 1 buffer, which allows using more memory for building
the initial runs.
Tom Lane [Thu, 22 Dec 2016 16:19:04 +0000 (11:19 -0500)]
Give a useful error message if uuid-ossp is built without preconfiguration.
Before commit b8cc8f947, it was possible to build contrib/uuid-ossp without
having told configure you meant to; you could just cd into that directory
and "make". That no longer works because the code depends on configure to
have done header and library probes, but the ensuing error messages are
not so easy to interpret if you're not an old C hand. We've gotten a
couple of complaints recently from people trying to do this the low-tech
way, so add an explicit #error directing the user to use --with-uuid.
(In principle we might want to do something similar in the other
optionally-built contrib modules; but I don't think any of the others have
ever worked without preconfiguration, so there are no bad habits to break
people of.)
Back-patch to 9.4 where the previous commit came in.
Joe Conway [Wed, 21 Dec 2016 23:47:54 +0000 (15:47 -0800)]
Improve dblink error message when remote does not provide it
When dblink or postgres_fdw detects an error on the remote side of the
connection, it will try to construct a local error message as best it
can using libpq's PQresultErrorField(). When no primary message is
available, it was bailing out with an unhelpful "unknown error". Make
that message better and more style guide compliant. Per discussion
on hackers.
Backpatch to 9.2 except postgres_fdw which didn't exist before 9.3.
Tom Lane [Wed, 21 Dec 2016 22:39:32 +0000 (17:39 -0500)]
Fix detection of unfinished Unicode surrogate pair at end of string.
The U&'...' and U&"..." syntaxes silently discarded a surrogate pair
start (that is, a code between U+D800 and U+DBFF) if it occurred at
the very end of the string. This seems like an obvious oversight,
since we throw an error for every other invalid combination of surrogate
characters, including the very same situation in E'...' syntax.
This has been wrong since the pair processing was added (in 9.0),
so back-patch to all supported branches.
Tom Lane [Wed, 21 Dec 2016 20:18:25 +0000 (15:18 -0500)]
Fix strange behavior (and possible crashes) in full text phrase search.
In an attempt to simplify the tsquery matching engine, the original
phrase search patch invented rewrite rules that would rearrange a
tsquery so that no AND/OR/NOT operator appeared below a PHRASE operator.
But this approach had numerous problems. The rearrangement step was
missed by ts_rewrite (and perhaps other places), allowing tsqueries
to be created that would cause Assert failures or perhaps crashes at
execution, as reported by Andreas Seltenreich. The rewrite rules
effectively defined semantics for operators underneath PHRASE that were
buggy, or at least unintuitive. And because rewriting was done in
tsqueryin() rather than at execution, the rearrangement was user-visible,
which is not very desirable --- for example, it might cause unexpected
matches or failures to match in ts_rewrite.
As a somewhat independent problem, the behavior of nested PHRASE operators
was only sane for left-deep trees; queries like "x <-> (y <-> z)" did not
behave intuitively at all.
To fix, get rid of the rewrite logic altogether, and instead teach the
tsquery execution engine to manage AND/OR/NOT below a PHRASE operator
by explicitly computing the match location(s) and match widths for these
operators.
This requires introducing some additional fields into the publicly visible
ExecPhraseData struct; but since there's no way for third-party code to
pass such a struct to TS_phrase_execute, it shouldn't create an ABI problem
as long as we don't move the offsets of the existing fields.
Another related problem was that index searches supposed that "!x <-> y"
could be lossily approximated as "!x & y", which isn't correct because
the latter will reject, say, "x q y" which the query itself accepts.
This required some tweaking in TS_execute_ternary along with the main
tsquery engine.
Back-patch to 9.6 where phrase operators were introduced. While this
could be argued to change behavior more than we'd like in a stable branch,
we have to do something about the crash hazards and index-vs-seqscan
inconsistency, and it doesn't seem desirable to let the unintuitive
behaviors induced by the rewriting implementation stand as precedent.
Stephen Frost [Wed, 21 Dec 2016 20:03:32 +0000 (15:03 -0500)]
Improve ALTER TABLE documentation
The ALTER TABLE documentation wasn't terribly clear when it came to
which commands could be combined together and what it meant when they
were.
In particular, SET TABLESPACE *can* be combined with other commands,
when it's operating against a single table, but not when multiple tables
are being moved with ALL IN TABLESPACE. Further, the actions are
applied together but not really in 'parallel', at least today.
Pointed out by: Amit Langote
Improved wording from Tom.
Back-patch to 9.4, where the ALL IN TABLESPACE option was added.
Stephen Frost [Wed, 21 Dec 2016 18:47:06 +0000 (13:47 -0500)]
Fix dumping of casts and transforms using built-in functions
In pg_dump.c dumpCast() and dumpTransform(), we would happily ignore the
cast or transform if it happened to use a built-in function because we
weren't including the information about built-in functions when querying
pg_proc from getFuncs().
Modify the query in getFuncs() to also gather information about
functions which are used by user-defined casts and transforms (where
"user-defined" means "has an OID >= FirstNormalObjectId"). This also
adds to the TAP regression tests for 9.6 and master to cover these
types of objects.
Back-patch all the way for casts, back to 9.5 for transforms.
Stephen Frost [Wed, 21 Dec 2016 18:47:06 +0000 (13:47 -0500)]
For 8.0 servers, get last built-in oid from pg_database
We didn't start ensuring that all built-in objects had OIDs less than
16384 until 8.1, so for 8.0 servers we still need to query the value out
of pg_database. We need this, in particular, to distinguish which casts
were built-in and which were user-defined.
For HEAD, we only worry about going back to 8.0, for the back-branches,
we also ensure that 7.0-7.4 work.
Dean Rasheed [Wed, 21 Dec 2016 16:58:18 +0000 (16:58 +0000)]
Fix order of operations in CREATE OR REPLACE VIEW.
When CREATE OR REPLACE VIEW acts on an existing view, don't update the
view options until after the view query has been updated.
This is necessary in the case where CREATE OR REPLACE VIEW is used on
an existing view that is not updatable, and the new view is updatable
and specifies the WITH CHECK OPTION. In this case, attempting to apply
the new options to the view before updating its query fails, because
the options are applied using the ALTER TABLE infrastructure which
checks that WITH CHECK OPTION is only applied to an updatable view.
If new columns are being added to the view, that is also done using
the ALTER TABLE infrastructure, but it is important that that still be
done before updating the view query, because the rules system checks
that the query columns match those on the view relation. Added a
comment to explain that, in case someone is tempted to move that to
where the view options are now being set.
Back-patch to 9.4 where WITH CHECK OPTION was added.
Robert Haas [Wed, 21 Dec 2016 16:47:13 +0000 (11:47 -0500)]
Convert elog() to ereport() and do some wordsmithing.
It's not entirely clear that we should log a message here at all, but
it's certainly wrong to use elog() for a message that should clearly
be translatable.
Robert Haas [Wed, 21 Dec 2016 16:01:48 +0000 (11:01 -0500)]
Fix corner-case bug in WaitEventSetWaitBlock on Windows.
If we do not reset the FD_READ event, WaitForMultipleObjects won't
return it again again unless we've meanwhile read from the socket,
which is generally true but not guaranteed. WaitEventSetWaitBlock
itself may fail to return the event to the caller if the latch is
also set, and even if we changed that, the caller isn't obliged to
handle all returned events at once. On non-Windows systems, the
socket-read event is purely level-triggered, so this issue does
not exist. To fix, make Windows reset the event when needed.
Robert Haas [Wed, 21 Dec 2016 14:44:33 +0000 (09:44 -0500)]
Refactor merge path generation code.
This shouldn't change the set of paths that get generated in any
way, but it is preparatory work for further changes to allow a
partial path to be merge-joined witih a non-partial path to produce
a partial join path.
Peter Eisentraut [Wed, 21 Dec 2016 17:00:00 +0000 (12:00 -0500)]
Reorder pg_sequence columns to avoid alignment issue
On AIX, doubles are aligned at 4 bytes, but int64 is aligned at 8 bytes.
Our code assumes that doubles have alignment that can also be applied to
int64, but that fails in this case. One effect is that
heap_form_tuple() writes tuples in a different layout than
Form_pg_sequence expects.
Rather than rewrite the whole alignment code, work around the issue by
reordering the columns in pg_sequence so that the first int64 column
naturally comes out at an 8-byte boundary.
Fujii Masao [Wed, 21 Dec 2016 11:27:37 +0000 (20:27 +0900)]
Forbid invalid combination of options in pg_basebackup.
Commit 56c7d8d4552180fd66fe48423bb2a9bb767c2d87 allowed pg_basebackup
to stream WAL in tar mode. But there is the restriction that WAL
streaming in tar mode works only when the value - (dash) is not
specified as output directory. This means that the combination of
three options "-D -", "-F t" and "-X stream" is invalid. However,
previously, even when those options were specified at the same time,
pg_basebackup background process unexpectedly started streaming WAL.
And then it exited with an error.
This commit changes pg_basebackup so that it errors out on such
invalid combination of options at the beginning.
Tom Lane [Wed, 21 Dec 2016 00:22:02 +0000 (19:22 -0500)]
Fix minor oversights in nodeAgg.c.
aggstate->evalproj is always set up by ExecInitAgg, so there's no
need to test. Doing so led Coverity to think that we might be
intending "slot" to be possibly NULL here, and it quite properly
complained that the rest of combine_aggregates() wasn't prepared
for that.
Also fix a couple of obvious thinkos in Asserts checking that
"inputoff" isn't past the end of the slot.
Errors introduced in commit 8ed3f11bb, so no need for back-patch.
Peter Eisentraut [Tue, 20 Dec 2016 17:00:00 +0000 (12:00 -0500)]
Add pg_sequence system catalog
Move sequence metadata (start, increment, etc.) into a proper system
catalog instead of storing it in the sequence heap object. This
separates the metadata from the sequence data. Sequence metadata is now
operated on transactionally by DDL commands, whereas previously
rollbacks of sequence-related DDL commands would be ignored.
Fix sharing Agg transition state of DISTINCT or ordered aggs.
If a query contained two aggregates that could share the transition value,
we would correctly collect the input into a tuplesort only once, but
incorrectly run the transition function over the accumulated input twice,
in finalize_aggregates(). That caused a crash, when we tried to call
tuplesort_performsort() on an already-freed NULL tuplestore.
Backport to 9.6, where sharing of transition state and this bug were
introduced.
Tom Lane [Mon, 19 Dec 2016 18:49:45 +0000 (13:49 -0500)]
Fix handling of phrase operator removal while removing tsquery stopwords.
The distance of a removed phrase operator should propagate up to a
parent phrase operator if there is one, but this only worked correctly
in left-deep trees. Throwing in a few parentheses confused it completely,
as indeed was illustrated by bizarre results in existing regression test
cases.
To fix, track unaccounted-for distances that should propagate to the left
and to the right of the current node, rather than trying to make it work
with only one returned distance.
Also make some adjustments to behave as well as we can for cases of
intermixed phrase and regular (AND/OR) operators. I don't think it's
possible to be 100% correct for that without a rethinking of the tsquery
representation; for example, maybe we should just not drop stopword nodes
at all underneath phrase operators. But this is better than it was,
and changing tsquery representation wouldn't be safely back-patchable.
While at it, I simplified the API of the clean_fakeval_intree function
a bit by getting rid of the "char *result" output parameter; that wasn't
doing anything that wasn't redundant with whether the result node is
NULL or not, and testing for NULL seems a lot clearer/safer.
This is part of a larger project to fix various infelicities in the
phrase-search implementation, but this part seems comittable on its own.
Back-patch to 9.6 where phrase operators were introduced.
Robert Haas [Mon, 19 Dec 2016 17:31:50 +0000 (12:31 -0500)]
Fix locking problem in _hash_squeezebucket() / _hash_freeovflpage().
A bucket squeeze operation needs to lock each page of the bucket
before releasing the prior page, but the previous coding fumbled the
locking when freeing an overflow page during a bucket squeeze
operation. Commit 6d46f4783efe457f74816a75173eb23ed8930020
introduced this bug.
Amit Kapila, with help from Kuntal Ghosh and Dilip Kumar, after
an initial trouble report by Jeff Janes. Reviewed by me. I also
fixed a problem with a comment.
Fujii Masao [Mon, 19 Dec 2016 12:15:30 +0000 (21:15 +0900)]
Support quorum-based synchronous replication.
This feature is also known as "quorum commit" especially in discussion
on pgsql-hackers.
This commit adds the following new syntaxes into synchronous_standby_names
GUC. By using FIRST and ANY keywords, users can specify the method to
choose synchronous standbys from the listed servers.
FIRST num_sync (standby_name [, ...])
ANY num_sync (standby_name [, ...])
The keyword FIRST specifies a priority-based synchronous replication
which was available also in 9.6 or before. This method makes transaction
commits wait until their WAL records are replicated to num_sync
synchronous standbys chosen based on their priorities.
The keyword ANY specifies a quorum-based synchronous replication
and makes transaction commits wait until their WAL records are
replicated to *at least* num_sync listed standbys. In this method,
the values of sync_state.pg_stat_replication for the listed standbys
are reported as "quorum". The priority is still assigned to each standby,
but not used in this method.
The existing syntaxes having neither FIRST nor ANY keyword are still
supported. They are the same as new syntax with FIRST keyword, i.e.,
a priorirty-based synchronous replication.
Author: Masahiko Sawada Reviewed-By: Michael Paquier, Amit Kapila and me
Discussion: <CAD21AoAACi9NeC_ecm+Vahm+MMA6nYh=Kqs3KB3np+MBOS_gZg@mail.gmail.com>
Many thanks to the various individuals who were involved in
discussing and developing this feature.
Magnus Hagander [Mon, 19 Dec 2016 09:11:04 +0000 (10:11 +0100)]
Fix base backup rate limiting in presence of slow i/o
When source i/o on disk was too slow compared to the rate limiting
specified, the system could end up with a negative value for sleep that
it never got out of, which caused rate limiting to effectively be
turned off.
Tom Lane [Sun, 18 Dec 2016 03:24:13 +0000 (22:24 -0500)]
In contrib/uuid-ossp, #include headers needed for ntohl() and ntohs().
Oversight in commit b8cc8f947. I just noticed this causes compiler
warnings on FreeBSD, and it really ought to cause warnings elsewhere too:
all references I can find say that <arpa/inet.h> is required for these.
We have a lot of code elsewhere that thinks that both <netinet/in.h>
and <arpa/inet.h> should be included for these functions, so do it that
way here too, even though <arpa/inet.h> ought to be sufficient according
to the references I consulted.
Back-patch to 9.4 where the previous commit landed.
Tom Lane [Sat, 17 Dec 2016 20:28:54 +0000 (15:28 -0500)]
Fix FK-based join selectivity estimation for semi/antijoins.
This case wasn't thought through sufficiently in commit 100340e2d.
It's true that the FK proves that every outer row has a match in the
inner table, but we forgot that some of the inner rows might be filtered
away by WHERE conditions located within the semijoin's RHS.
If the RHS is just one table, we can reasonably take the semijoin
selectivity as equal to the fraction of the referenced table's rows
that are expected to survive its restriction clauses.
If the RHS is a join, it's not clear how much of the referenced table
might get through the join, so fall back to the same rule we were
already using for other outer-join cases: use the minimum of the
regular per-clause selectivity estimates. This gives the same result
as if we hadn't considered the FK at all when there's a single FK
column, but it should still help for multi-column FKs, which is the
case that 100340e2d is really meant to help with.
Back-patch to 9.6 where the previous commit came in.
Fujii Masao [Fri, 16 Dec 2016 17:20:59 +0000 (02:20 +0900)]
Ensure that num_sync is greater than zero in synchronous_standby_names.
Previously num_sync could be set to zero and this setting caused
an assertion failure. This means that multiple synchronous standbys
code should assume that num_sync is greater than zero.
Also setting num_sync to zero is nonsense because it's basically
the configuration for synchronous replication. If users want not to
make transaction commits wait for any standbys,
synchronous_standby_names should be emptied to disable synchronous
replication instead of setting num_sync to zero.
This patch forbids users from setting num_sync to zero in
synchronous_standby_names. If zero is specified, an error will
happen during processing the parameter settings.
Back-patch to 9.6 where multiple synchronous standbys feature was added.
Patch by me. Reviewed by Tom Lane.
Discussion: <CAHGQGwHWB3izc6cXuFLh5kOcAbFXaRhhgwd-X5PeN9TEjxqXwg@mail.gmail.com>
Tom Lane [Fri, 16 Dec 2016 16:50:07 +0000 (11:50 -0500)]
Improve documentation around TS_execute().
I got frustrated by the lack of commentary in this area, so here is some
reverse-engineered documentation, along with minor stylistic cleanup.
No code changes more significant than removal of unused variables.
Back-patch to 9.6, not because that's useful in itself, but because
we have some bugs to fix in phrase search and this would cause merge
failures if it's only in HEAD.
Robert Haas [Fri, 16 Dec 2016 16:29:23 +0000 (11:29 -0500)]
Simplify LWLock tranche machinery by removing array_base/array_stride.
array_base and array_stride were added so that we could identify the
offset of an LWLock within a tranche, but this facility is only very
marginally used apart from the main tranche. So, give every lock in
the main tranche its own tranche ID and get rid of array_base,
array_stride, and all that's attached. For debugging facilities
(Trace_lwlocks and LWLOCK_STATS) print the pointer address of the
LWLock using %p instead of the offset. This is arguably more useful,
and certainly a lot cheaper. Drop the offset-within-tranche from
the information reported to dtrace and from one can't-happen message
inside lwlock.c.
The main user-visible impact of this change is that pg_stat_activity
will now report all waits for LWLocks as "LWLock" rather than
reporting some as "LWLockTranche" and others as "LWLockNamed".
The main motivation for this change is that the need to specify an
array_base and an array_stride is awkward for parallel query. There
is only a very limited supply of tranche IDs so we can't just keep
allocating new ones, and if we try to use the same tranche IDs every
time then we run into trouble when multiple parallel contexts are
use simultaneously. So if we didn't get rid of this mechanism we'd
have to make it even more complicated. By simplifying it in this
way, we instead reduce the size of the generated code for lwlock.c
by about 5%.
Robert Haas [Fri, 16 Dec 2016 15:03:08 +0000 (10:03 -0500)]
Unbreak Finalize HashAggregate over Partial HashAggregate.
Commit 5dfc198146b49ce7ecc8a1fc9d5e171fb75f6ba5 introduced the use
of a new type of hash table with linear reprobing for hash aggregates.
Such a hash table behaves very poorly if keys are inserted in hash
order, which does in fact happen in the case where a query use a
Finalize HashAggregate node fed (via Gather) by a Partial
HashAggregate node. In fact, queries with this type of plan tend
to run effectively forever.
Fix that by seeding the hash value differently in each worker
(and in the leader, if it participates).
Robert Haas [Fri, 16 Dec 2016 14:52:04 +0000 (09:52 -0500)]
Fix more hash index bugs around marking buffers dirty.
In _hash_freeovflpage(), if we're freeing the overflow page that
immediate follows the page to which tuples are being moved (the
confusingly-named "write buffer"), don't forget to mark that
page dirty after updating its hasho_nextblkno.
In _hash_squeezebucket(), it's not necessary to mark the primary
bucket page dirty if there are no overflow pages, because there's
nothing to squeeze in that case.
Amit Kapila, with help from Kuntal Ghosh and Dilip Kumar, after
an initial trouble report by Jeff Janes.
Robert Haas [Fri, 16 Dec 2016 14:29:21 +0000 (09:29 -0500)]
Remove _hash_wrtbuf() in favor of calling MarkBufferDirty().
The whole concept of _hash_wrtbuf() is that we need to know at the
time we're releasing the buffer lock (and pin) whether we dirtied the
buffer, but this is easy to get wrong. This patch actually fixes one
non-obvious bug of that form: hashbucketcleanup forgot to signal
_hash_squeezebucket, which gets the primary bucket page already
locked, as to whether it had already dirtied the page. Calling
MarkBufferDirty() at the places where we dirty the buffer is more
intuitive and lets us simplify the code in various places as well.
On top of all that, the ultimate goal here is to make hash indexes
WAL-logged, and as the comments to _hash_wrtbuf() note, it should
go away when that happens. Making it go away a little earlier than
that seems like a good preparatory step.
Report by Jeff Janes. Diagnosis by Amit Kapila, Kuntal Ghosh,
and Dilip Kumar. Patch by me, after studying an alternative patch
submitted by Amit Kapila.
Fix off-by-one in memory allocation for quote_literal_cstr().
The calculation didn't take into account the NULL terminator. That lead
to overwriting the palloc'd buffer by one byte, if the input consists
entirely of backslashes. For example "format('%L', E'\\')".
Fixes bug #14468. Backpatch to all supported versions.
Tom Lane [Thu, 15 Dec 2016 19:32:42 +0000 (14:32 -0500)]
Sync our copy of the timezone library with IANA release tzcode2016j.
This is a trivial update (consisting in fact only in the addition of
a comment). The point is just to get back to being synced with an
official release of tzcode, rather than some ad-hoc point in their
commit history, which is where commit 1f87181e1 left it.
Tom Lane [Tue, 13 Dec 2016 21:33:03 +0000 (16:33 -0500)]
Improve handling of array elements as getdiag_targets and cursor_variables.
There's no good reason why plpgsql's GET DIAGNOSTICS statement can't
support an array element as target variable, since the execution code
already uses the generic exec_assign_value() function to assign to it.
Hence, refactor the grammar to allow that, by making getdiag_target
depend on the assign_var production.
Ideally we'd also let a cursor_variable expand to an element of a
refcursor[] array, but that's substantially harder since those statements
also have to handle bound-cursor-variable cases. For now, just make sure
the reported error is sensible, ie "cursor variable must be a simple
variable" not "variable must be of type cursor or refcursor". The latter
was quite confusing from the user's viewpoint, since what he wrote
satisfies the claimed restriction.
Per bug #14463 from Zhou Digoal. Given the lack of previous complaints,
I see no need for a back-patch.
Tom Lane [Tue, 13 Dec 2016 18:20:16 +0000 (13:20 -0500)]
Prevent planagg.c from failing on queries containing CTEs.
The existing tests in preprocess_minmax_aggregates() usually prevent it
from trying to do anything with queries containing CTEs, but there's an
exception: a CTE could be present as a member of an appendrel, if we
flattened a UNION ALL that contains CTE references. If it did try to
generate an optimized path for a query using a CTE, it failed with
"could not find plan for CTE", as reported by Torsten Förtsch.
The proximate cause is an unwise decision in commit 3fc6e2d7f to clear
subroot->cte_plan_ids in build_minmax_path(). That left the subroot's
cte_plan_ids list out of step with its parse->cteList.
Removing the "subroot->cte_plan_ids = NIL;" assignment is enough to let
the case work again, but really it's pretty silly to be expending any
cycles at all in this module when there are CTEs: we always treat their
outputs as unordered so there's no way for the optimization to win.
Hence, also add an early-exit test so we don't waste time like that.
Back-patch to 9.6 where the misbehavior was introduced.
Robert Haas [Tue, 13 Dec 2016 17:16:02 +0000 (12:16 -0500)]
Fix bug in hashbulkdelete.
Commit 6d46f4783efe457f74816a75173eb23ed8930020 failed to account for
the possibility that hashbulkdelete() might encounter a bucket that
has been split since it began scanning the bucket array. Repair.
Extracted from a larger pathc by Amit Kapila; I rewrote the comment.
Robert Haas [Tue, 13 Dec 2016 13:18:00 +0000 (08:18 -0500)]
doc: Improve documentation related to table partitioning feature.
Commit f0e44751d7175fa3394da2c8f85e3ceb3cdbfe63 implemented table
partitioning, but failed to mention the "no row movement"
restriction in the documentation. Fix that and a few other issues.
Amit Langote, with some additional wordsmithing by me.
Robert Haas [Mon, 12 Dec 2016 20:57:35 +0000 (15:57 -0500)]
Remove should_free arguments to tuplesort routines.
Since commit e94568ecc10f2638e542ae34f2990b821bbf90ac, the answer is
always "false", and we do not need to complicate the API by arranging
to return a constant value.
Tom Lane [Mon, 12 Dec 2016 19:32:09 +0000 (14:32 -0500)]
Fix race condition in test_decoding "slot" test.
This test, just added in commit a924c327e, sometimes fails because
the old backend hasn't finished dropping the temporary replication slot
when the new backend looks. Borrow the previously-invented methodology
for waiting for the old process to disappear from pg_stat_activity.
Tom Lane [Mon, 12 Dec 2016 18:32:10 +0000 (13:32 -0500)]
Make the different Unix-y semaphore implementations ABI-compatible.
Previously, the "sem" field of PGPROC varied in size depending on which
kernel semaphore API we were using. That was okay as long as there was
only one likely choice per platform, but in the wake of commit ecb0d20a9,
that assumption seems rather shaky. It doesn't seem out of the question
anymore that an extension compiled against one API choice might be loaded
into a postmaster built with another choice. Moreover, this prevents any
possibility of selecting the semaphore API at postmaster startup, which
might be something we want to do in future.
Hence, change PGPROC.sem to be PGSemaphore (i.e. a pointer) for all Unix
semaphore APIs, and turn the pointed-to data into an opaque struct whose
contents are only known within the responsible modules.
For the SysV and unnamed-POSIX APIs, the pointed-to data has to be
allocated elsewhere in shared memory, which takes a little bit of
rejiggering of the InitShmemAllocation code sequence. (I invented a
ShmemAllocUnlocked() function to make that a little cleaner than it used
to be. That function is not meant for any uses other than the ones it
has now, but it beats having InitShmemAllocation() know explicitly about
allocation of space for semaphores and spinlocks.) This change means an
extra indirection to access the semaphore data, but since we only touch
that when blocking or awakening a process, there shouldn't be any
meaningful performance penalty. Moreover, at least for the unnamed-POSIX
case on Linux, the sem_t type is quite a bit wider than a pointer, so this
reduces sizeof(PGPROC) which seems like a good thing.
For the named-POSIX API, there's effectively no change: the PGPROC.sem
field was and still is a pointer to something returned by sem_open() in
the postmaster's memory space. Document and check the pre-existing
limitation that this case can't work in EXEC_BACKEND mode.
It did not seem worth unifying the Windows semaphore ABI with the Unix
cases, since there's no likelihood of needing ABI compatibility much less
runtime switching across those cases. However, we can simplify the Windows
code a bit if we define PGSemaphore as being directly a HANDLE, rather than
pointer to HANDLE, so let's do that while we're here. (This also ends up
being no change in what's physically stored in PGPROC.sem. We're just
moving the HANDLE fetch from callees to callers.)
It would take a bunch of additional code shuffling to get to the point of
actually choosing a semaphore API at postmaster start, but the effects
of that would now be localized in the port/XXX_sema.c files, so it seems
like fit material for a separate patch. The need for it is unproven as
yet, anyhow, whereas the ABI risk to extensions seems real enough.
Tom Lane [Mon, 12 Dec 2016 16:23:23 +0000 (11:23 -0500)]
Fix creative, but unportable, spelling of "ptr != NULL".
Or at least I suppose that's what was really meant here. But even
aside from the not-per-project-style use of "0" to mean "NULL",
I doubt it's safe to assume that all valid pointers are > NULL.
Per buildfarm member pademelon.
projects / postgresql / log