While poking at David Kubečka's issue I noticed an ancient logic error
in get_loop_count(): it used 1.0 as a "no data yet" indicator, but since
that is actually a valid rowcount estimate, this doesn't work. If we
have one input relation with 1.0 as rowcount and then another one with
a larger rowcount, we should use 1.0 as the result, but we picked the
larger rowcount instead. (I think when I coded this, I recognized the
conflict, but mistakenly thought that the logic would pick the desired
count anyway.)
Fixing this changed the plan for one existing regression test case.
Since the point of that test is to exercise creation of a particular
shape of nestloop plan, I tweaked the query a little bit so it still
results in the same plan choice.
This is definitely a bug, but I'm hesitant to back-patch since it might
change plan choices unexpectedly, and anyway failure to implement a
heuristic precisely as intended is a pretty low-grade bug.
If we have a semijoin, say
SELECT * FROM x WHERE x1 IN (SELECT y1 FROM y)
and we're estimating the cost of a parameterized indexscan on x, the number
of repetitions of the indexscan should not be taken as the size of y; it'll
really only be the number of distinct values of y1, because the only valid
plan with y on the outside of a nestloop would require y to be unique-ified
before joining it to x. Most of the time this doesn't make that much
difference, but sometimes it can lead to drastically underestimating the
cost of the indexscan and hence choosing a bad plan, as pointed out by
David Kubečka.
Fixing this is a bit difficult because parameterized indexscans are costed
out quite early in the planning process, before we have the information
that would be needed to call estimate_num_groups() and thereby estimate the
number of distinct values of the join column(s). However we can move the
code that extracts a semijoin RHS's unique-ification columns, so that it's
done in initsplan.c rather than on-the-fly in create_unique_path(). That
shouldn't make any difference speed-wise and it's really a bit cleaner too.
The other bit of information we need is the size of the semijoin RHS,
which is easy if it's a single relation (we make those estimates before
considering indexscan costs) but problematic if it's a join relation.
The solution adopted here is just to use the product of the sizes of the
join component rels. That will generally be an overestimate, but since
estimate_num_groups() only uses this input as a clamp, an overestimate
shouldn't hurt us too badly. In any case we don't allow this new logic
to produce a value larger than we would have chosen before, so that at
worst an overestimate leaves us no wiser than we were before.
In the spirit of 890192e99a, this time add support for the things
living in the pg_default_acl catalog. These are not really "objects",
but they show up as such in event triggers.
There is no "DROP DEFAULT PRIVILEGES" or similar command, so it doesn't
look like the new representation given would be useful anywhere else, so
I didn't try to use it outside objectaddress.c. (That might be a bug in
itself, but that would be material for another commit.)
Reviewed by Stephen Frost.
Since commit 72dd233d3e we were trying to obtain object addressing
information in sql_drop event triggers, but that caused failures when
the drops involved user mappings. This addition enables that to work
again. Naturally, pg_get_object_address can work with these objects
now, too.
I toyed with the idea of removing DropUserMappingStmt as a node and
using DropStmt instead in the DropUserMappingStmt grammar production,
but that didn't go very well: for one thing the messages thrown by the
specific code are specialized (you get "server not found" if you specify
the wrong server, instead of a generic "user mapping for ... not found"
which you'd get it we were to merge this with RemoveObjects --- unless
we added even more special cases). For another thing, it would require
to pass RoleSpec nodes through the objname/objargs representation used
by RemoveObjects, which works in isolation, but gets messy when
pg_get_object_address is involved. So I dropped this part for now.
Reviewed by Stephen Frost.
PL/Python uses str() to convert Python values back to PostgreSQL, but
str() is lossy for float values, so use repr() instead in that case.
Author: Marko Kreen <markokr@gmail.com>
While the SQL standard is pretty vague on the overall topic of operator
precedence (because it never presents a unified BNF for all expressions),
it does seem reasonable to conclude from the spec for <boolean value
expression> that OR has the lowest precedence, then AND, then NOT, then IS
tests, then the six standard comparison operators, then everything else
(since any non-boolean operator in a WHERE clause would need to be an
argument of one of these).
We were only sort of on board with that: most notably, while "<" ">" and
"=" had properly low precedence, "<=" ">=" and "<>" were treated as generic
operators and so had significantly higher precedence. And "IS" tests were
even higher precedence than those, which is very clearly wrong per spec.
Another problem was that "foo NOT SOMETHING bar" constructs, such as
"x NOT LIKE y", were treated inconsistently because of a bison
implementation artifact: they had the documented precedence with respect
to operators to their right, but behaved like NOT (i.e., very low priority)
with respect to operators to their left.
Fixing the precedence issues is just a small matter of rearranging the
precedence declarations in gram.y, except for the NOT problem, which
requires adding an additional lookahead case in base_yylex() so that we
can attach a different token precedence to NOT LIKE and allied two-word
operators.
The bulk of this patch is not the bug fix per se, but adding logic to
parse_expr.c to allow giving warnings if an expression has changed meaning
because of these precedence changes. These warnings are off by default
and are enabled by the new GUC operator_precedence_warning. It's believed
that very few applications will be affected by these changes, but it was
agreed that a warning mechanism is essential to help debug any that are.
setup_param_list() was allocating a fresh ParamListInfo for each query or
expression evaluation requested by a plpgsql function. There was probably
once good reason to do it like that, but for a long time we've had a
convention that there's a one-to-one mapping between the function's
PLpgSQL_datum array and the ParamListInfo slots, which means that a single
ParamListInfo can serve all the function's evaluation requests: the data
that would need to be passed is the same anyway.
In this patch, we retain the pattern of zeroing out the ParamListInfo
contents during each setup_param_list() call, because some of the slots may
be stale and we don't know exactly which ones. So this patch only saves a
palloc/pfree per evaluation cycle and nothing more; still, that seems to be
good for a couple percent overall speedup on simple-arithmetic type
statements. In future, though, we might be able to improve matters still
more by managing the param array contents more carefully.
Also, unify the former use of estate->cur_expr with that of
paramLI->parserSetupArg; they both were used to point to the active
expression, so we can combine the variables into just one.
Error messages informing the user that no such column exists can
sometimes provoke a perplexed response. This often happens due to
a subtle typo in the column name or, perhaps less likely, in the
alias name. To speed discovery of what the real issue is in such
cases, we'll now search the range table for approximate matches.
If there are one or two such matches that are good enough to think
that they might be what the user intended to type, and better than
all other approximate matches, we'll issue a hint suggesting that
the user might have intended to reference those columns.
Peter Geoghegan and Robert Haas
Until now __attribute__() was defined to be empty for all compilers but
gcc. That's problematic because it prevents using it in other compilers;
which is necessary e.g. for atomics portability. It's also just
generally dubious to do so in a header as widely included as c.h.
Instead add pg_attribute_format_arg, pg_attribute_printf,
pg_attribute_noreturn macros which are implemented in the compilers that
understand them. Also add pg_attribute_noreturn and pg_attribute_packed,
but don't provide fallbacks, since they can affect functionality.
This means that external code that, possibly unwittingly, relied on
__attribute__ defined to be empty on !gcc compilers may now run into
warnings or errors on those compilers. But there shouldn't be many
occurances of that and it's hard to work around...
Discussion: 54B58BA3.8040302@ohmu.fi
Author: Oskari Saarenmaa, with some minor changes by me.
When newly-added GUC parameter, wal_compression, is on, the PostgreSQL server
compresses a full page image written to WAL when full_page_writes is on or
during a base backup. A compressed page image will be decompressed during WAL
replay. Turning this parameter on can reduce the WAL volume without increasing
the risk of unrecoverable data corruption, but at the cost of some extra CPU
spent on the compression during WAL logging and on the decompression during
WAL replay.
This commit changes the WAL format (so bumping WAL version number) so that
the one-byte flag indicating whether a full page image is compressed or not is
included in its header information. This means that the commit increases the
WAL volume one-byte per a full page image even if WAL compression is not used
at all. We can save that one-byte by borrowing one-bit from the existing field
like hole_offset in the header and using it as the flag, for example. But which
would reduce the code readability and the extensibility of the feature.
Per discussion, it's not worth paying those prices to save only one-byte, so we
decided to add the one-byte flag to the header.
This commit doesn't introduce any new compression algorithm like lz4.
Currently a full page image is compressed using the existing PGLZ algorithm.
Per discussion, we decided to use it at least in the first version of the
feature because there were no performance reports showing that its compression
ratio is unacceptably lower than that of other algorithm. Of course,
in the future, it's worth considering the support of other compression
algorithm for the better compression.
Rahila Syed and Michael Paquier, reviewed in various versions by myself,
Andres Freund, Robert Haas, Abhijit Menon-Sen and many others.
Commit 865f14a2d3 was quite a few bricks
shy of a load: psql, ecpg, and plpgsql were all left out-of-step with
the core lexer. Of these only the last was likely to be a fatal
problem; but still, a minimal amount of grepping, or even just reading
the comments adjacent to the places that were changed, would have found
the other places that needed to be changed.
The introduction in the Shared Library Preloading section already
instructs the user to separate multiple library names with commas, so
just remove the fragment from here.
Author: Dagfinn Ilmari Mannsåker
... which is the usual convention among AMs, so that pg_filedump and
similar utilities can tell apart pages of different AMs. It was also
the intent of the original code, but I failed to realize that alignment
considerations would move the whole thing to the previous-to-last word
in the page.
The new definition of the associated macro makes surrounding code a bit
leaner, too.
Per note from Heikki at
http://www.postgresql.org/message-id/546A16EF.9070005@vmware.com
SQL has standardized on => as the use of to specify named parameters,
and we've wanted for many years to support the same syntax ourselves,
but this has been complicated by the possible use of => as an operator
name. In PostgreSQL 9.0, we began emitting a warning when an operator
named => was defined, and in PostgreSQL 9.2, we stopped shipping a
=>(text, text) operator as part of hstore. By the time the next major
version of PostgreSQL is released, => will have been deprecated for a
full five years, so hopefully there won't be too many people still
relying on it. We continue to support := for compatibility with
previous PostgreSQL releases.
Pavel Stehule, reviewed by Petr Jelinek, with a few documentation
tweaks by me.
We allow this module to be turned off on restarts, so a restart time
check is enough to activate or deactivate the module; however, if there
is a standby replaying WAL emitted from a master which is restarted, but
the standby isn't, the state in the standby becomes inconsistent and can
easily be crashed.
Fix by activating and deactivating the module during WAL replay on
parameter change as well as on system start.
Problem reported by Fujii Masao in
http://www.postgresql.org/message-id/CAHGQGwFhJ3CnHo1CELEfay18yg_RA-XZT-7D8NuWUoYSZ90r4Q@mail.gmail.com
Author: Petr Jelínek
ALTER DEFAULT PRIVILEGES was trying to decode the list of roles in the
FOR clause as a list of names rather than of RoleSpecs; and the IN
clause in CREATE ROLE was doing the same thing. This was evidenced by
crashes on some buildfarm machines, though on my platform this doesn't
cause a failure by mere chance; I can reproduce the failures only by
adding some padding in struct RoleSpecs.
Fix by dereferencing those lists as being of RoleSpecs, not string
Values.
Commands such as ALTER USER, ALTER GROUP, ALTER ROLE, GRANT, and the
various ALTER OBJECT / OWNER TO, as well as ad-hoc clauses related to
roles such as the AUTHORIZATION clause of CREATE SCHEMA, the FOR clause
of CREATE USER MAPPING, and the FOR ROLE clause of ALTER DEFAULT
PRIVILEGES can now take the keywords CURRENT_USER and SESSION_USER as
user specifiers in place of an explicit user name.
This commit also fixes some quite ugly handling of special standards-
mandated syntax in CREATE USER MAPPING, which in particular would fail
to work in presence of a role named "current_user".
The special role specifiers PUBLIC and NONE also have more consistent
handling now.
Also take the opportunity to add location tracking to user specifiers.
Authors: Kyotaro Horiguchi. Heavily reworked by Álvaro Herrera.
Reviewed by: Rushabh Lathia, Adam Brightwell, Marti Raudsepp.
Commit 5cefbf5a6c introduced an
assumption that this field would always be non-NULL when doing a merge
pass, but that's not true. Without this fix, you can crash the server
by building a hash index that is sufficiently large relative to
maintenance_work_mem, or by triggering a large datum sort.
Commit 5ea86e6e65 changed the comments
for that field to say that it would be set in all cases except for the
hash index case, but that wasn't (and still isn't) true.
The datum-sort failure was spotted by Tomas Vondra; initial analysis
of that failure was by Peter Geoghegan. The remaining issues were
spotted by me during review of the surrounding code, and the patch is
all my fault.
This makes it easier to write frontend programs that needs to understand
the WAL record format of CREATE/DROP DATABASE. dbcommands.h cannot easily
be #included in a frontend program, because it pulls in other header files
that need backend stuff, but the new dbcommands_xlog.h header file has
fewer dependencies.
This is a possibly-vain effort to silence a Coverity warning about
bogus endianness dependency. The code's fine, because it takes care
of endianness issues for itself, but Coverity sees an int64 being
passed to an int* argument and not unreasonably suspects something's
wrong. I'm not sure if putting the void* cast in the way will shut it
up; but it can't hurt and seems better from a documentation standpoint
anyway, since the pointer is not used as an int* in this code path.
Just for a bit of additional safety, verify that the result length
is 8 bytes as expected.
Back-patch to 9.3 where the code in question was added.
This struct is purely a client-side artifact. Perhaps there was once
reason for the server to know it, but any such reason is lost in the
mists of time. We certainly don't need two independent declarations
of it.
The SGML docs claimed that 1-byte integers could be sent or received with
the "isint" options, but no such behavior has ever been implemented in
pqGetInt() or pqPutInt(). The in-code documentation header for PQfn() was
even less in tune with reality, and the code itself used parameter names
matching neither the SGML docs nor its libpq-fe.h declaration. Do a bit
of additional wordsmithing on the SGML docs while at it.
Since the business about 1-byte integers is a clear documentation bug,
back-patch to all supported branches.
By building it unconditionally, libpgport inadvertently replaced any
libc version of the function. This is essentially a code cleanup; any
effect on performance is almost surely too small to notice.
This role attribute is an ancient PostgreSQL feature, but could only be
set by directly updating the system catalogs, and it doesn't have any
clearly defined use.
Author: Adam Brightwell <adam.brightwell@crunchydatasolutions.com>
Commit 7b583b20b1 created an unnecessary
dump failure hazard by applying pg_get_function_identity_arguments()
to every function in the database, even those that won't get dumped.
This could result in snapshot-related problems if concurrent sessions are,
for example, creating and dropping temporary functions, as noted by Marko
Tiikkaja in bug #12832. While this is by no means pg_dump's only such
issue with concurrent DDL, it's unfortunate that we added a new failure
mode for cases that used to work, and even more so that the failure was
created for basically cosmetic reasons (ie, to sort overloaded functions
more deterministically).
To fix, revert that patch and instead sort function arguments using
information that pg_dump has available anyway, namely the names of the
argument types. This will produce a slightly different sort ordering for
overloaded functions than the previous coding; but applying strcmp
directly to the output of pg_get_function_identity_arguments really was
a bit odd anyway. The sorting will still be name-based and hence
independent of possibly-installation-specific OID assignments. A small
additional benefit is that sorting now works regardless of server version.
Back-patch to 9.3, where the previous commit appeared.
We were using "user mapping for user XYZ" as description for user mappings, but
that's ambiguous because users can have mappings on multiple foreign
servers; therefore change it to "for user XYZ on server UVW" instead.
Object identities for user mappings are also updated in the same way, in
branches 9.3 and above.
The incomplete description string was introduced together with the whole
SQL/MED infrastructure by commit cae565e503 of 8.4 era, so backpatch all
the way back.
An OID return value was being used only for a (rather pointless) assert.
Silence by removing the variable and the assert.
Per note from Peter Geoghegan
I had thought that there was no need to maintain separate cache entries
for different source typmods, but further experimentation shows that there
is an advantage to doing so in some cases. In particular, if a domain has
a typmod (say, "CREATE DOMAIN d AS numeric(20,0)"), failing to notice the
source typmod leads to applying a length-coercion step even when the
source has the correct typmod.
This is because can_coerce_type thinks that RECORD can be cast to any
composite type, but coerce_record_to_complex only works for inputs that are
RowExprs or whole-row Vars, so we get a hard failure on a CaseTestExpr.
Perhaps these corner cases ought to be fixed so that coerce_to_target_type
actually returns NULL as per its specification, rather than failing ...
but for the moment an extra check here is the path of least resistance.
plpgsql's historical method for converting datatypes during assignments was
to apply the source type's output function and then the destination type's
input function. Aside from being miserably inefficient in most cases, this
method failed outright in many cases where a user might expect it to work;
an example is that "declare x int; ... x := 3.9;" would fail, not round the
value to 4.
Instead, let's convert by applying the appropriate assignment cast whenever
there is one. To avoid breaking compatibility unnecessarily, fall back to
the I/O conversion method if there is no assignment cast.
So far as I can tell, there is just one case where this method produces a
different result than the old code in a case where the old code would not
have thrown an error. That is assignment of a boolean value to a string
variable (type text, varchar, or bpchar); the old way gave boolean's output
representation, ie 't'/'f', while the new way follows the behavior of the
bool-to-text cast and so gives 'true' or 'false'. This will need to be
called out as an incompatibility in the 9.5 release notes.
Aside from handling many conversion cases more sanely, this method is
often significantly faster than the old way. In part that's because
of more effective caching of the conversion info.
genericcostestimate() and friends used the cost of the entire indexqual
expressions as the charge for initial evaluation of indexscan arguments.
But of course the index column is not evaluated, only the other side
of the qual expression, so this was a bad overestimate if the index
column was an expensive expression.
To fix, refactor the logic in this area so that there's a single routine
charged with deconstructing index quals and figuring out what is the index
column and what is the comparison expression. This is more or less free in
the case of btree indexes, since btcostestimate() was doing equivalent
deconstruction already. It probably adds a bit of new overhead in the cases
of other index types, but not a lot. (In the case of GIN I think I saved
something by getting rid of code that wasn't aware that the index column
associations were already available "for free".)
Per recent gripe from Jeff Janes.
Arguably this is a bug fix, but I'm hesitant to back-patch because of the
possibility of destabilizing plan choices that people may be happy with.
Tom Lane
Peter Eisentraut
Alvaro Herrera
Robert Haas
Andres Freund
Fujii Masao
Michael Meskes
Heikki Linnakangas
Noah Misch