Obviously, in order to equality operator be satisfiable, target string must
contain all the trigrams of the search string. On this base, we implement
equality operator in GiST/GIN indexes with recheck.
Discussion: https://postgr.es/m/CAOBaU_YWwtT7tdggtROacjdOdeYHCz-tmSwuC-j-TOG-g97J0w%40mail.gmail.com
Author: Julien Rouhaud
Reviewed-by: Tom Lane, Alexander Korotkov, Georgios Kokolatos, Erik Rijkers
Whether from size overflow in gistSplit or from secondary splits,
picksplit is (rarely) called with exactly two items to split.
Formerly, due to special-case handling of the last item, this would
lead to access to an uninitialized cache entry; prior to PG 13 this
might have been harmless or at worst led to an incorrect union datum,
but in 13 onwards it can cause a backend crash from using an
uninitialized pointer.
Repair by removing the special case, which was deemed not to have been
appropriate anyway. Backpatch all the way, because this bug has
existed since pg_trgm was added.
Per report on IRC from user "ftzdomino". Analysis and testing by me,
patch from Alexander Korotkov.
Discussion: https://postgr.es/m/87k0usfdxg.fsf@news-spur.riddles.org.uk
911e702077 has introduced the opclass parameters including signature length
for a set of GiST opclasses. Due to copy-pasting, macro for getting the
signature length in trgm_gist.c was named LTREE_GET_ASIGLEN(). Fix that by
renaming this macro to just GET_SIGLEN().
Backpatch-through: 13
Hostile objects located within the installation-time search_path could
capture references in an extension's installation or upgrade script.
If the extension is being installed with superuser privileges, this
opens the door to privilege escalation. While such hazards have existed
all along, their urgency increases with the v13 "trusted extensions"
feature, because that lets a non-superuser control the installation path
for a superuser-privileged script. Therefore, make a number of changes
to make such situations more secure:
* Tweak the construction of the installation-time search_path to ensure
that references to objects in pg_catalog can't be subverted; and
explicitly add pg_temp to the end of the path to prevent attacks using
temporary objects.
* Disable check_function_bodies within installation/upgrade scripts,
so that any security gaps in SQL-language or PL-language function bodies
cannot create a risk of unwanted installation-time code execution.
* Adjust lookup of type input/receive functions and join estimator
functions to complain if there are multiple candidate functions. This
prevents capture of references to functions whose signature is not the
first one checked; and it's arguably more user-friendly anyway.
* Modify various contrib upgrade scripts to ensure that catalog
modification queries are executed with secure search paths. (These
are in-place modifications with no extension version changes, since
it is the update process itself that is at issue, not the end result.)
Extensions that depend on other extensions cannot be made fully secure
by these methods alone; therefore, revert the "trusted" marking that
commit eb67623c9 applied to earthdistance and hstore_plperl, pending
some better solution to that set of issues.
Also add documentation around these issues, to help extension authors
write secure installation scripts.
Patch by me, following an observation by Andres Freund; thanks
to Noah Misch for review.
Security: CVE-2020-14350
Writing a trailing semicolon in a macro is almost never the right thing,
because you almost always want to write a semicolon after each macro
call instead. (Even if there was some reason to prefer not to, pgindent
would probably make a hash of code formatted that way; so within PG the
rule should basically be "don't do it".) Thus, if we have a semi inside
the macro, the compiler sees "something;;". Much of the time the extra
empty statement is harmless, but it could lead to mysterious syntax
errors at call sites. In perhaps an overabundance of neatnik-ism, let's
run around and get rid of the excess semicolons whereever possible.
The only thing worse than a mysterious syntax error is a mysterious
syntax error that only happens in the back branches; therefore,
backpatch these changes where relevant, which is most of them because
most of these mistakes are old. (The lack of reported problems shows
that this is largely a hypothetical issue, but still, it could bite
us in some future patch.)
John Naylor and Tom Lane
Discussion: https://postgr.es/m/CACPNZCs0qWTqJ2QUSGJ07B7uvAvzMb-KbG2q+oo+J3tsWN5cqw@mail.gmail.com
Quite a few matching operators such as JSONB's @> used "contsel" and
"contjoinsel" as their selectivity estimators. That was a bad idea,
because (a) contsel is only a stub, yielding a fixed default estimate,
and (b) that default is 0.001, meaning we estimate these operators as
five times more selective than equality, which is surely pretty silly.
There's a good model for improving this in ltree's ltreeparentsel():
for any "var OP constant" query, we can try applying the operator
to all of the column's MCV and histogram values, taking the latter
as being a random sample of the non-MCV values. That code is
actually 100% generic, except for the question of exactly what
default selectivity ought to be plugged in when we don't have stats.
Hence, migrate the guts of ltreeparentsel() into the core code, provide
wrappers "matchingsel" and "matchingjoinsel" with a more-appropriate
default estimate, and use those for the non-geometric operators that
formerly used contsel (mostly JSONB containment operators and tsquery
matching).
Also apply this code to some match-like operators in hstore, ltree, and
pg_trgm, including the former users of ltreeparentsel as well as ones
that improperly used contsel. Since commit 911e70207 just created new
versions of those extensions that we haven't released yet, we can sneak
this change into those new versions instead of having to create an
additional generation of update scripts.
Patch by me, reviewed by Alexey Bashtanov
Discussion: https://postgr.es/m/12237.1582833074@sss.pgh.pa.us
PostgreSQL provides set of template index access methods, where opclasses have
much freedom in the semantics of indexing. These index AMs are GiST, GIN,
SP-GiST and BRIN. There opclasses define representation of keys, operations on
them and supported search strategies. So, it's natural that opclasses may be
faced some tradeoffs, which require user-side decision. This commit implements
opclass parameters allowing users to set some values, which tell opclass how to
index the particular dataset.
This commit doesn't introduce new storage in system catalog. Instead it uses
pg_attribute.attoptions, which is used for table column storage options but
unused for index attributes.
In order to evade changing signature of each opclass support function, we
implement unified way to pass options to opclass support functions. Options
are set to fn_expr as the constant bytea expression. It's possible due to the
fact that opclass support functions are executed outside of expressions, so
fn_expr is unused for them.
This commit comes with some examples of opclass options usage. We parametrize
signature length in GiST. That applies to multiple opclasses: tsvector_ops,
gist__intbig_ops, gist_ltree_ops, gist__ltree_ops, gist_trgm_ops and
gist_hstore_ops. Also we parametrize maximum number of integer ranges for
gist__int_ops. However, the main future usage of this feature is expected
to be json, where users would be able to specify which way to index particular
json parts.
Catversion is bumped.
Discussion: https://postgr.es/m/d22c3a18-31c7-1879-fc11-4c1ce2f5e5af%40postgrespro.ru
Author: Nikita Glukhov, revised by me
Reviwed-by: Nikolay Shaplov, Robert Haas, Tom Lane, Tomas Vondra, Alvaro Herrera
Our usual practice for "poor man's enum" catalog columns is to define
macros for the possible values and use those, not literal constants,
in C code. But for some reason lost in the mists of time, this was
never done for typalign/attalign or typstorage/attstorage. It's never
too late to make it better though, so let's do that.
The reason I got interested in this right now is the need to duplicate
some uses of the TYPSTORAGE constants in an upcoming ALTER TYPE patch.
But in general, this sort of change aids greppability and readability,
so it's a good idea even without any specific motivation.
I may have missed a few places that could be converted, and it's even
more likely that pending patches will re-introduce some hard-coded
references. But that's not fatal --- there's no expectation that
we'd actually change any of these values. We can clean up stragglers
over time.
Discussion: https://postgr.es/m/16457.1583189537@sss.pgh.pa.us
Andres Freund pointed out that allowing non-superusers to run
"CREATE EXTENSION ... FROM unpackaged" has security risks, since
the unpackaged-to-1.0 scripts don't try to verify that the existing
objects they're modifying are what they expect. Just attaching such
objects to an extension doesn't seem too dangerous, but some of them
do more than that.
We could have resolved this, perhaps, by still requiring superuser
privilege to use the FROM option. However, it's fair to ask just what
we're accomplishing by continuing to lug the unpackaged-to-1.0 scripts
forward. None of them have received any real testing since 9.1 days,
so they may not even work anymore (even assuming that one could still
load the previous "loose" object definitions into a v13 database).
And an installation that's trying to go from pre-9.1 to v13 or later
in one jump is going to have worse compatibility problems than whether
there's a trivial way to convert their contrib modules into extension
style.
Hence, let's just drop both those scripts and the core-code support
for "CREATE EXTENSION ... FROM".
Discussion: https://postgr.es/m/20200213233015.r6rnubcvl4egdh5r@alap3.anarazel.de
This allows these modules to be installed into a database without
superuser privileges (assuming that the DBA or sysadmin has installed
the module's files in the expected place). You only need CREATE
privilege on the current database, which by default would be
available to the database owner.
The following modules are marked trusted:
btree_gin
btree_gist
citext
cube
dict_int
earthdistance
fuzzystrmatch
hstore
hstore_plperl
intarray
isn
jsonb_plperl
lo
ltree
pg_trgm
pgcrypto
seg
tablefunc
tcn
tsm_system_rows
tsm_system_time
unaccent
uuid-ossp
In the future we might mark some more modules trusted, but there
seems to be no debate about these, and on the whole it seems wise
to be conservative with use of this feature to start out with.
Discussion: https://postgr.es/m/32315.1580326876@sss.pgh.pa.us
We used to strategically place newlines after some function call left
parentheses to make pgindent move the argument list a few chars to the
left, so that the whole line would fit under 80 chars. However,
pgindent no longer does that, so the newlines just made the code
vertically longer for no reason. Remove those newlines, and reflow some
of those lines for some extra naturality.
Reviewed-by: Michael Paquier, Tom Lane
Discussion: https://postgr.es/m/20200129200401.GA6303@alvherre.pgsql
The strategy of GIN index scan is driven by opclass-specific extract_query
method. This method that needed search mode is GIN_SEARCH_MODE_ALL. This
mode means that matching tuple may contain none of extracted entries. Simple
example is '!term' tsquery, which doesn't need any term to exist in matching
tsvector.
In order to handle such scan key GIN calculates virtual entry, which contains
all TIDs of all entries of attribute. In fact this is full scan of index
attribute. And typically this is very slow, but allows to handle some queries
correctly in GIN. However, current algorithm calculate such virtual entry for
each GIN_SEARCH_MODE_ALL scan key even if they are multiple for the same
attribute. This is clearly not optimal.
This commit improves the situation by introduction of "exclude only" scan keys.
Such scan keys are not capable to return set of matching TIDs. Instead, they
are capable only to filter TIDs produced by normal scan keys. Therefore,
each attribute should contain at least one normal scan key, while rest of them
may be "exclude only" if search mode is GIN_SEARCH_MODE_ALL.
The same optimization might be applied to the whole scan, not per-attribute.
But that leads to NULL values elimination problem. There is trade-off between
multiple possible ways to do this. We probably want to do this later using
some cost-based decision algorithm.
Discussion: https://postgr.es/m/CAOBaU_YGP5-BEt5Cc0%3DzMve92vocPzD%2BXiZgiZs1kjY0cj%3DXBg%40mail.gmail.com
Author: Nikita Glukhov, Alexander Korotkov, Tom Lane, Julien Rouhaud
Reviewed-by: Julien Rouhaud, Tomas Vondra, Tom Lane
When maintaining or merging patches, one of the most common sources
for conflicts are the list of objects in makefiles. Especially when
the split across lines has been changed on both sides, which is
somewhat common due to attempting to stay below 80 columns, those
conflicts are unnecessarily laborious to resolve.
By splitting, and alphabetically sorting, OBJS style lines into one
object per line, conflicts should be less frequent, and easier to
resolve when they still occur.
Author: Andres Freund
Discussion: https://postgr.es/m/20191029200901.vww4idgcxv74cwes@alap3.anarazel.de
This gives an alternative way of catching exceptions, for the common
case where the cleanup code is the same in the error and non-error
cases. So instead of
PG_TRY();
{
... code that might throw ereport(ERROR) ...
}
PG_CATCH();
{
cleanup();
PG_RE_THROW();
}
PG_END_TRY();
cleanup();
one can write
PG_TRY();
{
... code that might throw ereport(ERROR) ...
}
PG_FINALLY();
{
cleanup();
}
PG_END_TRY();
Discussion: https://www.postgresql.org/message-id/flat/95a822c3-728b-af0e-d7e5-71890507ae0c%402ndquadrant.com
The basic rule we follow here is to always first include 'postgres.h' or
'postgres_fe.h' whichever is applicable, then system header includes and
then Postgres header includes. In this, we also follow that all the
Postgres header includes are in order based on their ASCII value. We
generally follow these rules, but the code has deviated in many places.
This commit makes it consistent just for contrib modules. The later
commits will enforce similar rules in other parts of code.
Author: Vignesh C
Reviewed-by: Amit Kapila
Discussion: https://postgr.es/m/CALDaNm2Sznv8RR6Ex-iJO6xAdsxgWhCoETkaYX=+9DW3q0QCfA@mail.gmail.com
Originally, Postgres Lists were a more or less exact reimplementation of
Lisp lists, which consist of chains of separately-allocated cons cells,
each having a value and a next-cell link. We'd hacked that once before
(commit d0b4399d8) to add a separate List header, but the data was still
in cons cells. That makes some operations -- notably list_nth() -- O(N),
and it's bulky because of the next-cell pointers and per-cell palloc
overhead, and it's very cache-unfriendly if the cons cells end up
scattered around rather than being adjacent.
In this rewrite, we still have List headers, but the data is in a
resizable array of values, with no next-cell links. Now we need at
most two palloc's per List, and often only one, since we can allocate
some values in the same palloc call as the List header. (Of course,
extending an existing List may require repalloc's to enlarge the array.
But this involves just O(log N) allocations not O(N).)
Of course this is not without downsides. The key difficulty is that
addition or deletion of a list entry may now cause other entries to
move, which it did not before.
For example, that breaks foreach() and sister macros, which historically
used a pointer to the current cons-cell as loop state. We can repair
those macros transparently by making their actual loop state be an
integer list index; the exposed "ListCell *" pointer is no longer state
carried across loop iterations, but is just a derived value. (In
practice, modern compilers can optimize things back to having just one
loop state value, at least for simple cases with inline loop bodies.)
In principle, this is a semantics change for cases where the loop body
inserts or deletes list entries ahead of the current loop index; but
I found no such cases in the Postgres code.
The change is not at all transparent for code that doesn't use foreach()
but chases lists "by hand" using lnext(). The largest share of such
code in the backend is in loops that were maintaining "prev" and "next"
variables in addition to the current-cell pointer, in order to delete
list cells efficiently using list_delete_cell(). However, we no longer
need a previous-cell pointer to delete a list cell efficiently. Keeping
a next-cell pointer doesn't work, as explained above, but we can improve
matters by changing such code to use a regular foreach() loop and then
using the new macro foreach_delete_current() to delete the current cell.
(This macro knows how to update the associated foreach loop's state so
that no cells will be missed in the traversal.)
There remains a nontrivial risk of code assuming that a ListCell *
pointer will remain good over an operation that could now move the list
contents. To help catch such errors, list.c can be compiled with a new
define symbol DEBUG_LIST_MEMORY_USAGE that forcibly moves list contents
whenever that could possibly happen. This makes list operations
significantly more expensive so it's not normally turned on (though it
is on by default if USE_VALGRIND is on).
There are two notable API differences from the previous code:
* lnext() now requires the List's header pointer in addition to the
current cell's address.
* list_delete_cell() no longer requires a previous-cell argument.
These changes are somewhat unfortunate, but on the other hand code using
either function needs inspection to see if it is assuming anything
it shouldn't, so it's not all bad.
Programmers should be aware of these significant performance changes:
* list_nth() and related functions are now O(1); so there's no
major access-speed difference between a list and an array.
* Inserting or deleting a list element now takes time proportional to
the distance to the end of the list, due to moving the array elements.
(However, it typically *doesn't* require palloc or pfree, so except in
long lists it's probably still faster than before.) Notably, lcons()
used to be about the same cost as lappend(), but that's no longer true
if the list is long. Code that uses lcons() and list_delete_first()
to maintain a stack might usefully be rewritten to push and pop at the
end of the list rather than the beginning.
* There are now list_insert_nth...() and list_delete_nth...() functions
that add or remove a list cell identified by index. These have the
data-movement penalty explained above, but there's no search penalty.
* list_concat() and variants now copy the second list's data into
storage belonging to the first list, so there is no longer any
sharing of cells between the input lists. The second argument is
now declared "const List *" to reflect that it isn't changed.
This patch just does the minimum needed to get the new implementation
in place and fix bugs exposed by the regression tests. As suggested
by the foregoing, there's a fair amount of followup work remaining to
do.
Also, the ENABLE_LIST_COMPAT macros are finally removed in this
commit. Code using those should have been gone a dozen years ago.
Patch by me; thanks to David Rowley, Jesper Pedersen, and others
for review.
Discussion: https://postgr.es/m/11587.1550975080@sss.pgh.pa.us
Descriptions of pg_trgm GUC options have % replaced with %% like it was
a printf-like format. But that's not needed since they are just plain strings.
This commit fixed that. Backpatch to last supported version since this error
present from the beginning.
Reported-by: Masahiko Sawada
Discussion: https://postgr.es/m/CAD21AoAgPKODUsu9gqUFiNqEOAqedStxJ-a0sapsJXWWAVp%3Dxg%40mail.gmail.com
Backpatch-through: 9.4
Test for the compiler builtins __builtin_clz, __builtin_ctz, and
__builtin_popcount, and make use of these in preference to
handwritten C code if they're available. Create src/port
infrastructure for "leftmost one", "rightmost one", and "popcount"
so as to centralize these decisions.
On x86_64, __builtin_popcount generally won't make use of the POPCNT
opcode because that's not universally supported yet. Provide code
that checks CPUID and then calls POPCNT via asm() if available.
This requires indirecting through a function pointer, which is
an annoying amount of overhead for a one-instruction operation,
but it's probably not worth working harder than this for our
current use-cases.
I'm not sure we've found all the existing places that could profit
from this new infrastructure; but we at least touched all the
ones that used copied-and-pasted versions of the bitmapset.c code,
and got rid of multiple copies of the associated constant arrays.
While at it, replace c-compiler.m4's one-per-builtin-function
macros with a single one that can handle all the cases we need
to worry about so far. Also, because I'm paranoid, make those
checks into AC_LINK checks rather than just AC_COMPILE; the
former coding failed to verify that libgcc has support for the
builtin, in cases where it's not inline code.
David Rowley, Thomas Munro, Alvaro Herrera, Tom Lane
Discussion: https://postgr.es/m/CAKJS1f9WTAGG1tPeJnD18hiQW5gAk59fQ6WK-vfdAKEHyRg2RA@mail.gmail.com
Previously, floating-point output was done by rounding to a specific
decimal precision; by default, to 6 or 15 decimal digits (losing
information) or as requested using extra_float_digits. Drivers that
wanted exact float values, and applications like pg_dump that must
preserve values exactly, set extra_float_digits=3 (or sometimes 2 for
historical reasons, though this isn't enough for float4).
Unfortunately, decimal rounded output is slow enough to become a
noticable bottleneck when dealing with large result sets or COPY of
large tables when many floating-point values are involved.
Floating-point output can be done much faster when the output is not
rounded to a specific decimal length, but rather is chosen as the
shortest decimal representation that is closer to the original float
value than to any other value representable in the same precision. The
recently published Ryu algorithm by Ulf Adams is both relatively
simple and remarkably fast.
Accordingly, change float4out/float8out to output shortest decimal
representations if extra_float_digits is greater than 0, and make that
the new default. Applications that need rounded output can set
extra_float_digits back to 0 or below, and take the resulting
performance hit.
We make one concession to portability for systems with buggy
floating-point input: we do not output decimal values that fall
exactly halfway between adjacent representable binary values (which
would rely on the reader doing round-to-nearest-even correctly). This
is known to be a problem at least for VS2013 on Windows.
Our version of the Ryu code originates from
https://github.com/ulfjack/ryu/ at commit c9c3fb1979, but with the
following (significant) modifications:
- Output format is changed to use fixed-point notation for small
exponents, as printf would, and also to use lowercase 'e', a
minimum of 2 exponent digits, and a mandatory sign on the exponent,
to keep the formatting as close as possible to previous output.
- The output of exact midpoint values is disabled as noted above.
- The integer fast-path code is changed somewhat (since we have
fixed-point output and the upstream did not).
- Our project style has been largely applied to the code with the
exception of C99 declaration-after-statement, which has been
retained as an exception to our present policy.
- Most of upstream's debugging and conditionals are removed, and we
use our own configure tests to determine things like uint128
availability.
Changing the float output format obviously affects a number of
regression tests. This patch uses an explicit setting of
extra_float_digits=0 for test output that is not expected to be
exactly reproducible (e.g. due to numerical instability or differing
algorithms for transcendental functions).
Conversions from floats to numeric are unchanged by this patch. These
may appear in index expressions and it is not yet clear whether any
change should be made, so that can be left for another day.
This patch assumes that the only supported floating point format is
now IEEE format, and the documentation is updated to reflect that.
Code by me, adapting the work of Ulf Adams and other contributors.
References:
https://dl.acm.org/citation.cfm?id=3192369
Reviewed-by: Tom Lane, Andres Freund, Donald Dong
Discussion: https://postgr.es/m/87r2el1bx6.fsf@news-spur.riddles.org.uk
Update typedefs.list from current buildfarm results. Adjust pgindent's
typedef blacklist to block some more unfortunate typedef names that have
snuck in since last time. Manually tweak a few places where I didn't
like the initial results of pgindent'ing.
The lower case spellings are C and C++ standard and are used in most
parts of the PostgreSQL sources. The upper case spellings are only used
in some files/modules. So standardize on the standard spellings.
The APIs for ICU, Perl, and Windows define their own TRUE and FALSE, so
those are left as is when using those APIs.
In code comments, we use the lower-case spelling for the C concepts and
keep the upper-case spelling for the SQL concepts.
Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
Change pg_bsd_indent to follow upstream rules for placement of comments
to the right of code, and remove pgindent hack that caused comments
following #endif to not obey the general rule.
Commit e3860ffa4d wasn't actually using
the published version of pg_bsd_indent, but a hacked-up version that
tried to minimize the amount of movement of comments to the right of
code. The situation of interest is where such a comment has to be
moved to the right of its default placement at column 33 because there's
code there. BSD indent has always moved right in units of tab stops
in such cases --- but in the previous incarnation, indent was working
in 8-space tab stops, while now it knows we use 4-space tabs. So the
net result is that in about half the cases, such comments are placed
one tab stop left of before. This is better all around: it leaves
more room on the line for comment text, and it means that in such
cases the comment uniformly starts at the next 4-space tab stop after
the code, rather than sometimes one and sometimes two tabs after.
Also, ensure that comments following #endif are indented the same
as comments following other preprocessor commands such as #else.
That inconsistency turns out to have been self-inflicted damage
from a poorly-thought-through post-indent "fixup" in pgindent.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
The new indent version includes numerous fixes thanks to Piotr Stefaniak.
The main changes visible in this commit are:
* Nicer formatting of function-pointer declarations.
* No longer unexpectedly removes spaces in expressions using casts,
sizeof, or offsetof.
* No longer wants to add a space in "struct structname *varname", as
well as some similar cases for const- or volatile-qualified pointers.
* Declarations using PG_USED_FOR_ASSERTS_ONLY are formatted more nicely.
* Fixes bug where comments following declarations were sometimes placed
with no space separating them from the code.
* Fixes some odd decisions for comments following case labels.
* Fixes some cases where comments following code were indented to less
than the expected column 33.
On the less good side, it now tends to put more whitespace around typedef
names that are not listed in typedefs.list. This might encourage us to
put more effort into typedef name collection; it's not really a bug in
indent itself.
There are more changes coming after this round, having to do with comment
indentation and alignment of lines appearing within parentheses. I wanted
to limit the size of the diffs to something that could be reviewed without
one's eyes completely glazing over, so it seemed better to split up the
changes as much as practical.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
Commit 9e43e8714 turns out to have been insufficient: not only is it
necessary to track tentative parent links while considering a set of
arc removals, but it's necessary to track tentative flag additions
as well. This is because we always merge arc target states into
arc source states; therefore, when considering a merge of the final
state with some other, it is the other state that will acquire a new
TSTATE_FIN bit. If there's another arc for the same color trigram
that would cause merging of that state with the initial state, we
failed to recognize the problem. The test cases for the prior commit
evidently only exercised situations where a tentative merge with the
initial state occurs before one with the final state. If it goes the
other way around, we'll happily merge the initial and final states,
either producing a broken final graph that would never match anything,
or triggering the Assert added by the prior commit.
It's tempting to consider switching the merge direction when the merge
involves the final state, but I lack the time to analyze that idea in
detail. Instead just keep track of the flag changes that would result
from proposed merges, in the same way that the prior commit tracked
proposed parent links.
Along the way, add some more debugging support, because I'm not entirely
confident that this is the last bug here. And tweak matters so that
the transformed.dot file uses small integers rather than pointer values
to identify states; that makes it more readable if you're just eyeballing
it rather than fooling with Graphviz. And rename a couple of identically
named struct fields to reduce confusion.
Per report from Corey Csuhta. Add a test case based on his example.
(Note: this case does not trigger the bug under 9.3, apparently because
its different measurement of costs causes it to stop merging states before
it hits the failure. I spent some time trying to find a variant that would
fail in 9.3, without success; but I'm sure such cases exist.)
Like the previous patch, back-patch to 9.3 where this code was added.
Report: https://postgr.es/m/E2B01A4B-4530-406B-8D17-2F67CF9A16BA@csuhta.com
regexport.c thought it could just ignore LACON arcs, but the correct
behavior is to treat them as satisfiable while consuming zero input
(rather reminiscently of commit 9f1e642d5). Otherwise, the emitted
simplified-NFA representation may contain no paths leading from initial
to final state, which unsurprisingly confuses pg_trgm, as seen in
bug #14623 from Jeff Janes.
Since regexport's output representation has no concept of an arc that
consumes zero input, recurse internally to find the next normal arc(s)
after any LACON transitions. We'd be forced into changing that
representation if a LACON could be the last arc reaching the final
state, but fortunately the regex library never builds NFAs with such
a configuration, so there always is a next normal arc.
Back-patch to 9.3 where this logic was introduced.
Discussion: https://postgr.es/m/20170413180503.25948.94871@wrigleys.postgresql.org
This makes almost all core code follow the policy introduced in the
previous commit. Specific decisions:
- Text search support functions with char* and length arguments, such as
prsstart and lexize, may receive unaligned strings. I doubt
maintainers of non-core text search code will notice.
- Use plain VARDATA() on values detoasted or synthesized earlier in the
same function. Use VARDATA_ANY() on varlenas sourced outside the
function, even if they happen to always have four-byte headers. As an
exception, retain the universal practice of using VARDATA() on return
values of SendFunctionCall().
- Retain PG_GETARG_BYTEA_P() in pageinspect. (Page images are too large
for a one-byte header, so this misses no optimization.) Sites that do
not call get_page_from_raw() typically need the four-byte alignment.
- For now, do not change btree_gist. Its use of four-byte headers in
memory is partly entangled with storage of 4-byte headers inside
GBT_VARKEY, on disk.
- For now, do not change gtrgm_consistent() or gtrgm_distance(). They
incorporate the varlena header into a cache, and there are multiple
credible implementation strategies to consider.
The logic for removing excess trigrams from the result was faulty.
It intends to avoid merging the initial and final states of the NFA,
which is necessary, but in testing whether removal of a specific trigram
would cause that, it failed to consider the combined effects of all the
state merges that that trigram's removal would cause. This could result
in a broken final graph that would never match anything, leading to GIN
or GiST indexscans not finding anything.
To fix, add a "tentParent" field that is used only within this loop,
and set it to show state merges that we are tentatively going to do.
While examining a particular arc, we must chase up through tentParent
links as well as regular parent links (the former can only appear atop
the latter), and we must account for state init/fin flag merges that
haven't actually been done yet.
To simplify the latter, combine the separate init and fin bool fields
into a bitmap flags field. I also chose to get rid of the "children"
state list, which seems entirely inessential.
Per bug #14563 from Alexey Isayko, which the added test cases are based on.
Back-patch to 9.3 where this code was added.
Report: https://postgr.es/m/20170222111446.1256.67547@wrigleys.postgresql.org
Discussion: https://postgr.es/m/8816.1487787594@sss.pgh.pa.us
I'd supposed that people would do this manually when creating new operator
classes, but the folly of that was exposed today. The tests seem fast
enough that we can just apply them during the normal regression tests.
contrib/isn fails the checks for lack of complete sets of cross-type
operators. That's a nice-to-have policy rather than a functional
requirement, so leave it as-is, but insert ORDER BY in the query to
ensure consistent cross-platform output.
Discussion: https://postgr.es/m/7076.1480446837@sss.pgh.pa.us
I found that half a dozen (nearly 5%) of our AllocSetContextCreate calls
had typos in the context-sizing parameters. While none of these led to
especially significant problems, they did create minor inefficiencies,
and it's now clear that expecting people to copy-and-paste those calls
accurately is not a great idea. Let's reduce the risk of future errors
by introducing single macros that encapsulate the common use-cases.
Three such macros are enough to cover all but two special-purpose contexts;
those two calls can be left as-is, I think.
While this patch doesn't in itself improve matters for third-party
extensions, it doesn't break anything for them either, and they can
gradually adopt the simplified notation over time.
In passing, change TopMemoryContext to use the default allocation
parameters. Formerly it could only be extended 8K at a time. That was
probably reasonable when this code was written; but nowadays we create
many more contexts than we did then, so that it's not unusual to have a
couple hundred K in TopMemoryContext, even without considering various
dubious code that sticks other things there. There seems no good reason
not to let it use growing blocks like most other contexts.
Back-patch to 9.6, mostly because that's still close enough to HEAD that
it's easy to do so, and keeping the branches in sync can be expected to
avoid some future back-patching pain. The bugs fixed by these changes
don't seem to be significant enough to justify fixing them further back.
Discussion: <21072.1472321324@sss.pgh.pa.us>
There was some very strange code here, dating to commit b525bf77, that
purported to work around an ancient gcc bug by forcing a float4 comparison
to be done as int instead. Commit 5871b8848 broke that when it changed
one side of the comparison to "double" but left the comparison code alone.
Commit f576b17cd doubled down on the weirdness by introducing a "volatile"
marker, which had nothing to do with the actual problem.
Guess that the gcc bug, even if it's still present in the wild, was
triggered by comparison of float4's and can be avoided if we store the
result of cnt_sml() into a double before comparing to the double "nlimit".
This will at least work correctly on non-broken compilers, and it's way
more readable.
Per bug #14202 from Greg Navis. Add a regression test based on his
example.
Report: <20160620115321.5792.10766@wrigleys.postgresql.org>
Commit 749a787c5b bumped the extension
version on all of these extensions already, and we haven't had a
release since then, so we can make further changes without bumping the
extension version again. Take this opportunity to mark all of the
functions exported by these modules PARALLEL SAFE -- except for
pg_trgm's set_limit(). Mark that one PARALLEL RESTRICTED, because it
makes a persistent change to a GUC value.
Note that some of the markings added by this commit don't have any
effect; for example, gseg_picksplit() isn't likely to be mentioned
explicitly in a query and therefore it's parallel-safety marking will
never be consulted. But this commit just marks everything for
consistency: if it were somehow used in a query, that would be fine as
far as parallel query is concerned, since it does not consult any
backend-private state, attempt to write data, etc.
Andreas Karlsson, with a few revisions by me.
Alexander Korotkov