Put the node-type-dependent operations into switches on nodeTag.
This should ease addition of new proof rules for other expression
node types. There is no functional change, although some tests
are made in a different order than before.
Also, add a couple of new cross-checks in test_predtest.c.
James Coleman (part of a larger patch series)
Discussion: https://postgr.es/m/CAAaqYe8Bo4bf_i6qKj8KBsmHMYXhe3Xt6vOe3OBQnOaf3_XBWg@mail.gmail.com
Since C99, there can be a trailing comma after the last value in an
enum definition. A lot of new code has been introducing this style on
the fly. Some new patches are now taking an inconsistent approach to
this. Some add the last comma on the fly if they add a new last
value, some are trying to preserve the existing style in each place,
some are even dropping the last comma if there was one. We could
nudge this all in a consistent direction if we just add the trailing
commas everywhere once.
I omitted a few places where there was a fixed "last" value that will
always stay last. I also skipped the header files of libpq and ecpg,
in case people want to use those with older compilers. There were
also a small number of cases where the enum type wasn't used anywhere
(but the enum values were), which ended up confusing pgindent a bit,
so I left those alone.
Discussion: https://www.postgresql.org/message-id/flat/386f8c45-c8ac-4681-8add-e3b0852c1620%40eisentraut.org
Some of these appear to be leftovers from when hash_search() took a
char * argument (changed in 5999e78fc45dcb91784b64b6e9ae43f4e4f68ca2).
Since after this there is some more horizontal space available, do
some light reformatting where suitable.
Reviewed-by: Corey Huinker <corey.huinker@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/fd9adf5d-b1aa-e82f-e4c7-263c30145807%40enterprisedb.com
The planner simplifies boolean comparisons such as "x = true" and
"x = false" down to "x" and "NOT x" respectively, to have a canonical
form to ease comparisons. However, if we want to use an index on x,
the index AM APIs require us to reconstitute the comparison-operator
form of the indexqual. While that works, in bitmap indexscans the
canonical form of the qual was emitted as a "filter" condition
although it really only needs to be a "recheck" condition, because
create_bitmap_scan_plan didn't recognize the equivalence of that
form with the generated indexqual. booleq() is pretty cheap so that
likely doesn't make very much difference, but it's unsightly so
let's clean it up.
To fix, add a case to predicate_implied_by() to recognize the
equivalence of such clauses. This is a relatively low-cost place to
add a check, and perhaps it will have additional use cases in future.
Richard Guo and Tom Lane, per discussion of bug #17618 from Sindy
Senorita.
Discussion: https://postgr.es/m/17618-7a2240bfaa7e84ae@postgresql.org
Invent a new flag bit HASH_STRINGS to specify C-string hashing, which
was formerly the default; and add assertions insisting that exactly
one of the bits HASH_STRINGS, HASH_BLOBS, and HASH_FUNCTION be set.
This is in hopes of preventing recurrences of the type of oversight
fixed in commit a1b8aa1e4 (i.e., mistakenly omitting HASH_BLOBS).
Also, when HASH_STRINGS is specified, insist that the keysize be
more than 8 bytes. This is a heuristic, but it should catch
accidental use of HASH_STRINGS for integer or pointer keys.
(Nearly all existing use-cases set the keysize to NAMEDATALEN or
more, so there's little reason to think this restriction should
be problematic.)
Tweak hash_create() to insist that the HASH_ELEM flag be set, and
remove the defaults it had for keysize and entrysize. Since those
defaults were undocumented and basically useless, no callers
omitted HASH_ELEM anyway.
Also, remove memset's zeroing the HASHCTL parameter struct from
those callers that had one. This has never been really necessary,
and while it wasn't a bad coding convention it was confusing that
some callers did it and some did not. We might as well save a few
cycles by standardizing on "not".
Also improve the documentation for hash_create().
In passing, improve reinit.c's usage of a hash table by storing
the key as a binary Oid rather than a string; and, since that's
a temporary hash table, allocate it in CurrentMemoryContext for
neatness.
Discussion: https://postgr.es/m/590625.1607878171@sss.pgh.pa.us
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
In particular, make it possible to prove/refute "x IS NULL" and
"x IS NOT NULL" predicates from a clause involving a ScalarArrayOpExpr
even when we are unable or unwilling to deconstruct the expression
into an AND/OR tree. This avoids a former unexpected degradation of
plan quality when the size of an ARRAY[] expression or array constant
exceeded the arbitrary MAX_SAOP_ARRAY_SIZE limit. For IS-NULL proofs,
we don't really care about the values of the individual array elements;
at most, we care whether there are any, and for some common cases we
needn't even know that.
The main user-visible effect of this is to let the optimizer recognize
applicability of partial indexes with "x IS NOT NULL" predicates to
queries with "x IN (array)" clauses in some cases where it previously
failed to recognize that. The structure of predtest.c is such that a
bunch of related proofs will now also succeed, but they're probably
much less useful in the wild.
James Coleman, reviewed by David Rowley
Discussion: https://postgr.es/m/CAAaqYe8yKSvzbyu8w-dThRs9aTFMwrFxn_BkTYeXgjqe3CbNjg@mail.gmail.com
PG type coercions are generally strict, ie a NULL input must produce
a NULL output (or, in domain cases, possibly an error). The planner's
understanding of that was a bit incomplete though, so improve it:
* Teach contain_nonstrict_functions() that CoerceViaIO can always be
considered strict. Previously it believed that only if the underlying
I/O functions were marked strict, which is often but not always true.
* Teach clause_is_strict_for() that CoerceViaIO, ArrayCoerceExpr,
ConvertRowtypeExpr, CoerceToDomain can all be considered strict.
Previously it knew nothing about any of them.
The main user-visible impact of this is that IS NOT NULL predicates
can be proven to hold from expressions involving casts in more cases
than before, allowing partial indexes with such predicates to be used
without extra pushups. This reduces the surprise factor for users,
who may well be used to ordinary (function-call-based) casts being
known to be strict.
Per a gripe from Samuel Williams. This doesn't rise to the level of
a bug, IMO, so no back-patch.
Discussion: https://postgr.es/m/27571.1550617881@sss.pgh.pa.us
The old name of this file was never a very good indication of what it
was for. Now that there's also access/relation.h, we have a potential
confusion hazard as well, so let's rename it to something more apropos.
Per discussion, "pathnodes.h" is reasonable, since a good fraction of
the file is Path node definitions.
While at it, tweak a couple of other headers that were gratuitously
importing relation.h into modules that don't need it.
Discussion: https://postgr.es/m/7719.1548688728@sss.pgh.pa.us
Create a new header optimizer/optimizer.h, which exposes just the
planner functions that can be used "at arm's length", without need
to access Paths or the other planner-internal data structures defined
in nodes/relation.h. This is intended to provide the whole planner
API seen by most of the rest of the system; although FDWs still need
to use additional stuff, and more thought is also needed about just
what selfuncs.c should rely on.
The main point of doing this now is to limit the amount of new
#include baggage that will be needed by "planner support functions",
which I expect to introduce later, and which will be in relevant
datatype modules rather than anywhere near the planner.
This commit just moves relevant declarations into optimizer.h from
other header files (a couple of which go away because everything
got moved), and adjusts #include lists to match. There's further
cleanup that could be done if we want to decide that some stuff
being exposed by optimizer.h doesn't belong in the planner at all,
but I'll leave that for another day.
Discussion: https://postgr.es/m/11460.1548706639@sss.pgh.pa.us
Move a few very simple node-creation and node-type-testing functions
from the planner's clauses.c to nodes/makefuncs and nodes/nodeFuncs.
There's nothing planner-specific about them, as evidenced by the
number of other places that were using them.
While at it, rename and_clause() etc to is_andclause() etc, to clarify
that they are node-type-testing functions not node-creation functions.
And use "static inline" implementations for the shortest ones.
Also, modify flatten_join_alias_vars() and some subsidiary functions
to take a Query not a PlannerInfo to define the join structure that
Vars should be translated according to. They were only using the
"parse" field of the PlannerInfo anyway, so this just requires removing
one level of indirection. The advantage is that now parse_agg.c can
use flatten_join_alias_vars() without the horrid kluge of creating an
incomplete PlannerInfo, which will allow that file to be decoupled from
relation.h in a subsequent patch.
Discussion: https://postgr.es/m/11460.1548706639@sss.pgh.pa.us
Currently, if operator_predicate_proof() is given an operator clause like
"something op NULL", it just throws up its hands and reports it can't prove
anything. But we can often do better than that, if the operator is strict,
because then we know that the clause returns NULL overall. Depending on
whether we're trying to prove or refute something, and whether we need
weak or strong semantics for NULL, this may be enough to prove the
implication, especially when we rely on the standard rule that "false
implies anything". In particular, this lets us do something useful with
questions like "does X IN (1,3,5,NULL) imply X <= 5?" The null entry
in the IN list can effectively be ignored for this purpose, but the
proof rules were not previously smart enough to deduce that.
This patch is by me, but it owes something to previous work by
Amit Langote to try to solve problems of the form mentioned.
Thanks also to Emre Hasegeli and Ashutosh Bapat for review.
Discussion: https://postgr.es/m/3bad48fc-f257-c445-feeb-8a2b2fb622ba@lab.ntt.co.jp
Commit b08df9cab left things rather poorly documented as far as the
exact semantics of "clause_is_check" mode went. Also, that mode did
not really work correctly for predicate_refuted_by; although given the
lack of specification as to what it should do, as well as the lack
of any actual use-case, that's perhaps not surprising.
Rename "clause_is_check" to "weak" proof mode, and provide specifications
for what it should do. I defined weak refutation as meaning "truth of A
implies non-truth of B", which makes it possible to use the mode in the
part of relation_excluded_by_constraints that checks for mutually
contradictory WHERE clauses. Fix up several places that did things wrong
for that definition. (As far as I can see, these errors would only lead
to failure-to-prove, not incorrect claims of proof, making them not
serious bugs even aside from the fact that v10 contains no use of this
mode. So there seems no need for back-patching.)
In addition, teach predicate_refuted_by_recurse that it can use
predicate_implied_by_recurse after all when processing a strong NOT-clause,
so long as it asks for the correct proof strength. This is an optimization
that could have been included in commit b08df9cab, but wasn't.
Also, simplify and generalize the logic that checks for whether nullness of
the argument of IS [NOT] NULL would force overall nullness of the predicate
or clause. (This results in a change in the partition_prune test's output,
as it is now able to prune an all-nulls partition that it did not recognize
before.)
In passing, in PartConstraintImpliedByRelConstraint, remove bogus
conversion of the constraint list to explicit-AND form and then right back
again; that accomplished nothing except forcing a useless extra level of
recursion inside predicate_implied_by.
Discussion: https://postgr.es/m/5983.1520487191@sss.pgh.pa.us
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 e3860ffa4dd0dad0dd9eea4be9cc1412373a8c89 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
In a CHECK clause, a null result means true, whereas in a WHERE clause
it means false. predtest.c provided different functions depending on
which set of semantics applied to the predicate being proved, but had
no option to control what a null meant in the clauses provided as
axioms. Add one.
Use that in the partitioning code when figuring out whether the
validation scan on a new partition can be skipped. Rip out the
old logic that attempted (not very successfully) to compensate
for the absence of the necessary support in predtest.c.
Ashutosh Bapat and Robert Haas, reviewed by Amit Langote and
incorporating feedback from Tom Lane.
Discussion: http://postgr.es/m/CAFjFpReT_kq_uwU_B8aWDxR7jNGE=P0iELycdq5oupi=xSQTOw@mail.gmail.com
Since 69f4b9c plain expression evaluation (and thus normal projection)
can't return sets of tuples anymore. Thus remove code dealing with
that possibility.
This will require adjustments in external code using
ExecEvalExpr()/ExecProject() - that should neither be hard nor very
common.
Author: Andres Freund and Tom Lane
Discussion: https://postgr.es/m/20160822214023.aaxz5l4igypowyri@alap3.anarazel.de
As noted by Andres Freund, we'd accumulated quite a few similar functions
in clauses.c that examine all functions in an expression tree to see if
they satisfy some boolean test. Reduce the duplication by inventing a
function check_functions_in_node() that applies a simple callback function
to each SQL function OID appearing in a given expression node. This also
fixes some arguable oversights; for example, contain_mutable_functions()
did not check aggregate or window functions for mutability. I doubt that
that represents a live bug at the moment, because we don't really consider
mutability for aggregates; but it might someday be one.
I chose to put check_functions_in_node() in nodeFuncs.c because it seemed
like other modules might wish to use it in future. That in turn forced
moving set_opfuncid() et al into nodeFuncs.c, as the alternative was for
nodeFuncs.c to depend on optimizer/setrefs.c which didn't seem very clean.
In passing, teach contain_leaked_vars_walker() about a few more expression
node types it can safely look through, and improve the rather messy and
undercommented code in has_parallel_hazard_walker().
Discussion: <20160527185853.ziol2os2zskahl7v@alap3.anarazel.de>
Per complaint from Peter Holzer. It's useful to cover this special case,
since for a boolean variable "foo", earlier parts of the planner will have
reduced variants like "foo = true" to just "foo", and thus we may fail
to recognize the applicability of a partial index with predicate
"foo IS NOT NULL".
Back-patch to 9.5, but not further; given the lack of previous complaints
this doesn't seem like behavior to change in stable branches.
For upcoming BRIN opclasses, it's convenient to have strategy numbers
defined in a single place. Since there's nothing appropriate, create
it. The StrategyNumber typedef now lives there, as well as existing
strategy numbers for B-trees (from skey.h) and R-tree-and-friends (from
gist.h). skey.h is forced to include stratnum.h because of the
StrategyNumber typedef, but gist.h is not; extensions that currently
rely on gist.h for rtree strategy numbers might need to add a new
A few .c files can stop including skey.h and/or gist.h, which is a nice
side benefit.
Per discussion:
https://www.postgresql.org/message-id/20150514232132.GZ2523@alvh.no-ip.org
Authored by Emre Hasegeli and Álvaro.
(It's not clear to me why bootscanner.l has any #include lines at all.)
Previously, if you wanted anything besides C-string hash keys, you had to
specify a custom hashing function to hash_create(). Nearly all such
callers were specifying tag_hash or oid_hash; which is tedious, and rather
error-prone, since a caller could easily miss the opportunity to optimize
by using hash_uint32 when appropriate. Replace this with a design whereby
callers using simple binary-data keys just specify HASH_BLOBS and don't
need to mess with specific support functions. hash_create() itself will
take care of optimizing when the key size is four bytes.
This nets out saving a few hundred bytes of code space, and offers
a measurable performance improvement in tidbitmap.c (which was not
exploiting the opportunity to use hash_uint32 for its 4-byte keys).
There might be some wins elsewhere too, I didn't analyze closely.
In future we could look into offering a similar optimized hashing function
for 8-byte keys. Under this design that could be done in a centralized
and machine-independent fashion, whereas getting it right for keys of
platform-dependent sizes would've been notationally painful before.
For the moment, the old way still works fine, so as not to break source
code compatibility for loadable modules. Eventually we might want to
remove tag_hash and friends from the exported API altogether, since there's
no real need for them to be explicitly referenced from outside dynahash.c.
Teodor Sigaev and Tom Lane
We have for a long time been able to prove implications and refutations
between clauses structured like "expr op const" with the same subexpression
and btree-related operators; for example that "x < 4" implies "x <= 5".
The implication machinery is needed to detect usability of partial indexes,
and the refutation machinery is needed to implement constraint exclusion.
This patch extends that machinery to make proofs for operator expressions
involving the same two immutable-but-not-necessarily-just-Const input
expressions, ie does "expr1 op1 expr2" prove or refute "expr1 op2 expr2" or
"expr2 op2 expr1"? An important example is that we can now prove "x = y"
given "y = x", which formerly the code could not deduce unless x or y was a
constant. We can make use of the system's knowledge of operator commutator
and negator pairs, and can also make use of btree opclass relationships,
for example "x < y" implies "x <= y" and refutes "x > y" (notice that
neither of these could be proven just from commutator or negator links).
Inspired by a gripe from Brian Dunavant. This seems more like a new
feature than a bug fix, though, so no back-patch.
walsender.h should depend on xlog.h, not vice versa. (Actually, the
inclusion was circular until a couple hours ago, which was even sillier;
but Bruce broke it in the expedient rather than logically correct
direction.) Because of that poor decision, plus blind application of
pgrminclude, we had a situation where half the system was depending on
xlog.h to include such unrelated stuff as array.h and guc.h. Clean up
the header inclusion, and manually revert a lot of what pgrminclude had
done so things build again.
This episode reinforces my feeling that pgrminclude should not be run
without adult supervision. Inclusion changes in header files in particular
need to be reviewed with great care. More generally, it'd be good if we
had a clearer notion of module layering to dictate which headers can sanely
include which others ... but that's a big task for another day.
This requires adjusting the API for syscache callback functions: they now
get a hash value, not a TID, to identify the target tuple. Most of them
weren't paying any attention to that argument anyway, but plancache did
require a small amount of fixing.
Also, improve performance a trifle by avoiding sending duplicate inval
messages when a heap_update isn't changing the catcache lookup columns.
get_op_btree_interpretation assumed this in order to save some duplication
of code, but it's not true in general anymore because we added <> support
to btree_gist. (We still assume it for btree opclasses, though.)
Also, essentially the same logic was baked into predtest.c. Get rid of
that duplication by generalizing get_op_btree_interpretation so that it
can be used by predtest.c.
Per bug report from Denis de Bernardy and investigation by Jeff Davis,
though I didn't use Jeff's patch exactly as-is.
Back-patch to 9.1; we do not support this usage before that.
I'm not sure these have any non-cosmetic implications, but I'm not sure
they don't, either. In particular, ensure the CaseTestExpr generated
by transformAssignmentIndirection to represent the base target column
carries the correct collation, because parse_collate.c won't fix that.
Tweak lsyscache.c API so that we can get the appropriate collation
without an extra syscache lookup.
All expression nodes now have an explicit output-collation field, unless
they are known to only return a noncollatable data type (such as boolean
or record). Also, nodes that can invoke collation-aware functions store
a separate field that is the collation value to pass to the function.
This avoids confusion that arises when a function has collatable inputs
and noncollatable output type, or vice versa.
Also, replace the parser's on-the-fly collation assignment method with
a post-pass over the completed expression tree. This allows us to use
a more complex (and hopefully more nearly spec-compliant) assignment
rule without paying for it in extra storage in every expression node.
Fix assorted bugs in the planner's handling of collations by making
collation one of the defining properties of an EquivalenceClass and
by converting CollateExprs into discardable RelabelType nodes during
expression preprocessing.
This adds collation support for columns and domains, a COLLATE clause
to override it per expression, and B-tree index support.
Peter Eisentraut
reviewed by Pavel Stehule, Itagaki Takahiro, Robert Haas, Noah Misch
