Commit Graph

1448 Commits

Author SHA1 Message Date
David Rowley 7d2c7f08d9 Fix query pullup issue with WindowClause runCondition
94985c210 added code to detect when WindowFuncs were monotonic and
allowed additional quals to be "pushed down" into the subquery to be
used as WindowClause runConditions in order to short-circuit execution
in nodeWindowAgg.c.

The Node representation of runConditions wasn't well selected and
because we do qual pushdown before planning the subquery, the planning
of the subquery could perform subquery pull-up of nested subqueries.
For WindowFuncs with args, the arguments could be changed after pushing
the qual down to the subquery.

This was made more difficult by the fact that the code duplicated the
WindowFunc inside an OpExpr to include in the WindowClauses runCondition
field.  This could result in duplication of subqueries and a pull-up of
such a subquery could result in another initplan parameter being issued
for the 2nd version of the subplan.  This could result in errors such as:

ERROR:  WindowFunc not found in subplan target lists

To fix this, we change the node representation of these run conditions
and instead of storing an OpExpr containing the WindowFunc in a list
inside WindowClause, we now store a new node type named
WindowFuncRunCondition within a new field in the WindowFunc.  These get
transformed into OpExprs later in planning once subquery pull-up has been
performed.

This problem did exist in v15 and v16, but that was fixed by 9d36b883b
and e5d20bbd.

Cat version bump due to new node type and modifying WindowFunc struct.

Bug: #18305
Reported-by: Zuming Jiang
Discussion: https://postgr.es/m/18305-33c49b4c830b37b3%40postgresql.org
2024-05-05 12:54:46 +12:00
David Rowley a42fc1c903 Fix an assortment of typos
Author: Alexander Lakhin
Discussion: https://postgr.es/m/ae9f2fcb-4b24-5bb0-4240-efbbbd944ca1@gmail.com
2024-05-04 02:33:25 +12:00
Alexander Korotkov ff9f72c68f revert: Transform OR clauses to ANY expression
This commit reverts 72bd38cc99 due to implementation and design issues.

Reported-by: Tom Lane
Discussion: https://postgr.es/m/3604469.1712628736%40sss.pgh.pa.us
2024-04-10 02:28:09 +03:00
Amit Langote bb766cde63 JSON_TABLE: Add support for NESTED paths and columns
A NESTED path allows to extract data from nested levels of JSON
objects given by the parent path expression, which are projected as
columns specified using a nested COLUMNS clause, just like the parent
COLUMNS clause.  Rows comprised from a NESTED columns are "joined"
to the row comprised from the parent columns.  If a particular NESTED
path evaluates to 0 rows, then the nested COLUMNS will emit NULLs,
making it an OUTER join.

NESTED columns themselves may include NESTED paths to allow
extracting data from arbitrary nesting levels, which are likewise
joined against the rows at the parent level.

Multiple NESTED paths at a given level are called "sibling" paths
and their rows are combined by UNIONing them, that is, after being
joined against the parent row as described above.

Author: Nikita Glukhov <n.gluhov@postgrespro.ru>
Author: Teodor Sigaev <teodor@sigaev.ru>
Author: Oleg Bartunov <obartunov@gmail.com>
Author: Alexander Korotkov <aekorotkov@gmail.com>
Author: Andrew Dunstan <andrew@dunslane.net>
Author: Amit Langote <amitlangote09@gmail.com>
Author: Jian He <jian.universality@gmail.com>

Reviewers have included (in no particular order):

Andres Freund, Alexander Korotkov, Pavel Stehule, Andrew Alsup,
Erik Rijkers, Zihong Yu, Himanshu Upadhyaya, Daniel Gustafsson,
Justin Pryzby, Álvaro Herrera, Jian He

Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
Discussion: https://postgr.es/m/20220616233130.rparivafipt6doj3@alap3.anarazel.de
Discussion: https://postgr.es/m/abd9b83b-aa66-f230-3d6d-734817f0995d%40postgresql.org
Discussion: https://postgr.es/m/CA+HiwqE4XTdfb1nW=Ojoy_tQSRhYt-q_kb6i5d4xcKyrLC1Nbg@mail.gmail.com
2024-04-08 16:14:13 +09:00
Alexander Korotkov 72bd38cc99 Transform OR clauses to ANY expression
Replace (expr op C1) OR (expr op C2) ... with expr op ANY(ARRAY[C1, C2, ...])
on the preliminary stage of optimization when we are still working with the
expression tree.

Here Cn is a n-th constant expression, 'expr' is non-constant expression, 'op'
is an operator which returns boolean result and has a commuter (for the case
of reverse order of constant and non-constant parts of the expression,
like 'Cn op expr').

Sometimes it can lead to not optimal plan.  This is why there is a
or_to_any_transform_limit GUC.  It specifies a threshold value of length of
arguments in an OR expression that triggers the OR-to-ANY transformation.
Generally, more groupable OR arguments mean that transformation will be more
likely to win than to lose.

Discussion: https://postgr.es/m/567ED6CA.2040504%40sigaev.ru
Author: Alena Rybakina <lena.ribackina@yandex.ru>
Author: Andrey Lepikhov <a.lepikhov@postgrespro.ru>
Reviewed-by: Peter Geoghegan <pg@bowt.ie>
Reviewed-by: Ranier Vilela <ranier.vf@gmail.com>
Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Jian He <jian.universality@gmail.com>
2024-04-08 01:27:52 +03:00
David Rowley 29f6a959cf Introduce a bump memory allocator
This introduces a bump MemoryContext type.  The bump context is best
suited for short-lived memory contexts which require only allocations
of memory and never a pfree or repalloc, which are unsupported.

Memory palloc'd into a bump context has no chunk header.  This makes
bump a useful context type when lots of small allocations need to be
done without any need to pfree those allocations.  Allocation sizes are
rounded up to the next MAXALIGN boundary, so with this and no chunk
header, allocations are very compact indeed.

Allocations are also very fast as bump does not check any freelists to
try and make use of previously free'd chunks.  It just checks if there
is enough room on the current block, and if so it bumps the freeptr
beyond this chunk and returns the value that the freeptr was previously
pointing to.  Simple and fast.  A new block is malloc'd when there's not
enough space in the current block.

Code using the bump allocator must take care never to call any functions
which could try to call realloc() (or variants), pfree(),
GetMemoryChunkContext() or GetMemoryChunkSpace() on a bump allocated
chunk.  Due to lack of chunk headers, these operations are unsupported.
To increase the chances of catching such issues, when compiled with
MEMORY_CONTEXT_CHECKING, bump allocated chunks are given a header and
any attempt to perform an unsupported operation will result in an ERROR.
Without MEMORY_CONTEXT_CHECKING, code attempting an unsupported
operation could result in a segfault.

A follow-on commit will implement the first user of bump.

Author: David Rowley
Reviewed-by: Nathan Bossart
Reviewed-by: Matthias van de Meent
Reviewed-by: Tomas Vondra
Reviewed-by: John Naylor
Discussion: https://postgr.es/m/CAApHDvqGSpCU95TmM=Bp=6xjL_nLys4zdZOpfNyWBk97Xrdj2w@mail.gmail.com
2024-04-08 00:02:43 +12:00
Amit Langote de3600452b Add basic JSON_TABLE() functionality
JSON_TABLE() allows JSON data to be converted into a relational view
and thus used, for example, in a FROM clause, like other tabular
data.  Data to show in the view is selected from a source JSON object
using a JSON path expression to get a sequence of JSON objects that's
called a "row pattern", which becomes the source to compute the
SQL/JSON values that populate the view's output columns.  Column
values themselves are computed using JSON path expressions applied to
each of the JSON objects comprising the "row pattern", for which the
SQL/JSON query functions added in 6185c9737c are used.

To implement JSON_TABLE() as a table function, this augments the
TableFunc and TableFuncScanState nodes that are currently used to
support XMLTABLE() with some JSON_TABLE()-specific fields.

Note that the JSON_TABLE() spec includes NESTED COLUMNS and PLAN
clauses, which are required to provide more flexibility to extract
data out of nested JSON objects, but they are not implemented here
to keep this commit of manageable size.

Author: Nikita Glukhov <n.gluhov@postgrespro.ru>
Author: Teodor Sigaev <teodor@sigaev.ru>
Author: Oleg Bartunov <obartunov@gmail.com>
Author: Alexander Korotkov <aekorotkov@gmail.com>
Author: Andrew Dunstan <andrew@dunslane.net>
Author: Amit Langote <amitlangote09@gmail.com>
Author: Jian He <jian.universality@gmail.com>

Reviewers have included (in no particular order):

Andres Freund, Alexander Korotkov, Pavel Stehule, Andrew Alsup,
Erik Rijkers, Zihong Yu, Himanshu Upadhyaya, Daniel Gustafsson,
Justin Pryzby, Álvaro Herrera, Jian He

Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
Discussion: https://postgr.es/m/20220616233130.rparivafipt6doj3@alap3.anarazel.de
Discussion: https://postgr.es/m/abd9b83b-aa66-f230-3d6d-734817f0995d%40postgresql.org
Discussion: https://postgr.es/m/CA+HiwqE4XTdfb1nW=Ojoy_tQSRhYt-q_kb6i5d4xcKyrLC1Nbg@mail.gmail.com
2024-04-04 20:20:15 +09:00
Dean Rasheed 0294df2f1f Add support for MERGE ... WHEN NOT MATCHED BY SOURCE.
This allows MERGE commands to include WHEN NOT MATCHED BY SOURCE
actions, which operate on rows that exist in the target relation, but
not in the data source. These actions can execute UPDATE, DELETE, or
DO NOTHING sub-commands.

This is in contrast to already-supported WHEN NOT MATCHED actions,
which operate on rows that exist in the data source, but not in the
target relation. To make this distinction clearer, such actions may
now be written as WHEN NOT MATCHED BY TARGET.

Writing WHEN NOT MATCHED without specifying BY SOURCE or BY TARGET is
equivalent to writing WHEN NOT MATCHED BY TARGET.

Dean Rasheed, reviewed by Alvaro Herrera, Ted Yu and Vik Fearing.

Discussion: https://postgr.es/m/CAEZATCWqnKGc57Y_JanUBHQXNKcXd7r=0R4NEZUVwP+syRkWbA@mail.gmail.com
2024-03-30 10:00:26 +00:00
Peter Eisentraut d20d8fbd3e Do not output actual value of location fields in node serialization by default
This changes nodeToString() to not output the actual value of location
fields in nodes, but instead it writes -1.  This mirrors the fact that
stringToNode() also does not read location field values but always
stores -1.

For most uses of nodeToString(), which is to store nodes in catalog
fields, this is more useful.  We don't store original query texts in
catalogs, so any lingering query location values are not meaningful.

For debugging purposes, there is a new nodeToStringWithLocations(),
which mirrors the existing stringToNodeWithLocations().  This is used
for WRITE_READ_PARSE_PLAN_TREES and nodes/print.c functions, which
covers all the debugging uses.

Reviewed-by: Matthias van de Meent <boekewurm+postgres@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAEze2WgrCiR3JZmWyB0YTc8HV7ewRdx13j0CqD6mVkYAW+SFGQ@mail.gmail.com
2024-03-22 09:49:12 +01:00
Peter Eisentraut b4080fa3dc Make RangeTblEntry dump order consistent
Put the fields alias and eref earlier in the struct, so that it
matches the order in _outRangeTblEntry()/_readRangeTblEntry().  This
helps if we ever want to fully automate out/read of RangeTblEntry.
Also, it makes dumps in the debugger easier to read in the same way.
Internally, this makes no difference.

Reviewed-by: Andrew Dunstan <andrew@dunslane.net>
Discussion: https://www.postgresql.org/message-id/flat/4b27fc50-8cd6-46f5-ab20-88dbaadca645@eisentraut.org
2024-03-22 07:28:33 +01:00
Peter Eisentraut 367c989cd8 Remove custom _jumbleRangeTblEntry()
This is part of an effort to reduce the number of special cases in the
automatically generated node support functions.

This patch removes _jumbleRangeTblEntry() and instead adds per-field
query_jumble_ignore annotations to match the behavior of the previous
custom code.  The pg_stat_statements test suite has some coverage of
this.  It gets rid of the switch on rtekind; this should be
technically correct, since we do the equal and copy functions like
this also.

The list of fields to jumble has been checked and is considered
correct as of 8b29a119fd.

Reviewed-by: Andrew Dunstan <andrew@dunslane.net>
Discussion: https://www.postgresql.org/message-id/flat/4b27fc50-8cd6-46f5-ab20-88dbaadca645@eisentraut.org
2024-03-22 07:23:47 +01:00
Amit Langote 6185c9737c Add SQL/JSON query functions
This introduces the following SQL/JSON functions for querying JSON
data using jsonpath expressions:

JSON_EXISTS(), which can be used to apply a jsonpath expression to a
JSON value to check if it yields any values.

JSON_QUERY(), which can be used to to apply a jsonpath expression to
a JSON value to get a JSON object, an array, or a string.  There are
various options to control whether multi-value result uses array
wrappers and whether the singleton scalar strings are quoted or not.

JSON_VALUE(), which can be used to apply a jsonpath expression to a
JSON value to return a single scalar value, producing an error if it
multiple values are matched.

Both JSON_VALUE() and JSON_QUERY() functions have options for
handling EMPTY and ERROR conditions, which can be used to specify
the behavior when no values are matched and when an error occurs
during jsonpath evaluation, respectively.

Author: Nikita Glukhov <n.gluhov@postgrespro.ru>
Author: Teodor Sigaev <teodor@sigaev.ru>
Author: Oleg Bartunov <obartunov@gmail.com>
Author: Alexander Korotkov <aekorotkov@gmail.com>
Author: Andrew Dunstan <andrew@dunslane.net>
Author: Amit Langote <amitlangote09@gmail.com>
Author: Peter Eisentraut <peter@eisentraut.org>
Author: Jian He <jian.universality@gmail.com>

Reviewers have included (in no particular order):

Andres Freund, Alexander Korotkov, Pavel Stehule, Andrew Alsup,
Erik Rijkers, Zihong Yu, Himanshu Upadhyaya, Daniel Gustafsson,
Justin Pryzby, Álvaro Herrera, Jian He, Anton A. Melnikov,
Nikita Malakhov, Peter Eisentraut, Tomas Vondra

Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
Discussion: https://postgr.es/m/20220616233130.rparivafipt6doj3@alap3.anarazel.de
Discussion: https://postgr.es/m/abd9b83b-aa66-f230-3d6d-734817f0995d%40postgresql.org
Discussion: https://postgr.es/m/CA+HiwqHROpf9e644D8BRqYvaAPmgBZVup-xKMDPk-nd4EpgzHw@mail.gmail.com
Discussion: https://postgr.es/m/CA+HiwqE4XTdfb1nW=Ojoy_tQSRhYt-q_kb6i5d4xcKyrLC1Nbg@mail.gmail.com
2024-03-21 17:07:03 +09:00
Peter Eisentraut 605721f819 gen_node_support.pl: Mark location fields as type alias ParseLoc
Instead of the rather ugly type=int + name ~= location$, we now have a
marker type for offset pointers or sizes that are only relevant when a
query text is included, which decreases the complexity required in
gen_node_support.pl for handling these values.

Author: Matthias van de Meent <boekewurm+postgres@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAEze2WgrCiR3JZmWyB0YTc8HV7ewRdx13j0CqD6mVkYAW+SFGQ@mail.gmail.com
2024-03-19 16:56:44 +01:00
Dean Rasheed c649fa24a4 Add RETURNING support to MERGE.
This allows a RETURNING clause to be appended to a MERGE query, to
return values based on each row inserted, updated, or deleted. As with
plain INSERT, UPDATE, and DELETE commands, the returned values are
based on the new contents of the target table for INSERT and UPDATE
actions, and on its old contents for DELETE actions. Values from the
source relation may also be returned.

As with INSERT/UPDATE/DELETE, the output of MERGE ... RETURNING may be
used as the source relation for other operations such as WITH queries
and COPY commands.

Additionally, a special function merge_action() is provided, which
returns 'INSERT', 'UPDATE', or 'DELETE', depending on the action
executed for each row. The merge_action() function can be used
anywhere in the RETURNING list, including in arbitrary expressions and
subqueries, but it is an error to use it anywhere outside of a MERGE
query's RETURNING list.

Dean Rasheed, reviewed by Isaac Morland, Vik Fearing, Alvaro Herrera,
Gurjeet Singh, Jian He, Jeff Davis, Merlin Moncure, Peter Eisentraut,
and Wolfgang Walther.

Discussion: http://postgr.es/m/CAEZATCWePEGQR5LBn-vD6SfeLZafzEm2Qy_L_Oky2=qw2w3Pzg@mail.gmail.com
2024-03-17 13:58:59 +00:00
Peter Eisentraut 6d470211e5 Fix description and grouping of RangeTblEntry.inh
The inh field of RangeTblEntry was doubly confusingly documented.
Some parts of the code insisted that it was only valid for
RTE_RELATION entries, other parts said the field was valid for all
entries.  Neither was quite correct.  More correctly, the field is
valid for RTE_RELATION entries but is also used in the planner for
RTE_SUBQUERY entries.  So it makes more sense to group it with other
fields that are primarily for RTE_RELATION but borrowed by
RTE_SUBQUERY.  (The exact position was chosen so that it is next to
relkind for better struct packing, and next to relid, since relid and
inh are sort of the input fields and the others are filled in later.)
Also add documentation for the planner's use at the struct definition.

Discussion: https://www.postgresql.org/message-id/6c1fbccc-85c8-40d3-b08b-4f47f2093711@eisentraut.org
2024-03-07 12:13:09 +01:00
John Naylor 3e76a806cb Move some bitmap logic out of bitmapset.c
Move the logic for selecting appropriate pg_bitutils.h
functions based on word size to bitmapset.h for wider
visibility.

Reviewed (in a previous version) by Tom Lane
Discussion: https://postgr.es/m/CAFBsxsFW2JjTo58jtDB%2B3sZhxMx3t-3evew8%3DAcr%2BGGhC%2BkFaA%40mail.gmail.com
2024-03-06 14:30:16 +07:00
Peter Eisentraut e03349144b Improve field order in RangeTblEntry
When perminfoindex was added, it was just added at the end of the
block.  It would make sense to keep it closer to more related fields.
In passing, also add an inline comment, like the other fields have.
(Other field reorderings and documentation improvements in
RangeTblEntry are being discussed, but it's better not to mix them
together.)

Discussion: https://www.postgresql.org/message-id/flat/6c1fbccc-85c8-40d3-b08b-4f47f2093711%40eisentraut.org
2024-03-05 13:34:43 +01:00
Peter Eisentraut dbbca2cf29 Remove unused #include's from backend .c files
as determined by include-what-you-use (IWYU)

While IWYU also suggests to *add* a bunch of #include's (which is its
main purpose), this patch does not do that.  In some cases, a more
specific #include replaces another less specific one.

Some manual adjustments of the automatic result:

- IWYU currently doesn't know about includes that provide global
  variable declarations (like -Wmissing-variable-declarations), so
  those includes are being kept manually.

- All includes for port(ability) headers are being kept for now, to
  play it safe.

- No changes of catalog/pg_foo.h to catalog/pg_foo_d.h, to keep the
  patch from exploding in size.

Note that this patch touches just *.c files, so nothing declared in
header files changes in hidden ways.

As a small example, in src/backend/access/transam/rmgr.c, some IWYU
pragma annotations are added to handle a special case there.

Discussion: https://www.postgresql.org/message-id/flat/af837490-6b2f-46df-ba05-37ea6a6653fc%40eisentraut.org
2024-03-04 12:02:20 +01:00
Peter Eisentraut 8b29a119fd Add missing RangeTblEntry field to jumble
RangeTblEntry.funcordinality should be jumbled, because the WITH
ORDINALITY clause changes the query result.

This was apparently an oversight in the past.

Discussion: https://www.postgresql.org/message-id/flat/d7f421f8-fd6d-4759-adc3-247090a5d44b%40eisentraut.org
2024-02-29 14:09:09 +01:00
Peter Eisentraut fbc93b8b5f Remove custom Constraint node read/write implementations
This is part of an effort to reduce the number of special cases in the
automatically generated node support functions.

Allegedly, only certain fields of the Constraint node are valid based
on contype.  But this has historically not been kept up to date in the
read/write functions.  The Constraint node is only used for debugging
DDL statements, so there are no strong requirements for its output,
and there is no enforcement for its correctness.  (There was no read
support before a6bc3301925.)  Commits e7a552f303 and abf46ad9c7 are
examples of where omissions were fixed.

This patch just removes the custom read/write implementations for the
Constraint node type.  Now we just output all the fields, which is a
bit more than before, but at least we don't have to maintain these
functions anymore.  Also, we lose the string representation of the
contype field, but for this marginal use case that seems tolerable.
This patch also changes the documentation of the Constraint struct to
put less emphasis on grouping fields by constraint type but rather
document for each field how it's used.

Reviewed-by: Paul Jungwirth <pj@illuminatedcomputing.com>
Discussion: https://www.postgresql.org/message-id/flat/4b27fc50-8cd6-46f5-ab20-88dbaadca645@eisentraut.org
2024-02-22 07:07:12 +01:00
Peter Eisentraut 74563f6b90 Revert "Improve compression and storage support with inheritance"
This reverts commit 0413a55699.

pg_dump cannot currently dump all the structures that are allowed by
this patch.  This needs more work in pg_dump and more test coverage.

Discussion: https://www.postgresql.org/message-id/flat/24656cec-d6ef-4d15-8b5b-e8dfc9c833a7@eisentraut.org
2024-02-20 11:10:59 +01:00
Nathan Bossart 3b42bdb471 Use new overflow-safe integer comparison functions.
Commit 6b80394781 introduced integer comparison functions designed
to be as efficient as possible while avoiding overflow.  This
commit makes use of these functions in many of the in-tree qsort()
comparators to help ensure transitivity.  Many of these comparator
functions should also see a small performance boost.

Author: Mats Kindahl
Reviewed-by: Andres Freund, Fabrízio de Royes Mello
Discussion: https://postgr.es/m/CA%2B14426g2Wa9QuUpmakwPxXFWG_1FaY0AsApkvcTBy-YfS6uaw%40mail.gmail.com
2024-02-16 14:05:36 -06:00
Peter Eisentraut 0413a55699 Improve compression and storage support with inheritance
A child table can specify a compression or storage method different
from its parents.  This was previously an error.  (But this was
inconsistently enforced because for example the settings could be
changed later using ALTER TABLE.)  This now also allows an explicit
override if multiple parents have different compression or storage
settings, which was previously an error that could not be overridden.

The compression and storage properties remains unchanged in a child
inheriting from parent(s) after its creation, i.e., when using ALTER
TABLE ...  INHERIT.  (This is not changed.)

Before this change, the error detail would mention the first pair of
conflicting parent compression or storage methods.  But with this
change it waits till the child specification is considered by which
time we may have encountered many such conflicting pairs.  Hence the
error detail after this change does not include the conflicting
compression/storage methods.  Those can be obtained from parent
definitions if necessary.  The code to maintain list of all
conflicting methods or even the first conflicting pair does not seem
worth the convenience it offers.  This change is inline with what we
do with conflicting default values.

Before this commit, the specified storage method could be stored in
ColumnDef::storage (CREATE TABLE ... LIKE) or ColumnDef::storage_name
(CREATE TABLE ...).  This caused the MergeChildAttribute() and
MergeInheritedAttribute() to ignore a storage method specified in the
child definition since it looked only at ColumnDef::storage.  This
commit removes ColumnDef::storage and instead uses
ColumnDef::storage_name to save any storage method specification. This
is similar to how compression method specification is handled.

Author: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/24656cec-d6ef-4d15-8b5b-e8dfc9c833a7@eisentraut.org
2024-02-16 13:27:46 +01:00
Michael Paquier f854dae888 Improve comment about query_id_enabled in queryjumblefuncs.c
The comment was inexact because query_id_enabled will not be switched to
"true" even if compute_query_id is "on", unless a module requests for
it.

While on it, this adds a comment to mention that IsQueryIdEnabled()
should be used to check if query ID computation is enabled or not.

Author: Yugo Nagata
Reviewed-by: Julien Rouhaud
Discussion: https://postgr.es/m/20240209153823.e29a68cadb14225f1362a2cf@sraoss.co.jp
2024-02-14 07:20:15 +09:00
Tom Lane 0736a8ef6f Use a safer outfuncs/readfuncs representation for BitStrings.
For a long time, our outfuncs.c code has supposed that the string
contents of a BitString node could just be printed literally with
no concern for quoting/escaping.  Now, that's okay if the string
literal contains only valid binary or hex digits ... but our lexer
doesn't check that, preferring to let bitin() be the sole authority
on what's valid.  So we could have raw parse trees that contain
incorrect BitString literals, and that can result in failures when
WRITE_READ_PARSE_PLAN_TREES debugging is enabled.

Fix by using outToken() to print the string field, and debackslash()
to read it.  This results in a change in the emitted representation
only in cases that would have failed before, and don't represent valid
SQL in the first place.  Between that and the fact that we don't store
raw parse trees in the catalogs, I judge this safe to apply without a
catversion bump.

Per bug #18340 from Alexander Lakhin.  Back-patch to v16; before that,
we lacked readfuncs support for BitString nodes, so that the problem
was only cosmetic.

Discussion: https://postgr.es/m/18340-4aa1ae6ed4121912@postgresql.org
2024-02-13 12:18:25 -05:00
Peter Eisentraut 46a0cd4cef Add temporal PRIMARY KEY and UNIQUE constraints
Add WITHOUT OVERLAPS clause to PRIMARY KEY and UNIQUE constraints.
These are backed by GiST indexes instead of B-tree indexes, since they
are essentially exclusion constraints with = for the scalar parts of
the key and && for the temporal part.

Author: Paul A. Jungwirth <pj@illuminatedcomputing.com>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Reviewed-by: jian he <jian.universality@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CA+renyUApHgSZF9-nd-a0+OPGharLQLO=mDHcY4_qQ0+noCUVg@mail.gmail.com
2024-01-24 16:34:37 +01:00
David Rowley 4b31063643 Fix broken Bitmapset optimization in DiscreteKnapsack()
Some code in DiscreteKnapsack() attempted to zero all words in a
Bitmapset by performing bms_del_members() to delete all the members from
itself before replacing those members with members from another set.
When that code was written, this was a valid way to manipulate the set
in such a way to save from palloc having to be called to allocate a new
Bitmapset.  However, 00b41463c modified Bitmapsets so that an empty set is
*always* represented as NULL and this breaks the optimization as the
Bitmapset code will always pfree the memory when the set becomes empty.

Since DiscreteKnapsack() has been coded to avoid as many unneeded
allocations as possible, it seems risky to not fix this.  Here we add
bms_replace_members() to effectively perform an in-place copy of another
set, reusing the memory of the existing set, when possible.

This got broken in v16, but no backpatch for now as there've been no
complaints.

Reviewed-by: Richard Guo
Discussion: https://postgr.es/m/CAApHDvoTCBkBU2PJghNOFUiO0q=QP4WAWHi5sJP6_4=b2WodrA@mail.gmail.com
2024-01-19 10:44:36 +13:00
David Rowley c7e5e994b2 Fix REALLOCATE_BITMAPSETS code
7d58f2342 added a compile-time option to have bitmapset.c reallocate the
set before returning when a set is modified.  That commit failed to do
its job in various cases and returned the input set when it shouldn't
have in these cases.  Here we fix those missing cases.

This commit also adds some documentation about what
REALLOCATE_BITMAPSETS is for.  This is important as future functions
that go inside bitmapset.c need to know if they need to do anything
special when this compile-time option is defined.

Also, between 71a3e8c43 and 7d58f2342 some Asserts seem to have become
duplicated.  Tidy these up.  Rather than having the Assert check each
aspect of what makes a set invalid, here we introduce a helper function
which returns false when a set is invalid and have the Asserts use this
instead.

Also, make a pass on improving the comments in bitmapset.c.  Various
comments mentioned the input sets being "recycled".  This could be
interpreted to mean that the output set will always point to the same
memory as the given input parameter.  Here we try to make it clear that
this must not be relied upon and that callers must ensure that all
references to a given set are updated on each modification.

In passing, improve comments for bms_union(), bms_intersect() and
bms_difference() to detail what they do.  I (David) have too often had to
remind myself by reading the code each time to find out if I need, for
example, to use bms_union() or bms_join().  I also removed some
low-value comments that were trying to convey information about "these
operations" without mentioning which operations it was talking about.
It seems better to document these things in the function header comment
instead.

Author: Richard Guo, David Rowley
Discussion: https://postgr.es/m/CAMbWs4-djy9qYux2gZrtmxA0StrYXJjvB-oqLxn-d7J88t=PQQ@mail.gmail.com
2024-01-17 09:30:21 +13:00
Tom Lane d641b827af Handle WindowClause.runCondition in tree walker/mutator functions.
Commit 9d9c02ccd, which added the notion of a "run condition" for
window functions, neglected to teach nodeFuncs.c to process the new
field.  Remarkably, that doesn't seem to have had any ill effects
before we invented Var.varnullingrels, but now it can cause visible
failures in join-removal scenarios.

I have no faith that there's not reachable problems in v15 too,
so back-patch the code change to v15 where 9d9c02ccd came in.
The test case seems irrelevant to v15, though.

Per bug #18277 from Zuming Jiang.  Diagnosis and patch by
Richard Guo.

Discussion: https://postgr.es/m/18277-089ead83b329a2fd@postgresql.org
2024-01-10 13:36:33 -05:00
Bruce Momjian 29275b1d17 Update copyright for 2024
Reported-by: Michael Paquier

Discussion: https://postgr.es/m/ZZKTDPxBBMt3C0J9@paquier.xyz

Backpatch-through: 12
2024-01-03 20:49:05 -05:00
Peter Eisentraut c538592959 Make all Perl warnings fatal
There are a lot of Perl scripts in the tree, mostly code generation
and TAP tests.  Occasionally, these scripts produce warnings.  These
are probably always mistakes on the developer side (true positives).
Typical examples are warnings from genbki.pl or related when you make
a mess in the catalog files during development, or warnings from tests
when they massage a config file that looks different on different
hosts, or mistakes during merges (e.g., duplicate subroutine
definitions), or just mistakes that weren't noticed because there is a
lot of output in a verbose build.

This changes all warnings into fatal errors, by replacing

    use warnings;

by

    use warnings FATAL => 'all';

in all Perl files.

Discussion: https://www.postgresql.org/message-id/flat/06f899fd-1826-05ab-42d6-adeb1fd5e200%40eisentraut.org
2023-12-29 18:20:00 +01:00
Alexander Korotkov 7d58f2342b REALLOCATE_BITMAPSETS manual compile-time option
This option forces each bitmapset modification to reallocate bitmapset.  This
is useful for debugging hangling pointers to bitmapset's.

Discussion: https://postgr.es/m/CAMbWs4_wJthNtYBL%2BSsebpgF-5L2r5zFFk6xYbS0A78GKOTFHw%40mail.gmail.com
Reviewed-by: Richard Guo, Andres Freund, Ashutosh Bapat, Andrei Lepikhov
2023-12-27 03:57:57 +02:00
Alexander Korotkov 71a3e8c43b Add asserts to bimapset manipulation functions
New asserts validate that arguments are really bitmapsets.  This should help
to early detect accesses to dangling pointers.

Discussion: https://postgr.es/m/CAMbWs4_wJthNtYBL%2BSsebpgF-5L2r5zFFk6xYbS0A78GKOTFHw%40mail.gmail.com
Reviewed-by: Richard Guo, Andres Freund, Ashutosh Bapat, Andrei Lepikhov
2023-12-27 03:57:57 +02:00
Heikki Linnakangas 3c080fb4fa Simplify newNode() by removing special cases
- Remove MemoryContextAllocZeroAligned(). It was supposed to be a
  faster version of MemoryContextAllocZero(), but modern compilers turn
  the MemSetLoop() into a call to memset() anyway, making it more or
  less identical to MemoryContextAllocZero(). That was the only user of
  MemSetTest, MemSetLoop, so remove those too, as well as palloc0fast().

- Convert newNode() to a static inline function. When this was
  originally originally written, it was written as a macro because
  testing showed that gcc didn't inline the size check as we
  intended. Modern compiler versions do, and now that it just calls
  palloc0() there is no size-check to inline anyway.

One nice effect is that the palloc0() takes one less argument than
MemoryContextAllocZeroAligned(), which saves a few instructions in the
callers of newNode().

Reviewed-by: Peter Eisentraut, Tom Lane, John Naylor, Thomas Munro
Discussion: https://www.postgresql.org/message-id/b51f1fa7-7e6a-4ecc-936d-90a8a1659e7c@iki.fi
2023-12-19 12:11:47 +02:00
Alvaro Herrera d3fe6e90ba
Simplify productions for FORMAT JSON [ ENCODING name ]
This removes the production json_encoding_clause_opt, instead merging
it into json_format_clause.  Also remove the auxiliary
makeJsonEncoding() function.

Reviewed-by: Amit Langote <amitlangote09@gmail.com>
Discussion: https://postgr.es/m/202312071841.u2gueb5dsrbk%40alvherre.pgsql
2023-12-11 11:55:34 +01:00
Peter Eisentraut 721856ff24 Remove distprep
A PostgreSQL release tarball contains a number of prebuilt files, in
particular files produced by bison, flex, perl, and well as html and
man documentation.  We have done this consistent with established
practice at the time to not require these tools for building from a
tarball.  Some of these tools were hard to get, or get the right
version of, from time to time, and shipping the prebuilt output was a
convenience to users.

Now this has at least two problems:

One, we have to make the build system(s) work in two modes: Building
from a git checkout and building from a tarball.  This is pretty
complicated, but it works so far for autoconf/make.  It does not
currently work for meson; you can currently only build with meson from
a git checkout.  Making meson builds work from a tarball seems very
difficult or impossible.  One particular problem is that since meson
requires a separate build directory, we cannot make the build update
files like gram.h in the source tree.  So if you were to build from a
tarball and update gram.y, you will have a gram.h in the source tree
and one in the build tree, but the way things work is that the
compiler will always use the one in the source tree.  So you cannot,
for example, make any gram.y changes when building from a tarball.
This seems impossible to fix in a non-horrible way.

Second, there is increased interest nowadays in precisely tracking the
origin of software.  We can reasonably track contributions into the
git tree, and users can reasonably track the path from a tarball to
packages and downloads and installs.  But what happens between the git
tree and the tarball is obscure and in some cases non-reproducible.

The solution for both of these issues is to get rid of the step that
adds prebuilt files to the tarball.  The tarball now only contains
what is in the git tree (*).  Getting the additional build
dependencies is no longer a problem nowadays, and the complications to
keep these dual build modes working are significant.  And of course we
want to get the meson build system working universally.

This commit removes the make distprep target altogether.  The make
dist target continues to do its job, it just doesn't call distprep
anymore.

(*) - The tarball also contains the INSTALL file that is built at make
dist time, but not by distprep.  This is unchanged for now.

The make maintainer-clean target, whose job it is to remove the
prebuilt files in addition to what make distclean does, is now just an
alias to make distprep.  (In practice, it is probably obsolete given
that git clean is available.)

The following programs are now hard build requirements in configure
(they were already required by meson.build):

- bison
- flex
- perl

Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://www.postgresql.org/message-id/flat/e07408d9-e5f2-d9fd-5672-f53354e9305e@eisentraut.org
2023-11-06 15:18:04 +01:00
Peter Eisentraut 611806cd72 Add trailing commas to enum definitions
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
2023-10-26 09:20:54 +02:00
Peter Eisentraut 7841623571 Remove IndexInfo.ii_OpclassOptions field
It is unnecessary to include this field in IndexInfo.  It is only used
by DDL code, not during execution.  It is really only used to pass
local information around between functions in index.c and indexcmds.c,
for which it is clearer to use local variables, like in similar cases.

Discussion: https://www.postgresql.org/message-id/flat/f84640e3-00d3-5abd-3f41-e6a19d33c40b@eisentraut.org
2023-10-03 17:51:02 +02:00
Alvaro Herrera b0e96f3119
Catalog not-null constraints
We now create contype='n' pg_constraint rows for not-null constraints.

We propagate these constraints to other tables during operations such as
adding inheritance relationships, creating and attaching partitions and
creating tables LIKE other tables.  We also spawn not-null constraints
for inheritance child tables when their parents have primary keys.
These related constraints mostly follow the well-known rules of
conislocal and coninhcount that we have for CHECK constraints, with some
adaptations: for example, as opposed to CHECK constraints, we don't
match not-null ones by name when descending a hierarchy to alter it,
instead matching by column name that they apply to.  This means we don't
require the constraint names to be identical across a hierarchy.

For now, we omit them for system catalogs.  Maybe this is worth
reconsidering.  We don't support NOT VALID nor DEFERRABLE clauses
either; these can be added as separate features later (this patch is
already large and complicated enough.)

psql shows these constraints in \d+.

pg_dump requires some ad-hoc hacks, particularly when dumping a primary
key.  We now create one "throwaway" not-null constraint for each column
in the PK together with the CREATE TABLE command, and once the PK is
created, all those throwaway constraints are removed.  This avoids
having to check each tuple for nullness when the dump restores the
primary key creation.

pg_upgrading from an older release requires a somewhat brittle procedure
to create a constraint state that matches what would be created if the
database were being created fresh in Postgres 17.  I have tested all the
scenarios I could think of, and it works correctly as far as I can tell,
but I could have neglected weird cases.

This patch has been very long in the making.  The first patch was
written by Bernd Helmle in 2010 to add a new pg_constraint.contype value
('n'), which I (Álvaro) then hijacked in 2011 and 2012, until that one
was killed by the realization that we ought to use contype='c' instead:
manufactured CHECK constraints.  However, later SQL standard
development, as well as nonobvious emergent properties of that design
(mostly, failure to distinguish them from "normal" CHECK constraints as
well as the performance implication of having to test the CHECK
expression) led us to reconsider this choice, so now the current
implementation uses contype='n' again.  During Postgres 16 this had
already been introduced by commit e056c557ae, but there were some
problems mainly with the pg_upgrade procedure that couldn't be fixed in
reasonable time, so it was reverted.

In 2016 Vitaly Burovoy also worked on this feature[1] but found no
consensus for his proposed approach, which was claimed to be closer to
the letter of the standard, requiring an additional pg_attribute column
to track the OID of the not-null constraint for that column.
[1] https://postgr.es/m/CAKOSWNkN6HSyatuys8xZxzRCR-KL1OkHS5-b9qd9bf1Rad3PLA@mail.gmail.com

Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Author: Bernd Helmle <mailings@oopsware.de>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Reviewed-by: Dean Rasheed <dean.a.rasheed@gmail.com>
2023-08-25 13:31:24 +02:00
Amit Langote 03734a7fed Add more SQL/JSON constructor functions
This Patch introduces three SQL standard JSON functions:

JSON()
JSON_SCALAR()
JSON_SERIALIZE()

JSON() produces json values from text, bytea, json or jsonb values,
and has facilitites for handling duplicate keys.

JSON_SCALAR() produces a json value from any scalar sql value,
including json and jsonb.

JSON_SERIALIZE() produces text or bytea from input which containis
or represents json or jsonb;

For the most part these functions don't add any significant new
capabilities, but they will be of use to users wanting standard
compliant JSON handling.

Catversion bumped as this changes ruleutils.c.

Author: Nikita Glukhov <n.gluhov@postgrespro.ru>
Author: Teodor Sigaev <teodor@sigaev.ru>
Author: Oleg Bartunov <obartunov@gmail.com>
Author: Alexander Korotkov <aekorotkov@gmail.com>
Author: Andrew Dunstan <andrew@dunslane.net>
Author: Amit Langote <amitlangote09@gmail.com>

Reviewers have included (in no particular order) Andres Freund, Alexander
Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zihong Yu,
Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby, Álvaro Herrera,
Peter Eisentraut

Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
Discussion: https://postgr.es/m/20220616233130.rparivafipt6doj3@alap3.anarazel.de
Discussion: https://postgr.es/m/abd9b83b-aa66-f230-3d6d-734817f0995d%40postgresql.org
Discussion: https://postgr.es/m/CA+HiwqE4XTdfb1nW=Ojoy_tQSRhYt-q_kb6i5d4xcKyrLC1Nbg@mail.gmail.com
2023-07-26 17:08:33 +09:00
Amit Langote 7c7412cae3 Code review for commit b6e1157e7d
b6e1157e7d made some changes to enforce that
JsonValueExpr.formatted_expr is always set and is the expression that
gives a JsonValueExpr its runtime value, but that's not really
apparent from the comments about and the code manipulating
formatted_expr.  This commit fixes that.

Per suggestion from Álvaro Herrera.

Discussion: https://postgr.es/m/20230718155313.3wqg6encgt32adqb%40alvherre.pgsql
2023-07-21 19:15:34 +09:00
Amit Langote b6e1157e7d Don't include CaseTestExpr in JsonValueExpr.formatted_expr
A CaseTestExpr is currently being put into
JsonValueExpr.formatted_expr as placeholder for the result of
evaluating JsonValueExpr.raw_expr, which in turn is evaluated
separately.  Though, there's no need for this indirection if
raw_expr itself can be embedded into formatted_expr and evaluated
as part of evaluating the latter, especially as there is no
special reason to evaluate it separately.  So this commit makes it
so.  As a result, JsonValueExpr.raw_expr no longer needs to be
evaluated in ExecInterpExpr(), eval_const_exprs_mutator() etc. and
is now only used for displaying the original "unformatted"
expression in ruleutils.c.

While at it, this also removes the function makeCaseTestExpr(),
because the code in makeJsonConstructorExpr() looks more readable
without it IMO and isn't used by anyone else either.

Finally, a note is added in the comment above CaseTestExpr's
definition that JsonConstructorExpr is also using it.

Reviewed-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/CA+HiwqE4XTdfb1nW=Ojoy_tQSRhYt-q_kb6i5d4xcKyrLC1Nbg@mail.gmail.com
2023-07-13 12:13:58 +09:00
David Rowley a8c09daa8b Remove trailing zero words from Bitmapsets
Prior to this, Bitmapsets could contain trailing words which had no
members set.  Many places in bitmapset.c had to loop over trailing words
to check for empty words.  If we ensure we always remove these trailing
zero words then we can perform various optimizations such as fast
pathing bms_is_subset to return false when 'a' has more words than 'b'.
A similar optimization is possible in bms_equal.  Both of these together
can yield quite significant performance increases in the query planner
when querying a partitioned table with around 100 or more partitions.

While we're at it, since the minimum number of words a Bitmapset can
contain is 1, we can make use of do/while loops instead of for loops
when looping over all words in a set.  This means checking the loop
condition 1 less time, which for single-word sets cuts the loop
condition checks in half.

Author: David Rowley
Reviewed-by: Yuya Watari
Discussion: https://postgr.es/m/CAApHDvr5O41MuUjw0DQKqmAnv7QqvmLqXReEd5o4nXTzWp8-+w@mail.gmail.com
2023-07-04 12:34:48 +12:00
Peter Eisentraut efcf55f8fe Remove inappropriate raw_expression_tree_walker() code
It was walking into the ColumnDef->compression field, which is not a
node but a string.  This code is currently not reachable (because the
compression field is only set in situations that don't go through
raw_expression_tree_walker()), but if it had been, this could have
behaved erratically.
2023-06-29 10:34:53 +02:00
Michael Paquier 2ecbb0a493 Remove dependency to query text in JumbleQuery()
Since 3db72eb, the query ID of utilities is generated using the Query
structure, making the use of the query string in JumbleQuery()
unnecessary.  This commit removes the argument "querytext" from
JumbleQuery().

Reported-by: Joe Conway
Reviewed-by: Nathan Bossart
Discussion: https://postgr.es/m/ZJlQAWE4COFqHuAV@paquier.xyz
2023-06-28 08:59:36 +09:00
Noah Misch f9f31aa91f Make parseNodeString() C idiom compatible with Visual Studio 2015.
Between v15 and now, this function's "else if" chain grew from 252 lines
to 592 lines, exceeding a compiler limit that manifests as "fatal error
C1026: parser stack overflow, program too complex (compiling source file
src/backend/nodes/readfuncs.c)".  Use "if (...)  return ...;" instead.

Reviewed by Tom Lane, Peter Eisentraut and Michael Paquier.  Not all
reviewers endorse this.

Discussion: https://postgr.es/m/20230607185458.GA1334487@rfd.leadboat.com
2023-06-14 05:31:54 -07:00
Amit Langote 0f8cfaf892 Retain relkind too in RTE_SUBQUERY entries for views.
47bb9db75 modified the ApplyRetrieveRule()'s conversion of a view's
original RTE_RELATION entry into an RTE_SUBQUERY one to retain relid,
rellockmode, and perminfoindex so that the executor can lock the view
and check its permissions.  It seems better to also retain
relkind for cross-checking that the exception of an
RTE_SUBQUERY entry being allowed to carry relation details only
applies to views, so do so.

Bump catversion because this changes the output format of
RTE_SUBQUERY RTEs.

Suggested-by: David Steele <david@pgmasters.net>
Reviewed-by: David Steele <david@pgmasters.net>
Reviewed-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/3953179e-9540-e5d1-a743-4bef368785b0%40pgmasters.net
2023-06-14 12:00:10 +09:00
Tom Lane 0245f8db36 Pre-beta mechanical code beautification.
Run pgindent, pgperltidy, and reformat-dat-files.

This set of diffs is a bit larger than typical.  We've updated to
pg_bsd_indent 2.1.2, which properly indents variable declarations that
have multi-line initialization expressions (the continuation lines are
now indented one tab stop).  We've also updated to perltidy version
20230309 and changed some of its settings, which reduces its desire to
add whitespace to lines to make assignments etc. line up.  Going
forward, that should make for fewer random-seeming changes to existing
code.

Discussion: https://postgr.es/m/20230428092545.qfb3y5wcu4cm75ur@alvherre.pgsql
2023-05-19 17:24:48 -04:00
Michael Paquier d8c3106bb6 Add back SQLValueFunction for SQL keywords
This is equivalent to a revert of f193883 and fb32748, with the addition
that the declaration of the SQLValueFunction node needs to gain a couple
of node_attr for query jumbling.  The performance impact of removing the
function call inlining is proving to be too huge for some workloads
where these are used.  A worst-case test case of involving only simple
SELECT queries with a SQL keyword is proving to lead to a reduction of
10% in TPS via pgbench and prepared queries on a high-end machine.

None of the tests I ran back for this set of changes saw such a huge
gap, but Alexander Lakhin and Andres Freund have found that this can be
noticeable.  Keeping the older performance would mean to do more
inlining in the executor when using COERCE_SQL_SYNTAX for a function
expression, similarly to what SQLValueFunction does.  This requires more
redesign work and there is little time until 16beta1 is released, so for
now reverting the change is the best way forward, bringing back the
previous performance.

Bump catalog version.

Reported-by: Alexander Lakhin
Discussion: https://postgr.es/m/b32bed1b-0746-9b20-1472-4bdc9ca66d52@gmail.com
2023-05-17 10:19:17 +09:00
David Rowley e35ded2956 Fix list_copy_head() with empty Lists
list_copy_head() given an empty List would crash from trying to
dereference the List to obtain its length.  Since NIL is how we represent
an empty List, we should just be returning another empty List in this
case.

list_copy_head() is new to v16, so let's fix it now before too many people
start coding around the buggy NIL behavior.

Reported-by: Miroslav Bendik
Discussion: https://postgr.es/m/CAPoEpV02WhawuWnmnKet6BqU63bEu7oec0pJc=nKMtPsHMzTXQ@mail.gmail.com
2023-04-20 10:34:46 +12:00