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Catalog NOT NULL constraints

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We now create pg_constaint rows for NOT NULL constraints with
contype='n'.

We propagate these constraints during operations such as adding
inheritance relationships, creating and attaching partitions, creating
tables LIKE other tables.  We 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 we match by column number.  This means we don't require the
constraint names to be identical across a hierarchy.

For now, we omit them from 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.)

This 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.

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 additional pg_attribute columns 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>

Discussion: https://postgr.es/m/CACA0E642A0267EDA387AF2B%40%5B172.26.14.62%5D
Discussion: https://postgr.es/m/AANLkTinLXMOEMz+0J29tf1POokKi4XDkWJ6-DDR9BKgU@mail.gmail.com
Discussion: https://postgr.es/m/20110707213401.GA27098@alvh.no-ip.org
Discussion: https://postgr.es/m/1343682669-sup-2532@alvh.no-ip.org
Discussion: https://postgr.es/m/CAKOSWNkN6HSyatuys8xZxzRCR-KL1OkHS5-b9qd9bf1Rad3PLA@mail.gmail.com
Discussion: https://postgr.es/m/20220817181249.q7qvj3okywctra3c@alvherre.pgsql
This commit is contained in:
Alvaro Herrera
2023-04-07 19:20:53 +02:00
parent ff245a3788
commit e056c557ae
42 changed files with 2877 additions and 634 deletions
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1
doc/src/sgml/catalogs.sgml
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@ -2552,6 +2552,7 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
<para>
<literal>c</literal> = check constraint,
<literal>f</literal> = foreign key constraint,
<literal>n</literal> = not null constraint,
<literal>p</literal> = primary key constraint,
<literal>u</literal> = unique constraint,
<literal>t</literal> = constraint trigger,

14
doc/src/sgml/ref/alter_table.sgml
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@ -117,7 +117,9 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
PRIMARY KEY ( <replaceable class="parameter">column_name</replaceable> [, ... ] ) <replaceable class="parameter">index_parameters</replaceable> |
EXCLUDE [ USING <replaceable class="parameter">index_method</replaceable> ] ( <replaceable class="parameter">exclude_element</replaceable> WITH <replaceable class="parameter">operator</replaceable> [, ... ] ) <replaceable class="parameter">index_parameters</replaceable> [ WHERE ( <replaceable class="parameter">predicate</replaceable> ) ] |
FOREIGN KEY ( <replaceable class="parameter">column_name</replaceable> [, ... ] ) REFERENCES <replaceable class="parameter">reftable</replaceable> [ ( <replaceable class="parameter">refcolumn</replaceable> [, ... ] ) ]
[ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ] [ ON DELETE <replaceable class="parameter">referential_action</replaceable> ] [ ON UPDATE <replaceable class="parameter">referential_action</replaceable> ] }
[ MATCH FULL | MATCH PARTIAL | MATCH SIMPLE ] [ ON DELETE <replaceable class="parameter">referential_action</replaceable> ] [ ON UPDATE <replaceable class="parameter">referential_action</replaceable> ] |
NOT NULL <replaceable class="parameter">column_name</replaceable> [ NO INHERIT ]
}
[ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
<phrase>and <replaceable class="parameter">table_constraint_using_index</replaceable> is:</phrase>
@ -1763,11 +1765,17 @@ ALTER TABLE measurement
<title>Compatibility</title>
<para>
The forms <literal>ADD</literal> (without <literal>USING INDEX</literal>),
The forms <literal>ADD COLUMN</literal>
<literal>DROP [COLUMN]</literal>, <literal>DROP IDENTITY</literal>, <literal>RESTART</literal>,
<literal>SET DEFAULT</literal>, <literal>SET DATA TYPE</literal> (without <literal>USING</literal>),
<literal>SET GENERATED</literal>, and <literal>SET <replaceable>sequence_option</replaceable></literal>
conform with the SQL standard. The other forms are
conform with the SQL standard.
The form <literal>ADD <replaceable>table_constraint</replaceable></literal>
conforms with the SQL standard when the <literal>USING INDEX</literal> and
<literal>NOT VALID</literal> clauses are omitted and the constraint type is
one of <literal>UNIQUE</literal>, <literal>PRIMARY KEY</literal>
or <literal>REFERENCES</literal>.
The other forms are
<productname>PostgreSQL</productname> extensions of the SQL standard.
Also, the ability to specify more than one manipulation in a single
<command>ALTER TABLE</command> command is an extension.

8
doc/src/sgml/ref/create_table.sgml
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@ -77,6 +77,7 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXI
[ CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> ]
{ CHECK ( <replaceable class="parameter">expression</replaceable> ) [ NO INHERIT ] |
NOT NULL <replaceable class="parameter">column_name</replaceable> |
UNIQUE [ NULLS [ NOT ] DISTINCT ] ( <replaceable class="parameter">column_name</replaceable> [, ... ] ) <replaceable class="parameter">index_parameters</replaceable> |
PRIMARY KEY ( <replaceable class="parameter">column_name</replaceable> [, ... ] ) <replaceable class="parameter">index_parameters</replaceable> |
EXCLUDE [ USING <replaceable class="parameter">index_method</replaceable> ] ( <replaceable class="parameter">exclude_element</replaceable> WITH <replaceable class="parameter">operator</replaceable> [, ... ] ) <replaceable class="parameter">index_parameters</replaceable> [ WHERE ( <replaceable class="parameter">predicate</replaceable> ) ] |
@ -2314,13 +2315,6 @@ CREATE TABLE cities_partdef
constraint, and index names must be unique across all relations within
the same schema.
</para>
<para>
Currently, <productname>PostgreSQL</productname> does not record names
for <literal>NOT NULL</literal> constraints at all, so they are not
subject to the uniqueness restriction. This might change in a future
release.
</para>
</refsect2>
<refsect2>