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Commit14e87ff

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Add pg_constraint rows for not-null constraints
We now create contype='n' pg_constraint rows for not-null constraints onuser tables. Only one such constraint is allowed for a column.We propagate these constraints to other tables during operations such asadding inheritance relationships, creating and attaching partitions andcreating tables LIKE other tables. These related constraints mostlyfollow the well-known rules of conislocal and coninhcount that we havefor CHECK constraints, with some adaptations: for example, as opposed toCHECK constraints, we don't match not-null ones by name when descendinga hierarchy to alter or remove it, instead matching by the name of thecolumn that they apply to. This means we don't require the constraintnames to be identical across a hierarchy.The inheritance status of these constraints can be controlled: now wecan be sure that if a parent table has one, then all children will haveit as well. They can optionally be marked NO INHERIT, and then childrenare free not to have one. (There's currently no support for altering aNO INHERIT constraint into inheriting down the hierarchy, but that's adesirable future feature.)This also opens the door for having these constraints be marked NOTVALID, as well as allowing UNIQUE+NOT NULL to be used for functionaldependency determination, as envisioned by commite49ae8d. It'slikely possible to allow DEFERRABLE constraints as followup work, aswell.psql shows these constraints in \d+, though we may want to reconsider ifthis turns out to be too noisy. Earlier versions of this patch hidconstraints that were on the same columns of the primary key, but I'mnot sure that that's very useful. If clutter is a problem, we might bebetter off inventing a new \d++ command and not showing the constraintsin \d+.For now, we omit these constraints on system catalog columns, becausethey're unlikely to achieve anything.The main difference to the previous attempt at this (b0e96f3) isthat we now require that such a constraint always exists when a primarykey is in the column; we didn't require this previously which had anumber of unpalatable consequences. With this requirement, the code iseasier to reason about. For example:- We no longer have "throwaway constraints" during pg_dump. We needed those for the case where a table had a PK without a not-null underneath, to prevent a slow scan of the data during restore of the PK creation, which was particularly problematic for pg_upgrade.- We no longer have to cope with attnotnull being set spuriously in case a primary key is dropped indirectly (e.g., via DROP COLUMN).Some bits of code in this patch were authored by Jian He.Author: Álvaro Herrera <alvherre@alvh.no-ip.org>Author: Bernd Helmle <mailings@oopsware.de>Reviewed-by: 何建 (jian he) <jian.universality@gmail.com>Reviewed-by: 王刚 (Tender Wang) <tndrwang@gmail.com>Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>Reviewed-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>Reviewed-by: Dean Rasheed <dean.a.rasheed@gmail.com>Discussion:https://postgr.es/m/202408310358.sdhumtyuy2ht@alvherre.pgsql
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‎contrib/sepgsql/expected/alter.out

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@@ -164,7 +164,6 @@ LOG: SELinux: allowed { setattr } scontext=unconfined_u:unconfined_r:sepgsql_re
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LOG: SELinux: allowed { setattr } scontext=unconfined_u:unconfined_r:sepgsql_regtest_superuser_t:s0 tcontext=unconfined_u:object_r:sepgsql_table_t:s0 tclass=db_column name="regtest_schema.regtest_table_2.b" permissive=0
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ALTER TABLE regtest_table ALTER b DROP NOT NULL;
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LOG: SELinux: allowed { setattr } scontext=unconfined_u:unconfined_r:sepgsql_regtest_superuser_t:s0 tcontext=unconfined_u:object_r:sepgsql_table_t:s0 tclass=db_column name="regtest_schema_2.regtest_table.b" permissive=0
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LOG: SELinux: allowed { setattr } scontext=unconfined_u:unconfined_r:sepgsql_regtest_superuser_t:s0 tcontext=unconfined_u:object_r:sepgsql_table_t:s0 tclass=db_column name="regtest_schema.regtest_table_2.b" permissive=0
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ALTER TABLE regtest_table ALTER b SET STATISTICS -1;
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LOG: SELinux: allowed { setattr } scontext=unconfined_u:unconfined_r:sepgsql_regtest_superuser_t:s0 tcontext=unconfined_u:object_r:sepgsql_table_t:s0 tclass=db_column name="regtest_schema_2.regtest_table.b" permissive=0
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LOG: SELinux: allowed { setattr } scontext=unconfined_u:unconfined_r:sepgsql_regtest_superuser_t:s0 tcontext=unconfined_u:object_r:sepgsql_table_t:s0 tclass=db_column name="regtest_schema.regtest_table_2.b" permissive=0
@@ -249,8 +248,6 @@ LOG: SELinux: allowed { setattr } scontext=unconfined_u:unconfined_r:sepgsql_re
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LOG: SELinux: allowed { setattr } scontext=unconfined_u:unconfined_r:sepgsql_regtest_superuser_t:s0 tcontext=unconfined_u:object_r:sepgsql_table_t:s0 tclass=db_column name="regtest_schema.regtest_ptable_1_tens.p" permissive=0
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ALTER TABLE regtest_ptable ALTER p DROP NOT NULL;
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LOG: SELinux: allowed { setattr } scontext=unconfined_u:unconfined_r:sepgsql_regtest_superuser_t:s0 tcontext=unconfined_u:object_r:sepgsql_table_t:s0 tclass=db_column name="regtest_schema_2.regtest_ptable.p" permissive=0
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LOG: SELinux: allowed { setattr } scontext=unconfined_u:unconfined_r:sepgsql_regtest_superuser_t:s0 tcontext=unconfined_u:object_r:sepgsql_table_t:s0 tclass=db_column name="regtest_schema_2.regtest_table_part.p" permissive=0
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LOG: SELinux: allowed { setattr } scontext=unconfined_u:unconfined_r:sepgsql_regtest_superuser_t:s0 tcontext=unconfined_u:object_r:sepgsql_table_t:s0 tclass=db_column name="regtest_schema.regtest_ptable_1_tens.p" permissive=0
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ALTER TABLE regtest_ptable ALTER p SET STATISTICS -1;
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LOG: SELinux: allowed { setattr } scontext=unconfined_u:unconfined_r:sepgsql_regtest_superuser_t:s0 tcontext=unconfined_u:object_r:sepgsql_table_t:s0 tclass=db_column name="regtest_schema_2.regtest_ptable.p" permissive=0
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LOG: SELinux: allowed { setattr } scontext=unconfined_u:unconfined_r:sepgsql_regtest_superuser_t:s0 tcontext=unconfined_u:object_r:sepgsql_table_t:s0 tclass=db_column name="regtest_schema_2.regtest_table_part.p" permissive=0

‎contrib/test_decoding/expected/ddl.out

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@@ -492,6 +492,9 @@ WITH (user_catalog_table = true)
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options | text[] | | | | extended | |
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Indexes:
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"replication_metadata_pkey" PRIMARY KEY, btree (id)
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Not-null constraints:
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"replication_metadata_id_not_null" NOT NULL "id"
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"replication_metadata_relation_not_null" NOT NULL "relation"
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Options: user_catalog_table=true
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INSERT INTO replication_metadata(relation, options)
@@ -506,6 +509,9 @@ ALTER TABLE replication_metadata RESET (user_catalog_table);
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options | text[] | | | | extended | |
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Indexes:
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"replication_metadata_pkey" PRIMARY KEY, btree (id)
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Not-null constraints:
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"replication_metadata_id_not_null" NOT NULL "id"
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"replication_metadata_relation_not_null" NOT NULL "relation"
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INSERT INTO replication_metadata(relation, options)
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VALUES ('bar', ARRAY['a', 'b']);
@@ -519,6 +525,9 @@ ALTER TABLE replication_metadata SET (user_catalog_table = true);
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options | text[] | | | | extended | |
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Indexes:
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"replication_metadata_pkey" PRIMARY KEY, btree (id)
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Not-null constraints:
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"replication_metadata_id_not_null" NOT NULL "id"
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"replication_metadata_relation_not_null" NOT NULL "relation"
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Options: user_catalog_table=true
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INSERT INTO replication_metadata(relation, options)
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rewritemeornot | integer | | | | plain | |
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Indexes:
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"replication_metadata_pkey" PRIMARY KEY, btree (id)
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Not-null constraints:
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"replication_metadata_id_not_null" NOT NULL "id"
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"replication_metadata_relation_not_null" NOT NULL "relation"
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Options: user_catalog_table=false
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INSERT INTO replication_metadata(relation, options)

‎doc/src/sgml/catalogs.sgml

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<structfield>attnotnull</structfield> <type>bool</type>
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</para>
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<para>
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Thisrepresents a not-null constraint.
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Thiscolumn has a not-null constraint.
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</para></entry>
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</row>
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</indexterm>
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<para>
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The catalog <structname>pg_constraint</structname> stores check, primary
2506-
key, unique, foreign key, and exclusion constraints on tables, as well as
2507-
not-null constraints on domains.
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The catalog <structname>pg_constraint</structname> stores check, not-null,
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primary key, unique, foreign key, and exclusion constraints on tables.
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(Column constraints are not treated specially. Every column constraint is
25092508
equivalent to some table constraint.)
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Not-null constraints on relations are represented in the
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<link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>
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catalog, not here.
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</para>
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<para>
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<para>
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<literal>c</literal> = check constraint,
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<literal>f</literal> = foreign key constraint,
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<literal>n</literal> = not-null constraint (domains only),
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<literal>n</literal> = not-null constraint,
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<literal>p</literal> = primary key constraint,
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<literal>u</literal> = unique constraint,
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<literal>t</literal> = constraint trigger,

‎doc/src/sgml/ddl.sgml

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@@ -772,17 +772,38 @@ CREATE TABLE products (
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price numeric
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);
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</programlisting>
775+
An explicit constraint name can also be specified, for example:
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<programlisting>
777+
CREATE TABLE products (
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product_no integer NOT NULL,
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name text <emphasis>CONSTRAINT products_name_not_null</emphasis> NOT NULL,
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price numeric
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);
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</programlisting>
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</para>
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<para>
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A not-null constraint is usually written as a column constraint. The
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syntax for writing it as a table constraint is
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<programlisting>
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CREATE TABLE products (
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product_no integer,
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name text,
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price numeric,
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<emphasis>NOT NULL product_no</emphasis>,
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<emphasis>NOT NULL name</emphasis>
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);
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</programlisting>
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But this syntax is not standard and mainly intended for use by
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<application>pg_dump</application>.
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</para>
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<para>
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A not-null constraint is always written as a column constraint. A
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not-null constraint is functionally equivalent to creating a check
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A not-null constraint is functionally equivalent to creating a check
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constraint <literal>CHECK (<replaceable>column_name</replaceable>
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IS NOT NULL)</literal>, but in
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<productname>PostgreSQL</productname> creating an explicit
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not-null constraint is more efficient. The drawback is that you
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cannot give explicit names to not-null constraints created this
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way.
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not-null constraint is more efficient.
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</para>
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<para>
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order the constraints are checked.
800821
</para>
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823+
<para>
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However, a column can have at most one explicit not-null constraint.
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</para>
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<para>
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The <literal>NOT NULL</literal> constraint has an inverse: the
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<literal>NULL</literal> constraint. This does not mean that the
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9931018
<para>
9941019
A table can have at most one primary key. (There can be any number
995-
of uniqueandnot-null constraints, which are functionally almost the
1020+
of uniqueconstraints, which combined withnot-null constraints are functionally almost the
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same thing, but only one can be identified as the primary key.)
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Relational database theory
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dictates that every table must have a primary key. This rule is
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ALTER TABLE products ADD CONSTRAINT some_name UNIQUE (product_no);
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ALTER TABLE products ADD FOREIGN KEY (product_group_id) REFERENCES product_groups;
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</programlisting>
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To add a not-null constraint, which cannot be written as a table
1656-
constraint, use this syntax:
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</para>
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<para>
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To add a not-null constraint, which is normally not written as a table
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constraint, this special syntax is available:
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<programlisting>
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ALTER TABLE products ALTER COLUMN product_no SET NOT NULL;
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</programlisting>
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This command silently does nothing if the column already has a
1689+
not-null constraint.
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</para>
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<para>
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</para>
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<para>
1700-
This works the same for all constraint types except not-null
1701-
constraints. To drop a not-null constraint use:
1730+
Simplified syntax is available to drop a not-null constraint:
17021731
<programlisting>
17031732
ALTER TABLE products ALTER COLUMN product_no DROP NOT NULL;
17041733
</programlisting>
1705-
(Recall that not-null constraints do not have names.)
1734+
This mirrors the <literal>SET NOT NULL</literal> syntax for adding a
1735+
not-null constraint. This command will silently do nothing if the column
1736+
does not have a not-null constraint. (Recall that a column can have at
1737+
most one not-null constraint, so it is never ambiguous which constraint
1738+
this command acts on.)
17061739
</para>
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</sect2>
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44464479
<para>
44474480
Both <literal>CHECK</literal> and <literal>NOT NULL</literal>
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constraints of a partitioned table are always inherited by all its
4449-
partitions. <literal>CHECK</literal> constraints that are marked
4450-
<literal>NO INHERIT</literal> are not allowed to be created on
4451-
partitioned tables.
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You cannot drop a <literal>NOT NULL</literal> constraint on a
4453-
partition's column if the same constraint is present in the parent
4454-
table.
4482+
partitions; it is not allowed to create <literal>NO INHERIT</literal>
4483+
constraints of those types.
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You cannot drop a constraint of those types if the same constraint
4485+
is present in the parent table.
44554486
</para>
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</listitem>
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‎doc/src/sgml/ref/alter_foreign_table.sgml

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@@ -173,7 +173,8 @@ ALTER FOREIGN TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceab
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<para>
174174
This form adds a new constraint to a foreign table, using the same
175175
syntax as <link linkend="sql-createforeigntable"><command>CREATE FOREIGN TABLE</command></link>.
176-
Currently only <literal>CHECK</literal> constraints are supported.
176+
Currently only <literal>CHECK</literal> and <literal>NOT NULL</literal>
177+
constraints are supported.
177178
</para>
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179180
<para>
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182183
declares that some new condition should be assumed to hold for all rows
183184
in the foreign table. (See the discussion
184185
in <link linkend="sql-createforeigntable"><command>CREATE FOREIGN TABLE</command></link>.)
185-
If the constraint is marked <literal>NOT VALID</literal>, then it isn't
186+
If the constraint is marked <literal>NOT VALID</literal> (allowed only for
187+
the <literal>CHECK</literal> case), then it isn't
186188
assumed to hold, but is only recorded for possible future use.
187189
</para>
188190
</listitem>

‎doc/src/sgml/ref/alter_table.sgml

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<phrase>and <replaceable class="parameter">column_constraint</replaceable> is:</phrase>
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100100
[ CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> ]
101-
{ NOT NULL |
101+
{ NOT NULL[ NO INHERIT ]|
102102
NULL |
103103
CHECK ( <replaceable class="parameter">expression</replaceable> ) [ NO INHERIT ] |
104104
DEFAULT <replaceable>default_expr</replaceable> |
@@ -114,6 +114,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
114114

115115
[ CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> ]
116116
{ CHECK ( <replaceable class="parameter">expression</replaceable> ) [ NO INHERIT ] |
117+
NOT NULL <replaceable class="parameter">column_name</replaceable> [ NO INHERIT ] |
117118
UNIQUE [ NULLS [ NOT ] DISTINCT ] ( <replaceable class="parameter">column_name</replaceable> [, ... ] ) <replaceable class="parameter">index_parameters</replaceable> |
118119
PRIMARY KEY ( <replaceable class="parameter">column_name</replaceable> [, ... ] ) <replaceable class="parameter">index_parameters</replaceable> |
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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> ) ] |
@@ -849,19 +850,16 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
849850
table. Subsequently, queries against the parent will include records
850851
of the target table. To be added as a child, the target table must
851852
already contain all the same columns as the parent (it could have
852-
additional columns, too). The columns must have matching data types,
853-
and if they have <literal>NOT NULL</literal> constraints in the parent
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then they must also have <literal>NOT NULL</literal> constraints in the
855-
child.
853+
additional columns, too). The columns must have matching data types.
856854
</para>
857855

858856
<para>
859-
There must also be matching child-table constraints for all
860-
<literal>CHECK</literal>constraintsof the parent, except those
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marked non-inheritable (that is, created with <literal>ALTER TABLE ... ADD CONSTRAINT ... NO INHERIT</literal>)
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in the parent, which are ignored; all child-table constraints matched
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must not be marked non-inheritable.
864-
Currently
857+
In addition, all <literal>CHECK</literal> and <literal>NOT NULL</literal>
858+
constraintson the parent must also exist on the child, except those
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marked non-inheritable (that is, created with
860+
<literal>ALTER TABLE ... ADD CONSTRAINT ... NO INHERIT</literal>), which
861+
are ignored. All child-table constraints matchedmust not be marked
862+
non-inheritable.Currently
865863
<literal>UNIQUE</literal>, <literal>PRIMARY KEY</literal>, and
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<literal>FOREIGN KEY</literal> constraints are not considered, but
867865
this might change in the future.
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17931791
<title>Compatibility</title>
17941792

17951793
<para>
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The forms <literal>ADD</literal> (without <literal>USING INDEX</literal>),
1794+
The forms <literal>ADD [COLUMN]</literal>,
17971795
<literal>DROP [COLUMN]</literal>, <literal>DROP IDENTITY</literal>, <literal>RESTART</literal>,
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<literal>SET DEFAULT</literal>, <literal>SET DATA TYPE</literal> (without <literal>USING</literal>),
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<literal>SET GENERATED</literal>, and <literal>SET <replaceable>sequence_option</replaceable></literal>
1800-
conform with the SQL standard. The other forms are
1798+
conform with the SQL standard.
1799+
The form <literal>ADD <replaceable>table_constraint</replaceable></literal>
1800+
conforms with the SQL standard when the <literal>USING INDEX</literal> and
1801+
<literal>NOT VALID</literal> clauses are omitted and the constraint type is
1802+
one of <literal>CHECK</literal>, <literal>UNIQUE</literal>, <literal>PRIMARY KEY</literal>,
1803+
or <literal>REFERENCES</literal>.
1804+
The other forms are
18011805
<productname>PostgreSQL</productname> extensions of the SQL standard.
18021806
Also, the ability to specify more than one manipulation in a single
18031807
<command>ALTER TABLE</command> command is an extension.

‎doc/src/sgml/ref/create_foreign_table.sgml

Lines changed: 8 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -43,7 +43,7 @@ CREATE FOREIGN TABLE [ IF NOT EXISTS ] <replaceable class="parameter">table_name
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<phrase>where <replaceable class="parameter">column_constraint</replaceable> is:</phrase>
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4545
[ CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> ]
46-
{ NOT NULL |
46+
{ NOT NULL[ NO INHERIT ]|
4747
NULL |
4848
CHECK ( <replaceable class="parameter">expression</replaceable> ) [ NO INHERIT ] |
4949
DEFAULT <replaceable>default_expr</replaceable> |
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5252
<phrase>and <replaceable class="parameter">table_constraint</replaceable> is:</phrase>
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5454
[ CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> ]
55+
NOT NULL <replaceable class="parameter">column_name</replaceable> [ NO INHERIT ] |
5556
CHECK ( <replaceable class="parameter">expression</replaceable> ) [ NO INHERIT ]
5657

5758
<phrase>and <replaceable class="parameter">partition_bound_spec</replaceable> is:</phrase>
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203204
</varlistentry>
204205

205206
<varlistentry>
206-
<term><literal>NOT NULL</literal></term>
207+
<term><literal>NOT NULL</literal> [ NO INHERIT ]</term>
207208
<listitem>
208209
<para>
209210
The column is not allowed to contain null values.
210211
</para>
212+
213+
<para>
214+
A constraint marked with <literal>NO INHERIT</literal> will not propagate to
215+
child tables.
216+
</para>
211217
</listitem>
212218
</varlistentry>
213219

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