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| author | Peter Eisentraut <peter@eisentraut.org> | 2024-04-15 08:20:34 +0200 |
|---|---|---|
| committer | Peter Eisentraut <peter@eisentraut.org> | 2024-04-15 08:34:45 +0200 |
| commit | 9895b35cb88edc30b836661dbc26d7665716b5a0 (patch) | |
| tree | 951ebe60a7af44a3e5246b323459c84e19f9b2d7 /doc/src | |
| parent | d21d61b96f7a4d89e4b2e7cc9b9a1ec3f642fa12 (diff) | |
| download | postgresql-9895b35cb88edc30b836661dbc26d7665716b5a0.tar.gz postgresql-9895b35cb88edc30b836661dbc26d7665716b5a0.zip | |
Fix ALTER DOMAIN NOT NULL syntax
This addresses a few problems with commit e5da0fe3c22 ("Catalog domain
not-null constraints").
In CREATE DOMAIN, a NOT NULL constraint looks like
CREATE DOMAIN d1 AS int [ CONSTRAINT conname ] NOT NULL
(Before e5da0fe3c22, the constraint name was accepted but ignored.)
But in ALTER DOMAIN, a NOT NULL constraint looks like
ALTER DOMAIN d1 ADD [ CONSTRAINT conname ] NOT NULL VALUE
where VALUE is where for a table constraint the column name would be.
(This works as of e5da0fe3c22. Before e5da0fe3c22, this syntax
resulted in an internal error.)
But for domains, this latter syntax is confusing and needlessly
inconsistent between CREATE and ALTER. So this changes it to just
ALTER DOMAIN d1 ADD [ CONSTRAINT conname ] NOT NULL
(None of these syntaxes are per SQL standard; we are just living with
the bits of inconsistency that have built up over time.)
In passing, this also changes the psql \dD output to not show not-null
constraints in the column "Check", since it's already shown in the
column "Nullable". This has also been off since e5da0fe3c22.
Reviewed-by: jian he <jian.universality@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/9ec24d7b-633d-463a-84c6-7acff769c9e8%40eisentraut.org
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/ref/create_domain.sgml | 17 |
1 files changed, 14 insertions, 3 deletions
diff --git a/doc/src/sgml/ref/create_domain.sgml b/doc/src/sgml/ref/create_domain.sgml index 73f9f28d6cf..ce555203486 100644 --- a/doc/src/sgml/ref/create_domain.sgml +++ b/doc/src/sgml/ref/create_domain.sgml @@ -24,9 +24,9 @@ PostgreSQL documentation CREATE DOMAIN <replaceable class="parameter">name</replaceable> [ AS ] <replaceable class="parameter">data_type</replaceable> [ COLLATE <replaceable>collation</replaceable> ] [ DEFAULT <replaceable>expression</replaceable> ] - [ <replaceable class="parameter">constraint</replaceable> [ ... ] ] + [ <replaceable class="parameter">domain_constraint</replaceable> [ ... ] ] -<phrase>where <replaceable class="parameter">constraint</replaceable> is:</phrase> +<phrase>where <replaceable class="parameter">domain_constraint</replaceable> is:</phrase> [ CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> ] { NOT NULL | NULL | CHECK (<replaceable class="parameter">expression</replaceable>) } @@ -190,7 +190,7 @@ CREATE DOMAIN <replaceable class="parameter">name</replaceable> [ AS ] <replacea </variablelist> </refsect1> - <refsect1> + <refsect1 id="sql-createdomain-notes"> <title>Notes</title> <para> @@ -279,6 +279,17 @@ CREATE TABLE us_snail_addy ( The command <command>CREATE DOMAIN</command> conforms to the SQL standard. </para> + + <para> + The syntax <literal>NOT NULL</literal> in this command is a + <productname>PostgreSQL</productname> extension. (A standard-conforming + way to write the same would be <literal>CHECK (VALUE IS NOT + NULL)</literal>. However, per <xref linkend="sql-createdomain-notes"/>, + such constraints are best avoided in practice anyway.) The + <literal>NULL</literal> <quote>constraint</quote> is a + <productname>PostgreSQL</productname> extension (see also <xref + linkend="sql-createtable-compatibility"/>). + </para> </refsect1> <refsect1 id="sql-createdomain-see-also"> |