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Doc: mention foreign keys can reference unique indexes

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We seem to have only documented a foreign key can reference the columns of
a primary key or unique constraint.  Here we adjust the documentation
to mention columns in a non-partial unique index can be mentioned too.

The header comment for transformFkeyCheckAttrs() also didn't mention
unique indexes, so fix that too.  In passing make that header comment
reflect reality in the various other aspects where it deviated from it.

Bug: 18295
Reported-by: Gilles PARC
Author: Laurenz Albe, David Rowley
Discussion: https://www.postgresql.org/message-id/18295-0ed0fac5c9f7b17b%40postgresql.org
Backpatch-through: 12
This commit is contained in:
David Rowley
2024-01-30 10:15:51 +13:00
parent 1b924a86e6
commit 1c8336e3e2
3 changed files with 32 additions and 21 deletions
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19
doc/src/sgml/ref/create_table.sgml
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@@ -1137,10 +1137,11 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
column(s) of some row of the referenced table. If the <replaceable
class="parameter">refcolumn</replaceable> list is omitted, the
primary key of the <replaceable class="parameter">reftable</replaceable>
is used. The referenced columns must be the columns of a non-deferrable
unique or primary key constraint in the referenced table. The user
must have <literal>REFERENCES</literal> permission on the referenced table
(either the whole table, or the specific referenced columns). The
is used. Otherwise, the <replaceable class="parameter">refcolumn</replaceable>
list must refer to the columns of a non-deferrable unique or primary key
constraint or be the columns of a non-partial unique index. The user
must have <literal>REFERENCES</literal> permission on the referenced
table (either the whole table, or the specific referenced columns). The
addition of a foreign key constraint requires a
<literal>SHARE ROW EXCLUSIVE</literal> lock on the referenced table.
Note that foreign key constraints cannot be defined between temporary
@@ -2277,13 +2278,19 @@ CREATE TABLE cities_partdef
</refsect2>
<refsect2>
<title>Foreign-Key Constraint Actions</title>
<title>Foreign Key Constraints</title>
<para>
The ability to specify column lists in the foreign-key actions
The ability to specify column lists in the foreign key actions
<literal>SET DEFAULT</literal> and <literal>SET NULL</literal> is a
<productname>PostgreSQL</productname> extension.
</para>
<para>
It is a <productname>PostgreSQL</productname> extension that a
foreign key constraint may reference columns of a unique index instead of
columns of a primary key or unique constraint.
</para>
</refsect2>
<refsect2>