[PATCH] docs: Document the automatically generated names for indices

From: Jade Lovelace <jadel(at)mercury(dot)com>

I have intentionally been careful to not guarantee that the
automatically generated name *is* what's documented, but instead give
the general idea.

Knowing the format is useful for people writing migrations/ORM tools
which need to name their unique indices and may wish to use the
automatic naming system.

Signed-off-by: Jade Lovelace <jadel(at)mercury(dot)com>
---
doc/src/sgml/ref/create_index.sgml | 9 +++++++--
doc/src/sgml/ref/create_table.sgml | 30 ++++++++++++++++++++++++++++++
2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/doc/src/sgml/ref/create_index.sgml b/doc/src/sgml/ref/create_index.sgml
index a5bac9f..7354267 100644
--- a/doc/src/sgml/ref/create_index.sgml
+++ b/doc/src/sgml/ref/create_index.sgml
@@ -206,9 +206,14 @@ CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ [ IF NOT EXISTS ] <replaceable class=
table. The name of the index must be distinct from the name of any
other relation (table, sequence, index, view, materialized view, or
foreign table) in that schema.
+ </para>
+ <para>
If the name is omitted, <productname>PostgreSQL</productname> chooses a
- suitable name based on the parent table's name and the indexed column
- name(s).
+ suitable name based on the parent table's name and the indexed
+ column name(s). Generally, teh generated name will be something of the
+ shape <literal>tablename_columnname_idx</literal>, but this may vary in
+ the event of long table names, where it is truncated, or if the index
+ already exists, where a number is appended.
</para>
</listitem>
</varlistentry>
diff --git a/doc/src/sgml/ref/create_table.sgml b/doc/src/sgml/ref/create_table.sgml
index 6bbf15e..bdabd86 100644
--- a/doc/src/sgml/ref/create_table.sgml
+++ b/doc/src/sgml/ref/create_table.sgml
@@ -796,6 +796,36 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
(Double-quotes are needed to specify constraint names that contain spaces.)
If a constraint name is not specified, the system generates a name.
</para>
+ <para>
+ Generally, the generated name will be something of the shape
+ <literal>tablename_columnname_constrainttype</literal>, but this may vary in the
+ event of long table names, where it is truncated, or if the index
+ already exists, where a number is appended.
+ <literal>constrainttype</literal> is one of the following:
+
+ <itemizedlist>
+ <listitem>
+ <para><literal>pkey</literal> in the case of primary keys</para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>excl</literal> in the case of
+ <link linkend="sql-createtable-exclude">
+ <literal>EXCLUDE</literal>
+ </link> constraints.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <literal>key</literal> in the case of
+ <link linkend="sql-createtrigger"><firstterm>constraint triggers</firstterm></link>.
+ </para>
+ </listitem>
+ <listitem>
+ <para><literal>idx</literal> in other cases.</para>
+ </listitem>
+ </itemizedlist>
+ </para>
</listitem>
</varlistentry>

--
2.37.1