doc: Clarify that COLUMN is optional in ALTER TABLE ... ADD/DROP COLUMN.

In ALTER TABLE ... ADD/DROP COLUMN, the COLUMN keyword is optional. However,
part of the documentation could be read as if COLUMN were required, which may
mislead users about the command syntax.

This commit updates the ALTER TABLE documentation to clearly state that
COLUMN is optional for ADD and DROP.

Also this commit adds regression tests covering ALTER TABLE ... ADD/DROP
without the COLUMN keyword.

Backpatch to all supported versions.

Author: Chao Li <lic@highgo.com>
Reviewed-by: Robert Treat <rob@xzilla.net>
Reviewed-by: Fujii Masao <masao.fujii@gmail.com>
Discussion: https://postgr.es/m/CAEoWx2n6ShLMOnjOtf63TjjgGbgiTVT5OMsSOFmbjGb6Xue1Bw@mail.gmail.com
Backpatch-through: 14

diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index 89548cda0bc977a53d8fb994be3a2ea7845f2c5e..7f8048ac1c9d542c729d0cd57ee799b342d5cd7a 100644 (file)
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -154,7 +154,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
 
   <variablelist>
    <varlistentry id="sql-altertable-desc-add-column">
-    <term><literal>ADD COLUMN [ IF NOT EXISTS ]</literal></term>
+    <term><literal>ADD [ COLUMN ] [ IF NOT EXISTS ]</literal></term>
     <listitem>
      <para>
       This form adds a new column to the table, using the same syntax as
@@ -166,7 +166,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
    </varlistentry>
 
    <varlistentry id="sql-altertable-desc-drop-column">
-    <term><literal>DROP COLUMN [ IF EXISTS ]</literal></term>
+    <term><literal>DROP [ COLUMN ] [ IF EXISTS ]</literal></term>
     <listitem>
      <para>
       This form drops a column from a table.  Indexes and

diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index 859d8647f05037a7472451dcc4b38d9cce74f0a1..5ecf000c70fd69e8e4c66b308095600eb138cb3d 100644 (file)
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -3739,6 +3739,16 @@ Referenced by:
 ALTER TABLE test_add_column
        ADD COLUMN IF NOT EXISTS c5 SERIAL CHECK (c5 > 10);
 NOTICE:  column "c5" of relation "test_add_column" already exists, skipping
+ALTER TABLE test_add_column
+       ADD c6 integer; -- omit COLUMN
+ALTER TABLE test_add_column
+       ADD IF NOT EXISTS c6 integer;
+NOTICE:  column "c6" of relation "test_add_column" already exists, skipping
+ALTER TABLE test_add_column
+       DROP c6; -- omit COLUMN
+ALTER TABLE test_add_column
+       DROP IF EXISTS c6;
+NOTICE:  column "c6" of relation "test_add_column" does not exist, skipping
 \d test_add_column*
                             Table "public.test_add_column"
  Column |  Type   | Collation | Nullable |                   Default                   

diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 545411339ff27dfe825f4e7c78ec446e59cddcc1..b448dea01cce920dab34e07402164d96dd28fbd0 100644 (file)
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -2308,6 +2308,14 @@ ALTER TABLE test_add_column
 \d test_add_column
 ALTER TABLE test_add_column
        ADD COLUMN IF NOT EXISTS c5 SERIAL CHECK (c5 > 10);
+ALTER TABLE test_add_column
+       ADD c6 integer; -- omit COLUMN
+ALTER TABLE test_add_column
+       ADD IF NOT EXISTS c6 integer;
+ALTER TABLE test_add_column
+       DROP c6; -- omit COLUMN
+ALTER TABLE test_add_column
+       DROP IF EXISTS c6;
 \d test_add_column*
 DROP TABLE test_add_column;
 \d test_add_column*