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 2953639a0a83f732a78505ca064d91e189ae27f7..4a2f46d2396c224876dded9346c08a671929aba7 100644 (file)
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -149,7 +149,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
 
   <variablelist>
    <varlistentry>
-    <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
@@ -161,7 +161,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
    </varlistentry>
 
    <varlistentry>
-    <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 5cdf64e829b36eb01f00a9d3082751ce8a47baa1..7fdcdc1c6c03bc689ecb6a21357a9b99f2f2a689 100644 (file)
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -3737,6 +3737,16 @@ 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 a4c7dfadece256f7cb1fc3887885a20f5c351d51..6454369c7df438d903f313383c5014bcaeb0f721 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*