From 1eac20063ecf122e6d081fc22497a33013d505dc Mon Sep 17 00:00:00 2001 From: "Chao Li (Evan)" Date: Tue, 3 Mar 2026 09:51:41 +0800 Subject: [PATCH v6] doc: clarify ALTER FOREIGN TABLE ADD/DROP COLUMN syntax Update the ALTER FOREIGN TABLE reference page to reflect that: - COLUMN is optional for ADD and DROP. - IF NOT EXISTS is supported for ADD. The syntax has long allowed these forms, but the documentation did not fully reflect them. Add regression tests for ALTER FOREIGN TABLE covering: - ADD without COLUMN. - ADD IF NOT EXISTS behavior. - DROP without COLUMN. - DROP IF EXISTS behavior. Suggested-by: Fujii Masao Author: Chao Li Reviewed-by: Fujii Masao Reviewed-by: Robert Treat Discussion: https://postgr.es/m/CAEoWx2n6ShLMOnjOtf63TjjgGbgiTVT5OMsSOFmbjGb6Xue1Bw@mail.gmail.com --- doc/src/sgml/ref/alter_foreign_table.sgml | 8 +++++--- src/test/regress/expected/foreign_data.out | 6 ++++++ src/test/regress/sql/foreign_data.sql | 4 ++++ 3 files changed, 15 insertions(+), 3 deletions(-) diff --git a/doc/src/sgml/ref/alter_foreign_table.sgml b/doc/src/sgml/ref/alter_foreign_table.sgml index e6d99e99016..228067f087c 100644 --- a/doc/src/sgml/ref/alter_foreign_table.sgml +++ b/doc/src/sgml/ref/alter_foreign_table.sgml @@ -32,7 +32,7 @@ ALTER FOREIGN TABLE [ IF EXISTS ] namewhere action is one of: - ADD [ COLUMN ] column_name data_type [ COLLATE collation ] [ column_constraint [ ... ] ] + ADD [ COLUMN ] [ IF NOT EXISTS ] column_name data_type [ COLLATE collation ] [ column_constraint [ ... ] ] DROP [ COLUMN ] [ IF EXISTS ] column_name [ RESTRICT | CASCADE ] ALTER [ COLUMN ] column_name [ SET DATA ] TYPE data_type [ COLLATE collation ] ALTER [ COLUMN ] column_name SET DEFAULT expression @@ -67,11 +67,13 @@ ALTER FOREIGN TABLE [ IF EXISTS ] name - ADD COLUMN + ADD [ COLUMN ] [ IF NOT EXISTS ] This form adds a new column to the foreign table, using the same syntax as CREATE FOREIGN TABLE. + If IF NOT EXISTS is specified and a column already + exists with this name, no error is thrown. Unlike the case when adding a column to a regular table, nothing happens to the underlying storage: this action simply declares that some new column is now accessible through the foreign table. @@ -80,7 +82,7 @@ ALTER FOREIGN TABLE [ IF EXISTS ] name - DROP COLUMN [ IF EXISTS ] + DROP [ COLUMN ] [ IF EXISTS ] This form drops a column from a foreign table. diff --git a/src/test/regress/expected/foreign_data.out b/src/test/regress/expected/foreign_data.out index cce49e509ab..908d7a38a78 100644 --- a/src/test/regress/expected/foreign_data.out +++ b/src/test/regress/expected/foreign_data.out @@ -827,11 +827,15 @@ COMMENT ON COLUMN ft1.c1 IS 'foreign column'; COMMENT ON COLUMN ft1.c1 IS NULL; ALTER FOREIGN TABLE ft1 ADD COLUMN c4 integer; ALTER FOREIGN TABLE ft1 ADD COLUMN c5 integer DEFAULT 0; +ALTER FOREIGN TABLE ft1 ADD COLUMN IF NOT EXISTS c5 integer; +NOTICE: column "c5" of relation "ft1" already exists, skipping ALTER FOREIGN TABLE ft1 ADD COLUMN c6 integer; ALTER FOREIGN TABLE ft1 ADD COLUMN c7 integer NOT NULL; ALTER FOREIGN TABLE ft1 ADD COLUMN c8 integer; ALTER FOREIGN TABLE ft1 ADD COLUMN c9 integer; ALTER FOREIGN TABLE ft1 ADD COLUMN c10 integer OPTIONS (p1 'v1'); +ALTER FOREIGN TABLE ft1 ADD c11 integer; -- omit COLUMN +ALTER FOREIGN TABLE ft1 DROP c11; -- omit COLUMN ALTER FOREIGN TABLE ft1 ALTER COLUMN c4 SET DEFAULT 0; ALTER FOREIGN TABLE ft1 ALTER COLUMN c5 DROP DEFAULT; ALTER FOREIGN TABLE ft1 ALTER COLUMN c6 SET NOT NULL; @@ -896,6 +900,8 @@ ALTER FOREIGN TABLE ft1 DROP COLUMN no_column; -- ERROR ERROR: column "no_column" of relation "ft1" does not exist ALTER FOREIGN TABLE ft1 DROP COLUMN IF EXISTS no_column; NOTICE: column "no_column" of relation "ft1" does not exist, skipping +ALTER FOREIGN TABLE ft1 DROP IF EXISTS no_column; +NOTICE: column "no_column" of relation "ft1" does not exist, skipping ALTER FOREIGN TABLE ft1 DROP COLUMN c9; ALTER FOREIGN TABLE ft1 ADD COLUMN c11 serial; ALTER FOREIGN TABLE ft1 SET SCHEMA foreign_schema; diff --git a/src/test/regress/sql/foreign_data.sql b/src/test/regress/sql/foreign_data.sql index aa147b14a90..7ad19f6a341 100644 --- a/src/test/regress/sql/foreign_data.sql +++ b/src/test/regress/sql/foreign_data.sql @@ -382,11 +382,14 @@ COMMENT ON COLUMN ft1.c1 IS NULL; ALTER FOREIGN TABLE ft1 ADD COLUMN c4 integer; ALTER FOREIGN TABLE ft1 ADD COLUMN c5 integer DEFAULT 0; +ALTER FOREIGN TABLE ft1 ADD COLUMN IF NOT EXISTS c5 integer; ALTER FOREIGN TABLE ft1 ADD COLUMN c6 integer; ALTER FOREIGN TABLE ft1 ADD COLUMN c7 integer NOT NULL; ALTER FOREIGN TABLE ft1 ADD COLUMN c8 integer; ALTER FOREIGN TABLE ft1 ADD COLUMN c9 integer; ALTER FOREIGN TABLE ft1 ADD COLUMN c10 integer OPTIONS (p1 'v1'); +ALTER FOREIGN TABLE ft1 ADD c11 integer; -- omit COLUMN +ALTER FOREIGN TABLE ft1 DROP c11; -- omit COLUMN ALTER FOREIGN TABLE ft1 ALTER COLUMN c4 SET DEFAULT 0; ALTER FOREIGN TABLE ft1 ALTER COLUMN c5 DROP DEFAULT; @@ -418,6 +421,7 @@ ALTER FOREIGN TABLE ft1 OWNER TO regress_test_role; ALTER FOREIGN TABLE ft1 OPTIONS (DROP delimiter, SET quote '~', ADD escape '@'); ALTER FOREIGN TABLE ft1 DROP COLUMN no_column; -- ERROR ALTER FOREIGN TABLE ft1 DROP COLUMN IF EXISTS no_column; +ALTER FOREIGN TABLE ft1 DROP IF EXISTS no_column; ALTER FOREIGN TABLE ft1 DROP COLUMN c9; ALTER FOREIGN TABLE ft1 ADD COLUMN c11 serial; ALTER FOREIGN TABLE ft1 SET SCHEMA foreign_schema; -- 2.50.1 (Apple Git-155)