Support renaming an existing value of an enum type.

Not much to be said about this patch: it does what it says on the tin.

In passing, rename AlterEnumStmt.skipIfExists to skipIfNewValExists
to clarify what it actually does.  In the discussion of this patch
we considered supporting other similar options, such as IF EXISTS
on the type as a whole or IF NOT EXISTS on the target name.  This
patch doesn't actually add any such feature, but it might happen later.

Dagfinn Ilmari Mannsåker, reviewed by Emre Hasegeli

Discussion: <CAO=2mx6uvgPaPDf-rHqG8=1MZnGyVDMQeh8zS4euRyyg4D35OQ@mail.gmail.com>

2 files changed, 33 insertions, 0 deletions

diff --git a/src/test/regress/expected/enum.out b/src/test/regress/expected/enum.out
index d4a45a306bc..514d1d01a10 100644
--- a/src/test/regress/expected/enum.out
+++ b/src/test/regress/expected/enum.out
@@ -556,6 +556,28 @@ CREATE TABLE enumtest_bogus_child(parent bogus REFERENCES enumtest_parent);
 ERROR:  foreign key constraint "enumtest_bogus_child_parent_fkey" cannot be implemented
 DETAIL:  Key columns "parent" and "id" are of incompatible types: bogus and rainbow.
 DROP TYPE bogus;
+-- check renaming a value
+ALTER TYPE rainbow RENAME VALUE 'red' TO 'crimson';
+SELECT enumlabel, enumsortorder
+FROM pg_enum
+WHERE enumtypid = 'rainbow'::regtype
+ORDER BY 2;
+ enumlabel | enumsortorder 
+-----------+---------------
+ crimson   |             1
+ orange    |             2
+ yellow    |             3
+ green     |             4
+ blue      |             5
+ purple    |             6
+(6 rows)
+
+-- check that renaming a non-existent value fails
+ALTER TYPE rainbow RENAME VALUE 'red' TO 'crimson';
+ERROR:  "red" is not an existing enum label
+-- check that renaming to an existent value fails
+ALTER TYPE rainbow RENAME VALUE 'blue' TO 'green';
+ERROR:  enum label "green" already exists
 --
 -- check transactional behaviour of ALTER TYPE ... ADD VALUE
 --
diff --git a/src/test/regress/sql/enum.sql b/src/test/regress/sql/enum.sql
index d25e8dedb6c..d7e87143a01 100644
--- a/src/test/regress/sql/enum.sql
+++ b/src/test/regress/sql/enum.sql
@@ -257,6 +257,17 @@ CREATE TYPE bogus AS ENUM('good', 'bad', 'ugly');
 CREATE TABLE enumtest_bogus_child(parent bogus REFERENCES enumtest_parent);
 DROP TYPE bogus;
 
+-- check renaming a value
+ALTER TYPE rainbow RENAME VALUE 'red' TO 'crimson';
+SELECT enumlabel, enumsortorder
+FROM pg_enum
+WHERE enumtypid = 'rainbow'::regtype
+ORDER BY 2;
+-- check that renaming a non-existent value fails
+ALTER TYPE rainbow RENAME VALUE 'red' TO 'crimson';
+-- check that renaming to an existent value fails
+ALTER TYPE rainbow RENAME VALUE 'blue' TO 'green';
+
 --
 -- check transactional behaviour of ALTER TYPE ... ADD VALUE
 --