dropenum.diff

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Format: unified

File	+	−
src/backend/parser/gram.y	23	0
src/test/regress/expected/enum.out	5	0
src/test/regress/sql/enum.sql	3	0

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 7d2032885e..f8d70cdaa0 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -6404,6 +6404,29 @@ AlterEnumStmt:
 				n->skipIfNewValExists = false;
 				$$ = (Node *) n;
 			}
+		 | ALTER TYPE_P any_name DROP VALUE_P Sconst
+			{
+				/*
+				 * The following problems must be solved before this can be
+				 * implemented:
+				 *
+				 * - There can be no data of this type using this value in
+				 *   any table
+				 *
+				 * - The value may not appear in any non-leaf page of a
+				 *   btree (and similar issues with other index types)
+				 *
+				 * - Concurrent sessions must not be able to insert this
+				 *   value while the preceding conditions are being checked
+				 *
+				 * - Possibly more...
+				 */
+
+				ereport(ERROR,
+						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+						 errmsg("dropping an enum value is not yet implemented"),
+						 parser_errposition(@4)));
+			}
 		 ;
 
 opt_if_not_exists: IF_P NOT EXISTS              { $$ = true; }
diff --git a/src/test/regress/expected/enum.out b/src/test/regress/expected/enum.out
index 01159688e5..105ae7a2f9 100644
--- a/src/test/regress/expected/enum.out
+++ b/src/test/regress/expected/enum.out
@@ -605,6 +605,11 @@ 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
+-- We still can't drop an enum value
+ALTER TYPE rainbow DROP VALUE 'green';
+ERROR:  dropping an enum value is not yet implemented
+LINE 1: ALTER TYPE rainbow DROP VALUE 'green';
+                           ^
 --
 -- 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 93171379f2..a98df40ed8 100644
--- a/src/test/regress/sql/enum.sql
+++ b/src/test/regress/sql/enum.sql
@@ -276,6 +276,9 @@ ALTER TYPE rainbow RENAME VALUE 'red' TO 'crimson';
 -- check that renaming to an existent value fails
 ALTER TYPE rainbow RENAME VALUE 'blue' TO 'green';
 
+-- We still can't drop an enum value
+ALTER TYPE rainbow DROP VALUE 'green';
+
 --
 -- check transactional behaviour of ALTER TYPE ... ADD VALUE
 --