diff options
Diffstat (limited to 'src/backend/commands')
| -rw-r--r-- | src/backend/commands/typecmds.c | 23 |
1 files changed, 21 insertions, 2 deletions
diff --git a/src/backend/commands/typecmds.c b/src/backend/commands/typecmds.c index 8418096c308..36de6d7e28b 100644 --- a/src/backend/commands/typecmds.c +++ b/src/backend/commands/typecmds.c @@ -1169,7 +1169,7 @@ DefineEnum(CreateEnumStmt *stmt) * Adds a new label to an existing enum. */ void -AlterEnum(AlterEnumStmt *stmt) +AlterEnum(AlterEnumStmt *stmt, bool isTopLevel) { Oid enum_type_oid; TypeName *typename; @@ -1183,12 +1183,31 @@ AlterEnum(AlterEnumStmt *stmt) if (!HeapTupleIsValid(tup)) elog(ERROR, "cache lookup failed for type %u", enum_type_oid); + /* + * Ordinarily we disallow adding values within transaction blocks, because + * we can't cope with enum OID values getting into indexes and then having + * their defining pg_enum entries go away. However, it's okay if the enum + * type was created in the current transaction, since then there can be + * no such indexes that wouldn't themselves go away on rollback. (We + * support this case because pg_dump --binary-upgrade needs it.) We test + * this by seeing if the pg_type row has xmin == current XID and is not + * HEAP_UPDATED. If it is HEAP_UPDATED, we can't be sure whether the + * type was created or only modified in this xact. So we are disallowing + * some cases that could theoretically be safe; but fortunately pg_dump + * only needs the simplest case. + */ + if (HeapTupleHeaderGetXmin(tup->t_data) == GetCurrentTransactionId() && + !(tup->t_data->t_infomask & HEAP_UPDATED)) + /* safe to do inside transaction block */ ; + else + PreventTransactionChain(isTopLevel, "ALTER TYPE ... ADD"); + /* Check it's an enum and check user has permission to ALTER the enum */ checkEnumOwner(tup); /* Add the new label */ AddEnumLabel(enum_type_oid, stmt->newVal, - stmt->newValNeighbor, stmt->newValIsAfter, + stmt->newValNeighbor, stmt->newValIsAfter, stmt->skipIfExists); ReleaseSysCache(tup); |