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Revert to 9.6 treatment of ALTER TYPE enumtype ADD VALUE.

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This reverts commit 15bc038f9, along with the followon commits 1635e80d3
and 984c92074 that tried to clean up the problems exposed by bug #14825.
The result was incomplete because it failed to address parallel-query
requirements.  With 10.0 release so close upon us, now does not seem like
the time to be adding more code to fix that.  I hope we can un-revert this
code and add the missing parallel query support during the v11 cycle.

Back-patch to v10.

Discussion: https://postgr.es/m/20170922185904.1448.16585@wrigleys.postgresql.org
This commit is contained in:
Tom Lane
2017-09-27 16:14:37 -04:00
parent 65c8656202
commit 28e0727076
11 changed files with 49 additions and 270 deletions
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5
doc/src/sgml/ref/alter_type.sgml
View File

@ -290,9 +290,8 @@ ALTER TYPE <replaceable class="PARAMETER">name</replaceable> RENAME VALUE <repla
<title>Notes</title>
<para>
If <command>ALTER TYPE ... ADD VALUE</> (the form that adds a new value to
an enum type) is executed inside a transaction block, the new value cannot
be used until after the transaction has been committed.
<command>ALTER TYPE ... ADD VALUE</> (the form that adds a new value to an
enum type) cannot be executed inside a transaction block.
</para>
<para>

4
src/backend/access/transam/xact.c
View File

@ -32,7 +32,6 @@
#include "access/xlogutils.h"
#include "catalog/catalog.h"
#include "catalog/namespace.h"
#include "catalog/pg_enum.h"
#include "catalog/storage.h"
#include "commands/async.h"
#include "commands/tablecmds.h"
@ -2129,7 +2128,6 @@ CommitTransaction(void)
AtCommit_Notify();
AtEOXact_GUC(true, 1);
AtEOXact_SPI(true);
AtEOXact_Enum();
AtEOXact_on_commit_actions(true);
AtEOXact_Namespace(true, is_parallel_worker);
AtEOXact_SMgr();
@ -2408,7 +2406,6 @@ PrepareTransaction(void)
/* PREPARE acts the same as COMMIT as far as GUC is concerned */
AtEOXact_GUC(true, 1);
AtEOXact_SPI(true);
AtEOXact_Enum();
AtEOXact_on_commit_actions(true);
AtEOXact_Namespace(true, false);
AtEOXact_SMgr();
@ -2611,7 +2608,6 @@ AbortTransaction(void)
AtEOXact_GUC(false, 1);
AtEOXact_SPI(false);
AtEOXact_Enum();
AtEOXact_on_commit_actions(false);
AtEOXact_Namespace(false, is_parallel_worker);
AtEOXact_SMgr();

64
src/backend/catalog/pg_enum.c
View File

@ -28,8 +28,6 @@
#include "utils/builtins.h"
#include "utils/catcache.h"
#include "utils/fmgroids.h"
#include "utils/hsearch.h"
#include "utils/memutils.h"
#include "utils/syscache.h"
#include "utils/tqual.h"
@ -37,17 +35,6 @@
/* Potentially set by pg_upgrade_support functions */
Oid binary_upgrade_next_pg_enum_oid = InvalidOid;
/*
* Hash table of enum value OIDs created during the current transaction by
* AddEnumLabel. We disallow using these values until the transaction is
* committed; otherwise, they might get into indexes where we can't clean
* them up, and then if the transaction rolls back we have a broken index.
* (See comments for check_safe_enum_use() in enum.c.) Values created by
* EnumValuesCreate are *not* blacklisted; we assume those are created during
* CREATE TYPE, so they can't go away unless the enum type itself does.
*/
static HTAB *enum_blacklist = NULL;
static void RenumberEnumType(Relation pg_enum, HeapTuple *existing, int nelems);
static int sort_order_cmp(const void *p1, const void *p2);
@ -473,24 +460,6 @@ restart:
heap_freetuple(enum_tup);
heap_close(pg_enum, RowExclusiveLock);
/* Set up the blacklist hash if not already done in this transaction */
if (enum_blacklist == NULL)
{
HASHCTL hash_ctl;
memset(&hash_ctl, 0, sizeof(hash_ctl));
hash_ctl.keysize = sizeof(Oid);
hash_ctl.entrysize = sizeof(Oid);
hash_ctl.hcxt = TopTransactionContext;
enum_blacklist = hash_create("Enum value blacklist",
32,
&hash_ctl,
HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
}
/* Add the new value to the blacklist */
(void) hash_search(enum_blacklist, &newOid, HASH_ENTER, NULL);
}
@ -578,39 +547,6 @@ RenameEnumLabel(Oid enumTypeOid,
}
/*
* Test if the given enum value is on the blacklist
*/
bool
EnumBlacklisted(Oid enum_id)
{
bool found;
/* If we've made no blacklist table, all values are safe */
if (enum_blacklist == NULL)
return false;
/* Else, is it in the table? */
(void) hash_search(enum_blacklist, &enum_id, HASH_FIND, &found);
return found;
}
/*
* Clean up enum stuff after end of top-level transaction.
*/
void
AtEOXact_Enum(void)
{
/*
* Reset the blacklist table, as all our enum values are now committed.
* The memory will go away automatically when TopTransactionContext is
* freed; it's sufficient to clear our pointer.
*/
enum_blacklist = NULL;
}
/*
* RenumberEnumType
* Renumber existing enum elements to have sort positions 1..n.

29
src/backend/commands/typecmds.c
View File

@ -1222,10 +1222,10 @@ DefineEnum(CreateEnumStmt *stmt)
/*
* AlterEnum
* Adds a new label to an existing enum.
* ALTER TYPE on an enum.
*/
ObjectAddress
AlterEnum(AlterEnumStmt *stmt)
AlterEnum(AlterEnumStmt *stmt, bool isTopLevel)
{
Oid enum_type_oid;
TypeName *typename;
@ -1243,8 +1243,6 @@ AlterEnum(AlterEnumStmt *stmt)
/* Check it's an enum and check user has permission to ALTER the enum */
checkEnumOwner(tup);
ReleaseSysCache(tup);
if (stmt->oldVal)
{
/* Rename an existing label */
@ -1253,6 +1251,27 @@ AlterEnum(AlterEnumStmt *stmt)
else
{
/* Add a new label */
/*
* 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");
AddEnumLabel(enum_type_oid, stmt->newVal,
stmt->newValNeighbor, stmt->newValIsAfter,
stmt->skipIfNewValExists);
@ -1262,6 +1281,8 @@ AlterEnum(AlterEnumStmt *stmt)
ObjectAddressSet(address, TypeRelationId, enum_type_oid);
ReleaseSysCache(tup);
return address;
}

2
src/backend/tcop/utility.c
View File

@ -1412,7 +1412,7 @@ ProcessUtilitySlow(ParseState *pstate,
break;
case T_AlterEnumStmt: /* ALTER TYPE (enum) */
address = AlterEnum((AlterEnumStmt *) parsetree);
address = AlterEnum((AlterEnumStmt *) parsetree, isTopLevel);
break;
case T_ViewStmt: /* CREATE VIEW */

90
src/backend/utils/adt/enum.c
View File

@ -19,7 +19,6 @@
#include "catalog/indexing.h"
#include "catalog/pg_enum.h"
#include "libpq/pqformat.h"
#include "storage/procarray.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
@ -32,79 +31,6 @@ static Oid enum_endpoint(Oid enumtypoid, ScanDirection direction);
static ArrayType *enum_range_internal(Oid enumtypoid, Oid lower, Oid upper);
/*
* Disallow use of an uncommitted pg_enum tuple.
*
* We need to make sure that uncommitted enum values don't get into indexes.
* If they did, and if we then rolled back the pg_enum addition, we'd have
* broken the index because value comparisons will not work reliably without
* an underlying pg_enum entry. (Note that removal of the heap entry
* containing an enum value is not sufficient to ensure that it doesn't appear
* in upper levels of indexes.) To do this we prevent an uncommitted row from
* being used for any SQL-level purpose. This is stronger than necessary,
* since the value might not be getting inserted into a table or there might
* be no index on its column, but it's easy to enforce centrally.
*
* However, it's okay to allow use of uncommitted values belonging to enum
* types that were themselves created in the same transaction, because then
* any such index would also be new and would go away altogether on rollback.
* We don't implement that fully right now, but we do allow free use of enum
* values created during CREATE TYPE AS ENUM, which are surely of the same
* lifespan as the enum type. (This case is required by "pg_restore -1".)
* Values added by ALTER TYPE ADD VALUE are currently restricted, but could
* be allowed if the enum type could be proven to have been created earlier
* in the same transaction. (Note that comparing tuple xmins would not work
* for that, because the type tuple might have been updated in the current
* transaction. Subtransactions also create hazards to be accounted for.)
*
* This function needs to be called (directly or indirectly) in any of the
* functions below that could return an enum value to SQL operations.
*/
static void
check_safe_enum_use(HeapTuple enumval_tup)
{
TransactionId xmin;
Form_pg_enum en;
/*
* If the row is hinted as committed, it's surely safe. This provides a
* fast path for all normal use-cases.
*/
if (HeapTupleHeaderXminCommitted(enumval_tup->t_data))
return;
/*
* Usually, a row would get hinted as committed when it's read or loaded
* into syscache; but just in case not, let's check the xmin directly.
*/
xmin = HeapTupleHeaderGetXmin(enumval_tup->t_data);
if (!TransactionIdIsInProgress(xmin) &&
TransactionIdDidCommit(xmin))
return;
/*
* Check if the enum value is blacklisted. If not, it's safe, because it
* was made during CREATE TYPE AS ENUM and can't be shorter-lived than its
* owning type. (This'd also be false for values made by other
* transactions; but the previous tests should have handled all of those.)
*/
if (!EnumBlacklisted(HeapTupleGetOid(enumval_tup)))
return;
/*
* There might well be other tests we could do here to narrow down the
* unsafe conditions, but for now just raise an exception.
*/
en = (Form_pg_enum) GETSTRUCT(enumval_tup);
ereport(ERROR,
(errcode(ERRCODE_UNSAFE_NEW_ENUM_VALUE_USAGE),
errmsg("unsafe use of new value \"%s\" of enum type %s",
NameStr(en->enumlabel),
format_type_be(en->enumtypid)),
errhint("New enum values must be committed before they can be used.")));
}
/* Basic I/O support */
Datum
@ -133,9 +59,6 @@ enum_in(PG_FUNCTION_ARGS)
format_type_be(enumtypoid),
name)));
/* check it's safe to use in SQL */
check_safe_enum_use(tup);
/*
* This comes from pg_enum.oid and stores system oids in user tables. This
* oid must be preserved by binary upgrades.
@ -201,9 +124,6 @@ enum_recv(PG_FUNCTION_ARGS)
format_type_be(enumtypoid),
name)));
/* check it's safe to use in SQL */
check_safe_enum_use(tup);
enumoid = HeapTupleGetOid(tup);
ReleaseSysCache(tup);
@ -411,16 +331,9 @@ enum_endpoint(Oid enumtypoid, ScanDirection direction)
enum_tuple = systable_getnext_ordered(enum_scan, direction);
if (HeapTupleIsValid(enum_tuple))
{
/* check it's safe to use in SQL */
check_safe_enum_use(enum_tuple);
minmax = HeapTupleGetOid(enum_tuple);
}
else
{
/* should only happen with an empty enum */
minmax = InvalidOid;
}
systable_endscan_ordered(enum_scan);
index_close(enum_idx, AccessShareLock);
@ -581,9 +494,6 @@ enum_range_internal(Oid enumtypoid, Oid lower, Oid upper)
if (left_found)
{
/* check it's safe to use in SQL */
check_safe_enum_use(enum_tuple);
if (cnt >= max)
{
max *= 2;

1
src/backend/utils/errcodes.txt
View File

@ -400,7 +400,6 @@ Section: Class 55 - Object Not In Prerequisite State
55006 E ERRCODE_OBJECT_IN_USE object_in_use
55P02 E ERRCODE_CANT_CHANGE_RUNTIME_PARAM cant_change_runtime_param
55P03 E ERRCODE_LOCK_NOT_AVAILABLE lock_not_available
55P04 E ERRCODE_UNSAFE_NEW_ENUM_VALUE_USAGE unsafe_new_enum_value_usage
Section: Class 57 - Operator Intervention

2
src/include/catalog/pg_enum.h
View File

@ -69,7 +69,5 @@ extern void AddEnumLabel(Oid enumTypeOid, const char *newVal,
bool skipIfExists);
extern void RenameEnumLabel(Oid enumTypeOid,
const char *oldVal, const char *newVal);
extern bool EnumBlacklisted(Oid enum_id);
extern void AtEOXact_Enum(void);
#endif /* PG_ENUM_H */

2
src/include/commands/typecmds.h
View File

@ -26,7 +26,7 @@ extern void RemoveTypeById(Oid typeOid);
extern ObjectAddress DefineDomain(CreateDomainStmt *stmt);
extern ObjectAddress DefineEnum(CreateEnumStmt *stmt);
extern ObjectAddress DefineRange(CreateRangeStmt *stmt);
extern ObjectAddress AlterEnum(AlterEnumStmt *stmt);
extern ObjectAddress AlterEnum(AlterEnumStmt *stmt, bool isTopLevel);
extern ObjectAddress DefineCompositeType(RangeVar *typevar, List *coldeflist);
extern Oid AssignTypeArrayOid(void);

78
src/test/regress/expected/enum.out
View File

@ -581,60 +581,19 @@ ERROR: enum label "green" already exists
-- check transactional behaviour of ALTER TYPE ... ADD VALUE
--
CREATE TYPE bogus AS ENUM('good');
-- check that we can add new values to existing enums in a transaction
-- but we can't use them
-- check that we can't add new values to existing enums in a transaction
BEGIN;
ALTER TYPE bogus ADD VALUE 'new';
SAVEPOINT x;
SELECT 'new'::bogus; -- unsafe
ERROR: unsafe use of new value "new" of enum type bogus
LINE 1: SELECT 'new'::bogus;
^
HINT: New enum values must be committed before they can be used.
ROLLBACK TO x;
SELECT enum_first(null::bogus); -- safe
enum_first
------------
good
(1 row)
SELECT enum_last(null::bogus); -- unsafe
ERROR: unsafe use of new value "new" of enum type bogus
HINT: New enum values must be committed before they can be used.
ROLLBACK TO x;
SELECT enum_range(null::bogus); -- unsafe
ERROR: unsafe use of new value "new" of enum type bogus
HINT: New enum values must be committed before they can be used.
ROLLBACK TO x;
ALTER TYPE bogus ADD VALUE 'bad';
ERROR: ALTER TYPE ... ADD cannot run inside a transaction block
COMMIT;
SELECT 'new'::bogus; -- now safe
bogus
-------
new
(1 row)
SELECT enumlabel, enumsortorder
FROM pg_enum
WHERE enumtypid = 'bogus'::regtype
ORDER BY 2;
enumlabel | enumsortorder
-----------+---------------
good | 1
new | 2
(2 rows)
-- check that we recognize the case where the enum already existed but was
-- modified in the current txn; this should not be considered safe
-- modified in the current txn
BEGIN;
ALTER TYPE bogus RENAME TO bogon;
ALTER TYPE bogon ADD VALUE 'bad';
SELECT 'bad'::bogon;
ERROR: unsafe use of new value "bad" of enum type bogon
LINE 1: SELECT 'bad'::bogon;
^
HINT: New enum values must be committed before they can be used.
ERROR: ALTER TYPE ... ADD cannot run inside a transaction block
ROLLBACK;
-- but a renamed value is safe to use later in same transaction
-- but ALTER TYPE RENAME VALUE is safe in a transaction
BEGIN;
ALTER TYPE bogus RENAME VALUE 'good' to 'bad';
SELECT 'bad'::bogus;
@ -645,27 +604,12 @@ SELECT 'bad'::bogus;
ROLLBACK;
DROP TYPE bogus;
-- check that values created during CREATE TYPE can be used in any case
-- check that we *can* add new values to existing enums in a transaction,
-- if the type is new as well
BEGIN;
CREATE TYPE bogus AS ENUM('good','bad','ugly');
ALTER TYPE bogus RENAME TO bogon;
select enum_range(null::bogon);
enum_range
-----------------
{good,bad,ugly}
(1 row)
ROLLBACK;
-- ideally, we'd allow this usage; but it requires keeping track of whether
-- the enum type was created in the current transaction, which is expensive
BEGIN;
CREATE TYPE bogus AS ENUM('good');
ALTER TYPE bogus RENAME TO bogon;
ALTER TYPE bogon ADD VALUE 'bad';
ALTER TYPE bogon ADD VALUE 'ugly';
select enum_range(null::bogon); -- fails
ERROR: unsafe use of new value "bad" of enum type bogon
HINT: New enum values must be committed before they can be used.
CREATE TYPE bogus AS ENUM();
ALTER TYPE bogus ADD VALUE 'good';
ALTER TYPE bogus ADD VALUE 'ugly';
ROLLBACK;
--
-- Cleanup

42
src/test/regress/sql/enum.sql
View File

@ -273,34 +273,19 @@ ALTER TYPE rainbow RENAME VALUE 'blue' TO 'green';
--
CREATE TYPE bogus AS ENUM('good');
-- check that we can add new values to existing enums in a transaction
-- but we can't use them
-- check that we can't add new values to existing enums in a transaction
BEGIN;
ALTER TYPE bogus ADD VALUE 'new';
SAVEPOINT x;
SELECT 'new'::bogus; -- unsafe
ROLLBACK TO x;
SELECT enum_first(null::bogus); -- safe
SELECT enum_last(null::bogus); -- unsafe
ROLLBACK TO x;
SELECT enum_range(null::bogus); -- unsafe
ROLLBACK TO x;
ALTER TYPE bogus ADD VALUE 'bad';
COMMIT;
SELECT 'new'::bogus; -- now safe
SELECT enumlabel, enumsortorder
FROM pg_enum
WHERE enumtypid = 'bogus'::regtype
ORDER BY 2;
-- check that we recognize the case where the enum already existed but was
-- modified in the current txn; this should not be considered safe
-- modified in the current txn
BEGIN;
ALTER TYPE bogus RENAME TO bogon;
ALTER TYPE bogon ADD VALUE 'bad';
SELECT 'bad'::bogon;
ROLLBACK;
-- but a renamed value is safe to use later in same transaction
-- but ALTER TYPE RENAME VALUE is safe in a transaction
BEGIN;
ALTER TYPE bogus RENAME VALUE 'good' to 'bad';
SELECT 'bad'::bogus;
@ -308,21 +293,12 @@ ROLLBACK;
DROP TYPE bogus;
-- check that values created during CREATE TYPE can be used in any case
-- check that we *can* add new values to existing enums in a transaction,
-- if the type is new as well
BEGIN;
CREATE TYPE bogus AS ENUM('good','bad','ugly');
ALTER TYPE bogus RENAME TO bogon;
select enum_range(null::bogon);
ROLLBACK;
-- ideally, we'd allow this usage; but it requires keeping track of whether
-- the enum type was created in the current transaction, which is expensive
BEGIN;
CREATE TYPE bogus AS ENUM('good');
ALTER TYPE bogus RENAME TO bogon;
ALTER TYPE bogon ADD VALUE 'bad';
ALTER TYPE bogon ADD VALUE 'ugly';
select enum_range(null::bogon); -- fails
CREATE TYPE bogus AS ENUM();
ALTER TYPE bogus ADD VALUE 'good';
ALTER TYPE bogus ADD VALUE 'ugly';
ROLLBACK;
--