From 1635e80d30b16df98aebead12f2b82f17efd9bc8 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Tue, 26 Sep 2017 13:12:03 -0400 Subject: [PATCH] Use a blacklist to distinguish original from add-on enum values. Commit 15bc038f9 allowed ALTER TYPE ADD VALUE to be executed inside transaction blocks, by disallowing the use of the added value later in the same transaction, except under limited circumstances. However, the test for "limited circumstances" was heuristic and could reject references to enum values that were created during CREATE TYPE AS ENUM, not just later. This breaks the use-case of restoring pg_dump scripts in a single transaction, as reported in bug #14825 from Balazs Szilfai. We can improve this by keeping a "blacklist" table of enum value OIDs created by ALTER TYPE ADD VALUE during the current transaction. Any visible-but-uncommitted value whose OID is not in the blacklist must have been created by CREATE TYPE AS ENUM, and can be used safely because it could not have a lifespan shorter than its parent enum type. This change also removes the restriction that a renamed enum value can't be used before being committed (unless it was on the blacklist). Andrew Dunstan, with cosmetic improvements by me. Back-patch to v10. Discussion: https://postgr.es/m/20170922185904.1448.16585@wrigleys.postgresql.org --- doc/src/sgml/ref/alter_type.sgml | 2 - src/backend/access/transam/xact.c | 4 ++ src/backend/catalog/pg_enum.c | 64 ++++++++++++++++++++++++++++++ src/backend/utils/adt/enum.c | 9 +++++ src/include/catalog/pg_enum.h | 2 + src/test/regress/expected/enum.out | 21 ++++++++++ src/test/regress/sql/enum.sql | 13 ++++++ 7 files changed, 113 insertions(+), 2 deletions(-) diff --git a/doc/src/sgml/ref/alter_type.sgml b/doc/src/sgml/ref/alter_type.sgml index d65f70f674..446e08b175 100644 --- a/doc/src/sgml/ref/alter_type.sgml +++ b/doc/src/sgml/ref/alter_type.sgml @@ -294,8 +294,6 @@ ALTER TYPE name RENAME VALUE diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c index 93dca7a72a..52408fc6b0 100644 --- a/src/backend/access/transam/xact.c +++ b/src/backend/access/transam/xact.c @@ -32,6 +32,7 @@ #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" @@ -2128,6 +2129,7 @@ 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(); @@ -2406,6 +2408,7 @@ 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(); @@ -2608,6 +2611,7 @@ AbortTransaction(void) AtEOXact_GUC(false, 1); AtEOXact_SPI(false); + AtEOXact_Enum(); AtEOXact_on_commit_actions(false); AtEOXact_Namespace(false, is_parallel_worker); AtEOXact_SMgr(); diff --git a/src/backend/catalog/pg_enum.c b/src/backend/catalog/pg_enum.c index fe61d4dacc..0f7b36e11d 100644 --- a/src/backend/catalog/pg_enum.c +++ b/src/backend/catalog/pg_enum.c @@ -28,6 +28,8 @@ #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" @@ -35,6 +37,17 @@ /* 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); @@ -460,6 +473,24 @@ 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); } @@ -547,6 +578,39 @@ 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. diff --git a/src/backend/utils/adt/enum.c b/src/backend/utils/adt/enum.c index 973397cc85..401e7299fa 100644 --- a/src/backend/utils/adt/enum.c +++ b/src/backend/utils/adt/enum.c @@ -76,6 +76,15 @@ check_safe_enum_use(HeapTuple enumval_tup) 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; + /* It is a new enum value, so check to see if the whole enum is new */ en = (Form_pg_enum) GETSTRUCT(enumval_tup); enumtyp_tup = SearchSysCache1(TYPEOID, ObjectIdGetDatum(en->enumtypid)); diff --git a/src/include/catalog/pg_enum.h b/src/include/catalog/pg_enum.h index 5938ba5cac..dff3d2f481 100644 --- a/src/include/catalog/pg_enum.h +++ b/src/include/catalog/pg_enum.h @@ -69,5 +69,7 @@ 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 */ diff --git a/src/test/regress/expected/enum.out b/src/test/regress/expected/enum.out index 0e6030443f..6bbe488736 100644 --- a/src/test/regress/expected/enum.out +++ b/src/test/regress/expected/enum.out @@ -633,8 +633,29 @@ 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. +ROLLBACK; +-- but a renamed value is safe to use later in same transaction +BEGIN; +ALTER TYPE bogus RENAME VALUE 'good' to 'bad'; +SELECT 'bad'::bogus; + bogus +------- + bad +(1 row) + ROLLBACK; DROP TYPE bogus; +-- check that values created during CREATE TYPE can be used in any case +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; -- check that we can add new values to existing enums in a transaction -- and use them, if the type is new as well BEGIN; diff --git a/src/test/regress/sql/enum.sql b/src/test/regress/sql/enum.sql index d7e87143a0..eb464a72c5 100644 --- a/src/test/regress/sql/enum.sql +++ b/src/test/regress/sql/enum.sql @@ -300,8 +300,21 @@ ALTER TYPE bogon ADD VALUE 'bad'; SELECT 'bad'::bogon; ROLLBACK; +-- but a renamed value is safe to use later in same transaction +BEGIN; +ALTER TYPE bogus RENAME VALUE 'good' to 'bad'; +SELECT 'bad'::bogus; +ROLLBACK; + DROP TYPE bogus; +-- check that values created during CREATE TYPE can be used in any case +BEGIN; +CREATE TYPE bogus AS ENUM('good','bad','ugly'); +ALTER TYPE bogus RENAME TO bogon; +select enum_range(null::bogon); +ROLLBACK; + -- check that we can add new values to existing enums in a transaction -- and use them, if the type is new as well BEGIN; -- 2.40.0