From 0a482f6d7434964ce51f66c260bde4a74dac4da0 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Dagfinn=20Ilmari=20Manns=C3=A5ker?= Date: Thu, 24 Mar 2016 17:50:58 +0000 Subject: [PATCH] Add ALTER TYPE ... ALTER VALUE '...' TO '...' Unlike adding values, altering a value can be done in a transaction, since it doesn't affect the OID values or ordering, so is safe to rollback. TODO: documentation, IF (NOT) EXISTS support(?) --- src/backend/catalog/pg_enum.c | 88 ++++++++++++++++++++++++++++++++++++++ src/backend/commands/typecmds.c | 50 ++++++++++++---------- src/backend/parser/gram.y | 14 ++++++ src/include/catalog/pg_enum.h | 2 + src/include/nodes/parsenodes.h | 1 + src/test/regress/expected/enum.out | 58 +++++++++++++++++++++++++ src/test/regress/sql/enum.sql | 27 ++++++++++++ 7 files changed, 218 insertions(+), 22 deletions(-) diff --git a/src/backend/catalog/pg_enum.c b/src/backend/catalog/pg_enum.c index af89daa..1079e6c 100644 --- a/src/backend/catalog/pg_enum.c +++ b/src/backend/catalog/pg_enum.c @@ -464,6 +464,94 @@ restart: /* + * RenameEnumLabel + * Add a new label to the enum set. By default it goes at + * the end, but the user can choose to place it before or + * after any existing set member. + */ +void +RenameEnumLabel(Oid enumTypeOid, + const char *oldVal, + const char *newVal) +{ + Relation pg_enum; + HeapTuple old_tup = NULL; + HeapTuple enum_tup; + CatCList *list; + int nelems; + int nbr_index; + Form_pg_enum nbr_en; + bool found_new = false; + + /* check length of new label is ok */ + if (strlen(newVal) > (NAMEDATALEN - 1)) + ereport(ERROR, + (errcode(ERRCODE_INVALID_NAME), + errmsg("invalid enum label \"%s\"", newVal), + errdetail("Labels must be %d characters or less.", + NAMEDATALEN - 1))); + + /* + * Acquire a lock on the enum type, which we won't release until commit. + * This ensures that two backends aren't concurrently modifying the same + * enum type. Without that, we couldn't be sure to get a consistent view + * of the enum members via the syscache. Note that this does not block + * other backends from inspecting the type; see comments for + * RenumberEnumType. + */ + LockDatabaseObject(TypeRelationId, enumTypeOid, 0, ExclusiveLock); + + pg_enum = heap_open(EnumRelationId, RowExclusiveLock); + + /* Get the list of existing members of the enum */ + list = SearchSysCacheList1(ENUMTYPOIDNAME, + ObjectIdGetDatum(enumTypeOid)); + nelems = list->n_members; + + /* Locate the element to rename and check if the new label is already in + * use. The unique index on pg_enum would catch this anyway, but we + * prefer a friendlier error message. + */ + for (nbr_index = 0; nbr_index < nelems; nbr_index++) + { + enum_tup = &(list->members[nbr_index]->tuple); + nbr_en = (Form_pg_enum) GETSTRUCT(enum_tup); + + if (strcmp(NameStr(nbr_en->enumlabel), oldVal) == 0) + old_tup = enum_tup; + + if (strcmp(NameStr(nbr_en->enumlabel), newVal) == 0) + found_new = true; + } + if (!old_tup) + ereport(ERROR, + (errcode(ERRCODE_INVALID_PARAMETER_VALUE), + errmsg("\"%s\" is not an existing enum label", + oldVal))); + if (found_new) + ereport(ERROR, + (errcode(ERRCODE_DUPLICATE_OBJECT), + errmsg("enum label \"%s\" already exists", + newVal))); + + enum_tup = heap_copytuple(old_tup); + nbr_en = (Form_pg_enum) GETSTRUCT(enum_tup); + ReleaseCatCacheList(list); + + /* Update new pg_enum entry */ + namestrcpy(&nbr_en->enumlabel, newVal); + simple_heap_update(pg_enum, &enum_tup->t_self, enum_tup); + CatalogUpdateIndexes(pg_enum, enum_tup); + heap_freetuple(enum_tup); + + /* Make the updates visible */ + CommandCounterIncrement(); + + heap_close(pg_enum, RowExclusiveLock); +} + + +/* * RenumberEnumType * Renumber existing enum elements to have sort positions 1..n. * diff --git a/src/backend/commands/typecmds.c b/src/backend/commands/typecmds.c index 227d382..63f030b 100644 --- a/src/backend/commands/typecmds.c +++ b/src/backend/commands/typecmds.c @@ -1236,32 +1236,38 @@ AlterEnum(AlterEnumStmt *stmt, bool isTopLevel) 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"); + if (!stmt->oldVal) { + /* + * 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->skipIfExists); + if (stmt->oldVal) + /* Update the existing label */ + RenameEnumLabel(enum_type_oid, stmt->oldVal, stmt->newVal); + else + /* Add the new label */ + AddEnumLabel(enum_type_oid, stmt->newVal, + stmt->newValNeighbor, stmt->newValIsAfter, + stmt->skipIfExists); InvokeObjectPostAlterHook(TypeRelationId, enum_type_oid, 0); diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y index 1273352..b7fea7a 100644 --- a/src/backend/parser/gram.y +++ b/src/backend/parser/gram.y @@ -5253,6 +5253,7 @@ AlterEnumStmt: { AlterEnumStmt *n = makeNode(AlterEnumStmt); n->typeName = $3; + n->oldVal = NULL; n->newVal = $7; n->newValNeighbor = NULL; n->newValIsAfter = true; @@ -5263,6 +5264,7 @@ AlterEnumStmt: { AlterEnumStmt *n = makeNode(AlterEnumStmt); n->typeName = $3; + n->oldVal = NULL; n->newVal = $7; n->newValNeighbor = $9; n->newValIsAfter = false; @@ -5273,12 +5275,24 @@ AlterEnumStmt: { AlterEnumStmt *n = makeNode(AlterEnumStmt); n->typeName = $3; + n->oldVal = NULL; n->newVal = $7; n->newValNeighbor = $9; n->newValIsAfter = true; n->skipIfExists = $6; $$ = (Node *) n; } + | ALTER TYPE_P any_name ALTER VALUE_P Sconst TO Sconst + { + AlterEnumStmt *n = makeNode(AlterEnumStmt); + n->typeName = $3; + n->oldVal = $6; + n->newVal = $8; + n->newValNeighbor = NULL; + n->newValIsAfter = true; + n->skipIfExists = false; + $$ = (Node *) n; + } ; opt_if_not_exists: IF_P NOT EXISTS { $$ = true; } diff --git a/src/include/catalog/pg_enum.h b/src/include/catalog/pg_enum.h index dd32443..1a06482 100644 --- a/src/include/catalog/pg_enum.h +++ b/src/include/catalog/pg_enum.h @@ -67,5 +67,7 @@ extern void EnumValuesDelete(Oid enumTypeOid); extern void AddEnumLabel(Oid enumTypeOid, const char *newVal, const char *neighbor, bool newValIsAfter, bool skipIfExists); +extern void RenameEnumLabel(Oid enumTypeOid, const char *oldVal, + const char *newVal); #endif /* PG_ENUM_H */ diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h index 8b958b4..0fc65d4 100644 --- a/src/include/nodes/parsenodes.h +++ b/src/include/nodes/parsenodes.h @@ -2693,6 +2693,7 @@ typedef struct AlterEnumStmt NodeTag type; List *typeName; /* qualified name (list of Value strings) */ char *newVal; /* new enum value's name */ + char *oldVal; /* old enum value's name when renaming */ char *newValNeighbor; /* neighboring enum value, if specified */ bool newValIsAfter; /* place new enum value after neighbor? */ bool skipIfExists; /* no error if label already exists */ diff --git a/src/test/regress/expected/enum.out b/src/test/regress/expected/enum.out index 1a61a5b..39bf239 100644 --- a/src/test/regress/expected/enum.out +++ b/src/test/regress/expected/enum.out @@ -556,6 +556,64 @@ 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 that we can rename a value +ALTER TYPE rainbow ALTER 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 ALTER VALUE 'red' TO 'crimson'; +ERROR: "red" is not an existing enum label +-- check that renaming to an existent value fails +ALTER TYPE rainbow ALTER VALUE 'blue' TO 'green'; +ERROR: enum label "green" already exists +-- check that renaming a type in a transaction works +BEGIN; +ALTER TYPE rainbow ALTER VALUE 'blue' TO 'bleu'; +COMMIT; +SELECT enumlabel, enumsortorder +FROM pg_enum +WHERE enumtypid = 'rainbow'::regtype +ORDER BY 2; + enumlabel | enumsortorder +-----------+--------------- + crimson | 1 + orange | 2 + yellow | 3 + green | 4 + bleu | 5 + purple | 6 +(6 rows) + +-- check that rolling back a rename works +BEGIN; +ALTER TYPE rainbow ALTER VALUE 'bleu' TO 'blue'; +ROLLBACK; +SELECT enumlabel, enumsortorder +FROM pg_enum +WHERE enumtypid = 'rainbow'::regtype +ORDER BY 2; + enumlabel | enumsortorder +-----------+--------------- + crimson | 1 + orange | 2 + yellow | 3 + green | 4 + bleu | 5 + purple | 6 +(6 rows) + -- -- 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 88a835e..0863df8 100644 --- a/src/test/regress/sql/enum.sql +++ b/src/test/regress/sql/enum.sql @@ -257,6 +257,33 @@ CREATE TYPE bogus AS ENUM('good', 'bad', 'ugly'); CREATE TABLE enumtest_bogus_child(parent bogus REFERENCES enumtest_parent); DROP TYPE bogus; +-- check that we can rename a value +ALTER TYPE rainbow ALTER 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 ALTER VALUE 'red' TO 'crimson'; +-- check that renaming to an existent value fails +ALTER TYPE rainbow ALTER VALUE 'blue' TO 'green'; +-- check that renaming a type in a transaction works +BEGIN; +ALTER TYPE rainbow ALTER VALUE 'blue' TO 'bleu'; +COMMIT; +SELECT enumlabel, enumsortorder +FROM pg_enum +WHERE enumtypid = 'rainbow'::regtype +ORDER BY 2; +-- check that rolling back a rename works +BEGIN; +ALTER TYPE rainbow ALTER VALUE 'bleu' TO 'blue'; +ROLLBACK; +SELECT enumlabel, enumsortorder +FROM pg_enum +WHERE enumtypid = 'rainbow'::regtype +ORDER BY 2; + -- -- check transactional behaviour of ALTER TYPE ... ADD VALUE -- -- 2.8.0.rc3