ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> SET DEFAULT <replaceable class="parameter">expression</replaceable>
ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> DROP DEFAULT
ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> { SET | DROP } NOT NULL
+ ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> DROP EXPRESSION [ IF EXISTS ]
ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> ADD GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY [ ( <replaceable>sequence_options</replaceable> ) ]
ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> { SET GENERATED { ALWAYS | BY DEFAULT } | SET <replaceable>sequence_option</replaceable> | RESTART [ [ WITH ] <replaceable class="parameter">restart</replaceable> ] } [...]
ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> DROP IDENTITY [ IF EXISTS ]
</listitem>
</varlistentry>
+ <varlistentry>
+ <term><literal>DROP EXPRESSION [ IF EXISTS ]</literal></term>
+ <listitem>
+ <para>
+ This form turns a stored generated column into a normal base column.
+ Existing data in the columns is retained, but future changes will no
+ longer apply the generation expression.
+ </para>
+
+ <para>
+ If <literal>DROP EXPRESSION IF EXISTS</literal> is specified and the
+ column is not a stored generated column, no error is thrown. In this
+ case a notice is issued instead.
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry>
<term><literal>ADD GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY</literal></term>
<term><literal>SET GENERATED { ALWAYS | BY DEFAULT }</literal></term>
F382 Alter column data type YES
F383 Set column not null clause YES
F384 Drop identity property clause YES
-F385 Drop column generation expression clause NO
+F385 Drop column generation expression clause YES
F386 Set identity column generation clause YES
F391 Long identifiers YES
F392 Unicode escapes in identifiers YES
static ObjectAddress ATExecSetIdentity(Relation rel, const char *colName,
Node *def, LOCKMODE lockmode);
static ObjectAddress ATExecDropIdentity(Relation rel, const char *colName, bool missing_ok, LOCKMODE lockmode);
+static void ATPrepDropExpression(Relation rel, AlterTableCmd *cmd, bool recursing);
+static ObjectAddress ATExecDropExpression(Relation rel, const char *colName, bool missing_ok, LOCKMODE lockmode);
static ObjectAddress ATExecSetStatistics(Relation rel, const char *colName, int16 colNum,
Node *newValue, LOCKMODE lockmode);
static ObjectAddress ATExecSetOptions(Relation rel, const char *colName,
case AT_AddIdentity:
case AT_DropIdentity:
case AT_SetIdentity:
+ case AT_DropExpression:
cmd_lockmode = AccessExclusiveLock;
break;
/* No command-specific prep needed */
pass = AT_PASS_COL_ATTRS;
break;
+ case AT_DropExpression: /* ALTER COLUMN DROP EXPRESSION */
+ ATSimplePermissions(rel, ATT_TABLE | ATT_FOREIGN_TABLE);
+ ATSimpleRecursion(wqueue, rel, cmd, recurse, lockmode);
+ ATPrepDropExpression(rel, cmd, recursing);
+ pass = AT_PASS_DROP;
+ break;
case AT_SetStatistics: /* ALTER COLUMN SET STATISTICS */
ATSimplePermissions(rel, ATT_TABLE | ATT_MATVIEW | ATT_INDEX | ATT_PARTITIONED_INDEX | ATT_FOREIGN_TABLE);
ATSimpleRecursion(wqueue, rel, cmd, recurse, lockmode);
case AT_CheckNotNull: /* check column is already marked NOT NULL */
ATExecCheckNotNull(tab, rel, cmd->name, lockmode);
break;
+ case AT_DropExpression:
+ address = ATExecDropExpression(rel, cmd->name, cmd->missing_ok, lockmode);
+ break;
case AT_SetStatistics: /* ALTER COLUMN SET STATISTICS */
address = ATExecSetStatistics(rel, cmd->name, cmd->num, cmd->def, lockmode);
break;
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("column \"%s\" of relation \"%s\" is a generated column",
- colName, RelationGetRelationName(rel))));
+ colName, RelationGetRelationName(rel)),
+ newDefault || TupleDescAttr(tupdesc, attnum - 1)->attgenerated != ATTRIBUTE_GENERATED_STORED ? 0 :
+ errhint("Use ALTER TABLE ... ALTER COLUMN ... DROP EXPRESSION instead.")));
/*
* Remove any old default for the column. We use RESTRICT here for
return address;
}
+/*
+ * ALTER TABLE ALTER COLUMN DROP EXPRESSION
+ */
+static void
+ATPrepDropExpression(Relation rel, AlterTableCmd *cmd, bool recursing)
+{
+ /*
+ * Cannot drop generation expression from inherited columns.
+ */
+ if (!recursing)
+ {
+ HeapTuple tuple;
+ Form_pg_attribute attTup;
+
+ tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), cmd->name);
+ if (!HeapTupleIsValid(tuple))
+ ereport(ERROR,
+ (errcode(ERRCODE_UNDEFINED_COLUMN),
+ errmsg("column \"%s\" of relation \"%s\" does not exist",
+ cmd->name, RelationGetRelationName(rel))));
+
+ attTup = (Form_pg_attribute) GETSTRUCT(tuple);
+
+ if (attTup->attinhcount > 0)
+ ereport(ERROR,
+ (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
+ errmsg("cannot drop generation expression from inherited column")));
+ }
+}
+
+/*
+ * Return the address of the affected column.
+ */
+static ObjectAddress
+ATExecDropExpression(Relation rel, const char *colName, bool missing_ok, LOCKMODE lockmode)
+{
+ HeapTuple tuple;
+ Form_pg_attribute attTup;
+ AttrNumber attnum;
+ Relation attrelation;
+ ObjectAddress address;
+
+ attrelation = table_open(AttributeRelationId, RowExclusiveLock);
+ tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), colName);
+ if (!HeapTupleIsValid(tuple))
+ ereport(ERROR,
+ (errcode(ERRCODE_UNDEFINED_COLUMN),
+ errmsg("column \"%s\" of relation \"%s\" does not exist",
+ colName, RelationGetRelationName(rel))));
+
+ attTup = (Form_pg_attribute) GETSTRUCT(tuple);
+ attnum = attTup->attnum;
+
+ if (attnum <= 0)
+ ereport(ERROR,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("cannot alter system column \"%s\"",
+ colName)));
+
+ if (attTup->attgenerated != ATTRIBUTE_GENERATED_STORED)
+ {
+ if (!missing_ok)
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("column \"%s\" of relation \"%s\" is not a stored generated column",
+ colName, RelationGetRelationName(rel))));
+ else
+ {
+ ereport(NOTICE,
+ (errmsg("column \"%s\" of relation \"%s\" is not a stored generated column, skipping",
+ colName, RelationGetRelationName(rel))));
+ heap_freetuple(tuple);
+ table_close(attrelation, RowExclusiveLock);
+ return InvalidObjectAddress;
+ }
+ }
+
+ attTup->attgenerated = '\0';
+ CatalogTupleUpdate(attrelation, &tuple->t_self, tuple);
+
+ InvokeObjectPostAlterHook(RelationRelationId,
+ RelationGetRelid(rel),
+ attTup->attnum);
+ ObjectAddressSubSet(address, RelationRelationId,
+ RelationGetRelid(rel), attnum);
+ heap_freetuple(tuple);
+
+ table_close(attrelation, RowExclusiveLock);
+
+ CommandCounterIncrement();
+
+ RemoveAttrDefault(RelationGetRelid(rel), attnum, DROP_RESTRICT, false, false);
+
+ /*
+ * Remove all dependencies of this (formerly generated) column on other
+ * columns in the same table. (See StoreAttrDefault() for which
+ * dependencies are created.) We don't expect there to be dependencies
+ * between columns of the same table for other reasons, so it's okay to
+ * remove all of them.
+ */
+ {
+ Relation depRel;
+ ScanKeyData key[3];
+ SysScanDesc scan;
+ HeapTuple tup;
+
+ depRel = table_open(DependRelationId, RowExclusiveLock);
+
+ ScanKeyInit(&key[0],
+ Anum_pg_depend_classid,
+ BTEqualStrategyNumber, F_OIDEQ,
+ ObjectIdGetDatum(RelationRelationId));
+ ScanKeyInit(&key[1],
+ Anum_pg_depend_objid,
+ BTEqualStrategyNumber, F_OIDEQ,
+ ObjectIdGetDatum(RelationGetRelid(rel)));
+ ScanKeyInit(&key[2],
+ Anum_pg_depend_objsubid,
+ BTEqualStrategyNumber, F_INT4EQ,
+ Int32GetDatum(attnum));
+
+ scan = systable_beginscan(depRel, DependDependerIndexId, true,
+ NULL, 3, key);
+
+ while (HeapTupleIsValid(tup = systable_getnext(scan)))
+ {
+ Form_pg_depend depform = (Form_pg_depend) GETSTRUCT(tup);
+
+ if (depform->refclassid == RelationRelationId &&
+ depform->refobjid == RelationGetRelid(rel) &&
+ depform->refobjsubid != 0 &&
+ depform->deptype == DEPENDENCY_AUTO)
+ {
+ CatalogTupleDelete(depRel, &tup->t_self);
+ }
+ }
+
+ systable_endscan(scan);
+
+ table_close(depRel, RowExclusiveLock);
+ }
+
+ return address;
+}
+
/*
* ALTER TABLE ALTER COLUMN SET STATISTICS
*
DOUBLE_P DROP
EACH ELSE ENABLE_P ENCODING ENCRYPTED END_P ENUM_P ESCAPE EVENT EXCEPT
- EXCLUDE EXCLUDING EXCLUSIVE EXECUTE EXISTS EXPLAIN
+ EXCLUDE EXCLUDING EXCLUSIVE EXECUTE EXISTS EXPLAIN EXPRESSION
EXTENSION EXTERNAL EXTRACT
FALSE_P FAMILY FETCH FILTER FIRST_P FLOAT_P FOLLOWING FOR
n->name = $3;
$$ = (Node *)n;
}
+ /* ALTER TABLE <name> ALTER [COLUMN] <colname> DROP EXPRESSION */
+ | ALTER opt_column ColId DROP EXPRESSION
+ {
+ AlterTableCmd *n = makeNode(AlterTableCmd);
+ n->subtype = AT_DropExpression;
+ n->name = $3;
+ $$ = (Node *)n;
+ }
+ /* ALTER TABLE <name> ALTER [COLUMN] <colname> DROP EXPRESSION IF EXISTS */
+ | ALTER opt_column ColId DROP EXPRESSION IF_P EXISTS
+ {
+ AlterTableCmd *n = makeNode(AlterTableCmd);
+ n->subtype = AT_DropExpression;
+ n->name = $3;
+ n->missing_ok = true;
+ $$ = (Node *)n;
+ }
/* ALTER TABLE <name> ALTER [COLUMN] <colname> SET STATISTICS <SignedIconst> */
| ALTER opt_column ColId SET STATISTICS SignedIconst
{
| EXCLUSIVE
| EXECUTE
| EXPLAIN
+ | EXPRESSION
| EXTENSION
| EXTERNAL
| FAMILY
/* ALTER TABLE ALTER [COLUMN] <foo> DROP */
else if (Matches("ALTER", "TABLE", MatchAny, "ALTER", "COLUMN", MatchAny, "DROP") ||
Matches("ALTER", "TABLE", MatchAny, "ALTER", MatchAny, "DROP"))
- COMPLETE_WITH("DEFAULT", "IDENTITY", "NOT NULL");
+ COMPLETE_WITH("DEFAULT", "EXPRESSION", "IDENTITY", "NOT NULL");
else if (Matches("ALTER", "TABLE", MatchAny, "CLUSTER"))
COMPLETE_WITH("ON");
else if (Matches("ALTER", "TABLE", MatchAny, "CLUSTER", "ON"))
AT_ColumnDefault, /* alter column default */
AT_DropNotNull, /* alter column drop not null */
AT_SetNotNull, /* alter column set not null */
+ AT_DropExpression, /* alter column drop expression */
AT_CheckNotNull, /* check column is already marked not null */
AT_SetStatistics, /* alter column set statistics */
AT_SetOptions, /* alter column set ( options ) */
PG_KEYWORD("execute", EXECUTE, UNRESERVED_KEYWORD)
PG_KEYWORD("exists", EXISTS, COL_NAME_KEYWORD)
PG_KEYWORD("explain", EXPLAIN, UNRESERVED_KEYWORD)
+PG_KEYWORD("expression", EXPRESSION, UNRESERVED_KEYWORD)
PG_KEYWORD("extension", EXTENSION, UNRESERVED_KEYWORD)
PG_KEYWORD("external", EXTERNAL, UNRESERVED_KEYWORD)
PG_KEYWORD("extract", EXTRACT, COL_NAME_KEYWORD)
ERROR: generation expression for column "x" cannot be cast automatically to type boolean
ALTER TABLE gtest27 ALTER COLUMN x DROP DEFAULT; -- error
ERROR: column "x" of relation "gtest27" is a generated column
+HINT: Use ALTER TABLE ... ALTER COLUMN ... DROP EXPRESSION instead.
-- It's possible to alter the column types this way:
ALTER TABLE gtest27
DROP COLUMN x,
4 | 11 | 30
(2 rows)
+-- ALTER TABLE ... ALTER COLUMN ... DROP EXPRESSION
+CREATE TABLE gtest29 (
+ a int,
+ b int GENERATED ALWAYS AS (a * 2) STORED
+);
+INSERT INTO gtest29 (a) VALUES (3), (4);
+ALTER TABLE gtest29 ALTER COLUMN a DROP EXPRESSION; -- error
+ERROR: column "a" of relation "gtest29" is not a stored generated column
+ALTER TABLE gtest29 ALTER COLUMN a DROP EXPRESSION IF EXISTS; -- notice
+NOTICE: column "a" of relation "gtest29" is not a stored generated column, skipping
+ALTER TABLE gtest29 ALTER COLUMN b DROP EXPRESSION;
+INSERT INTO gtest29 (a) VALUES (5);
+INSERT INTO gtest29 (a, b) VALUES (6, 66);
+SELECT * FROM gtest29;
+ a | b
+---+----
+ 3 | 6
+ 4 | 8
+ 5 |
+ 6 | 66
+(4 rows)
+
+\d gtest29
+ Table "public.gtest29"
+ Column | Type | Collation | Nullable | Default
+--------+---------+-----------+----------+---------
+ a | integer | | |
+ b | integer | | |
+
+-- check that dependencies between columns have also been removed
+ALTER TABLE gtest29 DROP COLUMN a; -- should not drop b
+\d gtest29
+ Table "public.gtest29"
+ Column | Type | Collation | Nullable | Default
+--------+---------+-----------+----------+---------
+ b | integer | | |
+
+-- with inheritance
+CREATE TABLE gtest30 (
+ a int,
+ b int GENERATED ALWAYS AS (a * 2) STORED
+);
+CREATE TABLE gtest30_1 () INHERITS (gtest30);
+ALTER TABLE gtest30 ALTER COLUMN b DROP EXPRESSION;
+\d gtest30
+ Table "public.gtest30"
+ Column | Type | Collation | Nullable | Default
+--------+---------+-----------+----------+---------
+ a | integer | | |
+ b | integer | | |
+Number of child tables: 1 (Use \d+ to list them.)
+
+\d gtest30_1
+ Table "public.gtest30_1"
+ Column | Type | Collation | Nullable | Default
+--------+---------+-----------+----------+---------
+ a | integer | | |
+ b | integer | | |
+Inherits: gtest30
+
+DROP TABLE gtest30 CASCADE;
+NOTICE: drop cascades to table gtest30_1
+CREATE TABLE gtest30 (
+ a int,
+ b int GENERATED ALWAYS AS (a * 2) STORED
+);
+CREATE TABLE gtest30_1 () INHERITS (gtest30);
+ALTER TABLE ONLY gtest30 ALTER COLUMN b DROP EXPRESSION;
+\d gtest30
+ Table "public.gtest30"
+ Column | Type | Collation | Nullable | Default
+--------+---------+-----------+----------+---------
+ a | integer | | |
+ b | integer | | |
+Number of child tables: 1 (Use \d+ to list them.)
+
+\d gtest30_1
+ Table "public.gtest30_1"
+ Column | Type | Collation | Nullable | Default
+--------+---------+-----------+----------+------------------------------------
+ a | integer | | |
+ b | integer | | | generated always as (a * 2) stored
+Inherits: gtest30
+
+ALTER TABLE gtest30_1 ALTER COLUMN b DROP EXPRESSION; -- error
+ERROR: cannot drop generation expression from inherited column
-- triggers
CREATE TABLE gtest26 (
a int PRIMARY KEY,
\d gtest27
SELECT * FROM gtest27;
+-- ALTER TABLE ... ALTER COLUMN ... DROP EXPRESSION
+CREATE TABLE gtest29 (
+ a int,
+ b int GENERATED ALWAYS AS (a * 2) STORED
+);
+INSERT INTO gtest29 (a) VALUES (3), (4);
+ALTER TABLE gtest29 ALTER COLUMN a DROP EXPRESSION; -- error
+ALTER TABLE gtest29 ALTER COLUMN a DROP EXPRESSION IF EXISTS; -- notice
+ALTER TABLE gtest29 ALTER COLUMN b DROP EXPRESSION;
+INSERT INTO gtest29 (a) VALUES (5);
+INSERT INTO gtest29 (a, b) VALUES (6, 66);
+SELECT * FROM gtest29;
+\d gtest29
+
+-- check that dependencies between columns have also been removed
+ALTER TABLE gtest29 DROP COLUMN a; -- should not drop b
+\d gtest29
+
+-- with inheritance
+CREATE TABLE gtest30 (
+ a int,
+ b int GENERATED ALWAYS AS (a * 2) STORED
+);
+CREATE TABLE gtest30_1 () INHERITS (gtest30);
+ALTER TABLE gtest30 ALTER COLUMN b DROP EXPRESSION;
+\d gtest30
+\d gtest30_1
+DROP TABLE gtest30 CASCADE;
+CREATE TABLE gtest30 (
+ a int,
+ b int GENERATED ALWAYS AS (a * 2) STORED
+);
+CREATE TABLE gtest30_1 () INHERITS (gtest30);
+ALTER TABLE ONLY gtest30 ALTER COLUMN b DROP EXPRESSION;
+\d gtest30
+\d gtest30_1
+ALTER TABLE gtest30_1 ALTER COLUMN b DROP EXPRESSION; -- error
+
-- triggers
CREATE TABLE gtest26 (
a int PRIMARY KEY,
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