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ALTER TABLE ... ALTER COLUMN ... DROP EXPRESSION

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Add an ALTER TABLE subcommand for dropping the generated property from
a column, per SQL standard.

Reviewed-by: Sergei Kornilov <sk@zsrv.org>
Discussion: https://www.postgresql.org/message-id/flat/2f7f1d9c-946e-0453-d841-4f38eb9d69b6%402ndquadrant.com
This commit is contained in:
Peter Eisentraut
2020-01-14 13:09:31 +01:00
parent d751ba5235
commit f595117e24
9 changed files with 326 additions and 4 deletions
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161
src/backend/commands/tablecmds.c
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@ -388,6 +388,8 @@ static ObjectAddress ATExecAddIdentity(Relation rel, const char *colName,
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,
@ -3672,6 +3674,7 @@ AlterTableGetLockLevel(List *cmds)
case AT_AddIdentity:
case AT_DropIdentity:
case AT_SetIdentity:
case AT_DropExpression:
cmd_lockmode = AccessExclusiveLock;
break;
@ -3946,6 +3949,12 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
/* 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);
@ -4265,6 +4274,9 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
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;
@ -6457,7 +6469,9 @@ ATExecColumnDefault(Relation rel, const char *colName,
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
@ -6725,6 +6739,151 @@ ATExecDropIdentity(Relation rel, const char *colName, bool missing_ok, LOCKMODE
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
*