opensourcemirror
/
postgresql
mirror of git://git.postgresql.org/git/postgresql.git
1
0
Fork 0
Code Issues Releases Wiki Activity

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

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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
doc/src/sgml/ref/alter_table.sgml
View File

@ -46,6 +46,7 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
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 ]
@ -241,6 +242,23 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
</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>

2
src/backend/catalog/sql_features.txt
View File

@ -252,7 +252,7 @@ F381 Extended schema manipulation 03 ALTER TABLE statement: DROP CONSTRAINT clau
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

161
src/backend/commands/tablecmds.c
View File

@ -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
*

20
src/backend/parser/gram.y
View File

@ -639,7 +639,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
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
@ -2129,6 +2129,23 @@ alter_table_cmd:
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
{
@ -15196,6 +15213,7 @@ unreserved_keyword:
| EXCLUSIVE
| EXECUTE
| EXPLAIN
| EXPRESSION
| EXTENSION
| EXTERNAL
| FAMILY

2
src/bin/psql/tab-complete.c
View File

@ -2015,7 +2015,7 @@ psql_completion(const char *text, int start, int end)
/* 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"))

1
src/include/nodes/parsenodes.h
View File

@ -1785,6 +1785,7 @@ typedef enum AlterTableType
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 ) */

1
src/include/parser/kwlist.h
View File

@ -155,6 +155,7 @@ PG_KEYWORD("exclusive", EXCLUSIVE, UNRESERVED_KEYWORD)
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)

87
src/test/regress/expected/generated.out
View File

@ -648,6 +648,7 @@ ALTER TABLE gtest27 ALTER COLUMN x TYPE boolean USING x <> 0; -- error
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,
@ -683,6 +684,92 @@ SELECT * FROM gtest27;
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,

38
src/test/regress/sql/generated.sql
View File

@ -351,6 +351,44 @@ ALTER TABLE gtest27
\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,