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Add support for SET ACCESS METHOD in ALTER TABLE 

The logic used to support a change of access method for a table is
similar to changes for tablespace or relation persistence, requiring a
table rewrite with an exclusive lock of the relation changed.  Table
rewrites done in ALTER TABLE already go through the table AM layer when
scanning tuples from the old relation and inserting them into the new
one, making this implementation straight-forward.

Note that partitioned tables are not supported as these have no access
methods defined.

Author: Justin Pryzby, Jeff Davis
Reviewed-by: Michael Paquier, Vignesh C
Discussion: https://postgr.es/m/20210228222530.GD20769@telsasoft.com
This commit is contained in:
Michael Paquier 2021-07-28 10:10:44 +09:00
parent 4b763ff642
commit b0483263dd
11 changed files with 173 additions and 15 deletions
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20
doc/src/sgml/ref/alter_table.sgml
View File

@ -75,6 +75,7 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
CLUSTER ON <replaceable class="parameter">index_name</replaceable>
SET WITHOUT CLUSTER
SET WITHOUT OIDS
SET ACCESS METHOD <replaceable class="parameter">new_access_method</replaceable>
SET TABLESPACE <replaceable class="parameter">new_tablespace</replaceable>
SET { LOGGED | UNLOGGED }
SET ( <replaceable class="parameter">storage_parameter</replaceable> [= <replaceable class="parameter">value</replaceable>] [, ... ] )
@ -692,6 +693,16 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
</listitem>
</varlistentry>
<varlistentry>
<term><literal>SET ACCESS METHOD</literal></term>
<listitem>
<para>
This form changes the access method of the table by rewriting it. See
<xref linkend="tableam"/> for more information.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>SET TABLESPACE</literal></term>
<listitem>
@ -1228,6 +1239,15 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">new_access_method</replaceable></term>
<listitem>
<para>
The name of the access method to which the table will be converted.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">new_tablespace</replaceable></term>
<listitem>

21
src/backend/commands/cluster.c
View File

@ -576,6 +576,7 @@ static void
rebuild_relation(Relation OldHeap, Oid indexOid, bool verbose)
{
Oid tableOid = RelationGetRelid(OldHeap);
Oid accessMethod = OldHeap->rd_rel->relam;
Oid tableSpace = OldHeap->rd_rel->reltablespace;
Oid OIDNewHeap;
char relpersistence;
@ -597,6 +598,7 @@ rebuild_relation(Relation OldHeap, Oid indexOid, bool verbose)
/* Create the transient table that will receive the re-ordered data */
OIDNewHeap = make_new_heap(tableOid, tableSpace,
accessMethod,
relpersistence,
AccessExclusiveLock);
@ -618,16 +620,16 @@ rebuild_relation(Relation OldHeap, Oid indexOid, bool verbose)
/*
* Create the transient table that will be filled with new data during
* CLUSTER, ALTER TABLE, and similar operations. The transient table
* duplicates the logical structure of the OldHeap, but is placed in
* NewTableSpace which might be different from OldHeap's. Also, it's built
* with the specified persistence, which might differ from the original's.
* duplicates the logical structure of the OldHeap; but will have the
* specified physical storage properties NewTableSpace, NewAccessMethod, and
* relpersistence.
*
* After this, the caller should load the new heap with transferred/modified
* data, then call finish_heap_swap to complete the operation.
*/
Oid
make_new_heap(Oid OIDOldHeap, Oid NewTableSpace, char relpersistence,
LOCKMODE lockmode)
make_new_heap(Oid OIDOldHeap, Oid NewTableSpace, Oid NewAccessMethod,
char relpersistence, LOCKMODE lockmode)
{
TupleDesc OldHeapDesc;
char NewHeapName[NAMEDATALEN];
@ -686,7 +688,7 @@ make_new_heap(Oid OIDOldHeap, Oid NewTableSpace, char relpersistence,
InvalidOid,
InvalidOid,
OldHeap->rd_rel->relowner,
OldHeap->rd_rel->relam,
NewAccessMethod,
OldHeapDesc,
NIL,
RELKIND_RELATION,
@ -1036,6 +1038,10 @@ swap_relation_files(Oid r1, Oid r2, bool target_is_pg_class,
relform1->reltablespace = relform2->reltablespace;
relform2->reltablespace = swaptemp;
swaptemp = relform1->relam;
relform1->relam = relform2->relam;
relform2->relam = swaptemp;
swptmpchr = relform1->relpersistence;
relform1->relpersistence = relform2->relpersistence;
relform2->relpersistence = swptmpchr;
@ -1071,6 +1077,9 @@ swap_relation_files(Oid r1, Oid r2, bool target_is_pg_class,
if (relform1->relpersistence != relform2->relpersistence)
elog(ERROR, "cannot change persistence of mapped relation \"%s\"",
NameStr(relform1->relname));
if (relform1->relam != relform2->relam)
elog(ERROR, "cannot change access method of mapped relation \"%s\"",
NameStr(relform1->relname));
if (!swap_toast_by_content &&
(relform1->reltoastrelid || relform2->reltoastrelid))
elog(ERROR, "cannot swap toast by links for mapped relation \"%s\"",

5
src/backend/commands/matview.c
View File

@ -298,8 +298,9 @@ ExecRefreshMatView(RefreshMatViewStmt *stmt, const char *queryString,
* it against access by any other process until commit (by which time it
* will be gone).
*/
OIDNewHeap = make_new_heap(matviewOid, tableSpace, relpersistence,
ExclusiveLock);
OIDNewHeap = make_new_heap(matviewOid, tableSpace,
matviewRel->rd_rel->relam,
relpersistence, ExclusiveLock);
LockRelationOid(OIDNewHeap, AccessExclusiveLock);
dest = CreateTransientRelDestReceiver(OIDNewHeap);

66
src/backend/commands/tablecmds.c
View File

@ -176,6 +176,7 @@ typedef struct AlteredTableInfo
List *afterStmts; /* List of utility command parsetrees */
bool verify_new_notnull; /* T if we should recheck NOT NULL */
int rewrite; /* Reason for forced rewrite, if any */
Oid newAccessMethod; /* new access method; 0 means no change */
Oid newTableSpace; /* new tablespace; 0 means no change */
bool chgPersistence; /* T if SET LOGGED/UNLOGGED is used */
char newrelpersistence; /* if above is true */
@ -538,6 +539,7 @@ static void change_owner_recurse_to_sequences(Oid relationOid,
static ObjectAddress ATExecClusterOn(Relation rel, const char *indexName,
LOCKMODE lockmode);
static void ATExecDropCluster(Relation rel, LOCKMODE lockmode);
static void ATPrepSetAccessMethod(AlteredTableInfo *tab, Relation rel, const char *amname);
static bool ATPrepChangePersistence(Relation rel, bool toLogged);
static void ATPrepSetTableSpace(AlteredTableInfo *tab, Relation rel,
const char *tablespacename, LOCKMODE lockmode);
@ -4096,6 +4098,7 @@ AlterTableGetLockLevel(List *cmds)
*/
case AT_AddColumn: /* may rewrite heap, in some cases and visible
* to SELECT */
case AT_SetAccessMethod: /* must rewrite heap */
case AT_SetTableSpace: /* must rewrite heap */
case AT_AlterColumnType: /* must rewrite heap */
cmd_lockmode = AccessExclusiveLock;
@ -4622,6 +4625,24 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
ATSimplePermissions(cmd->subtype, rel, ATT_TABLE | ATT_FOREIGN_TABLE);
pass = AT_PASS_DROP;
break;
case AT_SetAccessMethod: /* SET ACCESS METHOD */
ATSimplePermissions(cmd->subtype, rel, ATT_TABLE | ATT_MATVIEW);
/* partitioned tables don't have an access method */
if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("cannot change access method of a partitioned table")));
/* check if another access method change was already requested */
if (OidIsValid(tab->newAccessMethod))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot have multiple SET ACCESS METHOD subcommands")));
ATPrepSetAccessMethod(tab, rel, cmd->name);
pass = AT_PASS_MISC; /* does not matter; no work in Phase 2 */
break;
case AT_SetTableSpace: /* SET TABLESPACE */
ATSimplePermissions(cmd->subtype, rel, ATT_TABLE | ATT_MATVIEW | ATT_INDEX |
ATT_PARTITIONED_INDEX);
@ -4997,6 +5018,9 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab,
case AT_DropOids: /* SET WITHOUT OIDS */
/* nothing to do here, oid columns don't exist anymore */
break;
case AT_SetAccessMethod: /* SET ACCESS METHOD */
/* handled specially in Phase 3 */
break;
case AT_SetTableSpace: /* SET TABLESPACE */
/*
@ -5324,7 +5348,7 @@ ATRewriteTables(AlterTableStmt *parsetree, List **wqueue, LOCKMODE lockmode,
/*
* We only need to rewrite the table if at least one column needs to
* be recomputed, or we are changing its persistence.
* be recomputed, or we are changing its persistence or access method.
*
* There are two reasons for requiring a rewrite when changing
* persistence: on one hand, we need to ensure that the buffers
@ -5338,6 +5362,7 @@ ATRewriteTables(AlterTableStmt *parsetree, List **wqueue, LOCKMODE lockmode,
/* Build a temporary relation and copy data */
Relation OldHeap;
Oid OIDNewHeap;
Oid NewAccessMethod;
Oid NewTableSpace;
char persistence;
@ -5378,6 +5403,15 @@ ATRewriteTables(AlterTableStmt *parsetree, List **wqueue, LOCKMODE lockmode,
else
NewTableSpace = OldHeap->rd_rel->reltablespace;
/*
* Select destination access method (same as original unless user
* requested a change)
*/
if (OidIsValid(tab->newAccessMethod))
NewAccessMethod = tab->newAccessMethod;
else
NewAccessMethod = OldHeap->rd_rel->relam;
/*
* Select persistence of transient table (same as original unless
* user requested a change)
@ -5417,8 +5451,8 @@ ATRewriteTables(AlterTableStmt *parsetree, List **wqueue, LOCKMODE lockmode,
* persistence. That wouldn't work for pg_class, but that can't be
* unlogged anyway.
*/
OIDNewHeap = make_new_heap(tab->relid, NewTableSpace, persistence,
lockmode);
OIDNewHeap = make_new_heap(tab->relid, NewTableSpace, NewAccessMethod,
persistence, lockmode);
/*
* Copy the heap data into the new table with the desired
@ -5933,6 +5967,8 @@ ATGetQueueEntry(List **wqueue, Relation rel)
tab->rel = NULL; /* set later */
tab->relkind = rel->rd_rel->relkind;
tab->oldDesc = CreateTupleDescCopyConstr(RelationGetDescr(rel));
tab->newAccessMethod = InvalidOid;
tab->newTableSpace = InvalidOid;
tab->newrelpersistence = RELPERSISTENCE_PERMANENT;
tab->chgPersistence = false;
@ -6003,6 +6039,8 @@ alter_table_type_to_string(AlterTableType cmdtype)
return "CLUSTER ON";
case AT_DropCluster:
return "SET WITHOUT CLUSTER";
case AT_SetAccessMethod:
return "SET ACCESS METHOD";
case AT_SetLogged:
return "SET LOGGED";
case AT_SetUnLogged:
@ -13609,6 +13647,28 @@ ATExecDropCluster(Relation rel, LOCKMODE lockmode)
mark_index_clustered(rel, InvalidOid, false);
}
/*
* Preparation phase for SET ACCESS METHOD
*
* Check that access method exists. If it is the same as the table's current
* access method, it is a no-op. Otherwise, a table rewrite is necessary.
*/
static void
ATPrepSetAccessMethod(AlteredTableInfo *tab, Relation rel, const char *amname)
{
Oid amoid;
/* Check that the table access method exists */
amoid = get_table_am_oid(amname, false);
if (rel->rd_rel->relam == amoid)
return;
/* Save info for Phase 3 to do the real work */
tab->rewrite |= AT_REWRITE_ACCESS_METHOD;
tab->newAccessMethod = amoid;
}
/*
* ALTER TABLE SET TABLESPACE
*/

8
src/backend/parser/gram.y
View File

@ -2623,6 +2623,14 @@ alter_table_cmd:
n->newowner = $3;
$$ = (Node *)n;
}
/* ALTER TABLE <name> SET ACCESS METHOD <amname> */
| SET ACCESS METHOD name
{
AlterTableCmd *n = makeNode(AlterTableCmd);
n->subtype = AT_SetAccessMethod;
n->name = $4;
$$ = (Node *)n;
}
/* ALTER TABLE <name> SET TABLESPACE <tablespacename> */
| SET TABLESPACE name
{

11
src/bin/psql/tab-complete.c
View File

@ -2141,8 +2141,15 @@ psql_completion(const char *text, int start, int end)
}
/* If we have ALTER TABLE <sth> SET, provide list of attributes and '(' */
else if (Matches("ALTER", "TABLE", MatchAny, "SET"))
COMPLETE_WITH("(", "LOGGED", "SCHEMA", "TABLESPACE", "UNLOGGED",
"WITH", "WITHOUT");
COMPLETE_WITH("(", "ACCESS METHOD", "LOGGED", "SCHEMA",
"TABLESPACE", "UNLOGGED", "WITH", "WITHOUT");
/*
* If we have ALTER TABLE <smt> SET ACCESS METHOD provide a list of table
* AMs.
*/
else if (Matches("ALTER", "TABLE", MatchAny, "SET", "ACCESS", "METHOD"))
COMPLETE_WITH_QUERY(Query_for_list_of_table_access_methods);
/*
* If we have ALTER TABLE <sth> SET TABLESPACE provide a list of

4
src/include/commands/cluster.h
View File

@ -35,8 +35,8 @@ extern void check_index_is_clusterable(Relation OldHeap, Oid indexOid,
bool recheck, LOCKMODE lockmode);
extern void mark_index_clustered(Relation rel, Oid indexOid, bool is_internal);
extern Oid make_new_heap(Oid OIDOldHeap, Oid NewTableSpace, char relpersistence,
LOCKMODE lockmode);
extern Oid make_new_heap(Oid OIDOldHeap, Oid NewTableSpace, Oid NewAccessMethod,
char relpersistence, LOCKMODE lockmode);
extern void finish_heap_swap(Oid OIDOldHeap, Oid OIDNewHeap,
bool is_system_catalog,
bool swap_toast_by_content,

1
src/include/commands/event_trigger.h
View File

@ -32,6 +32,7 @@ typedef struct EventTriggerData
#define AT_REWRITE_ALTER_PERSISTENCE 0x01
#define AT_REWRITE_DEFAULT_VAL 0x02
#define AT_REWRITE_COLUMN_REWRITE 0x04
#define AT_REWRITE_ACCESS_METHOD 0x08
/*
* EventTriggerData is the node type that is passed as fmgr "context" info

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

@ -1901,6 +1901,7 @@ typedef enum AlterTableType
AT_SetLogged, /* SET LOGGED */
AT_SetUnLogged, /* SET UNLOGGED */
AT_DropOids, /* SET WITHOUT OIDS */
AT_SetAccessMethod, /* SET ACCESS METHOD */
AT_SetTableSpace, /* SET TABLESPACE */
AT_SetRelOptions, /* SET (...) -- AM specific parameters */
AT_ResetRelOptions, /* RESET (...) -- AM specific parameters */

34
src/test/regress/expected/create_am.out
View File

@ -230,6 +230,40 @@ ORDER BY classid, objid, objsubid;
table tableam_parted_d_heap2
(5 rows)
-- ALTER TABLE SET ACCESS METHOD
CREATE TABLE heaptable USING heap AS
SELECT a, repeat(a::text, 100) FROM generate_series(1,9) AS a;
SELECT amname FROM pg_class c, pg_am am
WHERE c.relam = am.oid AND c.oid = 'heaptable'::regclass;
amname
--------
heap
(1 row)
ALTER TABLE heaptable SET ACCESS METHOD heap2;
SELECT amname FROM pg_class c, pg_am am
WHERE c.relam = am.oid AND c.oid = 'heaptable'::regclass;
amname
--------
heap2
(1 row)
SELECT COUNT(a), COUNT(1) FILTER(WHERE a=1) FROM heaptable;
count | count
-------+-------
9 | 1
(1 row)
-- No support for multiple subcommands
ALTER TABLE heaptable SET ACCESS METHOD heap, SET ACCESS METHOD heap2;
ERROR: cannot have multiple SET ACCESS METHOD subcommands
DROP TABLE heaptable;
-- No support for partitioned tables.
CREATE TABLE am_partitioned(x INT, y INT)
PARTITION BY hash (x);
ALTER TABLE am_partitioned SET ACCESS METHOD heap2;
ERROR: cannot change access method of a partitioned table
DROP TABLE am_partitioned;
-- Second, create objects in the new AM by changing the default AM
BEGIN;
SET LOCAL default_table_access_method = 'heap2';

17
src/test/regress/sql/create_am.sql
View File

@ -161,6 +161,23 @@ WHERE pg_depend.refclassid = 'pg_am'::regclass
AND pg_am.amname = 'heap2'
ORDER BY classid, objid, objsubid;
-- ALTER TABLE SET ACCESS METHOD
CREATE TABLE heaptable USING heap AS
SELECT a, repeat(a::text, 100) FROM generate_series(1,9) AS a;
SELECT amname FROM pg_class c, pg_am am
WHERE c.relam = am.oid AND c.oid = 'heaptable'::regclass;
ALTER TABLE heaptable SET ACCESS METHOD heap2;
SELECT amname FROM pg_class c, pg_am am
WHERE c.relam = am.oid AND c.oid = 'heaptable'::regclass;
SELECT COUNT(a), COUNT(1) FILTER(WHERE a=1) FROM heaptable;
-- No support for multiple subcommands
ALTER TABLE heaptable SET ACCESS METHOD heap, SET ACCESS METHOD heap2;
DROP TABLE heaptable;
-- No support for partitioned tables.
CREATE TABLE am_partitioned(x INT, y INT)
PARTITION BY hash (x);
ALTER TABLE am_partitioned SET ACCESS METHOD heap2;
DROP TABLE am_partitioned;
-- Second, create objects in the new AM by changing the default AM
BEGIN;