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Dept. of second thoughts: rejigger the TRUNCATE ... CASCADE patch so that

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relations are still checked for permissions etc as soon as they are
opened.  The original form of the patch could hold exclusive lock for a
long time on relations that the user doesn't even have permissions to
access, let alone truncate.
This commit is contained in:
Tom Lane 2006-03-03 18:25:14 +00:00
parent a6add72ac3
commit 4e086f7cb5
1 changed files with 63 additions and 68 deletions
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143
src/backend/commands/tablecmds.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.178 2006/03/03 03:30:52 tgl Exp $
* $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.179 2006/03/03 18:25:14 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -156,6 +156,7 @@ typedef struct NewColumnValue
} NewColumnValue;
static void truncate_check_rel(Relation rel);
static List *MergeAttributes(List *schema, List *supers, bool istemp,
List **supOids, List **supconstr, int *supOidCount);
static bool change_varattnos_of_a_node(Node *node, const AttrNumber *newattno);
@ -539,33 +540,33 @@ void
ExecuteTruncate(TruncateStmt *stmt)
{
List *rels = NIL;
List *directRelids = NIL;
List *relids = NIL;
ListCell *cell;
Oid relid;
Relation rel;
/*
* Open and exclusive-lock all the explicitly-specified relations
* Open, exclusive-lock, and check all the explicitly-specified relations
*/
foreach(cell, stmt->relations)
{
RangeVar *rv = lfirst(cell);
Relation rel;
rel = heap_openrv(rv, AccessExclusiveLock);
truncate_check_rel(rel);
rels = lappend(rels, rel);
directRelids = lappend_oid(directRelids, RelationGetRelid(rel));
relids = lappend_oid(relids, RelationGetRelid(rel));
}
/*
* In CASCADE mode, suck in all referencing relations as well. This
* requires multiple iterations to find indirectly-dependent relations.
* At each phase, we need to exclusive-lock new rels before looking
* for their dependencies, else we might miss something.
* for their dependencies, else we might miss something. Also, we
* check each rel as soon as we open it, to avoid a faux pas such as
* holding lock for a long time on a rel we have no permissions for.
*/
if (stmt->behavior == DROP_CASCADE)
{
List *relids = list_copy(directRelids);
for (;;)
{
List *newrelids;
@ -576,31 +577,76 @@ ExecuteTruncate(TruncateStmt *stmt)
foreach(cell, newrelids)
{
relid = lfirst_oid(cell);
Oid relid = lfirst_oid(cell);
Relation rel;
rel = heap_open(relid, AccessExclusiveLock);
ereport(NOTICE,
(errmsg("truncate cascades to table \"%s\"",
RelationGetRelationName(rel))));
truncate_check_rel(rel);
rels = lappend(rels, rel);
relids = lappend_oid(relids, relid);
}
}
}
/* now check all involved relations */
foreach(cell, rels)
{
rel = (Relation) lfirst(cell);
relid = RelationGetRelid(rel);
/*
* Check foreign key references. In CASCADE mode, this should be
* unnecessary since we just pulled in all the references; but as
* a cross-check, do it anyway if in an Assert-enabled build.
*/
#ifdef USE_ASSERT_CHECKING
heap_truncate_check_FKs(rels, false);
#else
if (stmt->behavior == DROP_RESTRICT)
heap_truncate_check_FKs(rels, false);
#endif
/*
* If this table was added to the command by CASCADE, report it.
* We don't do this earlier because if we error out on one of the
* tables, it'd be confusing to list subsequently-added tables.
* OK, truncate each table.
*/
if (stmt->behavior == DROP_CASCADE &&
!list_member_oid(directRelids, relid))
ereport(NOTICE,
(errmsg("truncate cascades to table \"%s\"",
RelationGetRelationName(rel))));
foreach(cell, rels)
{
Relation rel = (Relation) lfirst(cell);
Oid heap_relid;
Oid toast_relid;
/*
* Create a new empty storage file for the relation, and assign it as
* the relfilenode value. The old storage file is scheduled for
* deletion at commit.
*/
setNewRelfilenode(rel);
heap_relid = RelationGetRelid(rel);
toast_relid = rel->rd_rel->reltoastrelid;
heap_close(rel, NoLock);
/*
* The same for the toast table, if any.
*/
if (OidIsValid(toast_relid))
{
rel = relation_open(toast_relid, AccessExclusiveLock);
setNewRelfilenode(rel);
heap_close(rel, NoLock);
}
/*
* Reconstruct the indexes to match, and we're done.
*/
reindex_relation(heap_relid, true);
}
}
/*
* Check that a given rel is safe to truncate. Subroutine for ExecuteTruncate
*/
static void
truncate_check_rel(Relation rel)
{
/* Only allow truncate on regular tables */
if (rel->rd_rel->relkind != RELKIND_RELATION)
ereport(ERROR,
@ -638,57 +684,6 @@ ExecuteTruncate(TruncateStmt *stmt)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot truncate temporary tables of other sessions")));
}
/*
* Check foreign key references. In CASCADE mode, this should be
* unnecessary since we just pulled in all the references; but as
* a cross-check, do it anyway if in an Assert-enabled build.
*/
#ifdef USE_ASSERT_CHECKING
heap_truncate_check_FKs(rels, false);
#else
if (stmt->behavior == DROP_RESTRICT)
heap_truncate_check_FKs(rels, false);
#endif
/*
* OK, truncate each table.
*/
foreach(cell, rels)
{
Oid heap_relid;
Oid toast_relid;
rel = (Relation) lfirst(cell);
/*
* Create a new empty storage file for the relation, and assign it as
* the relfilenode value. The old storage file is scheduled for
* deletion at commit.
*/
setNewRelfilenode(rel);
heap_relid = RelationGetRelid(rel);
toast_relid = rel->rd_rel->reltoastrelid;
heap_close(rel, NoLock);
/*
* The same for the toast table, if any.
*/
if (OidIsValid(toast_relid))
{
rel = relation_open(toast_relid, AccessExclusiveLock);
setNewRelfilenode(rel);
heap_close(rel, NoLock);
}
/*
* Reconstruct the indexes to match, and we're done.
*/
reindex_relation(heap_relid, true);
}
}
/*----------