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postgres/src/backend/commands/comment.c
Tom Lane ab02896510 Provide CatalogTupleDelete() as a wrapper around simple_heap_delete(). 
This extends the work done in commit 2f5c9d9c9 to provide a more nearly
complete abstraction layer hiding the details of index updating for catalog
changes.  That commit only invented abstractions for catalog inserts and
updates, leaving nearby code for catalog deletes still calling the
heap-level routines directly.  That seems rather ugly from here, and it
does little to help if we ever want to shift to a storage system in which
indexing work is needed at delete time.

Hence, create a wrapper function CatalogTupleDelete(), and replace calls
of simple_heap_delete() on catalog tuples with it.  There are now very
few direct calls of [simple_]heap_delete remaining in the tree.

Discussion: https://postgr.es/m/462.1485902736@sss.pgh.pa.us
2017-02-01 16:13:30 -05:00

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/*-------------------------------------------------------------------------
*
* comment.c
*
* PostgreSQL object comments utility code.
*
* Copyright (c) 1996-2017, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/backend/commands/comment.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/genam.h"
#include "access/heapam.h"
#include "access/htup_details.h"
#include "catalog/indexing.h"
#include "catalog/objectaddress.h"
#include "catalog/pg_description.h"
#include "catalog/pg_shdescription.h"
#include "commands/comment.h"
#include "commands/dbcommands.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/rel.h"
#include "utils/tqual.h"
/*
* CommentObject --
*
* This routine is used to add the associated comment into
* pg_description for the object specified by the given SQL command.
*/
ObjectAddress
CommentObject(CommentStmt *stmt)
{
Relation relation;
ObjectAddress address = InvalidObjectAddress;
/*
* When loading a dump, we may see a COMMENT ON DATABASE for the old name
* of the database. Erroring out would prevent pg_restore from completing
* (which is really pg_restore's fault, but for now we will work around
* the problem here). Consensus is that the best fix is to treat wrong
* database name as a WARNING not an ERROR; hence, the following special
* case. (If the length of stmt->objname is not 1, get_object_address
* will throw an error below; that's OK.)
*/
if (stmt->objtype == OBJECT_DATABASE && list_length(stmt->objname) == 1)
{
char *database = strVal(linitial(stmt->objname));
if (!OidIsValid(get_database_oid(database, true)))
{
ereport(WARNING,
(errcode(ERRCODE_UNDEFINED_DATABASE),
errmsg("database \"%s\" does not exist", database)));
return address;
}
}
/*
* Translate the parser representation that identifies this object into an
* ObjectAddress. get_object_address() will throw an error if the object
* does not exist, and will also acquire a lock on the target to guard
* against concurrent DROP operations.
*/
address = get_object_address(stmt->objtype, stmt->objname, stmt->objargs,
&relation, ShareUpdateExclusiveLock, false);
/* Require ownership of the target object. */
check_object_ownership(GetUserId(), stmt->objtype, address,
stmt->objname, stmt->objargs, relation);
/* Perform other integrity checks as needed. */
switch (stmt->objtype)
{
case OBJECT_COLUMN:
/*
* Allow comments only on columns of tables, views, materialized
* views, composite types, and foreign tables (which are the only
* relkinds for which pg_dump will dump per-column comments). In
* particular we wish to disallow comments on index columns,
* because the naming of an index's columns may change across PG
* versions, so dumping per-column comments could create reload
* failures.
*/
if (relation->rd_rel->relkind != RELKIND_RELATION &&
relation->rd_rel->relkind != RELKIND_VIEW &&
relation->rd_rel->relkind != RELKIND_MATVIEW &&
relation->rd_rel->relkind != RELKIND_COMPOSITE_TYPE &&
relation->rd_rel->relkind != RELKIND_FOREIGN_TABLE)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("\"%s\" is not a table, view, materialized view, composite type, or foreign table",
RelationGetRelationName(relation))));
break;
default:
break;
}
/*
* Databases, tablespaces, and roles are cluster-wide objects, so any
* comments on those objects are recorded in the shared pg_shdescription
* catalog. Comments on all other objects are recorded in pg_description.
*/
if (stmt->objtype == OBJECT_DATABASE || stmt->objtype == OBJECT_TABLESPACE
|| stmt->objtype == OBJECT_ROLE)
CreateSharedComments(address.objectId, address.classId, stmt->comment);
else
CreateComments(address.objectId, address.classId, address.objectSubId,
stmt->comment);
/*
* If get_object_address() opened the relation for us, we close it to keep
* the reference count correct - but we retain any locks acquired by
* get_object_address() until commit time, to guard against concurrent
* activity.
*/
if (relation != NULL)
relation_close(relation, NoLock);
return address;
}
/*
* CreateComments --
*
* Create a comment for the specified object descriptor. Inserts a new
* pg_description tuple, or replaces an existing one with the same key.
*
* If the comment given is null or an empty string, instead delete any
* existing comment for the specified key.
*/
void
CreateComments(Oid oid, Oid classoid, int32 subid, char *comment)
{
Relation description;
ScanKeyData skey[3];
SysScanDesc sd;
HeapTuple oldtuple;
HeapTuple newtuple = NULL;
Datum values[Natts_pg_description];
bool nulls[Natts_pg_description];
bool replaces[Natts_pg_description];
int i;
/* Reduce empty-string to NULL case */
if (comment != NULL && strlen(comment) == 0)
comment = NULL;
/* Prepare to form or update a tuple, if necessary */
if (comment != NULL)
{
for (i = 0; i < Natts_pg_description; i++)
{
nulls[i] = false;
replaces[i] = true;
}
values[Anum_pg_description_objoid - 1] = ObjectIdGetDatum(oid);
values[Anum_pg_description_classoid - 1] = ObjectIdGetDatum(classoid);
values[Anum_pg_description_objsubid - 1] = Int32GetDatum(subid);
values[Anum_pg_description_description - 1] = CStringGetTextDatum(comment);
}
/* Use the index to search for a matching old tuple */
ScanKeyInit(&skey[0],
Anum_pg_description_objoid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(oid));
ScanKeyInit(&skey[1],
Anum_pg_description_classoid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(classoid));
ScanKeyInit(&skey[2],
Anum_pg_description_objsubid,
BTEqualStrategyNumber, F_INT4EQ,
Int32GetDatum(subid));
description = heap_open(DescriptionRelationId, RowExclusiveLock);
sd = systable_beginscan(description, DescriptionObjIndexId, true,
NULL, 3, skey);
while ((oldtuple = systable_getnext(sd)) != NULL)
{
/* Found the old tuple, so delete or update it */
if (comment == NULL)
CatalogTupleDelete(description, &oldtuple->t_self);
else
{
newtuple = heap_modify_tuple(oldtuple, RelationGetDescr(description), values,
nulls, replaces);
CatalogTupleUpdate(description, &oldtuple->t_self, newtuple);
}
break; /* Assume there can be only one match */
}
systable_endscan(sd);
/* If we didn't find an old tuple, insert a new one */
if (newtuple == NULL && comment != NULL)
{
newtuple = heap_form_tuple(RelationGetDescr(description),
values, nulls);
CatalogTupleInsert(description, newtuple);
}
if (newtuple != NULL)
heap_freetuple(newtuple);
/* Done */
heap_close(description, NoLock);
}
/*
* CreateSharedComments --
*
* Create a comment for the specified shared object descriptor. Inserts a
* new pg_shdescription tuple, or replaces an existing one with the same key.
*
* If the comment given is null or an empty string, instead delete any
* existing comment for the specified key.
*/
void
CreateSharedComments(Oid oid, Oid classoid, char *comment)
{
Relation shdescription;
ScanKeyData skey[2];
SysScanDesc sd;
HeapTuple oldtuple;
HeapTuple newtuple = NULL;
Datum values[Natts_pg_shdescription];
bool nulls[Natts_pg_shdescription];
bool replaces[Natts_pg_shdescription];
int i;
/* Reduce empty-string to NULL case */
if (comment != NULL && strlen(comment) == 0)
comment = NULL;
/* Prepare to form or update a tuple, if necessary */
if (comment != NULL)
{
for (i = 0; i < Natts_pg_shdescription; i++)
{
nulls[i] = false;
replaces[i] = true;
}
values[Anum_pg_shdescription_objoid - 1] = ObjectIdGetDatum(oid);
values[Anum_pg_shdescription_classoid - 1] = ObjectIdGetDatum(classoid);
values[Anum_pg_shdescription_description - 1] = CStringGetTextDatum(comment);
}
/* Use the index to search for a matching old tuple */
ScanKeyInit(&skey[0],
Anum_pg_shdescription_objoid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(oid));
ScanKeyInit(&skey[1],
Anum_pg_shdescription_classoid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(classoid));
shdescription = heap_open(SharedDescriptionRelationId, RowExclusiveLock);
sd = systable_beginscan(shdescription, SharedDescriptionObjIndexId, true,
NULL, 2, skey);
while ((oldtuple = systable_getnext(sd)) != NULL)
{
/* Found the old tuple, so delete or update it */
if (comment == NULL)
CatalogTupleDelete(shdescription, &oldtuple->t_self);
else
{
newtuple = heap_modify_tuple(oldtuple, RelationGetDescr(shdescription),
values, nulls, replaces);
CatalogTupleUpdate(shdescription, &oldtuple->t_self, newtuple);
}
break; /* Assume there can be only one match */
}
systable_endscan(sd);
/* If we didn't find an old tuple, insert a new one */
if (newtuple == NULL && comment != NULL)
{
newtuple = heap_form_tuple(RelationGetDescr(shdescription),
values, nulls);
CatalogTupleInsert(shdescription, newtuple);
}
if (newtuple != NULL)
heap_freetuple(newtuple);
/* Done */
heap_close(shdescription, NoLock);
}
/*
* DeleteComments -- remove comments for an object
*
* If subid is nonzero then only comments matching it will be removed.
* If subid is zero, all comments matching the oid/classoid will be removed
* (this corresponds to deleting a whole object).
*/
void
DeleteComments(Oid oid, Oid classoid, int32 subid)
{
Relation description;
ScanKeyData skey[3];
int nkeys;
SysScanDesc sd;
HeapTuple oldtuple;
/* Use the index to search for all matching old tuples */
ScanKeyInit(&skey[0],
Anum_pg_description_objoid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(oid));
ScanKeyInit(&skey[1],
Anum_pg_description_classoid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(classoid));
if (subid != 0)
{
ScanKeyInit(&skey[2],
Anum_pg_description_objsubid,
BTEqualStrategyNumber, F_INT4EQ,
Int32GetDatum(subid));
nkeys = 3;
}
else
nkeys = 2;
description = heap_open(DescriptionRelationId, RowExclusiveLock);
sd = systable_beginscan(description, DescriptionObjIndexId, true,
NULL, nkeys, skey);
while ((oldtuple = systable_getnext(sd)) != NULL)
CatalogTupleDelete(description, &oldtuple->t_self);
/* Done */
systable_endscan(sd);
heap_close(description, RowExclusiveLock);
}
/*
* DeleteSharedComments -- remove comments for a shared object
*/
void
DeleteSharedComments(Oid oid, Oid classoid)
{
Relation shdescription;
ScanKeyData skey[2];
SysScanDesc sd;
HeapTuple oldtuple;
/* Use the index to search for all matching old tuples */
ScanKeyInit(&skey[0],
Anum_pg_shdescription_objoid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(oid));
ScanKeyInit(&skey[1],
Anum_pg_shdescription_classoid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(classoid));
shdescription = heap_open(SharedDescriptionRelationId, RowExclusiveLock);
sd = systable_beginscan(shdescription, SharedDescriptionObjIndexId, true,
NULL, 2, skey);
while ((oldtuple = systable_getnext(sd)) != NULL)
CatalogTupleDelete(shdescription, &oldtuple->t_self);
/* Done */
systable_endscan(sd);
heap_close(shdescription, RowExclusiveLock);
}
/*
* GetComment -- get the comment for an object, or null if not found.
*/
char *
GetComment(Oid oid, Oid classoid, int32 subid)
{
Relation description;
ScanKeyData skey[3];
SysScanDesc sd;
TupleDesc tupdesc;
HeapTuple tuple;
char *comment;
/* Use the index to search for a matching old tuple */
ScanKeyInit(&skey[0],
Anum_pg_description_objoid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(oid));
ScanKeyInit(&skey[1],
Anum_pg_description_classoid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(classoid));
ScanKeyInit(&skey[2],
Anum_pg_description_objsubid,
BTEqualStrategyNumber, F_INT4EQ,
Int32GetDatum(subid));
description = heap_open(DescriptionRelationId, AccessShareLock);
tupdesc = RelationGetDescr(description);
sd = systable_beginscan(description, DescriptionObjIndexId, true,
NULL, 3, skey);
comment = NULL;
while ((tuple = systable_getnext(sd)) != NULL)
{
Datum value;
bool isnull;
/* Found the tuple, get description field */
value = heap_getattr(tuple, Anum_pg_description_description, tupdesc, &isnull);
if (!isnull)
comment = TextDatumGetCString(value);
break; /* Assume there can be only one match */
}
systable_endscan(sd);
/* Done */
heap_close(description, AccessShareLock);
return comment;
}
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