comment.c

来自「PostgreSQL7.4.6 for Linux」· C语言 代码 · 共 916 行 · 第 1/2 页

/*-------------------------------------------------------------------------
 *
 * comment.c
 *
 * PostgreSQL object comments utility code.
 *
 * Copyright (c) 1996-2003, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/commands/comment.c,v 1.71 2003/09/25 06:57:58 petere Exp $
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/genam.h"
#include "access/heapam.h"
#include "catalog/catname.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_description.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_rewrite.h"
#include "catalog/pg_trigger.h"
#include "catalog/pg_type.h"
#include "commands/comment.h"
#include "commands/dbcommands.h"
#include "miscadmin.h"
#include "parser/parse_func.h"
#include "parser/parse_oper.h"
#include "parser/parse_type.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"


/*
 * Static Function Prototypes --
 *
 * The following protoypes are declared static so as not to conflict
 * with any other routines outside this module. These routines are
 * called by the public function CommentObject() routine to create
 * the appropriate comment for the specific object type.
 */

static void CommentRelation(int objtype, List *relname, char *comment);
static void CommentAttribute(List *qualname, char *comment);
static void CommentDatabase(List *qualname, char *comment);
static void CommentNamespace(List *qualname, char *comment);
static void CommentRule(List *qualname, char *comment);
static void CommentType(List *typename, char *comment);
static void CommentAggregate(List *aggregate, List *arguments, char *comment);
static void CommentProc(List *function, List *arguments, char *comment);
static void CommentOperator(List *opername, List *arguments, char *comment);
static void CommentTrigger(List *qualname, char *comment);
static void CommentConstraint(List *qualname, char *comment);


/*
 * CommentObject --
 *
 * This routine is used to add the associated comment into
 * pg_description for the object specified by the given SQL command.
 */
void
CommentObject(CommentStmt *stmt)
{
	switch (stmt->objtype)
	{
		case OBJECT_INDEX:
		case OBJECT_SEQUENCE:
		case OBJECT_TABLE:
		case OBJECT_VIEW:
			CommentRelation(stmt->objtype, stmt->objname, stmt->comment);
			break;
		case OBJECT_COLUMN:
			CommentAttribute(stmt->objname, stmt->comment);
			break;
		case OBJECT_DATABASE:
			CommentDatabase(stmt->objname, stmt->comment);
			break;
		case OBJECT_RULE:
			CommentRule(stmt->objname, stmt->comment);
			break;
		case OBJECT_TYPE:
			CommentType(stmt->objname, stmt->comment);
			break;
		case OBJECT_AGGREGATE:
			CommentAggregate(stmt->objname, stmt->objargs, stmt->comment);
			break;
		case OBJECT_FUNCTION:
			CommentProc(stmt->objname, stmt->objargs, stmt->comment);
			break;
		case OBJECT_OPERATOR:
			CommentOperator(stmt->objname, stmt->objargs, stmt->comment);
			break;
		case OBJECT_TRIGGER:
			CommentTrigger(stmt->objname, stmt->comment);
			break;
		case OBJECT_SCHEMA:
			CommentNamespace(stmt->objname, stmt->comment);
			break;
		case OBJECT_CONSTRAINT:
			CommentConstraint(stmt->objname, stmt->comment);
			break;
		default:
			elog(ERROR, "unrecognized object type: %d",
				 (int) stmt->objtype);
	}
}

/*
 * 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];
	char		nulls[Natts_pg_description];
	char		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] = ' ';
			replaces[i] = 'r';
		}
		i = 0;
		values[i++] = ObjectIdGetDatum(oid);
		values[i++] = ObjectIdGetDatum(classoid);
		values[i++] = Int32GetDatum(subid);
		values[i++] = DirectFunctionCall1(textin, CStringGetDatum(comment));
	}

	/* Use the index to search for a matching old tuple */

	ScanKeyEntryInitialize(&skey[0],
						   (bits16) 0x0,
						   (AttrNumber) 1,
						   (RegProcedure) F_OIDEQ,
						   ObjectIdGetDatum(oid));

	ScanKeyEntryInitialize(&skey[1],
						   (bits16) 0x0,
						   (AttrNumber) 2,
						   (RegProcedure) F_OIDEQ,
						   ObjectIdGetDatum(classoid));

	ScanKeyEntryInitialize(&skey[2],
						   (bits16) 0x0,
						   (AttrNumber) 3,
						   (RegProcedure) F_INT4EQ,
						   Int32GetDatum(subid));

	description = heap_openr(DescriptionRelationName, RowExclusiveLock);

	sd = systable_beginscan(description, DescriptionObjIndex, true,
							SnapshotNow, 3, skey);

	while ((oldtuple = systable_getnext(sd)) != NULL)
	{
		/* Found the old tuple, so delete or update it */

		if (comment == NULL)
			simple_heap_delete(description, &oldtuple->t_self);
		else
		{
			newtuple = heap_modifytuple(oldtuple, description, values,
										nulls, replaces);
			simple_heap_update(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_formtuple(RelationGetDescr(description),
								  values, nulls);
		simple_heap_insert(description, newtuple);
	}

	/* Update indexes, if necessary */
	if (newtuple != NULL)
	{
		CatalogUpdateIndexes(description, newtuple);
		heap_freetuple(newtuple);
	}

	/* Done */

	heap_close(description, 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 */

	ScanKeyEntryInitialize(&skey[0], 0x0,
						   Anum_pg_description_objoid, F_OIDEQ,
						   ObjectIdGetDatum(oid));

	ScanKeyEntryInitialize(&skey[1], 0x0,
						   Anum_pg_description_classoid, F_OIDEQ,
						   ObjectIdGetDatum(classoid));

	if (subid != 0)
	{
		ScanKeyEntryInitialize(&skey[2], 0x0,
							   Anum_pg_description_objsubid, F_INT4EQ,
							   Int32GetDatum(subid));
		nkeys = 3;
	}
	else
		nkeys = 2;

	description = heap_openr(DescriptionRelationName, RowExclusiveLock);

	sd = systable_beginscan(description, DescriptionObjIndex, true,
							SnapshotNow, nkeys, skey);

	while ((oldtuple = systable_getnext(sd)) != NULL)
		simple_heap_delete(description, &oldtuple->t_self);

	/* Done */

	systable_endscan(sd);
	heap_close(description, RowExclusiveLock);
}

/*
 * CommentRelation --
 *
 * This routine is used to add/drop a comment from a relation, where
 * a relation is a TABLE, SEQUENCE, VIEW or INDEX. The routine simply
 * finds the relation name by searching the system cache, locating
 * the appropriate tuple, and inserting a comment using that
 * tuple's oid. Its parameters are the relation name and comments.
 */
static void
CommentRelation(int objtype, List *relname, char *comment)
{
	Relation	relation;
	RangeVar   *tgtrel;

	tgtrel = makeRangeVarFromNameList(relname);

	/*
	 * Open the relation.  We do this mainly to acquire a lock that
	 * ensures no one else drops the relation before we commit.  (If they
	 * did, they'd fail to remove the entry we are about to make in
	 * pg_description.)
	 */
	relation = relation_openrv(tgtrel, AccessShareLock);

	/* Check object security */
	if (!pg_class_ownercheck(RelationGetRelid(relation), GetUserId()))
		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
					   RelationGetRelationName(relation));

	/* Next, verify that the relation type matches the intent */

	switch (objtype)
	{
		case OBJECT_INDEX:
			if (relation->rd_rel->relkind != RELKIND_INDEX)
				ereport(ERROR,
						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
						 errmsg("\"%s\" is not an index",
								RelationGetRelationName(relation))));
			break;
		case OBJECT_SEQUENCE:
			if (relation->rd_rel->relkind != RELKIND_SEQUENCE)
				ereport(ERROR,
						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
						 errmsg("\"%s\" is not a sequence",
								RelationGetRelationName(relation))));
			break;
		case OBJECT_TABLE:
			if (relation->rd_rel->relkind != RELKIND_RELATION)
				ereport(ERROR,
						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
						 errmsg("\"%s\" is not a table",
								RelationGetRelationName(relation))));
			break;
		case OBJECT_VIEW:
			if (relation->rd_rel->relkind != RELKIND_VIEW)
				ereport(ERROR,
						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
						 errmsg("\"%s\" is not a view",
								RelationGetRelationName(relation))));
			break;
	}

	/* Create the comment using the relation's oid */

	CreateComments(RelationGetRelid(relation), RelOid_pg_class, 0, comment);

	/* Done, but hold lock until commit */
	relation_close(relation, NoLock);
}

/*
 * CommentAttribute --
 *
 * This routine is used to add/drop a comment from an attribute
 * such as a table's column. The routine will check security
 * restrictions and then attempt to look up the specified
 * attribute. If successful, a comment is added/dropped, else an
 * ereport() exception is thrown.	The parameters are the relation
 * and attribute names, and the comment
 */
static void
CommentAttribute(List *qualname, char *comment)
{
	int			nnames;
	List	   *relname;
	char	   *attrname;
	RangeVar   *rel;
	Relation	relation;
	AttrNumber	attnum;

	/* Separate relname and attr name */
	nnames = length(qualname);
	if (nnames < 2)				/* parser messed up */
		elog(ERROR, "must specify relation and attribute");
	relname = ltruncate(nnames - 1, listCopy(qualname));
	attrname = strVal(llast(qualname));

	/* Open the containing relation to ensure it won't go away meanwhile */
	rel = makeRangeVarFromNameList(relname);
	relation = relation_openrv(rel, AccessShareLock);

	/* Check object security */

	if (!pg_class_ownercheck(RelationGetRelid(relation), GetUserId()))
		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
					   RelationGetRelationName(relation));

	/* Now, fetch the attribute number from the system cache */

	attnum = get_attnum(RelationGetRelid(relation), attrname);
	if (attnum == InvalidAttrNumber)
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
			 errmsg("column \"%s\" of relation \"%s\" does not exist",
					attrname, RelationGetRelationName(relation))));

	/* Create the comment using the relation's oid */

	CreateComments(RelationGetRelid(relation), RelOid_pg_class,
				   (int32) attnum, comment);

	/* Done, but hold lock until commit */

	relation_close(relation, NoLock);
}

/*
 * CommentDatabase --
 *
 * This routine is used to add/drop any user-comments a user might
 * have regarding the specified database. The routine will check
 * security for owner permissions, and, if successful, will then
 * attempt to find the oid of the database specified. Once found,
 * a comment is added/dropped using the CreateComments() routine.
 */
static void
CommentDatabase(List *qualname, char *comment)
{
	char	   *database;
	Oid			oid;

	if (length(qualname) != 1)
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
				 errmsg("database name may not be qualified")));
	database = strVal(lfirst(qualname));

	/*
	 * We cannot currently support cross-database comments (since other
	 * DBs cannot see pg_description of this database).  So, we reject
	 * attempts to comment on a database other than the current one.
	 * Someday this might be improved, but it would take a redesigned
	 * infrastructure.
	 *
	 * 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.
	 */

	/* First get the database OID */
	oid = get_database_oid(database);
	if (!OidIsValid(oid))
	{
		ereport(WARNING,
				(errcode(ERRCODE_UNDEFINED_DATABASE),
				 errmsg("database \"%s\" does not exist", database)));
		return;
	}

	/* Only allow comments on the current database */
	if (oid != MyDatabaseId)
	{
		ereport(WARNING,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("database comments may only be applied to the current database")));
		return;
	}

	/* Check object security */
	if (!pg_database_ownercheck(oid, GetUserId()))
		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_DATABASE,
					   database);

	/* Create the comment with the pg_database oid */