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Neil Conway authored
In the past, we used a 'Lispy' linked list implementation: a "list" was merely a pointer to the head node of the list. The problem with that design is that it makes lappend() and length() linear time. This patch fixes that problem (and others) by maintaining a count of the list length and a pointer to the tail node along with each head node pointer. A "list" is now a pointer to a structure containing some meta-data about the list; the head and tail pointers in that structure refer to ListCell structures that maintain the actual linked list of nodes. The function names of the list API have also been changed to, I hope, be more logically consistent. By default, the old function names are still available; they will be disabled-by-default once the rest of the tree has been updated to use the new API names.
Neil Conway authoredIn the past, we used a 'Lispy' linked list implementation: a "list" was merely a pointer to the head node of the list. The problem with that design is that it makes lappend() and length() linear time. This patch fixes that problem (and others) by maintaining a count of the list length and a pointer to the tail node along with each head node pointer. A "list" is now a pointer to a structure containing some meta-data about the list; the head and tail pointers in that structure refer to ListCell structures that maintain the actual linked list of nodes. The function names of the list API have also been changed to, I hope, be more logically consistent. By default, the old function names are still available; they will be disabled-by-default once the rest of the tree has been updated to use the new API names.
lockcmds.c 1.80 KiB
/*-------------------------------------------------------------------------
*
* lockcmds.c
* Lock command support code
*
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/lockcmds.c,v 1.10 2004/05/26 04:41:11 neilc Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/heapam.h"
#include "catalog/namespace.h"
#include "commands/lockcmds.h"
#include "miscadmin.h"
#include "utils/acl.h"
#include "utils/lsyscache.h"
/*
* LOCK TABLE
*/
void
LockTableCommand(LockStmt *lockstmt)
{
ListCell *p;
/*
* Iterate over the list and open, lock, and close the relations one
* at a time
*/
foreach(p, lockstmt->relations)
{
RangeVar *relation = lfirst(p);
Oid reloid;
AclResult aclresult;
Relation rel;
/*
* We don't want to open the relation until we've checked
* privilege. So, manually get the relation OID.
*/
reloid = RangeVarGetRelid(relation, false);
if (lockstmt->mode == AccessShareLock)
aclresult = pg_class_aclcheck(reloid, GetUserId(),
ACL_SELECT);
else
aclresult = pg_class_aclcheck(reloid, GetUserId(),
ACL_UPDATE | ACL_DELETE);
if (aclresult != ACLCHECK_OK)
aclcheck_error(aclresult, ACL_KIND_CLASS,
get_rel_name(reloid));
rel = conditional_relation_open(reloid, lockstmt->mode, lockstmt->nowait);
/* Currently, we only allow plain tables to be locked */
if (rel->rd_rel->relkind != RELKIND_RELATION)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("\"%s\" is not a table",
relation->relname)));
relation_close(rel, NoLock); /* close rel, keep lock */
}
}