/*-------------------------------------------------------------------------
 *
 * purge.c--
 *	  the POSTGRES purge command.
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /usr/local/cvsroot/pgsql/src/backend/commands/purge.c,v 1.8 1997/09/08 02:22:11 momjian Exp $
 *
 * Note:
 *		XXX There are many instances of int32 instead of ...Time.  These
 *		should be changed once it is decided the signed'ness will be.
 *
 *-------------------------------------------------------------------------
 */
#include <string.h>

#include <postgres.h>

#include <access/heapam.h>
#include <access/xact.h>
#include <utils/tqual.h>		/* for NowTimeQual */
#include <catalog/catname.h>
#include <catalog/indexing.h>
#include <fmgr.h>
#include <commands/purge.h>
#include <utils/builtins.h>		/* for isreltime() */

static char cmdname[] = "RelationPurge";

#define RELATIVE		01
#define ABSOLUTE		02

int32
RelationPurge(char *relationName,
			  char *absoluteTimeString,
			  char *relativeTimeString)
{
	register	i;
	AbsoluteTime absoluteTime = INVALID_ABSTIME;
	RelativeTime relativeTime = INVALID_RELTIME;
	bits8		dateTag;
	Relation	relation;
	HeapScanDesc scan;
	static ScanKeyData key[1] = {
		{0, Anum_pg_class_relname, F_NAMEEQ}
	};
	Buffer		buffer;
	HeapTuple	newTuple,
				oldTuple;
	AbsoluteTime currentTime;
	char	   *values[Natts_pg_class];
	char		nulls[Natts_pg_class];
	char		replace[Natts_pg_class];
	Relation	idescs[Num_pg_class_indices];

	/*
	 * XXX for some reason getmyrelids (in inval.c) barfs when you
	 * heap_replace tuples from these classes.	i thought setheapoverride
	 * would fix it but it didn't.  for now, just disallow purge on these
	 * classes.
	 */
	if (strcmp(RelationRelationName, relationName) == 0 ||
		strcmp(AttributeRelationName, relationName) == 0 ||
		strcmp(AccessMethodRelationName, relationName) == 0 ||
		strcmp(AccessMethodOperatorRelationName, relationName) == 0)
	{
		elog(WARN, "%s: cannot purge catalog \"%s\"",
			 cmdname, relationName);
	}

	if (PointerIsValid(absoluteTimeString))
	{
		absoluteTime = (int32) nabstimein(absoluteTimeString);
		absoluteTimeString[0] = '\0';
		if (absoluteTime == INVALID_ABSTIME)
		{
			elog(NOTICE, "%s: bad absolute time string \"%s\"",
				 cmdname, absoluteTimeString);
			elog(WARN, "purge not executed");
		}
	}

#ifdef	PURGEDEBUG
	elog(DEBUG, "%s: absolute time `%s' is %d.",
		 cmdname, absoluteTimeString, absoluteTime);
#endif							/* defined(PURGEDEBUG) */

	if (PointerIsValid(relativeTimeString))
	{
		if (isreltime(relativeTimeString) != 1)
		{
			elog(WARN, "%s: bad relative time string \"%s\"",
				 cmdname, relativeTimeString);
		}
		relativeTime = reltimein(relativeTimeString);

#ifdef	PURGEDEBUG
		elog(DEBUG, "%s: relative time `%s' is %d.",
			 cmdname, relativeTimeString, relativeTime);
#endif							/* defined(PURGEDEBUG) */
	}

	/*
	 * Find the RELATION relation tuple for the given relation.
	 */
	relation = heap_openr(RelationRelationName);
	key[0].sk_argument = PointerGetDatum(relationName);
	fmgr_info(key[0].sk_procedure, &key[0].sk_func, &key[0].sk_nargs);

	scan = heap_beginscan(relation, 0, NowTimeQual, 1, key);
	oldTuple = heap_getnext(scan, 0, &buffer);
	if (!HeapTupleIsValid(oldTuple))
	{
		heap_endscan(scan);
		heap_close(relation);
		elog(WARN, "%s: no such relation: %s", cmdname, relationName);
		return (0);
	}

	/*
	 * Dig around in the tuple.
	 */
	currentTime = GetCurrentTransactionStartTime();
	if (!RelativeTimeIsValid(relativeTime))
	{
		dateTag = ABSOLUTE;
		if (!AbsoluteTimeIsValid(absoluteTime))
			absoluteTime = currentTime;
	}
	else if (!AbsoluteTimeIsValid(absoluteTime))
		dateTag = RELATIVE;
	else
		dateTag = ABSOLUTE | RELATIVE;

	for (i = 0; i < Natts_pg_class; ++i)
	{
		nulls[i] = heap_attisnull(oldTuple, i + 1) ? 'n' : ' ';
		values[i] = NULL;
		replace[i] = ' ';
	}
	if (dateTag & ABSOLUTE)
	{
		values[Anum_pg_class_relexpires - 1] =
			(char *) UInt32GetDatum(absoluteTime);
		replace[Anum_pg_class_relexpires - 1] = 'r';
	}
	if (dateTag & RELATIVE)
	{
		values[Anum_pg_class_relpreserved - 1] =
			(char *) UInt32GetDatum(relativeTime);
		replace[Anum_pg_class_relpreserved - 1] = 'r';
	}

	/*
	 * Change the RELATION relation tuple for the given relation.
	 */
	newTuple = heap_modifytuple(oldTuple, buffer, relation, (Datum *) values,
								nulls, replace);

	/* XXX How do you detect an insertion error?? */
	heap_replace(relation, &newTuple->t_ctid, newTuple);

	/* keep the system catalog indices current */
	CatalogOpenIndices(Num_pg_class_indices, Name_pg_class_indices, idescs);
	CatalogIndexInsert(idescs, Num_pg_class_indices, relation, newTuple);
	CatalogCloseIndices(Num_pg_class_indices, idescs);

	pfree(newTuple);

	heap_endscan(scan);
	heap_close(relation);
	return (1);
}