version.c

关系型数据库 Postgresql 6.5.2

/*-------------------------------------------------------------------------
 *
 * version.c
 *	  This file contains all the rules that govern all version semantics.
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *	The version stuff has not been tested under postgres95 and probably
 *	doesn't work! - jolly 8/19/95
 *
 *
 *	$Id: version.c,v 1.19.2.1 1999/08/02 05:57:02 scrappy Exp $
 *
 * NOTES
 *	At the point the version is defined, 2 physical relations are created
 *	<vname>_added and <vname>_deleted.
 *
 *	In addition, 4 rules are defined which govern the semantics of
 *	versions w.r.t retrieves, appends, replaces and deletes.
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"


#define MAX_QUERY_LEN 1024

char		rule_buf[MAX_QUERY_LEN];

/*
 * problem: the version system assumes that the rules it declares will
 *			be fired in the order of declaration, it also assumes
 *			goh's silly instead semantics.  Unfortunately, it is a pain
 *			to make the version system work with the new semantics.
 *			However the whole problem can be solved, and some nice
 *			functionality can be achieved if we get multiple action rules
 *			to work.  So thats what I did						-- glass
 *
 * Well, at least they've been working for about 20 minutes.
 *
 * So any comments in this code about 1 rule per transction are false...:)
 *
 */

/*
 *	This is needed because the rule system only allows
 *	*1* rule to be defined per transaction.
 *
 * NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
 * OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
 * OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
 * OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
 * OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
 * OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
 * OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
 * OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
 * OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
 * OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
 * OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
 * OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
 * OOOOOOOOOOOOOOOOOOO!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 *
 * DONT DO THAT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 *
 * If you commit the current Xact all the palloced memory GOES AWAY
 * and could be re-palloced in the new Xact and the whole hell breaks
 * loose and poor people like me spend 2 hours of their live chassing
 * a strange memory bug instead of watching the "Get Smart" marathon
 * in NICK !
 * DO NOT COMMIT THE XACT, just increase the Cid counter!
 *														_sp.
 */
#ifdef NOT_USED
static void
eval_as_new_xact(char *query)
{

	/*
	 * WARNING! do not uncomment the following lines WARNING!
	 * CommitTransactionCommand(); StartTransactionCommand();
	 */
	CommandCounterIncrement();
	pg_exec_query(query);
}

#endif
/*
 *	Define a version.
 */
#ifdef NOT_USED
void
DefineVersion(char *name, char *fromRelname, char *date)
{
	char	   *bname;
	static char saved_basename[512];
	static char saved_snapshot[512];

	if (date == NULL)
	{
		/* no time ranges */
		bname = fromRelname;
		strcpy(saved_basename, (char *) bname);
		*saved_snapshot = (char) NULL;
	}
	else
	{
		/* version is a snapshot */
		bname = fromRelname;
		strcpy(saved_basename, (char *) bname);
		sprintf(saved_snapshot, "['%s']", date);
	}


	/*
	 * Calls the routine ``GetAttrList'' get the list of attributes from
	 * the base relation. Code is put here so that we only need to look up
	 * the attribute once for both appends and replaces.
	 */
	setAttrList(bname);

	VersionCreate(name, saved_basename);
	VersionAppend(name, saved_basename);
	VersionDelete(name, saved_basename, saved_snapshot);
	VersionReplace(name, saved_basename, saved_snapshot);
	VersionRetrieve(name, saved_basename, saved_snapshot);
}

#endif

/*
 *	Creates the deltas.
 */
#ifdef NOT_USED
void
VersionCreate(char *vname, char *bname)
{
	static char query_buf[MAX_QUERY_LEN];

	/*
	 * Creating the dummy version relation for triggering rules.
	 */
	sprintf(query_buf, "SELECT * INTO TABLE %s from %s where 1 =2",
			vname, bname);

	pg_exec_query(query_buf);

	/*
	 * Creating the ``v_added'' relation
	 */
	sprintf(query_buf, "SELECT * INTO TABLE %s_added from %s where 1 = 2",
			vname, bname);
	eval_as_new_xact(query_buf);

	/*
	 * Creating the ``v_deleted'' relation.
	 */
	sprintf(query_buf, "CREATE TABLE %s_del (DOID oid)", vname);
	eval_as_new_xact(query_buf);
}

#endif


/*
 * Given the relation name, does a catalog lookup for that relation and
 * sets the global variable 'attr_list' with the list of attributes (names)
 * for that relation.
 */
#ifdef NOT_USED
static void
setAttrList(char *bname)
{
	Relation	rel;
	int			i = 0;
	int			maxattrs = 0;
	char	   *attrname;
	char		temp_buf[512];
	int			notfirst = 0;

	rel = heap_openr(bname);
	if (rel == NULL)
	{
		elog(ERROR, "Unable to expand all -- amopenr failed ");
		return;
	}
	maxattrs = RelationGetNumberOfAttributes(rel);

	attr_list[0] = '\0';

	for (i = maxattrs - 1; i > -1; --i)
	{
		attrname = (rel->rd_att->attrs[i]->attname).data;

		if (notfirst == 1)
			sprintf(temp_buf, ", %s = new.%s", attrname, attrname);
		else
		{
			sprintf(temp_buf, "%s = new.%s", attrname, attrname);
			notfirst = 1;
		}
		strcat(attr_list, temp_buf);
	}

	heap_close(rel);

	return;
}

#endif

/*
 * This routine defines the rule governing the append semantics of
 * versions.  All tuples appended to a version gets appended to the
 * <vname>_added relation.
 */
#ifdef NOT_USED
static void
VersionAppend(char *vname, char *bname)
{
	sprintf(rule_buf,
			"define rewrite rule %s_append is on INSERT to %s do instead append %s_added(%s)",
			vname, vname, vname, attr_list);

	eval_as_new_xact(rule_buf);
}

#endif

/*
 * This routine defines the rule governing the retrieval semantics of
 * versions.  To retrieve tuples from a version , we need to:
 *
 *		1. Retrieve all tuples in the <vname>_added relation.
 *		2. Retrieve all tuples in the base relation which are not in
 *		   the <vname>_del relation.
 */
#ifdef NOT_USED
void
VersionRetrieve(char *vname, char *bname, char *snapshot)
{

	sprintf(rule_buf,
			"define rewrite rule %s_retrieve is on SELECT to %s do instead\n\
SELECT %s_1.oid, %s_1.* from _%s in %s%s, %s_1 in (%s_added | _%s) \
where _%s.oid !!= '%s_del.DOID'",
			vname, vname, vname, vname, bname,
			bname, snapshot,
			vname, vname, bname, bname, vname);

	eval_as_new_xact(rule_buf);

	/* printf("%s\n",rule_buf); */

}

#endif

/*
 * This routine defines the rules that govern the delete semantics of
 * versions. Two things happens when we delete a tuple from a version:
 *
 *	   1. If the tuple to be deleted was added to the version *after*
 *		  the version was created, then we simply delete the tuple
 *		  from the <vname>_added relation.
 *	   2. If the tuple to be deleted is actually in the base relation,
 *		  then we have to mark that tuple as being deleted by adding
 *		  it to the <vname>_del relation.
 */
#ifdef NOT_USED
void
VersionDelete(char *vname, char *bname, char *snapshot)
{

	sprintf(rule_buf,
			"define rewrite rule %s_delete1 is on delete to %s do instead\n \
[delete %s_added where current.oid = %s_added.oid\n \
 append %s_del(DOID = current.oid) from _%s in %s%s \
 where current.oid = _%s.oid] \n",
			vname, vname, vname, vname, vname,
			bname, bname, snapshot, bname);

	eval_as_new_xact(rule_buf);
#ifdef OLD_REWRITE
	sprintf(rule_buf,
			"define rewrite rule %s_delete2 is on delete to %s do instead \n \
    append %s_del(DOID = current.oid) from _%s in %s%s \
    where current.oid = _%s.oid \n",
			vname, vname, vname, bname, bname, snapshot, bname);

	eval_as_new_xact(rule_buf);
#endif	 /* OLD_REWRITE */
}

#endif

/*
 *	This routine defines the rules that govern the update semantics
 *	of versions. To update a tuple in a version:
 *
 *		1. If the tuple is in <vname>_added, we simply ``replace''
 *		   the tuple (as per postgres style).
 *		2. if the tuple is in the base relation, then two things have to
 *		   happen:
 *		   2.1	The tuple is marked ``deleted'' from the base relation by
 *				adding the tuple to the <vname>_del relation.
 *		   2.2	A copy of the tuple is appended to the <vname>_added relation
 */
#ifdef NOT_USED
void
VersionReplace(char *vname, char *bname, char *snapshot)
{
	sprintf(rule_buf,
			"define rewrite rule %s_replace1 is on replace to %s do instead \n\
[replace %s_added(%s) where current.oid = %s_added.oid \n\
 append %s_del(DOID = current.oid) from _%s in %s%s \
 where current.oid = _%s.oid\n\
 append %s_added(%s) from _%s in %s%s \
 where current.oid !!= '%s_added.oid' and current.oid = _%s.oid]\n",
			vname, vname, vname, attr_list, vname,
			vname, bname, bname, snapshot, bname,
			vname, attr_list, bname, bname, snapshot, vname, bname);

	eval_as_new_xact(rule_buf);

/*	printf("%s\n",rule_buf); */
#ifdef OLD_REWRITE
	sprintf(rule_buf,
			"define rewrite rule %s_replace2 is on replace to %s do \n\
    append %s_del(DOID = current.oid) from _%s in %s%s \
    where current.oid = _%s.oid\n",
			vname, vname, vname, bname, bname, snapshot, bname);

	eval_as_new_xact(rule_buf);

	sprintf(rule_buf,
			"define rewrite rule %s_replace3 is on replace to %s do instead\n\
    append %s_added(%s) from _%s in %s%s \
    where current.oid !!= '%s_added.oid' and current.oid = \
    _%s.oid\n",
	vname, vname, vname, attr_list, bname, bname, snapshot, vname, bname);

	eval_as_new_xact(rule_buf);
#endif	 /* OLD_REWRITE */
/*	printf("%s\n",rule_buf); */

}

#endif