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Routines for database initial access info and support.

This commit is contained in:
Thomas G. Lockhart 1997-11-07 07:05:46 +00:00
parent 8a7f79c83c
commit 4676b3034a
1 changed files with 279 additions and 0 deletions
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src/backend/utils/misc/database.c Normal file
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/*-------------------------------------------------------------------------
*
* database.c--
* miscellanious initialization support stuff
*
* Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/misc/Attic/database.c,v 1.1 1997/11/07 07:05:46 thomas Exp $
*
*-------------------------------------------------------------------------
*/
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include "postgres.h"
#include "miscadmin.h"
#include "utils/elog.h"
#include "utils/builtins.h"
#include "utils/syscache.h"
#include "access/heapam.h"
#include "storage/bufmgr.h"
#include "catalog/catname.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_database.h"
#include "access/xact.h"
#include "storage/bufpage.h"
/* GetDatabaseInfo()
* Pull database information from pg_database.
*/
int
GetDatabaseInfo(char *name, Oid *owner, char *path)
{
Oid dbowner,
dbid;
char dbpath[MAXPGPATH+1];
text *dbtext;
Relation dbrel;
HeapTuple dbtup;
HeapTuple tup;
Buffer buf;
HeapScanDesc scan;
ScanKeyData scanKey;
dbrel = heap_openr(DatabaseRelationName);
if (!RelationIsValid(dbrel))
elog(FATAL,"GetDatabaseInfo: cannot open relation \"%-.*s\"",
DatabaseRelationName);
ScanKeyEntryInitialize(&scanKey, 0, Anum_pg_database_datname,
NameEqualRegProcedure, NameGetDatum(name));
scan = heap_beginscan(dbrel, 0, NowTimeQual, 1, &scanKey);
if (!HeapScanIsValid(scan))
elog(WARN, "GetDatabaseInfo: cannot begin scan of %s", DatabaseRelationName);
/*
* Since we're going to close the relation, copy the tuple.
*/
tup = heap_getnext(scan, 0, &buf);
if (HeapTupleIsValid(tup))
{
dbtup = heap_copytuple(tup);
ReleaseBuffer(buf);
}
else
dbtup = tup;
heap_endscan(scan);
if (!HeapTupleIsValid(dbtup))
{
elog(NOTICE,"GetDatabaseInfo: %s entry not found %s",
DatabaseRelationName,name);
return TRUE;
}
dbowner = (Oid) heap_getattr(dbtup, InvalidBuffer,
Anum_pg_database_datdba,
RelationGetTupleDescriptor(dbrel),
(char *) NULL);
dbid = dbtup->t_oid;
dbtext = (text *) heap_getattr(dbtup, InvalidBuffer,
Anum_pg_database_datpath,
RelationGetTupleDescriptor(dbrel),
(char *) NULL);
memcpy(dbpath, VARDATA(dbtext), (VARSIZE(dbtext)-VARHDRSZ));
*(dbpath+(VARSIZE(dbtext)-VARHDRSZ)) = '\0';
heap_close(dbrel);
owner = palloc(sizeof(Oid));
*owner = dbowner;
path = palloc(strlen(dbpath)+1);
strcpy(path, dbpath);
return FALSE;
} /* GetDatabaseInfo() */
char *
ExpandDatabasePath(char *dbpath)
{
char *path;
char *cp;
char buf[MAXPGPATH+1];
/* leading path delimiter? then already absolute path */
if (*dbpath == SEP_CHAR)
{
cp = strrchr(dbpath, SEP_CHAR);
strncpy(buf,dbpath,(cp-dbpath));
sprintf(&buf[cp-dbpath], "%cbase%c%s", SEP_CHAR, SEP_CHAR, (cp+1));
}
/* path delimiter somewhere? then has leading environment variable */
else if (strchr(dbpath, SEP_CHAR) != NULL)
{
cp = strchr(dbpath, SEP_CHAR);
strncpy(buf,dbpath,(cp-dbpath));
buf[cp-dbpath] = '\0';
path = getenv(buf);
sprintf(buf, "%s%cbase%c%s", path, SEP_CHAR, SEP_CHAR, (cp+1));
}
/* no path delimiter? then add the default path prefixes */
else
{
sprintf(buf, "%s%cbase%c%s", DataDir, SEP_CHAR, SEP_CHAR, dbpath);
}
path = palloc(strlen(buf)+1);
strcpy(path,buf);
return path;
} /* ExpandDatabasePath() */
/* --------------------------------
* GetRawDatabaseInfo() -- Find the OID and path of the database.
*
* The database's oid forms half of the unique key for the system
* caches and lock tables. We therefore want it initialized before
* we open any relations, since opening relations puts things in the
* cache. To get around this problem, this code opens and scans the
* pg_database relation by hand.
*
* This algorithm relies on the fact that first attribute in the
* pg_database relation schema is the database name. It also knows
* about the internal format of tuples on disk and the length of
* the datname attribute. It knows the location of the pg_database
* file.
* Actually, the code looks as though it is using the pg_database
* tuple definition to locate the database name, so the above statement
* seems to be no longer correct. - thomas 1997-11-01
*
* This code is called from InitPostgres(), before we chdir() to the
* local database directory and before we open any relations.
* Used to be called after the chdir(), but we now want to confirm
* the location of the target database using pg_database info.
* - thomas 1997-11-01
* --------------------------------
*/
void
GetRawDatabaseInfo(char *name, Oid *owner, Oid *db_id, char *path)
{
int dbfd;
int fileflags;
int nbytes;
int max,
i;
HeapTuple tup;
Page pg;
PageHeader ph;
char *dbfname;
Form_pg_database tup_db;
dbfname = (char *) palloc(strlen(DataDir) + strlen("pg_database") + 2);
sprintf(dbfname, "%s%cpg_database", DataDir, SEP_CHAR);
fileflags = O_RDONLY;
if ((dbfd = open(dbfname, O_RDONLY, 0)) < 0)
elog(FATAL, "Cannot open %s", dbfname);
pfree(dbfname);
/* ----------------
* read and examine every page in pg_database
*
* Raw I/O! Read those tuples the hard way! Yow!
*
* Why don't we use the access methods or move this code
* someplace else? This is really pg_database schema dependent
* code. Perhaps it should go in lib/catalog/pg_database?
* -cim 10/3/90
*
* mao replies 4 apr 91: yeah, maybe this should be moved to
* lib/catalog. however, we CANNOT use the access methods since
* those use the buffer cache, which uses the relation cache, which
* requires that the dbid be set, which is what we're trying to do
* here.
* ----------------
*/
pg = (Page) palloc(BLCKSZ);
ph = (PageHeader) pg;
while ((nbytes = read(dbfd, pg, BLCKSZ)) == BLCKSZ)
{
max = PageGetMaxOffsetNumber(pg);
/* look at each tuple on the page */
for (i = 0; i <= max; i++)
{
int offset;
/* if it's a freed tuple, ignore it */
if (!(ph->pd_linp[i].lp_flags & LP_USED))
continue;
/* get a pointer to the tuple itself */
offset = (int) ph->pd_linp[i].lp_off;
tup = (HeapTuple) (((char *) pg) + offset);
/*
* if the tuple has been deleted (the database was destroyed),
* skip this tuple. XXX warning, will robinson: violation of
* transaction semantics happens right here. we should check
* to be sure that the xact that deleted this tuple actually
* committed. only way to do this at init time is to paw over
* the log relation by hand, too. let's be optimistic.
*
* XXX This is an evil type cast. tup->t_xmax is char[5] while
* TransactionId is struct * { char data[5] }. It works but
* if data is ever moved and no longer the first field this
* will be broken!! -mer 11 Nov 1991.
*/
if (TransactionIdIsValid((TransactionId) tup->t_xmax))
continue;
/*
* Okay, see if this is the one we want. XXX 1 july 91: mao
* and mer discover that tuples now squash t_bits. Why is
* this?
*
* 24 july 92: mer realizes that the t_bits field is only used
* in the event of null values. If no fields are null we
* reduce the header size by doing the squash. t_hoff tells
* you exactly how big the header actually is. use the PC
* means of getting at sys cat attrs.
*/
tup_db = (Form_pg_database) GETSTRUCT(tup);
if (strncmp(name,
&(tup_db->datname.data[0]),
16) == 0)
{
*db_id = tup->t_oid;
strncpy(path, VARDATA(&(tup_db->datpath)),
(VARSIZE(&(tup_db->datpath))-VARHDRSZ));
*(path+VARSIZE(&(tup_db->datpath))-VARHDRSZ) = '\0';
goto done;
}
}
}
done:
close(dbfd);
pfree(pg);
} /* GetRawDatabaseInfo() */