granicus.if.org Git - postgresql/blob - src/backend/commands/dbcommands.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * dbcommands.c
   4  *              Database management commands (create/drop database).
   5  *
   6  *
   7  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
   8  * Portions Copyright (c) 1994, Regents of the University of California
   9  *
  10  *
  11  * IDENTIFICATION
  12  *        $Header: /cvsroot/pgsql/src/backend/commands/dbcommands.c,v 1.98 2002/08/05 03:29:16 tgl Exp $
  13  *
  14  *-------------------------------------------------------------------------
  15  */
  16 #include "postgres.h"
  17
  18 #include <errno.h>
  19 #include <fcntl.h>
  20 #include <unistd.h>
  21 #include <sys/stat.h>
  22 #include <sys/types.h>
  23
  24 #include "access/heapam.h"
  25 #include "catalog/catname.h"
  26 #include "catalog/catalog.h"
  27 #include "catalog/pg_database.h"
  28 #include "catalog/pg_shadow.h"
  29 #include "catalog/indexing.h"
  30 #include "commands/comment.h"
  31 #include "commands/dbcommands.h"
  32 #include "miscadmin.h"
  33 #include "storage/freespace.h"
  34 #include "storage/sinval.h"
  35 #include "utils/array.h"
  36 #include "utils/builtins.h"
  37 #include "utils/fmgroids.h"
  38 #include "utils/guc.h"
  39 #include "utils/lsyscache.h"
  40 #include "utils/syscache.h"
  41
  42 #ifdef MULTIBYTE
  43 #include "mb/pg_wchar.h"                /* encoding check */
  44 #endif
  45
  46
  47 /* non-export function prototypes */
  48 static bool get_db_info(const char *name, Oid *dbIdP, int4 *ownerIdP,
  49                         int *encodingP, bool *dbIsTemplateP, Oid *dbLastSysOidP,
  50                         TransactionId *dbVacuumXidP, TransactionId *dbFrozenXidP,
  51                         char *dbpath);
  52 static bool have_createdb_privilege(void);
  53 static char *resolve_alt_dbpath(const char *dbpath, Oid dboid);
  54 static bool remove_dbdirs(const char *real_loc, const char *altloc);
  55
  56 /*
  57  * CREATE DATABASE
  58  */
  59
  60 void
  61 createdb(const CreatedbStmt *stmt)
  62 {
  63         char       *nominal_loc;
  64         char       *alt_loc;
  65         char       *target_dir;
  66         char            src_loc[MAXPGPATH];
  67         char            buf[2 * MAXPGPATH + 100];
  68         Oid                     src_dboid;
  69         int4            src_owner;
  70         int                     src_encoding;
  71         bool            src_istemplate;
  72         Oid                     src_lastsysoid;
  73         TransactionId src_vacuumxid;
  74         TransactionId src_frozenxid;
  75         char            src_dbpath[MAXPGPATH];
  76         Relation        pg_database_rel;
  77         HeapTuple       tuple;
  78         TupleDesc       pg_database_dsc;
  79         Datum           new_record[Natts_pg_database];
  80         char            new_record_nulls[Natts_pg_database];
  81         Oid                     dboid;
  82         int32           datdba;
  83         List       *option;
  84         DefElem    *downer = NULL;
  85         DefElem    *dpath = NULL;
  86         DefElem    *dtemplate = NULL;
  87         DefElem    *dencoding = NULL;
  88         char       *dbname = stmt->dbname;
  89         char       *dbowner = NULL;
  90         char       *dbpath = NULL;
  91         char       *dbtemplate = NULL;
  92         int                 encoding = -1;
  93
  94         /* Extract options from the statement node tree */
  95         foreach(option, stmt->options)
  96         {
  97                 DefElem    *defel = (DefElem *) lfirst(option);
  98
  99                 if (strcmp(defel->defname, "owner") == 0)
 100                 {
 101                         if (downer)
 102                                 elog(ERROR, "CREATE DATABASE: conflicting options");
 103                         downer = defel;
 104                 }
 105                 else if (strcmp(defel->defname, "location") == 0)
 106                 {
 107                         if (dpath)
 108                                 elog(ERROR, "CREATE DATABASE: conflicting options");
 109                         dpath = defel;
 110                 }
 111                 else if (strcmp(defel->defname, "template") == 0)
 112                 {
 113                         if (dtemplate)
 114                                 elog(ERROR, "CREATE DATABASE: conflicting options");
 115                         dtemplate = defel;
 116                 }
 117                 else if (strcmp(defel->defname, "encoding") == 0)
 118                 {
 119                         if (dencoding)
 120                                 elog(ERROR, "CREATE DATABASE: conflicting options");
 121                         dencoding = defel;
 122                 }
 123                 else
 124                         elog(ERROR, "CREATE DATABASE: option \"%s\" not recognized",
 125                                  defel->defname);
 126         }
 127
 128         if (downer)
 129                 dbowner = strVal(downer->arg);
 130         if (dpath)
 131                 dbpath = strVal(dpath->arg);
 132         if (dtemplate)
 133                 dbtemplate = strVal(dtemplate->arg);
 134         if (dencoding)
 135                 encoding = intVal(dencoding->arg);
 136
 137         /* obtain sysid of proposed owner */
 138         if (dbowner)
 139                 datdba = get_usesysid(dbowner); /* will elog if no such user */
 140         else
 141                 datdba = GetUserId();
 142
 143         if (datdba == (int32) GetUserId())
 144         {
 145                 /* creating database for self: can be superuser or createdb */
 146                 if (!superuser() && !have_createdb_privilege())
 147                         elog(ERROR, "CREATE DATABASE: permission denied");
 148         }
 149         else
 150         {
 151                 /* creating database for someone else: must be superuser */
 152                 /* note that the someone else need not have any permissions */
 153                 if (!superuser())
 154                         elog(ERROR, "CREATE DATABASE: permission denied");
 155         }
 156
 157         /* don't call this in a transaction block */
 158         if (IsTransactionBlock())
 159                 elog(ERROR, "CREATE DATABASE: may not be called in a transaction block");
 160
 161         /*
 162          * Check for db name conflict.  There is a race condition here, since
 163          * another backend could create the same DB name before we commit.
 164          * However, holding an exclusive lock on pg_database for the whole
 165          * time we are copying the source database doesn't seem like a good
 166          * idea, so accept possibility of race to create.  We will check again
 167          * after we grab the exclusive lock.
 168          */
 169         if (get_db_info(dbname, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL))
 170                 elog(ERROR, "CREATE DATABASE: database \"%s\" already exists", dbname);
 171
 172         /*
 173          * Lookup database (template) to be cloned.
 174          */
 175         if (!dbtemplate)
 176                 dbtemplate = "template1";               /* Default template database name */
 177
 178         if (!get_db_info(dbtemplate, &src_dboid, &src_owner, &src_encoding,
 179                                          &src_istemplate, &src_lastsysoid,
 180                                          &src_vacuumxid, &src_frozenxid,
 181                                          src_dbpath))
 182                 elog(ERROR, "CREATE DATABASE: template \"%s\" does not exist",
 183                          dbtemplate);
 184
 185         /*
 186          * Permission check: to copy a DB that's not marked datistemplate, you
 187          * must be superuser or the owner thereof.
 188          */
 189         if (!src_istemplate)
 190         {
 191                 if (!superuser() && GetUserId() != src_owner )
 192                         elog(ERROR, "CREATE DATABASE: permission to copy \"%s\" denied",
 193                                  dbtemplate);
 194         }
 195
 196         /*
 197          * Determine physical path of source database
 198          */
 199         alt_loc = resolve_alt_dbpath(src_dbpath, src_dboid);
 200         if (!alt_loc)
 201                 alt_loc = GetDatabasePath(src_dboid);
 202         strcpy(src_loc, alt_loc);
 203
 204         /*
 205          * The source DB can't have any active backends, except this one
 206          * (exception is to allow CREATE DB while connected to template1).
 207          * Otherwise we might copy inconsistent data.  This check is not
 208          * bulletproof, since someone might connect while we are copying...
 209          */
 210         if (DatabaseHasActiveBackends(src_dboid, true))
 211                 elog(ERROR, "CREATE DATABASE: source database \"%s\" is being accessed by other users", dbtemplate);
 212
 213         /* If encoding is defaulted, use source's encoding */
 214         if (encoding < 0)
 215                 encoding = src_encoding;
 216
 217 #ifdef MULTIBYTE
 218         /* Some encodings are client only */
 219         if (!PG_VALID_BE_ENCODING(encoding))
 220                 elog(ERROR, "CREATE DATABASE: invalid backend encoding");
 221 #else
 222         Assert(encoding == 0);          /* zero is PG_SQL_ASCII */
 223 #endif
 224
 225         /*
 226          * Preassign OID for pg_database tuple, so that we can compute db
 227          * path.
 228          */
 229         dboid = newoid();
 230
 231         /*
 232          * Compute nominal location (where we will try to access the
 233          * database), and resolve alternate physical location if one is
 234          * specified.
 235          *
 236          * If an alternate location is specified but is the same as the
 237          * normal path, just drop the alternate-location spec (this seems
 238          * friendlier than erroring out).  We must test this case to avoid
 239          * creating a circular symlink below.
 240          */
 241         nominal_loc = GetDatabasePath(dboid);
 242         alt_loc = resolve_alt_dbpath(dbpath, dboid);
 243
 244         if (alt_loc && strcmp(alt_loc, nominal_loc) == 0)
 245         {
 246                 alt_loc = NULL;
 247                 dbpath = NULL;
 248         }
 249
 250         if (strchr(nominal_loc, '\''))
 251                 elog(ERROR, "database path may not contain single quotes");
 252         if (alt_loc && strchr(alt_loc, '\''))
 253                 elog(ERROR, "database path may not contain single quotes");
 254         if (strchr(src_loc, '\''))
 255                 elog(ERROR, "database path may not contain single quotes");
 256         /* ... otherwise we'd be open to shell exploits below */
 257
 258         /*
 259          * Force dirty buffers out to disk, to ensure source database is
 260          * up-to-date for the copy.  (We really only need to flush buffers for
 261          * the source database...)
 262          */
 263         BufferSync();
 264
 265         /*
 266          * Close virtual file descriptors so the kernel has more available for
 267          * the mkdir() and system() calls below.
 268          */
 269         closeAllVfds();
 270
 271         /*
 272          * Check we can create the target directory --- but then remove it
 273          * because we rely on cp(1) to create it for real.
 274          */
 275         target_dir = alt_loc ? alt_loc : nominal_loc;
 276
 277         if (mkdir(target_dir, S_IRWXU) != 0)
 278                 elog(ERROR, "CREATE DATABASE: unable to create database directory '%s': %m",
 279                          target_dir);
 280         if (rmdir(target_dir) != 0)
 281                 elog(ERROR, "CREATE DATABASE: unable to remove temp directory '%s': %m",
 282                          target_dir);
 283
 284         /* Make the symlink, if needed */
 285         if (alt_loc)
 286         {
 287                 if (symlink(alt_loc, nominal_loc) != 0)
 288                         elog(ERROR, "CREATE DATABASE: could not link '%s' to '%s': %m",
 289                                  nominal_loc, alt_loc);
 290         }
 291
 292         /* Copy the template database to the new location */
 293         snprintf(buf, sizeof(buf), "cp -r '%s' '%s'", src_loc, target_dir);
 294
 295         if (system(buf) != 0)
 296         {
 297                 if (remove_dbdirs(nominal_loc, alt_loc))
 298                         elog(ERROR, "CREATE DATABASE: could not initialize database directory");
 299                 else
 300                         elog(ERROR, "CREATE DATABASE: could not initialize database directory; delete failed as well");
 301         }
 302
 303         /*
 304          * Now OK to grab exclusive lock on pg_database.
 305          */
 306         pg_database_rel = heap_openr(DatabaseRelationName, AccessExclusiveLock);
 307
 308         /* Check to see if someone else created same DB name meanwhile. */
 309         if (get_db_info(dbname, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL))
 310         {
 311                 /* Don't hold lock while doing recursive remove */
 312                 heap_close(pg_database_rel, AccessExclusiveLock);
 313                 remove_dbdirs(nominal_loc, alt_loc);
 314                 elog(ERROR, "CREATE DATABASE: database \"%s\" already exists", dbname);
 315         }
 316
 317         /*
 318          * Insert a new tuple into pg_database
 319          */
 320         pg_database_dsc = RelationGetDescr(pg_database_rel);
 321
 322         /* Form tuple */
 323         MemSet(new_record, 0, sizeof(new_record));
 324         MemSet(new_record_nulls, ' ', sizeof(new_record_nulls));
 325
 326         new_record[Anum_pg_database_datname - 1] =
 327                 DirectFunctionCall1(namein, CStringGetDatum(dbname));
 328         new_record[Anum_pg_database_datdba - 1] = Int32GetDatum(datdba);
 329         new_record[Anum_pg_database_encoding - 1] = Int32GetDatum(encoding);
 330         new_record[Anum_pg_database_datistemplate - 1] = BoolGetDatum(false);
 331         new_record[Anum_pg_database_datallowconn - 1] = BoolGetDatum(true);
 332         new_record[Anum_pg_database_datlastsysoid - 1] = ObjectIdGetDatum(src_lastsysoid);
 333         new_record[Anum_pg_database_datvacuumxid - 1] = TransactionIdGetDatum(src_vacuumxid);
 334         new_record[Anum_pg_database_datfrozenxid - 1] = TransactionIdGetDatum(src_frozenxid);
 335         /* do not set datpath to null, GetRawDatabaseInfo won't cope */
 336         new_record[Anum_pg_database_datpath - 1] =
 337                 DirectFunctionCall1(textin, CStringGetDatum(dbpath ? dbpath : ""));
 338
 339         new_record_nulls[Anum_pg_database_datconfig - 1] = 'n';
 340         new_record_nulls[Anum_pg_database_datacl - 1] = 'n';
 341
 342         tuple = heap_formtuple(pg_database_dsc, new_record, new_record_nulls);
 343
 344         AssertTupleDescHasOid(pg_database_dsc);
 345         HeapTupleSetOid(tuple, dboid);          /* override heap_insert's OID
 346                                                                                  * selection */
 347
 348         simple_heap_insert(pg_database_rel, tuple);
 349
 350         /* Update indexes */
 351         CatalogUpdateIndexes(pg_database_rel, tuple);
 352
 353         /* Close pg_database, but keep lock till commit */
 354         heap_close(pg_database_rel, NoLock);
 355
 356         /*
 357          * Force dirty buffers out to disk, so that newly-connecting backends
 358          * will see the new database in pg_database right away.  (They'll see
 359          * an uncommitted tuple, but they don't care; see GetRawDatabaseInfo.)
 360          */
 361         BufferSync();
 362 }
 363
 364
 365 /*
 366  * DROP DATABASE
 367  */
 368 void
 369 dropdb(const char *dbname)
 370 {
 371         int4            db_owner;
 372         bool            db_istemplate;
 373         Oid                     db_id;
 374         char       *alt_loc;
 375         char       *nominal_loc;
 376         char            dbpath[MAXPGPATH];
 377         Relation        pgdbrel;
 378         HeapScanDesc pgdbscan;
 379         ScanKeyData key;
 380         HeapTuple       tup;
 381
 382         AssertArg(dbname);
 383
 384         if (strcmp(dbname, DatabaseName) == 0)
 385                 elog(ERROR, "DROP DATABASE: cannot be executed on the currently open database");
 386
 387         if (IsTransactionBlock())
 388                 elog(ERROR, "DROP DATABASE: may not be called in a transaction block");
 389
 390         /*
 391          * Obtain exclusive lock on pg_database.  We need this to ensure that
 392          * no new backend starts up in the target database while we are
 393          * deleting it.  (Actually, a new backend might still manage to start
 394          * up, because it will read pg_database without any locking to
 395          * discover the database's OID.  But it will detect its error in
 396          * ReverifyMyDatabase and shut down before any serious damage is done.
 397          * See postinit.c.)
 398          */
 399         pgdbrel = heap_openr(DatabaseRelationName, AccessExclusiveLock);
 400
 401         if (!get_db_info(dbname, &db_id, &db_owner, NULL,
 402                                          &db_istemplate, NULL, NULL, NULL, dbpath))
 403                 elog(ERROR, "DROP DATABASE: database \"%s\" does not exist", dbname);
 404
 405         if (GetUserId() != db_owner && !superuser())
 406                 elog(ERROR, "DROP DATABASE: permission denied");
 407
 408         /*
 409          * Disallow dropping a DB that is marked istemplate.  This is just to
 410          * prevent people from accidentally dropping template0 or template1;
 411          * they can do so if they're really determined ...
 412          */
 413         if (db_istemplate)
 414                 elog(ERROR, "DROP DATABASE: database is marked as a template");
 415
 416         nominal_loc = GetDatabasePath(db_id);
 417         alt_loc = resolve_alt_dbpath(dbpath, db_id);
 418
 419         /*
 420          * Check for active backends in the target database.
 421          */
 422         if (DatabaseHasActiveBackends(db_id, false))
 423                 elog(ERROR, "DROP DATABASE: database \"%s\" is being accessed by other users", dbname);
 424
 425         /*
 426          * Find the database's tuple by OID (should be unique).
 427          */
 428         ScanKeyEntryInitialize(&key, 0, ObjectIdAttributeNumber,
 429                                                    F_OIDEQ, ObjectIdGetDatum(db_id));
 430
 431         pgdbscan = heap_beginscan(pgdbrel, SnapshotNow, 1, &key);
 432
 433         tup = heap_getnext(pgdbscan, ForwardScanDirection);
 434         if (!HeapTupleIsValid(tup))
 435         {
 436                 /*
 437                  * This error should never come up since the existence of the
 438                  * database is checked earlier
 439                  */
 440                 elog(ERROR, "DROP DATABASE: Database \"%s\" doesn't exist despite earlier reports to the contrary",
 441                          dbname);
 442         }
 443
 444         /* Remove the database's tuple from pg_database */
 445         simple_heap_delete(pgdbrel, &tup->t_self);
 446
 447         heap_endscan(pgdbscan);
 448
 449         /*
 450          * Delete any comments associated with the database
 451          *
 452          * NOTE: this is probably dead code since any such comments should have
 453          * been in that database, not mine.
 454          */
 455         DeleteComments(db_id, RelationGetRelid(pgdbrel), 0);
 456
 457         /*
 458          * Close pg_database, but keep exclusive lock till commit to ensure
 459          * that any new backend scanning pg_database will see the tuple dead.
 460          */
 461         heap_close(pgdbrel, NoLock);
 462
 463         /*
 464          * Drop pages for this database that are in the shared buffer cache.
 465          * This is important to ensure that no remaining backend tries to
 466          * write out a dirty buffer to the dead database later...
 467          */
 468         DropBuffers(db_id);
 469
 470         /*
 471          * Also, clean out any entries in the shared free space map.
 472          */
 473         FreeSpaceMapForgetDatabase(db_id);
 474
 475         /*
 476          * Remove the database's subdirectory and everything in it.
 477          */
 478         remove_dbdirs(nominal_loc, alt_loc);
 479
 480         /*
 481          * Force dirty buffers out to disk, so that newly-connecting backends
 482          * will see the database tuple marked dead in pg_database right away.
 483          * (They'll see an uncommitted deletion, but they don't care; see
 484          * GetRawDatabaseInfo.)
 485          */
 486         BufferSync();
 487 }
 488
 489
 490
 491 /*
 492  * ALTER DATABASE name SET ...
 493  */
 494 void
 495 AlterDatabaseSet(AlterDatabaseSetStmt *stmt)
 496 {
 497         char       *valuestr;
 498         HeapTuple       tuple,
 499                                 newtuple;
 500         Relation        rel;
 501         ScanKeyData     scankey;
 502         HeapScanDesc scan;
 503         Datum           repl_val[Natts_pg_database];
 504         char            repl_null[Natts_pg_database];
 505         char            repl_repl[Natts_pg_database];
 506
 507         valuestr = flatten_set_variable_args(stmt->variable, stmt->value);
 508
 509         rel = heap_openr(DatabaseRelationName, RowExclusiveLock);
 510         ScanKeyEntryInitialize(&scankey, 0, Anum_pg_database_datname,
 511                                                    F_NAMEEQ, NameGetDatum(stmt->dbname));
 512         scan = heap_beginscan(rel, SnapshotNow, 1, &scankey);
 513         tuple = heap_getnext(scan, ForwardScanDirection);
 514         if (!HeapTupleIsValid(tuple))
 515                 elog(ERROR, "database \"%s\" does not exist", stmt->dbname);
 516
 517         if (!(superuser()
 518                   || ((Form_pg_database) GETSTRUCT(tuple))->datdba == GetUserId()))
 519                 elog(ERROR, "permission denied");
 520
 521         MemSet(repl_repl, ' ', sizeof(repl_repl));
 522         repl_repl[Anum_pg_database_datconfig-1] = 'r';
 523
 524         if (strcmp(stmt->variable, "all")==0 && valuestr == NULL)
 525         {
 526                 /* RESET ALL */
 527                 repl_null[Anum_pg_database_datconfig-1] = 'n';
 528                 repl_val[Anum_pg_database_datconfig-1] = (Datum) 0;
 529         }
 530         else
 531         {
 532                 Datum datum;
 533                 bool isnull;
 534                 ArrayType *a;
 535
 536                 repl_null[Anum_pg_database_datconfig-1] = ' ';
 537
 538                 datum = heap_getattr(tuple, Anum_pg_database_datconfig,
 539                                                          RelationGetDescr(rel), &isnull);
 540
 541                 a = isnull ? ((ArrayType *) NULL) : DatumGetArrayTypeP(datum);
 542
 543                 if (valuestr)
 544                         a = GUCArrayAdd(a, stmt->variable, valuestr);
 545                 else
 546                         a = GUCArrayDelete(a, stmt->variable);
 547
 548                 repl_val[Anum_pg_database_datconfig-1] = PointerGetDatum(a);
 549         }
 550
 551         newtuple = heap_modifytuple(tuple, rel, repl_val, repl_null, repl_repl);
 552         simple_heap_update(rel, &tuple->t_self, newtuple);
 553
 554         /* Update indexes */
 555         CatalogUpdateIndexes(rel, newtuple);
 556
 557         heap_endscan(scan);
 558         heap_close(rel, RowExclusiveLock);
 559 }
 560
 561
 562
 563 /*
 564  * Helper functions
 565  */
 566
 567 static bool
 568 get_db_info(const char *name, Oid *dbIdP, int4 *ownerIdP,
 569                         int *encodingP, bool *dbIsTemplateP, Oid *dbLastSysOidP,
 570                         TransactionId *dbVacuumXidP, TransactionId *dbFrozenXidP,
 571                         char *dbpath)
 572 {
 573         Relation        relation;
 574         ScanKeyData scanKey;
 575         HeapScanDesc scan;
 576         HeapTuple       tuple;
 577         bool            gottuple;
 578
 579         AssertArg(name);
 580
 581         /* Caller may wish to grab a better lock on pg_database beforehand... */
 582         relation = heap_openr(DatabaseRelationName, AccessShareLock);
 583
 584         ScanKeyEntryInitialize(&scanKey, 0, Anum_pg_database_datname,
 585                                                    F_NAMEEQ, NameGetDatum(name));
 586
 587         scan = heap_beginscan(relation, SnapshotNow, 1, &scanKey);
 588
 589         tuple = heap_getnext(scan, ForwardScanDirection);
 590
 591         gottuple = HeapTupleIsValid(tuple);
 592         if (gottuple)
 593         {
 594                 Form_pg_database dbform = (Form_pg_database) GETSTRUCT(tuple);
 595
 596                 /* oid of the database */
 597                 if (dbIdP)
 598                 {
 599                         AssertTupleDescHasOid(relation->rd_att);
 600                         *dbIdP = HeapTupleGetOid(tuple);
 601                 }
 602                 /* sysid of the owner */
 603                 if (ownerIdP)
 604                         *ownerIdP = dbform->datdba;
 605                 /* multibyte encoding */
 606                 if (encodingP)
 607                         *encodingP = dbform->encoding;
 608                 /* allowed as template? */
 609                 if (dbIsTemplateP)
 610                         *dbIsTemplateP = dbform->datistemplate;
 611                 /* last system OID used in database */
 612                 if (dbLastSysOidP)
 613                         *dbLastSysOidP = dbform->datlastsysoid;
 614                 /* limit of vacuumed XIDs */
 615                 if (dbVacuumXidP)
 616                         *dbVacuumXidP = dbform->datvacuumxid;
 617                 /* limit of frozen XIDs */
 618                 if (dbFrozenXidP)
 619                         *dbFrozenXidP = dbform->datfrozenxid;
 620                 /* database path (as registered in pg_database) */
 621                 if (dbpath)
 622                 {
 623                         Datum           datum;
 624                         bool            isnull;
 625
 626                         datum = heap_getattr(tuple,
 627                                                                  Anum_pg_database_datpath,
 628                                                                  RelationGetDescr(relation),
 629                                                                  &isnull);
 630                         if (!isnull)
 631                         {
 632                                 text       *pathtext = DatumGetTextP(datum);
 633                                 int                     pathlen = VARSIZE(pathtext) - VARHDRSZ;
 634
 635                                 Assert(pathlen >= 0 && pathlen < MAXPGPATH);
 636                                 strncpy(dbpath, VARDATA(pathtext), pathlen);
 637                                 *(dbpath + pathlen) = '\0';
 638                         }
 639                         else
 640                                 strcpy(dbpath, "");
 641                 }
 642         }
 643
 644         heap_endscan(scan);
 645         heap_close(relation, AccessShareLock);
 646
 647         return gottuple;
 648 }
 649
 650 static bool
 651 have_createdb_privilege(void)
 652 {
 653         HeapTuple       utup;
 654         bool            retval;
 655
 656         utup = SearchSysCache(SHADOWSYSID,
 657                                                   ObjectIdGetDatum(GetUserId()),
 658                                                   0, 0, 0);
 659
 660         if (!HeapTupleIsValid(utup))
 661                 retval = false;
 662         else
 663                 retval = ((Form_pg_shadow) GETSTRUCT(utup))->usecreatedb;
 664
 665         ReleaseSysCache(utup);
 666
 667         return retval;
 668 }
 669
 670
 671 static char *
 672 resolve_alt_dbpath(const char *dbpath, Oid dboid)
 673 {
 674         const char *prefix;
 675         char       *ret;
 676         size_t          len;
 677
 678         if (dbpath == NULL || dbpath[0] == '\0')
 679                 return NULL;
 680
 681         if (strchr(dbpath, '/'))
 682         {
 683                 if (dbpath[0] != '/')
 684                         elog(ERROR, "Relative paths are not allowed as database locations");
 685 #ifndef ALLOW_ABSOLUTE_DBPATHS
 686                 elog(ERROR, "Absolute paths are not allowed as database locations");
 687 #endif
 688                 prefix = dbpath;
 689         }
 690         else
 691         {
 692                 /* must be environment variable */
 693                 char       *var = getenv(dbpath);
 694
 695                 if (!var)
 696                         elog(ERROR, "Postmaster environment variable '%s' not set", dbpath);
 697                 if (var[0] != '/')
 698                         elog(ERROR, "Postmaster environment variable '%s' must be absolute path", dbpath);
 699                 prefix = var;
 700         }
 701
 702         len = strlen(prefix) + 6 + sizeof(Oid) * 8 + 1;
 703         if (len >= MAXPGPATH - 100)
 704                 elog(ERROR, "Alternate path is too long");
 705
 706         ret = palloc(len);
 707         snprintf(ret, len, "%s/base/%u", prefix, dboid);
 708
 709         return ret;
 710 }
 711
 712
 713 static bool
 714 remove_dbdirs(const char *nominal_loc, const char *alt_loc)
 715 {
 716         const char *target_dir;
 717         char            buf[MAXPGPATH + 100];
 718         bool            success = true;
 719
 720         target_dir = alt_loc ? alt_loc : nominal_loc;
 721
 722         /*
 723          * Close virtual file descriptors so the kernel has more available for
 724          * the system() call below.
 725          */
 726         closeAllVfds();
 727
 728         if (alt_loc)
 729         {
 730                 /* remove symlink */
 731                 if (unlink(nominal_loc) != 0)
 732                 {
 733                         elog(WARNING, "could not remove '%s': %m", nominal_loc);
 734                         success = false;
 735                 }
 736         }
 737
 738         snprintf(buf, sizeof(buf), "rm -rf '%s'", target_dir);
 739
 740         if (system(buf) != 0)
 741         {
 742                 elog(WARNING, "database directory '%s' could not be removed",
 743                          target_dir);
 744                 success = false;
 745         }
 746
 747         return success;
 748 }