Index: src/backend/utils/adt/misc.c
===================================================================
RCS file: /projects/cvsroot/pgsql-server/src/backend/utils/adt/misc.c,v
retrieving revision 1.34
diff -u -r1.34 misc.c
--- src/backend/utils/adt/misc.c	2 Jun 2004 21:29:29 -0000	1.34
+++ src/backend/utils/adt/misc.c	28 Jun 2004 11:16:05 -0000
@@ -16,11 +16,16 @@
 
 #include <sys/file.h>
 #include <signal.h>
+#include <dirent.h>
 
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
 #include "storage/sinval.h"
+#include "storage/fd.h"
 #include "utils/builtins.h"
+#include "funcapi.h"
+#include "catalog/pg_type.h"
+#include "catalog/pg_tablespace.h"
 
 
 /*
@@ -102,4 +107,92 @@
 pg_cancel_backend(PG_FUNCTION_ARGS)
 {
 	PG_RETURN_INT32(pg_signal_backend(PG_GETARG_INT32(0),SIGINT));
+}
+
+
+typedef struct 
+{
+	char *location;
+	DIR *dirdesc;
+} ts_db_fctx;
+
+Datum pg_tablespace_databases(PG_FUNCTION_ARGS)
+{
+	FuncCallContext *funcctx;
+	struct dirent *de;
+	ts_db_fctx *fctx;
+
+	if (SRF_IS_FIRSTCALL())
+	{
+		MemoryContext oldcontext;
+		Oid tablespaceOid=PG_GETARG_OID(0);
+
+		funcctx=SRF_FIRSTCALL_INIT();
+		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
+
+		fctx = palloc(sizeof(ts_db_fctx));
+
+		fctx->location = (char*)palloc(strlen(DataDir)+16+10+1);
+		if (tablespaceOid == GLOBALTABLESPACE_OID)
+		{
+			fctx->dirdesc = NULL;
+			ereport(NOTICE,
+					(errcode(ERRCODE_WARNING),
+					 errmsg("global tablespace never has databases.")));
+		}
+		else
+		{
+			if (tablespaceOid == DEFAULTTABLESPACE_OID)
+				sprintf(fctx->location, "%s/base", DataDir);
+			else
+				sprintf(fctx->location, "%s/pg_tblspc/%u", DataDir, tablespaceOid);
+		
+			fctx->dirdesc = AllocateDir(fctx->location);
+
+			if (!fctx->dirdesc)  /* not a tablespace */
+				ereport(NOTICE,
+						(errcode(ERRCODE_WARNING),
+						 errmsg("%d is no tablespace oid.", tablespaceOid)));
+		}
+		funcctx->user_fctx = fctx;
+		MemoryContextSwitchTo(oldcontext);
+	}
+
+	funcctx=SRF_PERCALL_SETUP();
+	fctx = (ts_db_fctx*)funcctx->user_fctx;
+
+	if (!fctx->dirdesc)  /* not a tablespace */
+		SRF_RETURN_DONE(funcctx);
+
+	while ((de = readdir(fctx->dirdesc)) != NULL)
+	{
+		char *subdir;
+		DIR *dirdesc;
+
+		Oid datOid = atol(de->d_name);
+		if (!datOid)
+			continue;
+
+		subdir = palloc(strlen(fctx->location) + 1 + strlen(de->d_name) +1 );
+		sprintf(subdir, "%s/%s", fctx->location, de->d_name);
+		dirdesc = AllocateDir(subdir);
+		if (dirdesc)
+		{
+			while ((de = readdir(dirdesc)) != 0)
+			{
+				if (strcmp(de->d_name, ".") && strcmp(de->d_name, ".."))
+					break;
+			}
+			pfree(subdir);
+			FreeDir(dirdesc);
+
+			if (!de)   /* database subdir is empty; don't report tablespace as used */
+				continue;
+		}
+
+		SRF_RETURN_NEXT(funcctx, ObjectIdGetDatum(datOid));
+	}
+
+	FreeDir(fctx->dirdesc);
+	SRF_RETURN_DONE(funcctx);
 }
Index: src/include/catalog/pg_proc.h
===================================================================
RCS file: /projects/cvsroot/pgsql-server/src/include/catalog/pg_proc.h,v
retrieving revision 1.339
diff -u -r1.339 pg_proc.h
--- src/include/catalog/pg_proc.h	25 Jun 2004 17:20:28 -0000	1.339
+++ src/include/catalog/pg_proc.h	28 Jun 2004 11:16:32 -0000
@@ -3595,6 +3595,9 @@
 DATA(insert OID = 2243 ( bit_or						   PGNSP PGUID 12 t f f f i 1 1560 "1560" _null_ aggregate_dummy - _null_));
 DESCR("bitwise-or bit aggregate");

+DATA(insert OID = 2554(  pg_tablespace_databases       PGNSP PGUID 12 f f t t s 1 26 "26" _null_ pg_tablespace_databases - _null_ ));
+DESCR("returns database oids in a tablespace");
+
 /*
  * Symbolic values for provolatile column: these indicate whether the result
  * of a function is dependent *only* on the values of its explicit arguments,
Index: src/include/utils/builtins.h
===================================================================
RCS file: /projects/cvsroot/pgsql-server/src/include/utils/builtins.h,v
retrieving revision 1.244
diff -u -r1.244 builtins.h
--- src/include/utils/builtins.h	25 Jun 2004 17:20:29 -0000	1.244
+++ src/include/utils/builtins.h	28 Jun 2004 11:16:35 -0000
@@ -356,6 +356,7 @@
 extern Datum current_database(PG_FUNCTION_ARGS);
 extern Datum pg_terminate_backend(PG_FUNCTION_ARGS);
 extern Datum pg_cancel_backend(PG_FUNCTION_ARGS);
+extern Datum pg_tablespace_databases(PG_FUNCTION_ARGS);

 /* not_in.c */
 extern Datum int4notin(PG_FUNCTION_ARGS);