Add per-user and per-database connection limit options.

This patch also includes preliminary update of pg_dumpall for roles.
Petr Jelinek, with review by Bruce Momjian and Tom Lane.

doc/src/sgml/catalogs.sgml

 <!--
  Documentation of the system catalogs, directed toward PostgreSQL developers
- $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.109 2005/07/26 16:38:25 tgl Exp $
+ $PostgreSQL: pgsql/doc/src/sgml/catalogs.sgml,v 2.110 2005/07/31 17:19:16 tgl Exp $
  -->
 
 <chapter id="catalogs">
@@ -1018,6 +1018,16 @@
       </entry>
      </row>
 
+     <row>
+      <entry><structfield>rolconnlimit</structfield></entry>
+      <entry><type>int4</type></entry>
+      <entry></entry>
+      <entry>
+       For roles that can log in, this sets maximum number of concurrent 
+       connections this role can make.  -1 means no limit.
+      </entry>
+     </row>
+
      <row>
       <entry><structfield>rolpassword</structfield></entry>
       <entry><type>text</type></entry>
@@ -1921,6 +1931,16 @@
       </entry>
      </row>
 
+     <row>
+      <entry><structfield>datconnlimit</structfield></entry>
+      <entry><type>int4</type></entry>
+      <entry></entry>
+      <entry>
+       Sets maximum number of concurrent connections that can be made 
+       to this database.  -1 means no limit.
+      </entry>
+     </row>
+
      <row>
       <entry><structfield>datlastsysoid</structfield></entry>
       <entry><type>oid</type></entry>
@@ -4811,6 +4831,16 @@
       </entry>
      </row>
 
+     <row>
+      <entry><structfield>rolconnlimit</structfield></entry>
+      <entry><type>int4</type></entry>
+      <entry></entry>
+      <entry>
+       For roles that can log in, this sets maximum number of concurrent 
+       connections this role can make.  -1 means no limit.
+      </entry>
+     </row>
+
      <row>
       <entry><structfield>rolpassword</structfield></entry>
       <entry><type>text</type></entry>

doc/src/sgml/ref/alter_database.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/alter_database.sgml,v 1.15 2005/01/05 14:22:39 petere Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/alter_database.sgml,v 1.16 2005/07/31 17:19:16 tgl Exp $
 PostgreSQL documentation
 -->
 
@@ -20,6 +20,12 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
+ALTER DATABASE <replaceable class="PARAMETER">name</replaceable> [ [ WITH ] <replaceable class="PARAMETER">option</replaceable> [ ... ] ]
+
+where <replaceable class="PARAMETER">option</replaceable> can be:
+
+    CONNECTION LIMIT <replaceable class="PARAMETER">connlimit</replaceable>
+
 ALTER DATABASE <replaceable class="PARAMETER">name</replaceable> SET <replaceable>parameter</replaceable> { TO | = } { <replaceable>value</replaceable> | DEFAULT }
 ALTER DATABASE <replaceable class="PARAMETER">name</replaceable> RESET <replaceable>parameter</replaceable>
 
@@ -38,7 +44,12 @@ ALTER DATABASE <replaceable class="PARAMETER">name</replaceable> OWNER TO <repla
   </para>
 
   <para>
-   The first two forms change the session default for a run-time
+   The first form changes certain per-database settings.  (See below for
+   details.)  Only the database owner or a superuser can change these settings.
+  </para> 
+
+  <para>
+   The second and third forms change the session default for a run-time
    configuration variable for a <productname>PostgreSQL</productname>
    database. Whenever a new session is subsequently started in that
    database, the specified value becomes the session default value.
@@ -51,7 +62,7 @@ ALTER DATABASE <replaceable class="PARAMETER">name</replaceable> OWNER TO <repla
   </para>
 
   <para>
-   The third form changes the name of the database.  Only the database
+   The fourth form changes the name of the database.  Only the database
    owner or a superuser can rename a database; non-superuser owners must
    also have the
    <literal>CREATEDB</literal> privilege.  The current database cannot
@@ -60,7 +71,7 @@ ALTER DATABASE <replaceable class="PARAMETER">name</replaceable> OWNER TO <repla
   </para>
 
   <para>
-   The fourth form changes the owner of the database.  Only a superuser
+   The fifth form changes the owner of the database.  Only a superuser
    can change the database's owner.
   </para>
  </refsect1>
@@ -78,6 +89,16 @@ ALTER DATABASE <replaceable class="PARAMETER">name</replaceable> OWNER TO <repla
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><replaceable class="parameter">connlimit</replaceable></term>
+      <listitem>
+       <para>
+        How many concurrent connections can be made
+        to this database.  -1 means no limit.
+       </para>
+      </listitem>
+     </varlistentry> 
+
      <varlistentry>
       <term><replaceable>parameter</replaceable></term>
       <term><replaceable>value</replaceable></term>

doc/src/sgml/ref/alter_role.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/alter_role.sgml,v 1.1 2005/07/26 23:24:02 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/alter_role.sgml,v 1.2 2005/07/31 17:19:17 tgl Exp $
 PostgreSQL documentation
 -->
 
@@ -30,6 +30,7 @@ where <replaceable class="PARAMETER">option</replaceable> can be:
     | CREATEUSER | NOCREATEUSER
     | INHERIT | NOINHERIT
     | LOGIN | NOLOGIN
+    | CONNECTION LIMIT <replaceable class="PARAMETER">connlimit</replaceable>
     | [ ENCRYPTED | UNENCRYPTED ] PASSWORD '<replaceable class="PARAMETER">password</replaceable>'
     | VALID UNTIL '<replaceable class="PARAMETER">timestamp</replaceable>' 
 
@@ -118,6 +119,7 @@ ALTER ROLE <replaceable class="PARAMETER">name</replaceable> RESET <replaceable>
       <term><literal>NOINHERIT</literal></term>
       <term><literal>LOGIN</literal></term>
       <term><literal>NOLOGIN</literal></term>
+      <term><literal>CONNECTION LIMIT</literal> <replaceable class="parameter">connlimit</replaceable></term>
       <term><literal>PASSWORD</> <replaceable class="parameter">password</replaceable></term>
       <term><literal>ENCRYPTED</></term>
       <term><literal>UNENCRYPTED</></term>

doc/src/sgml/ref/alter_user.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/alter_user.sgml,v 1.38 2005/07/26 23:24:02 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/alter_user.sgml,v 1.39 2005/07/31 17:19:17 tgl Exp $
 PostgreSQL documentation
 -->
 
@@ -30,6 +30,7 @@ where <replaceable class="PARAMETER">option</replaceable> can be:
     | CREATEUSER | NOCREATEUSER
     | INHERIT | NOINHERIT
     | LOGIN | NOLOGIN
+    | CONNECTION LIMIT <replaceable class="PARAMETER">connlimit</replaceable>
     | [ ENCRYPTED | UNENCRYPTED ] PASSWORD '<replaceable class="PARAMETER">password</replaceable>'
     | VALID UNTIL '<replaceable class="PARAMETER">timestamp</replaceable>' 
 

doc/src/sgml/ref/create_database.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_database.sgml,v 1.43 2004/10/29 03:17:22 neilc Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_database.sgml,v 1.44 2005/07/31 17:19:17 tgl Exp $
 PostgreSQL documentation
 -->
 
@@ -24,7 +24,8 @@ CREATE DATABASE <replaceable class="PARAMETER">name</replaceable>
     [ [ WITH ] [ OWNER [=] <replaceable class="parameter">dbowner</replaceable> ]
            [ TEMPLATE [=] <replaceable class="parameter">template</replaceable> ]
            [ ENCODING [=] <replaceable class="parameter">encoding</replaceable> ]
-           [ TABLESPACE [=] <replaceable class="parameter">tablespace</replaceable> ] ]
+           [ TABLESPACE [=] <replaceable class="parameter">tablespace</replaceable> ]
+           [ CONNECTION LIMIT [=] <replaceable class="parameter">connlimit</replaceable> ] ]
 </synopsis>
  </refsynopsisdiv>
 
@@ -123,6 +124,16 @@ CREATE DATABASE <replaceable class="PARAMETER">name</replaceable>
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry>
+      <term><replaceable class="parameter">connlimit</replaceable></term>
+      <listitem>
+       <para>
+        How many concurrent connections can be made
+        to this database.  -1 (the default) means no limit.
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
 
   <para>
@@ -161,6 +172,13 @@ CREATE DATABASE <replaceable class="PARAMETER">name</replaceable>
    We recommend that databases used as templates be treated as read-only.
    See <xref linkend="manage-ag-templatedbs"> for more information.
   </para>
+
+  <para>
+   The <literal>CONNECTION LIMIT</> option is only enforced approximately;
+   if two new sessions start at about the same time when just one
+   connection <quote>slot</> remains for the database, it is possible that
+   both will fail.  Also, the limit is not enforced against superusers.
+  </para>
  </refsect1>
 
  <refsect1>

doc/src/sgml/ref/create_role.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_role.sgml,v 1.1 2005/07/26 23:24:02 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_role.sgml,v 1.2 2005/07/31 17:19:17 tgl Exp $
 PostgreSQL documentation
 -->
 
@@ -30,6 +30,7 @@ where <replaceable class="PARAMETER">option</replaceable> can be:
     | CREATEUSER | NOCREATEUSER
     | INHERIT | NOINHERIT
     | LOGIN | NOLOGIN
+    | CONNECTION LIMIT <replaceable class="PARAMETER">connlimit</replaceable>
     | [ ENCRYPTED | UNENCRYPTED ] PASSWORD '<replaceable class="PARAMETER">password</replaceable>'
     | VALID UNTIL '<replaceable class="PARAMETER">timestamp</replaceable>' 
     | IN ROLE <replaceable class="PARAMETER">rolename</replaceable> [, ...]
@@ -172,6 +173,16 @@ where <replaceable class="PARAMETER">option</replaceable> can be:
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><literal>CONNECTION LIMIT</literal> <replaceable class="parameter">connlimit</replaceable></term>
+      <listitem>
+       <para>
+        If role can log in, this specifies how many concurrent connections
+        the role can make.  -1 (the default) means no limit.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><literal>PASSWORD</> <replaceable class="parameter">password</replaceable></term>
       <listitem>
@@ -327,6 +338,13 @@ where <replaceable class="PARAMETER">option</replaceable> can be:
    the same functionality as <command>CREATE ROLE</command> (in fact,
    it calls this command) but can be run from the command shell.
   </para>
+
+  <para>
+   The <literal>CONNECTION LIMIT</> option is only enforced approximately;
+   if two new sessions start at about the same time when just one
+   connection <quote>slot</> remains for the role, it is possible that
+   both will fail.  Also, the limit is never enforced for superusers.
+  </para>
  </refsect1>
 
  <refsect1>

doc/src/sgml/ref/create_user.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/create_user.sgml,v 1.37 2005/07/26 23:24:02 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/create_user.sgml,v 1.38 2005/07/31 17:19:17 tgl Exp $
 PostgreSQL documentation
 -->
 
@@ -30,6 +30,7 @@ where <replaceable class="PARAMETER">option</replaceable> can be:
     | CREATEUSER | NOCREATEUSER
     | INHERIT | NOINHERIT
     | LOGIN | NOLOGIN
+    | CONNECTION LIMIT <replaceable class="PARAMETER">connlimit</replaceable>
     | [ ENCRYPTED | UNENCRYPTED ] PASSWORD '<replaceable class="PARAMETER">password</replaceable>'
     | VALID UNTIL '<replaceable class="PARAMETER">timestamp</replaceable>' 
     | IN ROLE <replaceable class="PARAMETER">rolename</replaceable> [, ...]

src/backend/access/transam/twophase.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *		$PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.8 2005/07/04 04:51:44 tgl Exp $
+ *		$PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.9 2005/07/31 17:19:17 tgl Exp $
  *
  * NOTES
  *		Each global transaction is associated with a global transaction
@@ -272,6 +272,7 @@ MarkAsPreparing(TransactionId xid, const char *gid,
 	gxact->proc.xmin = InvalidTransactionId;
 	gxact->proc.pid = 0;
 	gxact->proc.databaseId = databaseid;
+	gxact->proc.roleId = owner;
 	gxact->proc.lwWaiting = false;
 	gxact->proc.lwExclusive = false;
 	gxact->proc.lwWaitLink = NULL;

src/backend/catalog/system_views.sql

@@ -3,7 +3,7 @@
  *
  * Copyright (c) 1996-2005, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/backend/catalog/system_views.sql,v 1.17 2005/07/26 16:38:26 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/catalog/system_views.sql,v 1.18 2005/07/31 17:19:17 tgl Exp $
  */
 
 CREATE VIEW pg_roles AS 
@@ -15,6 +15,7 @@ CREATE VIEW pg_roles AS
         rolcreatedb,
         rolcatupdate,
         rolcanlogin,
+        rolconnlimit,
         '********'::text as rolpassword,
         rolvaliduntil,
         rolconfig,

src/backend/commands/dbcommands.c

@@ -15,7 +15,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/dbcommands.c,v 1.167 2005/07/14 21:46:29 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/dbcommands.c,v 1.168 2005/07/31 17:19:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -92,10 +92,12 @@ createdb(const CreatedbStmt *stmt)
 	DefElem    *downer = NULL;
 	DefElem    *dtemplate = NULL;
 	DefElem    *dencoding = NULL;
+	DefElem    *dconnlimit = NULL;
 	char	   *dbname = stmt->dbname;
 	char	   *dbowner = NULL;
 	const char *dbtemplate = NULL;
 	int			encoding = -1;
+	int			dbconnlimit = -1;
 
 #ifndef WIN32
 	char		buf[2 * MAXPGPATH + 100];
@@ -141,6 +143,14 @@ createdb(const CreatedbStmt *stmt)
 						 errmsg("conflicting or redundant options")));
 			dencoding = defel;
 		}
+		else if (strcmp(defel->defname, "connectionlimit") == 0)
+		{
+			if (dconnlimit)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+			dconnlimit = defel;
+		}
 		else if (strcmp(defel->defname, "location") == 0)
 		{
 			ereport(WARNING,
@@ -186,6 +196,8 @@ createdb(const CreatedbStmt *stmt)
 			elog(ERROR, "unrecognized node type: %d",
 				 nodeTag(dencoding->arg));
 	}
+	if (dconnlimit && dconnlimit->arg)
+		dbconnlimit = intVal(dconnlimit->arg);
 
 	/* obtain OID of proposed owner */
 	if (dbowner)
@@ -484,6 +496,7 @@ createdb(const CreatedbStmt *stmt)
 	new_record[Anum_pg_database_encoding - 1] = Int32GetDatum(encoding);
 	new_record[Anum_pg_database_datistemplate - 1] = BoolGetDatum(false);
 	new_record[Anum_pg_database_datallowconn - 1] = BoolGetDatum(true);
+	new_record[Anum_pg_database_datconnlimit - 1] = Int32GetDatum(dbconnlimit);
 	new_record[Anum_pg_database_datlastsysoid - 1] = ObjectIdGetDatum(src_lastsysoid);
 	new_record[Anum_pg_database_datvacuumxid - 1] = TransactionIdGetDatum(src_vacuumxid);
 	new_record[Anum_pg_database_datfrozenxid - 1] = TransactionIdGetDatum(src_frozenxid);
@@ -790,6 +803,98 @@ RenameDatabase(const char *oldname, const char *newname)
 }
 
 
+/*
+ * ALTER DATABASE name ...
+ */
+void
+AlterDatabase(AlterDatabaseStmt *stmt)
+{
+	Relation	rel;
+	HeapTuple	tuple,
+				newtuple;
+	ScanKeyData scankey;
+	SysScanDesc scan;
+	ListCell   *option;
+	int			connlimit = -1;
+	DefElem    *dconnlimit = NULL;
+	Datum		new_record[Natts_pg_database];
+	char		new_record_nulls[Natts_pg_database];
+	char		new_record_repl[Natts_pg_database];
+
+	/* Extract options from the statement node tree */
+	foreach(option, stmt->options)
+	{
+		DefElem    *defel = (DefElem *) lfirst(option);
+
+		if (strcmp(defel->defname, "connectionlimit") == 0)
+		{
+			if (dconnlimit)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+			dconnlimit = defel;
+		}
+		else
+			elog(ERROR, "option \"%s\" not recognized",
+				 defel->defname);
+	}
+
+	if (dconnlimit)
+		connlimit = intVal(dconnlimit->arg);
+
+	/*
+	 * We don't need ExclusiveLock since we aren't updating the
+	 * flat file.
+	 */
+	rel = heap_open(DatabaseRelationId, RowExclusiveLock);
+	ScanKeyInit(&scankey,
+				Anum_pg_database_datname,
+				BTEqualStrategyNumber, F_NAMEEQ,
+				NameGetDatum(stmt->dbname));
+	scan = systable_beginscan(rel, DatabaseNameIndexId, true,
+							  SnapshotNow, 1, &scankey);
+	tuple = systable_getnext(scan);
+	if (!HeapTupleIsValid(tuple))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_DATABASE),
+				 errmsg("database \"%s\" does not exist", stmt->dbname)));
+
+	if (!pg_database_ownercheck(HeapTupleGetOid(tuple), GetUserId()))
+		aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_DATABASE,
+					   stmt->dbname);
+
+	/*
+	 * Build an updated tuple, perusing the information just obtained
+	 */
+	MemSet(new_record, 0, sizeof(new_record));
+	MemSet(new_record_nulls, ' ', sizeof(new_record_nulls));
+	MemSet(new_record_repl, ' ', sizeof(new_record_repl));
+
+	if (dconnlimit)
+	{
+		new_record[Anum_pg_database_datconnlimit - 1] = Int32GetDatum(connlimit);
+		new_record_repl[Anum_pg_database_datconnlimit - 1] = 'r';
+	}
+
+	newtuple = heap_modifytuple(tuple, RelationGetDescr(rel), new_record,
+								new_record_nulls, new_record_repl);
+	simple_heap_update(rel, &tuple->t_self, newtuple);
+
+	/* Update indexes */
+	CatalogUpdateIndexes(rel, newtuple);
+
+	systable_endscan(scan);
+
+	/* Close pg_database, but keep lock till commit */
+	heap_close(rel, NoLock);
+
+	/*
+	 * We don't bother updating the flat file since the existing options
+	 * for ALTER DATABASE don't affect it.
+	 */
+}
+
+
 /*
  * ALTER DATABASE name SET ...
  */

src/backend/commands/user.c

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/commands/user.c,v 1.159 2005/07/26 22:37:49 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/commands/user.c,v 1.160 2005/07/31 17:19:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -86,6 +86,7 @@ CreateRole(CreateRoleStmt *stmt)
 	bool		createrole = false;		/* Can this user create roles? */
 	bool		createdb = false;		/* Can the user create databases? */
 	bool		canlogin = false;		/* Can this user login? */
+	int			connlimit = -1;			/* maximum connections allowed */
 	List	   *addroleto = NIL;		/* roles to make this a member of */
 	List	   *rolemembers = NIL;		/* roles to be members of this role */
 	List	   *adminmembers = NIL;		/* roles to be admins of this role */
@@ -96,6 +97,7 @@ CreateRole(CreateRoleStmt *stmt)
 	DefElem    *dcreaterole = NULL;
 	DefElem    *dcreatedb = NULL;
 	DefElem    *dcanlogin = NULL;
+	DefElem    *dconnlimit = NULL;
 	DefElem    *daddroleto = NULL;
 	DefElem    *drolemembers = NULL;
 	DefElem    *dadminmembers = NULL;
@@ -178,6 +180,14 @@ CreateRole(CreateRoleStmt *stmt)
 						 errmsg("conflicting or redundant options")));
 			dcanlogin = defel;
 		}
+		else if (strcmp(defel->defname, "connectionlimit") == 0)
+		{
+			if (dconnlimit)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+			dconnlimit = defel;
+		}
 		else if (strcmp(defel->defname, "addroleto") == 0)
 		{
 			if (daddroleto)
@@ -227,6 +237,8 @@ CreateRole(CreateRoleStmt *stmt)
 		createdb = intVal(dcreatedb->arg) != 0;
 	if (dcanlogin)
 		canlogin = intVal(dcanlogin->arg) != 0;
+	if (dconnlimit)
+		connlimit = intVal(dconnlimit->arg);
 	if (daddroleto)
 		addroleto = (List *) daddroleto->arg;
 	if (drolemembers)
@@ -292,6 +304,7 @@ CreateRole(CreateRoleStmt *stmt)
 	/* superuser gets catupdate right by default */
 	new_record[Anum_pg_authid_rolcatupdate - 1] = BoolGetDatum(issuper);
 	new_record[Anum_pg_authid_rolcanlogin - 1] = BoolGetDatum(canlogin);
+	new_record[Anum_pg_authid_rolconnlimit - 1] = Int32GetDatum(connlimit);
 
 	if (password)
 	{
@@ -401,6 +414,7 @@ AlterRole(AlterRoleStmt *stmt)
 	int			createrole = -1;		/* Can this user create roles? */
 	int			createdb = -1;			/* Can the user create databases? */
 	int			canlogin = -1;			/* Can this user login? */
+	int			connlimit = -1;			/* maximum connections allowed */
 	List	   *rolemembers = NIL;		/* roles to be added/removed */
 	char	   *validUntil = NULL;		/* time the login is valid until */
 	DefElem    *dpassword = NULL;
@@ -409,6 +423,7 @@ AlterRole(AlterRoleStmt *stmt)
 	DefElem    *dcreaterole = NULL;
 	DefElem    *dcreatedb = NULL;
 	DefElem    *dcanlogin = NULL;
+	DefElem    *dconnlimit = NULL;
 	DefElem    *drolemembers = NULL;
 	DefElem    *dvalidUntil = NULL;
 	Oid			roleid;
@@ -472,6 +487,14 @@ AlterRole(AlterRoleStmt *stmt)
 						 errmsg("conflicting or redundant options")));
 			dcanlogin = defel;
 		}
+		else if (strcmp(defel->defname, "connectionlimit") == 0)
+		{
+			if (dconnlimit)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+			dconnlimit = defel;
+		}
 		else if (strcmp(defel->defname, "rolemembers") == 0 &&
 				 stmt->action != 0)
 		{
@@ -506,6 +529,8 @@ AlterRole(AlterRoleStmt *stmt)
 		createdb = intVal(dcreatedb->arg);
 	if (dcanlogin)
 		canlogin = intVal(dcanlogin->arg);
+	if (dconnlimit)
+		connlimit = intVal(dconnlimit->arg);
 	if (drolemembers)
 		rolemembers = (List *) drolemembers->arg;
 	if (dvalidUntil)
@@ -545,6 +570,7 @@ AlterRole(AlterRoleStmt *stmt)
 			  createrole < 0 &&
 			  createdb < 0 &&
 			  canlogin < 0 &&
+			  !dconnlimit &&
 			  !rolemembers &&
 			  !validUntil &&
 			  password &&
@@ -602,6 +628,12 @@ AlterRole(AlterRoleStmt *stmt)
 		new_record_repl[Anum_pg_authid_rolcanlogin - 1] = 'r';
 	}
 
+	if (dconnlimit)
+	{
+		new_record[Anum_pg_authid_rolconnlimit - 1] = Int32GetDatum(connlimit);
+		new_record_repl[Anum_pg_authid_rolconnlimit - 1] = 'r';
+	}
+
 	/* password */
 	if (password)
 	{

src/backend/nodes/copyfuncs.c

@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.312 2005/07/26 16:38:27 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.313 2005/07/31 17:19:18 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2204,6 +2204,17 @@ _copyCreatedbStmt(CreatedbStmt *from)
 	return newnode;
 }
 
+static AlterDatabaseStmt *
+_copyAlterDatabaseStmt(AlterDatabaseStmt *from)
+{
+	AlterDatabaseStmt *newnode = makeNode(AlterDatabaseStmt);
+
+	COPY_STRING_FIELD(dbname);
+	COPY_NODE_FIELD(options);
+
+	return newnode;
+}
+
 static AlterDatabaseSetStmt *
 _copyAlterDatabaseSetStmt(AlterDatabaseSetStmt *from)
 {
@@ -3011,6 +3022,9 @@ copyObject(void *from)
 		case T_CreatedbStmt:
 			retval = _copyCreatedbStmt(from);
 			break;
+		case T_AlterDatabaseStmt:
+			retval = _copyAlterDatabaseStmt(from);
+			break;
 		case T_AlterDatabaseSetStmt:
 			retval = _copyAlterDatabaseSetStmt(from);
 			break;

src/backend/nodes/equalfuncs.c

@@ -18,7 +18,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.249 2005/07/26 16:38:27 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.250 2005/07/31 17:19:18 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1151,6 +1151,15 @@ _equalCreatedbStmt(CreatedbStmt *a, CreatedbStmt *b)
 	return true;
 }
 
+static bool
+_equalAlterDatabaseStmt(AlterDatabaseStmt *a, AlterDatabaseStmt *b)
+{
+	COMPARE_STRING_FIELD(dbname);
+	COMPARE_NODE_FIELD(options);
+
+	return true;
+}
+
 static bool
 _equalAlterDatabaseSetStmt(AlterDatabaseSetStmt *a, AlterDatabaseSetStmt *b)
 {
@@ -2059,6 +2068,9 @@ equal(void *a, void *b)
 		case T_CreatedbStmt:
 			retval = _equalCreatedbStmt(a, b);
 			break;
+		case T_AlterDatabaseStmt:
+			retval = _equalAlterDatabaseStmt(a, b);
+			break;
 		case T_AlterDatabaseSetStmt:
 			retval = _equalAlterDatabaseSetStmt(a, b);
 			break;

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.504 2005/07/26 22:37:50 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.505 2005/07/31 17:19:18 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -131,9 +131,9 @@ static void doNegateFloat(Value *v);
 }
 
 %type <node>	stmt schema_stmt
-		AlterDatabaseSetStmt AlterDomainStmt AlterGroupStmt AlterOwnerStmt
-		AlterSeqStmt AlterTableStmt AlterUserStmt AlterUserSetStmt
-		AlterRoleStmt AlterRoleSetStmt
+		AlterDatabaseStmt AlterDatabaseSetStmt AlterDomainStmt AlterGroupStmt
+		AlterOwnerStmt AlterSeqStmt AlterTableStmt 
+		AlterUserStmt AlterUserSetStmt AlterRoleStmt AlterRoleSetStmt
 		AnalyzeStmt ClosePortalStmt ClusterStmt CommentStmt
 		ConstraintsSetStmt CopyStmt CreateAsStmt CreateCastStmt
 		CreateDomainStmt CreateGroupStmt CreateOpClassStmt CreatePLangStmt
@@ -165,8 +165,10 @@ static void doNegateFloat(Value *v);
 
 %type <dbehavior>	opt_drop_behavior
 
-%type <list>	createdb_opt_list copy_opt_list transaction_mode_list
-%type <defelt>	createdb_opt_item copy_opt_item transaction_mode_item
+%type <list>	createdb_opt_list alterdb_opt_list copy_opt_list 
+				transaction_mode_list
+%type <defelt>	createdb_opt_item alterdb_opt_item copy_opt_item
+				transaction_mode_item
 
 %type <ival>	opt_lock lock_type cast_context
 %type <boolean>	opt_force opt_or_replace
@@ -257,7 +259,7 @@ static void doNegateFloat(Value *v);
 
 %type <boolean> copy_from opt_hold
 
-%type <ival>	fetch_count	opt_column event cursor_options
+%type <ival>	opt_column event cursor_options
 %type <objtype>	reindex_type drop_type comment_type
 
 %type <node>	fetch_direction select_limit_value select_offset_value
@@ -302,7 +304,7 @@ static void doNegateFloat(Value *v);
 %type <ival>	opt_numeric opt_decimal
 %type <boolean> opt_varying opt_timezone
 
-%type <ival>	Iconst
+%type <ival>	Iconst SignedIconst
 %type <str>		Sconst comment_text
 %type <str>		RoleId opt_granted_by opt_boolean ColId_or_Sconst
 %type <list>	var_list var_list_or_default
@@ -342,7 +344,7 @@ static void doNegateFloat(Value *v);
 	CACHE CALLED CASCADE CASE CAST CHAIN CHAR_P
 	CHARACTER CHARACTERISTICS CHECK CHECKPOINT CLASS CLOSE
 	CLUSTER COALESCE COLLATE COLUMN COMMENT COMMIT
-	COMMITTED CONSTRAINT CONSTRAINTS CONVERSION_P CONVERT COPY CREATE CREATEDB
+	COMMITTED CONNECTION CONSTRAINT CONSTRAINTS CONVERSION_P CONVERT COPY CREATE CREATEDB
 	CREATEROLE CREATEUSER CROSS CSV CURRENT_DATE CURRENT_ROLE CURRENT_TIME
 	CURRENT_TIMESTAMP CURRENT_USER CURSOR CYCLE
 
@@ -486,7 +488,8 @@ stmtmulti:	stmtmulti ';' stmt
 		;
 
 stmt :
-			AlterDatabaseSetStmt
+			AlterDatabaseStmt
+			| AlterDatabaseSetStmt
 			| AlterDomainStmt
 			| AlterFunctionStmt
 			| AlterGroupStmt
@@ -672,6 +675,10 @@ OptRoleElem:
 				{
 					$$ = makeDefElem("canlogin", (Node *)makeInteger(FALSE));
 				}
+			| CONNECTION LIMIT SignedIconst
+				{
+					$$ = makeDefElem("connectionlimit", (Node *)makeInteger($3));
+				}
 			| IN_P ROLE name_list
 				{
 					$$ = makeDefElem("addroleto", (Node *)$3);
@@ -2238,17 +2245,8 @@ FloatOnly:	FCONST									{ $$ = makeFloat($1); }
 				}
 		;
 
-IntegerOnly:
-			Iconst
-				{
-					$$ = makeInteger($1);
-				}
-			| '-' Iconst
-				{
-					$$ = makeInteger($2);
-					$$->val.ival = - $$->val.ival;
-				}
-		;
+IntegerOnly: SignedIconst							{ $$ = makeInteger($1); };
+
 
 /*****************************************************************************
  *
@@ -3044,21 +3042,21 @@ fetch_direction:
 					n->howMany = -1;
 					$$ = (Node *)n;
 				}
-			| ABSOLUTE_P fetch_count
+			| ABSOLUTE_P SignedIconst
 				{
 					FetchStmt *n = makeNode(FetchStmt);
 					n->direction = FETCH_ABSOLUTE;
 					n->howMany = $2;
 					$$ = (Node *)n;
 				}
-			| RELATIVE_P fetch_count
+			| RELATIVE_P SignedIconst
 				{
 					FetchStmt *n = makeNode(FetchStmt);
 					n->direction = FETCH_RELATIVE;
 					n->howMany = $2;
 					$$ = (Node *)n;
 				}
-			| fetch_count
+			| SignedIconst
 				{
 					FetchStmt *n = makeNode(FetchStmt);
 					n->direction = FETCH_FORWARD;
@@ -3079,7 +3077,7 @@ fetch_direction:
 					n->howMany = 1;
 					$$ = (Node *)n;
 				}
-			| FORWARD fetch_count
+			| FORWARD SignedIconst
 				{
 					FetchStmt *n = makeNode(FetchStmt);
 					n->direction = FETCH_FORWARD;
@@ -3100,7 +3098,7 @@ fetch_direction:
 					n->howMany = 1;
 					$$ = (Node *)n;
 				}
-			| BACKWARD fetch_count
+			| BACKWARD SignedIconst
 				{
 					FetchStmt *n = makeNode(FetchStmt);
 					n->direction = FETCH_BACKWARD;
@@ -3116,11 +3114,6 @@ fetch_direction:
 				}
 		;
 
-fetch_count:
-			Iconst									{ $$ = $1; }
-			| '-' Iconst							{ $$ = - $2; }
-		;
-
 from_in:	FROM									{}
 			| IN_P									{}
 		;
@@ -4473,6 +4466,10 @@ createdb_opt_item:
 				{
 					$$ = makeDefElem("encoding", NULL);
 				}
+			| CONNECTION LIMIT opt_equal SignedIconst
+				{
+					$$ = makeDefElem("connectionlimit", (Node *)makeInteger($4));
+				}
 			| OWNER opt_equal name
 				{
 					$$ = makeDefElem("owner", (Node *)makeString($3));
@@ -4485,8 +4482,7 @@ createdb_opt_item:
 
 /*
  *	Though the equals sign doesn't match other WITH options, pg_dump uses
- *	equals for backward compability, and it doesn't seem worth removing it.
- *	2002-02-25
+ *	equals for backward compatibility, and it doesn't seem worth removing it.
  */
 opt_equal:	'='										{}
 			| /*EMPTY*/								{}
@@ -4499,6 +4495,16 @@ opt_equal:	'='										{}
  *
  *****************************************************************************/
 
+AlterDatabaseStmt:
+ 			ALTER DATABASE database_name opt_with alterdb_opt_list
+				 {
+					AlterDatabaseStmt *n = makeNode(AlterDatabaseStmt);
+					n->dbname = $3;
+					n->options = $5;
+					$$ = (Node *)n;
+				 }
+		;
+
 AlterDatabaseSetStmt:
 			ALTER DATABASE database_name SET set_rest
 				{
@@ -4519,6 +4525,19 @@ AlterDatabaseSetStmt:
 		;
 
 
+alterdb_opt_list:
+			alterdb_opt_list alterdb_opt_item		{ $$ = lappend($1, $2); }
+			| /* EMPTY */							{ $$ = NIL; }
+		;
+
+alterdb_opt_item:
+			CONNECTION LIMIT opt_equal SignedIconst
+				{
+					$$ = makeDefElem("connectionlimit", (Node *)makeInteger($4));
+				}
+		;
+
+
 /*****************************************************************************
  *
  *		DROP DATABASE
@@ -7875,6 +7894,10 @@ Iconst:		ICONST									{ $$ = $1; };
 Sconst:		SCONST									{ $$ = $1; };
 RoleId:		ColId									{ $$ = $1; };
 
+SignedIconst: ICONST								{ $$ = $1; }
+			| '-' ICONST							{ $$ = - $2; }
+		;
+
 /*
  * Name classification hierarchy.
  *
@@ -7959,6 +7982,7 @@ unreserved_keyword:
 			| COMMENT
 			| COMMIT
 			| COMMITTED
+			| CONNECTION
 			| CONSTRAINTS
 			| CONVERSION_P
 			| COPY

src/backend/parser/keywords.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/keywords.c,v 1.163 2005/07/26 16:38:27 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/keywords.c,v 1.164 2005/07/31 17:19:18 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -83,6 +83,7 @@ static const ScanKeyword ScanKeywords[] = {
 	{"comment", COMMENT},
 	{"commit", COMMIT},
 	{"committed", COMMITTED},
+	{"connection", CONNECTION},
 	{"constraint", CONSTRAINT},
 	{"constraints", CONSTRAINTS},
 	{"conversion", CONVERSION_P},

src/backend/storage/ipc/procarray.c

@@ -23,7 +23,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.3 2005/06/17 22:32:45 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.4 2005/07/31 17:19:18 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -733,6 +733,60 @@ CountActiveBackends(void)
 	return count;
 }
 
+/*
+ * CountDBBackends --- count backends that are using specified database
+ */
+int
+CountDBBackends(Oid databaseid)
+{
+	ProcArrayStruct *arrayP = procArray;
+	int			count = 0;
+	int			index;
+
+	LWLockAcquire(ProcArrayLock, LW_SHARED);
+
+	for (index = 0; index < arrayP->numProcs; index++)
+	{
+		PGPROC	   *proc = arrayP->procs[index];
+
+		if (proc->pid == 0)
+			continue;			/* do not count prepared xacts */
+		if (proc->databaseId == databaseid)
+			count++;
+	}
+
+	LWLockRelease(ProcArrayLock);
+
+	return count;
+}
+
+/*
+ * CountUserBackends --- count backends that are used by specified user
+ */
+int
+CountUserBackends(Oid roleid)
+{
+	ProcArrayStruct *arrayP = procArray;
+	int			count = 0;
+	int			index;
+
+	LWLockAcquire(ProcArrayLock, LW_SHARED);
+
+	for (index = 0; index < arrayP->numProcs; index++)
+	{
+		PGPROC	   *proc = arrayP->procs[index];
+
+		if (proc->pid == 0)
+			continue;			/* do not count prepared xacts */
+		if (proc->roleId == roleid)
+			count++;
+	}
+
+	LWLockRelease(ProcArrayLock);
+
+	return count;
+}
+
 
 #define XidCacheRemove(i) \
 	do { \

src/backend/storage/lmgr/proc.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.160 2005/06/17 22:32:45 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.161 2005/07/31 17:19:19 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -254,6 +254,8 @@ InitProcess(void)
 	MyProc->xmin = InvalidTransactionId;
 	MyProc->pid = MyProcPid;
 	MyProc->databaseId = MyDatabaseId;
+	/* Will be set properly after the session role id is determined */
+	MyProc->roleId = InvalidOid;
 	MyProc->lwWaiting = false;
 	MyProc->lwExclusive = false;
 	MyProc->lwWaitLink = NULL;
@@ -331,6 +333,7 @@ InitDummyProcess(int proctype)
 	MyProc->xid = InvalidTransactionId;
 	MyProc->xmin = InvalidTransactionId;
 	MyProc->databaseId = MyDatabaseId;
+	MyProc->roleId = InvalidOid;
 	MyProc->lwWaiting = false;
 	MyProc->lwExclusive = false;
 	MyProc->lwWaitLink = NULL;

src/backend/tcop/utility.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.241 2005/07/14 05:13:41 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.242 2005/07/31 17:19:19 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -275,6 +275,7 @@ check_xact_readonly(Node *parsetree)
 
 	switch (nodeTag(parsetree))
 	{
+		case T_AlterDatabaseStmt:
 		case T_AlterDatabaseSetStmt:
 		case T_AlterDomainStmt:
 		case T_AlterFunctionStmt:
@@ -788,6 +789,10 @@ ProcessUtility(Node *parsetree,
 			createdb((CreatedbStmt *) parsetree);
 			break;
 
+		case T_AlterDatabaseStmt:
+			AlterDatabase((AlterDatabaseStmt *) parsetree);
+			break;
+
 		case T_AlterDatabaseSetStmt:
 			AlterDatabaseSet((AlterDatabaseSetStmt *) parsetree);
 			break;
@@ -1504,6 +1509,10 @@ CreateCommandTag(Node *parsetree)
 			tag = "CREATE DATABASE";
 			break;
 
+		case T_AlterDatabaseStmt:
+			tag = "ALTER DATABASE";
+			break;
+
 		case T_AlterDatabaseSetStmt:
 			tag = "ALTER DATABASE";
 			break;

src/backend/utils/init/miscinit.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/init/miscinit.c,v 1.147 2005/07/25 22:12:33 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/init/miscinit.c,v 1.148 2005/07/31 17:19:19 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -36,6 +36,8 @@
 #include "storage/fd.h"
 #include "storage/ipc.h"
 #include "storage/pg_shmem.h"
+#include "storage/proc.h"
+#include "storage/procarray.h" 
 #include "utils/builtins.h"
 #include "utils/guc.h"
 #include "utils/lsyscache.h"
@@ -404,17 +406,52 @@ InitializeSessionUserId(const char *rolename)
 	rform = (Form_pg_authid) GETSTRUCT(roleTup);
 	roleid = HeapTupleGetOid(roleTup);
 
-	if (!rform->rolcanlogin)
-		ereport(FATAL,
-				(errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
-				 errmsg("role \"%s\" is not permitted to log in", rolename)));
-
 	AuthenticatedUserId = roleid;
 	AuthenticatedUserIsSuperuser = rform->rolsuper;
 
 	/* This sets OuterUserId/CurrentUserId too */
 	SetSessionUserId(roleid, AuthenticatedUserIsSuperuser);
 
+	/* Also mark our PGPROC entry with the authenticated user id */
+	/* (We assume this is an atomic store so no lock is needed) */
+	MyProc->roleId = roleid;
+
+	/*
+	 * These next checks are not enforced when in standalone mode, so that
+	 * there is a way to recover from sillinesses like
+	 * "UPDATE pg_authid SET rolcanlogin = false;".
+	 *
+	 * We do not enforce them for the autovacuum process either.
+	 */
+	if (IsUnderPostmaster && !IsAutoVacuumProcess())
+	{
+		/*
+		 * Is role allowed to login at all?
+		 */
+		if (!rform->rolcanlogin)
+			ereport(FATAL,
+					(errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
+					 errmsg("role \"%s\" is not permitted to log in",
+							rolename)));
+		/*
+		 * Check connection limit for this role.
+		 *
+		 * There is a race condition here --- we create our PGPROC before
+		 * checking for other PGPROCs.  If two backends did this at about the
+		 * same time, they might both think they were over the limit, while
+		 * ideally one should succeed and one fail.  Getting that to work
+		 * exactly seems more trouble than it is worth, however; instead
+		 * we just document that the connection limit is approximate.
+		 */
+		if (rform->rolconnlimit >= 0 &&
+			!AuthenticatedUserIsSuperuser &&
+			CountUserBackends(roleid) > rform->rolconnlimit)
+			ereport(FATAL,
+					(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
+					 errmsg("too many connections for role \"%s\"",
+							rolename)));
+	}
+	
 	/* Record username and superuser status as GUC settings too */
 	SetConfigOption("session_authorization", rolename,
 					PGC_BACKEND, PGC_S_OVERRIDE);

src/backend/utils/init/postinit.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/init/postinit.c,v 1.154 2005/07/29 19:30:05 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/init/postinit.c,v 1.155 2005/07/31 17:19:19 tgl Exp $
  *
  *
  *-------------------------------------------------------------------------
@@ -169,18 +169,43 @@ ReverifyMyDatabase(const char *name)
 						name, MyDatabaseId)));
 	}
 
+	dbform = (Form_pg_database) GETSTRUCT(tup);
+
 	/*
-	 * Also check that the database is currently allowing connections.
-	 * (We do not enforce this in standalone mode, however, so that there is
-	 * a way to recover from "UPDATE pg_database SET datallowconn = false;".
-	 * We do not enforce it for the autovacuum process either.)
+	 * These next checks are not enforced when in standalone mode, so that
+	 * there is a way to recover from disabling all access to all databases,
+	 * for example "UPDATE pg_database SET datallowconn = false;".
+	 *
+	 * We do not enforce them for the autovacuum process either.
 	 */
-	dbform = (Form_pg_database) GETSTRUCT(tup);
-	if (IsUnderPostmaster && !IsAutoVacuumProcess() && !dbform->datallowconn)
-		ereport(FATAL,
-				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
-		 errmsg("database \"%s\" is not currently accepting connections",
-				name)));
+	if (IsUnderPostmaster && !IsAutoVacuumProcess())
+	{
+		/*
+		 * Check that the database is currently allowing connections.
+		 */
+		if (!dbform->datallowconn)
+			ereport(FATAL,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("database \"%s\" is not currently accepting connections",
+							name)));
+		/*
+		 * Check connection limit for this database.
+		 *
+		 * There is a race condition here --- we create our PGPROC before
+		 * checking for other PGPROCs.  If two backends did this at about the
+		 * same time, they might both think they were over the limit, while
+		 * ideally one should succeed and one fail.  Getting that to work
+		 * exactly seems more trouble than it is worth, however; instead
+		 * we just document that the connection limit is approximate.
+		 */
+		if (dbform->datconnlimit >= 0 &&
+			!superuser() &&
+			CountDBBackends(MyDatabaseId) > dbform->datconnlimit)
+			ereport(FATAL,
+					(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
+					 errmsg("too many connections for database \"%s\"",
+							name)));
+	}
 
 	/*
 	 * OK, we're golden.  Next to-do item is to save the encoding

src/include/catalog/catversion.h

@@ -37,7 +37,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.293 2005/07/29 15:04:22 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.294 2005/07/31 17:19:20 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	200507291
+#define CATALOG_VERSION_NO	200507301
 
 #endif

src/include/catalog/pg_authid.h

@@ -10,7 +10,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_authid.h,v 1.2 2005/07/26 16:38:28 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_authid.h,v 1.3 2005/07/31 17:19:21 tgl Exp $
  *
  * NOTES
  *	  the genbki.sh script reads this file and generates .bki
@@ -49,6 +49,7 @@ CATALOG(pg_authid,1260) BKI_SHARED_RELATION
 	bool		rolcreatedb;	/* allowed to create databases? */
 	bool		rolcatupdate;	/* allowed to alter catalogs manually? */
 	bool		rolcanlogin;	/* allowed to log in as session user? */
+	int4		rolconnlimit;	/* max connections allowed (-1=no limit) */
 
 	/* remaining fields may be null; use heap_getattr to read them! */
 	text		rolpassword;	/* password, if any */
@@ -70,7 +71,7 @@ typedef FormData_pg_authid *Form_pg_authid;
  *		compiler constants for pg_authid
  * ----------------
  */
-#define Natts_pg_authid					10
+#define Natts_pg_authid					11
 #define Anum_pg_authid_rolname			1
 #define Anum_pg_authid_rolsuper			2
 #define Anum_pg_authid_rolinherit		3
@@ -78,9 +79,10 @@ typedef FormData_pg_authid *Form_pg_authid;
 #define Anum_pg_authid_rolcreatedb		5
 #define Anum_pg_authid_rolcatupdate		6
 #define Anum_pg_authid_rolcanlogin		7
-#define Anum_pg_authid_rolpassword		8
-#define Anum_pg_authid_rolvaliduntil	9
-#define Anum_pg_authid_rolconfig		10
+#define Anum_pg_authid_rolconnlimit		8
+#define Anum_pg_authid_rolpassword		9
+#define Anum_pg_authid_rolvaliduntil	10
+#define Anum_pg_authid_rolconfig		11
 
 /* ----------------
  *		initial contents of pg_authid
@@ -89,7 +91,7 @@ typedef FormData_pg_authid *Form_pg_authid;
  * user choices.
  * ----------------
  */
-DATA(insert OID = 10 ( "POSTGRES" t t t t t t _null_ _null_ _null_ ));
+DATA(insert OID = 10 ( "POSTGRES" t t t t t t -1 _null_ _null_ _null_ ));
 
 #define BOOTSTRAP_SUPERUSERID 10
 

src/include/catalog/pg_database.h

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/pg_database.h,v 1.36 2005/06/28 05:09:06 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/pg_database.h,v 1.37 2005/07/31 17:19:21 tgl Exp $
  *
  * NOTES
  *	  the genbki.sh script reads this file and generates .bki
@@ -40,6 +40,7 @@ CATALOG(pg_database,1262) BKI_SHARED_RELATION
 	int4		encoding;		/* character encoding */
 	bool		datistemplate;	/* allowed as CREATE DATABASE template? */
 	bool		datallowconn;	/* new connections allowed? */
+	int4		datconnlimit;	/* max connections allowed (-1=no limit) */
 	Oid			datlastsysoid;	/* highest OID to consider a system OID */
 	TransactionId datvacuumxid; /* all XIDs before this are vacuumed */
 	TransactionId datfrozenxid; /* all XIDs before this are frozen */
@@ -59,20 +60,21 @@ typedef FormData_pg_database *Form_pg_database;
  *		compiler constants for pg_database
  * ----------------
  */
-#define Natts_pg_database				11
+#define Natts_pg_database				12
 #define Anum_pg_database_datname		1
 #define Anum_pg_database_datdba			2
 #define Anum_pg_database_encoding		3
 #define Anum_pg_database_datistemplate	4
 #define Anum_pg_database_datallowconn	5
-#define Anum_pg_database_datlastsysoid	6
-#define Anum_pg_database_datvacuumxid	7
-#define Anum_pg_database_datfrozenxid	8
-#define Anum_pg_database_dattablespace	9
-#define Anum_pg_database_datconfig		10
-#define Anum_pg_database_datacl			11
+#define Anum_pg_database_datconnlimit	6
+#define Anum_pg_database_datlastsysoid	7
+#define Anum_pg_database_datvacuumxid	8
+#define Anum_pg_database_datfrozenxid	9
+#define Anum_pg_database_dattablespace	10
+#define Anum_pg_database_datconfig		11
+#define Anum_pg_database_datacl			12
 
-DATA(insert OID = 1 (  template1 PGUID ENCODING t t 0 0 0 1663 _null_ _null_ ));
+DATA(insert OID = 1 (  template1 PGUID ENCODING t t -1 0 0 0 1663 _null_ _null_ ));
 DESCR("Default template database");
 #define TemplateDbOid			1
 

src/include/commands/dbcommands.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/commands/dbcommands.h,v 1.40 2005/07/08 04:12:27 neilc Exp $
+ * $PostgreSQL: pgsql/src/include/commands/dbcommands.h,v 1.41 2005/07/31 17:19:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -55,6 +55,7 @@ typedef struct xl_dbase_drop_rec
 extern void createdb(const CreatedbStmt *stmt);
 extern void dropdb(const char *dbname);
 extern void RenameDatabase(const char *oldname, const char *newname);
+extern void AlterDatabase(AlterDatabaseStmt *stmt);
 extern void AlterDatabaseSet(AlterDatabaseSetStmt *stmt);
 extern void AlterDatabaseOwner(const char *dbname, Oid newOwnerId);
 

src/include/nodes/nodes.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/nodes.h,v 1.172 2005/06/28 05:09:13 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/nodes.h,v 1.173 2005/07/31 17:19:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -270,6 +270,7 @@ typedef enum NodeTag
 	T_ReindexStmt,
 	T_CheckPointStmt,
 	T_CreateSchemaStmt,
+	T_AlterDatabaseStmt,
 	T_AlterDatabaseSetStmt,
 	T_AlterRoleSetStmt,
 	T_CreateConversionStmt,

src/include/nodes/parsenodes.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/nodes/parsenodes.h,v 1.286 2005/07/26 16:38:28 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/parsenodes.h,v 1.287 2005/07/31 17:19:21 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1624,6 +1624,13 @@ typedef struct CreatedbStmt
  *	Alter Database
  * ----------------------
  */
+typedef struct AlterDatabaseStmt
+{
+	NodeTag		type;
+	char	   *dbname;			/* name of database to alter */
+	List	   *options;		/* List of DefElem nodes */
+} AlterDatabaseStmt;
+
 typedef struct AlterDatabaseSetStmt
 {
 	NodeTag		type;

src/include/storage/proc.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/proc.h,v 1.79 2005/06/17 22:32:50 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/storage/proc.h,v 1.80 2005/07/31 17:19:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -71,6 +71,7 @@ struct PGPROC
 
 	int			pid;			/* This backend's process id, or 0 */
 	Oid			databaseId;		/* OID of database this backend is using */
+	Oid			roleId;			/* OID of role using this backend */
 
 	/* Info about LWLock the process is currently waiting for, if any. */
 	bool		lwWaiting;		/* true if waiting for an LW lock */

src/include/storage/procarray.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/procarray.h,v 1.2 2005/06/17 22:32:50 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/storage/procarray.h,v 1.3 2005/07/31 17:19:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -31,6 +31,8 @@ extern bool IsBackendPid(int pid);
 extern bool DatabaseHasActiveBackends(Oid databaseId, bool ignoreMyself);
 
 extern int	CountActiveBackends(void);
+extern int	CountDBBackends(Oid databaseid);
+extern int	CountUserBackends(Oid roleid);
 
 extern void XidCacheRemoveRunningXids(TransactionId xid,
 						  int nxids, TransactionId *xids);

src/test/regress/expected/rules.out

@@ -1281,7 +1281,7 @@ SELECT viewname, definition FROM pg_views WHERE schemaname <> 'information_schem
  pg_indexes               | SELECT n.nspname AS schemaname, c.relname AS tablename, i.relname AS indexname, t.spcname AS "tablespace", pg_get_indexdef(i.oid) AS indexdef FROM ((((pg_index x JOIN pg_class c ON ((c.oid = x.indrelid))) JOIN pg_class i ON ((i.oid = x.indexrelid))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) LEFT JOIN pg_tablespace t ON ((t.oid = i.reltablespace))) WHERE ((c.relkind = 'r'::"char") AND (i.relkind = 'i'::"char"));
  pg_locks                 | SELECT l.locktype, l."database", l.relation, l.page, l.tuple, l.transactionid, l.classid, l.objid, l.objsubid, l."transaction", l.pid, l."mode", l."granted" FROM pg_lock_status() l(locktype text, "database" oid, relation oid, page integer, tuple smallint, transactionid xid, classid oid, objid oid, objsubid smallint, "transaction" xid, pid integer, "mode" text, "granted" boolean);
  pg_prepared_xacts        | SELECT p."transaction", p.gid, p."prepared", u.rolname AS "owner", d.datname AS "database" FROM ((pg_prepared_xact() p("transaction" xid, gid text, "prepared" timestamp with time zone, ownerid oid, dbid oid) LEFT JOIN pg_authid u ON ((p.ownerid = u.oid))) LEFT JOIN pg_database d ON ((p.dbid = d.oid)));
- pg_roles                 | SELECT pg_authid.rolname, pg_authid.rolsuper, pg_authid.rolinherit, pg_authid.rolcreaterole, pg_authid.rolcreatedb, pg_authid.rolcatupdate, pg_authid.rolcanlogin, '********'::text AS rolpassword, pg_authid.rolvaliduntil, pg_authid.rolconfig, pg_authid.oid FROM pg_authid;
+ pg_roles                 | SELECT pg_authid.rolname, pg_authid.rolsuper, pg_authid.rolinherit, pg_authid.rolcreaterole, pg_authid.rolcreatedb, pg_authid.rolcatupdate, pg_authid.rolcanlogin, pg_authid.rolconnlimit, '********'::text AS rolpassword, pg_authid.rolvaliduntil, pg_authid.rolconfig, pg_authid.oid FROM pg_authid;
  pg_rules                 | SELECT n.nspname AS schemaname, c.relname AS tablename, r.rulename, pg_get_ruledef(r.oid) AS definition FROM ((pg_rewrite r JOIN pg_class c ON ((c.oid = r.ev_class))) LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace))) WHERE (r.rulename <> '_RETURN'::name);
  pg_settings              | SELECT a.name, a.setting, a.category, a.short_desc, a.extra_desc, a.context, a.vartype, a.source, a.min_val, a.max_val FROM pg_show_all_settings() a(name text, setting text, category text, short_desc text, extra_desc text, context text, vartype text, source text, min_val text, max_val text);
  pg_shadow                | SELECT pg_authid.rolname AS usename, pg_authid.oid AS usesysid, pg_authid.rolcreatedb AS usecreatedb, pg_authid.rolsuper AS usesuper, pg_authid.rolcatupdate AS usecatupd, pg_authid.rolpassword AS passwd, (pg_authid.rolvaliduntil)::abstime AS valuntil, pg_authid.rolconfig AS useconfig FROM pg_authid WHERE pg_authid.rolcanlogin;