*** a/doc/src/sgml/func.sgml
--- b/doc/src/sgml/func.sgml
***************
*** 16576,16581 **** SELECT collation for ('foo' COLLATE "de_DE");
--- 16576,16594 ----
         <entry><type>text</type></entry>
         <entry>set parameter and return new value</entry>
        </row>
+ 	  <row>
+        <entry>
+         <indexterm>
+          <primary>pg_hba_lookup</primary>
+         </indexterm>
+         <literal><function>pg_hba_lookup(<parameter>database</> <type>text</>,
+ 							<parameter>user</> <type>text</>
+ 							[, <parameter>address</> <type>text</>]
+ 							[, <parameter>hostname</> <type>text</>)</function></literal>
+        </entry>
+        <entry><type>record</type></entry>
+        <entry>Returns authentication method of the matching entry found in pg_hba.conf</entry>
+       </row>
       </tbody>
      </tgroup>
     </table>
***************
*** 16633,16638 **** SELECT set_config('log_statement_stats', 'off', false);
--- 16646,16665 ----
  </programlisting>
     </para>
  
+    <para>
+     <function>pg_hba_lookup</function> returns first matching
+ 	entry authentication method in pg_hba.conf with the given
+ 	input values. Typical usages include:
+ <programlisting>
+ SELECT pg_hba_lookup('test_database', 'test_user');
+ 
+  pg_hba_lookup 
+ ---------------
+  trust
+ (1 row)
+ </programlisting>
+    </para>
+    
    </sect2>
  
    <sect2 id="functions-admin-signal">
*** a/src/backend/libpq/hba.c
--- b/src/backend/libpq/hba.c
***************
*** 28,38 ****
--- 28,40 ----
  #include "catalog/pg_collation.h"
  #include "libpq/ip.h"
  #include "libpq/libpq.h"
+ #include "miscadmin.h"
  #include "postmaster/postmaster.h"
  #include "regex/regex.h"
  #include "replication/walsender.h"
  #include "storage/fd.h"
  #include "utils/acl.h"
+ #include "utils/builtins.h"
  #include "utils/guc.h"
  #include "utils/lsyscache.h"
  #include "utils/memutils.h"
***************
*** 74,79 **** typedef struct HbaToken
--- 76,84 ----
  	bool		quoted;
  } HbaToken;
  
+ /* Flag to indicate the failure of reloading pg_hba.conf file */
+ bool		load_hba_failure = false;
+ 
  /*
   * pre-parsed content of HBA config file: list of HbaLine structs.
   * parsed_hba_context is the memory context where it lives.
***************
*** 99,104 **** static List *tokenize_inc_file(List *tokens, const char *outer_filename,
--- 104,110 ----
  				  const char *inc_filename);
  static bool parse_hba_auth_opt(char *name, char *val, HbaLine *hbaline,
  				   int line_num);
+ static bool pg_hba_match(HbaLine *hba, char *user, char *database, char *address, char *hostname);
  
  /*
   * isblank() exists in the ISO C99 spec, but it's not very portable yet,
***************
*** 2233,2235 **** hba_getauthmethod(hbaPort *port)
--- 2239,2382 ----
  {
  	check_hba(port);
  }
+ 
+ 
+ static bool
+ pg_hba_match(HbaLine *hba, char *user, char *database, char *address, char *hostname)
+ {
+ 	Oid			roleid;
+ 
+ 	/* Get the target role's OID.  Note we do not error out for bad role. */
+ 	roleid = get_role_oid(user, true);
+ 
+ 	if (!check_db(database, user, roleid, hba->databases))
+ 		return false;
+ 
+ 	if (!check_role(user, roleid, hba->roles))
+ 		return false;
+ 
+ 	return true;
+ }
+ 
+ 
+ /*
+ * SQL-accessible SRF to return all the settings from the pg_hba.conf
+ * file.
+ */
+ Datum
+ pg_hba_lookup_2args(PG_FUNCTION_ARGS)
+ {
+ 	return pg_hba_lookup(fcinfo);
+ }
+ 
+ /*
+  * SQL-accessible SRF to return all the settings from the pg_hba.conf
+  * file. 
+  */
+ Datum
+ pg_hba_lookup(PG_FUNCTION_ARGS)
+ {
+ 	char	*user;
+ 	char	*database;
+ 	char	*address;
+ 	char    *hostname;
+ 	ListCell   *line;
+ 
+ 	if (!superuser())
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+ 				 (errmsg("only superuser can view pg_hba.conf settings"))));
+ 
+ 	if (PG_ARGISNULL(0))
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+ 				(errmsg("user name is required to match pg_hba configuration entry"))));
+ 	else
+ 		user = TextDatumGetCString(PG_GETARG_DATUM(0));
+ 
+ 	if (PG_ARGISNULL(1))
+ 		ereport(ERROR,
+ 				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+ 				(errmsg("database name is required to match pg_hba configuration entry"))));
+ 	else
+ 		database = TextDatumGetCString(PG_GETARG_DATUM(1));
+ 
+ 	if (PG_NARGS() != 2)
+ 	{
+ 		if (!PG_ARGISNULL(2))
+ 			address = TextDatumGetCString(PG_GETARG_DATUM(2));
+ 
+ 		if (!PG_ARGISNULL(3))
+ 			hostname = TextDatumGetCString(PG_GETARG_DATUM(3));
+ 	}
+ 
+ 	if (load_hba_failure)
+ 		ereport(WARNING,
+ 				(errmsg("There was some failure in reloading pg_hba.conf file. "
+ 				"The pg_hba.conf settings data may contains stale information")));
+ 
+ 	/*
+ 	* Loop through the list and deparse each entry as it comes, storing it in
+ 	* the tuplestore. Any temporary memory allocations here live only for the
+ 	* function call lifetime.
+ 	*/
+ 	foreach(line, parsed_hba_lines)
+ 	{
+ 		HbaLine    *hba = (HbaLine *)lfirst(line);
+ 		Datum		value;
+ 
+ 		CHECK_FOR_INTERRUPTS();
+ 
+ 		if (pg_hba_match(hba, user, database, address, hostname))
+ 		{
+ 			switch (hba->auth_method)
+ 			{
+ 			case uaReject:
+ 				value = CStringGetTextDatum("reject");
+ 				break;
+ 			case uaTrust:
+ 				value = CStringGetTextDatum("trust");
+ 				break;
+ 			case uaIdent:
+ 				value = CStringGetTextDatum("ident");
+ 				break;
+ 			case uaPassword:
+ 				value = CStringGetTextDatum("password");
+ 				break;
+ 			case uaMD5:
+ 				value = CStringGetTextDatum("md5");
+ 				break;
+ 			case uaGSS:
+ 				value = CStringGetTextDatum("gss");
+ 				break;
+ 			case uaSSPI:
+ 				value = CStringGetTextDatum("sspi");
+ 				break;
+ 			case uaPAM:
+ 				value = CStringGetTextDatum("pam");
+ 				break;
+ 			case uaLDAP:
+ 				value = CStringGetTextDatum("ldap");
+ 				break;
+ 			case uaCert:
+ 				value = CStringGetTextDatum("cert");
+ 				break;
+ 			case uaRADIUS:
+ 				value = CStringGetTextDatum("radius");
+ 				break;
+ 			case uaPeer:
+ 				value = CStringGetTextDatum("peer");
+ 				break;
+ 			default:
+ 				elog(ERROR, "unexpected authentication method in parsed HBA entry");
+ 				break;
+ 			}
+ 
+ 			PG_RETURN_TEXT_P(value);
+ 		}
+ 	}
+ 
+ 	PG_RETURN_NULL();
+ }
+ 
+ 
*** a/src/backend/tcop/postgres.c
--- b/src/backend/tcop/postgres.c
***************
*** 4005,4010 **** PostgresMain(int argc, char *argv[],
--- 4005,4023 ----
  		{
  			got_SIGHUP = false;
  			ProcessConfigFile(PGC_SIGHUP);
+ 			
+ 			/* 
+ 			 * Reload authentication config files too to refresh 
+ 			 * pg_hba_conf view data.
+ 			 */
+ 			if (!load_hba())
+ 			{
+ 				ereport(DEBUG1,
+ 					(errmsg("Falure in reloading pg_hba.conf, pg_hba_conf view may show stale information")));
+ 				load_hba_failure = true;
+ 			}
+ 			
+ 			load_hba_failure = false;
  		}
  
  		/*
*** a/src/include/catalog/pg_proc.h
--- b/src/include/catalog/pg_proc.h
***************
*** 3079,3084 **** DATA(insert OID = 2084 (  pg_show_all_settings	PGNSP PGUID 12 1 1000 0 0 f f f f
--- 3079,3088 ----
  DESCR("SHOW ALL as a function");
  DATA(insert OID = 3329 (  pg_show_all_file_settings PGNSP PGUID 12 1 1000 0 0 f f f f t t v s 0 0 2249 "" "{25,23,23,25,25,16,25}" "{o,o,o,o,o,o,o}" "{sourcefile,sourceline,seqno,name,setting,applied,error}" _null_ _null_ show_all_file_settings _null_ _null_ _null_ ));
  DESCR("show config file settings");
+ DATA(insert OID = 3997 (pg_hba_lookup PGNSP PGUID 12 1 1000 0 0 f f f f t t v s 2 0 25 "25 25" _null_ _null_ _null_ _null_ _null_ pg_hba_lookup_2args _null_ _null_ _null_));
+ DESCR("view client authentication settings");
+ DATA(insert OID = 3998 (pg_hba_lookup PGNSP PGUID 12 1 1000 0 0 f f f f t t v s 4 0 25 "25 25 25 25" _null_ _null_ _null_ _null_ _null_ pg_hba_lookup _null_ _null_ _null_));
+ DESCR("view client authentication settings");
  DATA(insert OID = 1371 (  pg_lock_status   PGNSP PGUID 12 1 1000 0 0 f f f f t t v s 0 0 2249 "" "{25,26,26,23,21,25,28,26,26,21,25,23,25,16,16}" "{o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}" "{locktype,database,relation,page,tuple,virtualxid,transactionid,classid,objid,objsubid,virtualtransaction,pid,mode,granted,fastpath}" _null_ _null_ pg_lock_status _null_ _null_ _null_ ));
  DESCR("view system lock information");
  DATA(insert OID = 1065 (  pg_prepared_xact PGNSP PGUID 12 1 1000 0 0 f f f f t t v s 0 0 2249 "" "{28,25,1184,26,26}" "{o,o,o,o,o}" "{transaction,gid,prepared,ownerid,dbid}" _null_ _null_ pg_prepared_xact _null_ _null_ _null_ ));
*** a/src/include/libpq/hba.h
--- b/src/include/libpq/hba.h
***************
*** 96,101 **** typedef struct IdentLine
--- 96,103 ----
  /* kluge to avoid including libpq/libpq-be.h here */
  typedef struct Port hbaPort;
  
+ extern bool load_hba_failure;
+ 
  extern bool load_hba(void);
  extern bool load_ident(void);
  extern void hba_getauthmethod(hbaPort *port);
*** a/src/include/utils/builtins.h
--- b/src/include/utils/builtins.h
***************
*** 1122,1127 **** extern Datum show_config_by_name_missing_ok(PG_FUNCTION_ARGS);
--- 1122,1129 ----
  extern Datum set_config_by_name(PG_FUNCTION_ARGS);
  extern Datum show_all_settings(PG_FUNCTION_ARGS);
  extern Datum show_all_file_settings(PG_FUNCTION_ARGS);
+ extern Datum pg_hba_lookup_2args(PG_FUNCTION_ARGS);
+ extern Datum pg_hba_lookup(PG_FUNCTION_ARGS);
  
  /* rls.c */
  extern Datum row_security_active(PG_FUNCTION_ARGS);