Allow ON MASTER for external file protocol

src/backend/optimizer/plan/createplan.c

@@ -1592,7 +1592,7 @@ create_external_scan_uri_list(ExtTableEntry *ext, bool *ismasteronly)
 	 * protocols only */
 	on_clause = (char *) strVal(linitial(ext->execlocations));
 	if ((strcmp(on_clause, "MASTER_ONLY") == 0)
-		&& using_location && (uri->protocol != URI_CUSTOM)) {
+		&& using_location && (uri->protocol != URI_CUSTOM && uri->protocol != URI_FILE)) {
 		ereport(ERROR, (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
 				errmsg("\'ON MASTER\' is not supported by this protocol yet")));
 	}
@@ -1670,6 +1670,12 @@ create_external_scan_uri_list(ExtTableEntry *ext, bool *ismasteronly)
 			found_candidate = false;
 			found_match = false;
 
+			if ((strcmp(on_clause, "MASTER_ONLY") == 0) && uri->protocol == URI_FILE)
+			{
+				found_match = true;
+				segdb_file_map[0] = pstrdup(uri_str);
+				*ismasteronly = true;
+			}
 			/*
 			 * look through our segment database list and try to find a
 			 * database that can handle this uri.

src/test/regress/input/external_table.source

@@ -1385,10 +1385,22 @@ SELECT COUNT(*) FROM gp_read_error_log('exttab_heap_join_1');
 \! rm @abs_srcdir@/data/tableless.csv
 
 -- start_ignore
+DROP EXTERNAL TABLE IF EXISTS ext_nation_on_master;
 DROP EXTERNAL TABLE IF EXISTS exttab_with_on_master;
 -- end_ignore
 
--- Create external table with on clause
+-- Create external table on master
+-- good, should fetch data from master
+CREATE EXTERNAL TABLE ext_nation_on_master ( N_NATIONKEY  INTEGER ,
+                            N_NAME       CHAR(25) ,
+                            N_REGIONKEY  INTEGER ,
+                            N_COMMENT    VARCHAR(152))
+location ('file://@hostname@@abs_srcdir@/data/nation.tbl' ) ON MASTER
+FORMAT 'text' (delimiter '|');
+SELECT gp_segment_id, * FROM ext_nation_on_master ORDER BY N_NATIONKEY DESC LIMIT 5;
+DROP EXTERNAL TABLE IF EXISTS ext_nation_on_master;
+
+-- bad, should error
 CREATE EXTERNAL TABLE exttab_with_on_master( i int, j text )
 LOCATION ('file://@hostname@@abs_srcdir@/data/exttab_few_errors.data') ON MASTER FORMAT 'TEXT' (DELIMITER '|');
 

src/test/regress/output/external_table.source

@@ -2680,14 +2680,36 @@ SELECT COUNT(*) FROM gp_read_error_log('exttab_heap_join_1');
 
 \! rm @abs_srcdir@/data/tableless.csv
 -- start_ignore
+DROP EXTERNAL TABLE IF EXISTS ext_nation_on_master;
+NOTICE:  table "ext_nation_on_master" does not exist, skipping
 DROP EXTERNAL TABLE IF EXISTS exttab_with_on_master;
 NOTICE:  table "exttab_with_on_master" does not exist, skipping
 -- end_ignore
--- Create external table with on clause
+-- Create external table on master
+-- good, should fetch data from master
+CREATE EXTERNAL TABLE ext_nation_on_master ( N_NATIONKEY  INTEGER ,
+                            N_NAME       CHAR(25) ,
+                            N_REGIONKEY  INTEGER ,
+                            N_COMMENT    VARCHAR(152))
+location ('file://@hostname@@abs_srcdir@/data/nation.tbl' ) ON MASTER
+FORMAT 'text' (delimiter '|');
+SELECT gp_segment_id, * FROM ext_nation_on_master ORDER BY N_NATIONKEY DESC LIMIT 5;
+ gp_segment_id | n_nationkey |          n_name           | n_regionkey |                                                   n_comment                                                    
+---------------+-------------+---------------------------+-------------+----------------------------------------------------------------------------------------------------------------
+            -1 |          24 | UNITED STATES             |           1 | y final packages. slow foxes cajole quickly. quickly silent platelets breach ironic accounts. unusual pinto be
+            -1 |          23 | UNITED KINGDOM            |           3 | eans boost carefully special requests. accounts are. carefull
+            -1 |          22 | RUSSIA                    |           3 |  requests against the platelets use never according to the quickly regular pint
+            -1 |          21 | VIETNAM                   |           2 | hely enticingly express accounts. even, final 
+            -1 |          20 | SAUDI ARABIA              |           4 | ts. silent requests haggle. closely express packages sleep across the blithely
+(5 rows)
+
+DROP EXTERNAL TABLE IF EXISTS ext_nation_on_master;
+-- bad, should error
 CREATE EXTERNAL TABLE exttab_with_on_master( i int, j text )
 LOCATION ('file://@hostname@@abs_srcdir@/data/exttab_few_errors.data') ON MASTER FORMAT 'TEXT' (DELIMITER '|');
 SELECT * FROM exttab_with_on_master;
-ERROR:  'ON MASTER' is not supported by this protocol yet
+ERROR:  invalid input syntax for integer: "error_0"
+CONTEXT:  External table exttab_with_on_master, line 3 of file://@hostname@@abs_srcdir@/data/exttab_few_errors.data, column i
 DROP EXTERNAL TABLE IF EXISTS exttab_with_on_master;
 -- start_ignore
 DROP EXTERNAL TABLE IF EXISTS exttab_with_option_empty;