Fix url stored in error log, when reading from gpfdist external table.

The URL stored in the 'filename' field of the error log was stored
incorrectly:

    postgres=# SELECT filename FROM gp_read_error_log('sreh_ext_err_tbl');
                                          filename
    ------------------------------------------------------------------------------------
     (null) [/home/heikki/git-sandbox-gpdb/master/src/test/regress/data/bad_data1.data]
     (null) [/home/heikki/git-sandbox-gpdb/master/src/test/regress/data/bad_data1.data]
    ...

On 5X_STABLE, the URL is stored in place of the '(null)'. This got broken
in 6X_STABLE. The root cause is that we no longer keep the 'url' in the
CopyState->filename field for gpfdist external tables.

Fixes https://github.com/greenplum-db/gpdb/issues/10542Reviewed-by: N(Jerome)Junfeng Yang <jeyang@pivotal.io>

src/backend/access/external/url_curl.c

@@ -1584,7 +1584,8 @@ gp_proto1_read(char *buf, int bufsz, URL_CURL_FILE *file, CopyState pstate, char
 
 				memcpy(fname, file->in.ptr + file->in.bot, len);
 				fname[len] = 0;
-				snprintf(pstate->cdbsreh->filename, sizeof pstate->cdbsreh->filename,"%s [%s]", pstate->filename, fname);
+				snprintf(pstate->cdbsreh->filename, sizeof pstate->cdbsreh->filename, "%s [%s]",
+						 file->common.url, fname);
 			}
 
 			file->in.bot += len;

src/test/regress/input/sreh.source

@@ -181,7 +181,9 @@ LOG ERRORS INTO WHATEVER
 SEGMENT REJECT LIMIT 1000;
 
 SELECT * FROM sreh_ext_err_tbl ORDER BY a;
-WITH error_log AS (SELECT gp_read_error_log('sreh_ext_err_tbl')) select count(*) from error_log;
+-- Verify the fields that we easily can.
+WITH error_log AS (SELECT * FROM gp_read_error_log('sreh_ext_err_tbl'))
+  SELECT relname, filename LIKE 'gpfdist://@hostname@:8080/bad_data1.data [%]' as filename_ok, linenum, errmsg from error_log;
 
 CREATE EXTERNAL TABLE sreh_ext(a int, b int, c int)
 LOCATION ('gpfdist://@hostname@:8080/bad_data1.data' )

src/test/regress/output/sreh.source

@@ -320,11 +320,22 @@ NOTICE:  found 10 data formatting errors (10 or more input rows), rejected relat
  14 | 14 | 14
 (6 rows)
 
-WITH error_log AS (SELECT gp_read_error_log('sreh_ext_err_tbl')) select count(*) from error_log;
- count 
--------
-    10
-(1 row)
+-- Verify the fields that we easily can.
+WITH error_log AS (SELECT * FROM gp_read_error_log('sreh_ext_err_tbl'))
+  SELECT relname, filename LIKE 'gpfdist://@hostname@:8080/bad_data1.data [%]' as filename_ok, linenum, errmsg from error_log;
+     relname      | filename_ok | linenum |                        errmsg                         
+------------------+-------------+---------+-------------------------------------------------------
+ sreh_ext_err_tbl | t           |       2 | missing data for column "b"
+ sreh_ext_err_tbl | t           |       3 | invalid input syntax for integer: "", column b
+ sreh_ext_err_tbl | t           |       4 | extra data after last expected column, column b
+ sreh_ext_err_tbl | t           |       7 | invalid input syntax for integer: "bad", column c
+ sreh_ext_err_tbl | t           |       8 | invalid input syntax for integer: "bad", column a
+ sreh_ext_err_tbl | t           |      11 | invalid input syntax for integer: "eleven", column a
+ sreh_ext_err_tbl | t           |      12 | extra data after last expected column, column a
+ sreh_ext_err_tbl | t           |      13 | invalid input syntax for integer: ",13,", column b
+ sreh_ext_err_tbl | t           |      15 | missing data for column "b"
+ sreh_ext_err_tbl | t           |      16 | invalid input syntax for integer: "sixteen", column a
+(10 rows)
 
 CREATE EXTERNAL TABLE sreh_ext(a int, b int, c int)
 LOCATION ('gpfdist://@hostname@:8080/bad_data1.data' )