bug: copy progress reporting of backends which run multiple COPYs

[Justin Pryzby]

pg_stat_progress_copy was added in v14 (8a4f618e7, 9d2d45700).

But if a command JOINs file_fdw tables, the progress report gets bungled
up.  This will warn/assert during file_fdw tests.

diff --git a/src/backend/utils/activity/backend_progress.c 
b/src/backend/utils/activity/backend_progress.c
index 6743e68cef6..7abcb4f60db 100644
--- a/src/backend/utils/activity/backend_progress.c
+++ b/src/backend/utils/activity/backend_progress.c
@@ -10,6 +10,7 @@
  */
 #include "postgres.h"
 
+#include "commands/progress.h"
 #include "port/atomics.h"              /* for memory barriers */
 #include "utils/backend_progress.h"
 #include "utils/backend_status.h"
@@ -105,6 +106,20 @@ pgstat_progress_end_command(void)
        if (beentry->st_progress_command == PROGRESS_COMMAND_INVALID)
                return;
 
+// This currently fails file_fdw tests, since pgstat_progress evidently fails
+// to support simultaneous copy commands, as happens during JOIN.
+       /* bytes progress is not available in all cases */
+       if (beentry->st_progress_command == PROGRESS_COMMAND_COPY &&
+                       beentry->st_progress_param[PROGRESS_COPY_BYTES_TOTAL] > 
0)
+       {
+               volatile int64 *a = beentry->st_progress_param;
+               if (a[PROGRESS_COPY_BYTES_PROCESSED] > 
a[PROGRESS_COPY_BYTES_TOTAL])
+                       elog(WARNING, "PROGRESS_COPY_BYTES_PROCESSED %ld %ld",
+                                       a[PROGRESS_COPY_BYTES_PROCESSED],
+                                       a[PROGRESS_COPY_BYTES_TOTAL]);
+               // Assert(a[PROGRESS_COPY_BYTES_PROCESSED] <= 
a[PROGRESS_COPY_BYTES_TOTAL]);
+       }
+
        PGSTAT_BEGIN_WRITE_ACTIVITY(beentry);
        beentry->st_progress_command = PROGRESS_COMMAND_INVALID;
        beentry->st_progress_command_target = InvalidOid;