Be more user-friendly about unsupported cases for parallel pg_restore.

If we are unable to do a parallel restore because the input file is stdin
or is otherwise unseekable, we should complain and fail immediately, not
after having done some of the restore.  Complaining once per thread isn't
so cool either, and the messages should be worded to make it clear this is
an unsupported case not some weird race-condition bug.  Per complaint from
Lonni Friedman.

Back-patch to 8.4, where parallel restore was introduced.

diff --git a/src/bin/pg_dump/pg_backup_archiver.c b/src/bin/pg_dump/pg_backup_archiver.c
index 6b930e2f234c779b1f9ec586f1996c71f441bbc6..31915ae94c1b5f755893e95210a1b12b706dead4 100644 (file)
--- a/src/bin/pg_dump/pg_backup_archiver.c
+++ b/src/bin/pg_dump/pg_backup_archiver.c
@@ -3125,6 +3125,12 @@ restore_toc_entries_parallel(ArchiveHandle *AH)
        if (AH->version < K_VERS_1_8)
                die_horribly(AH, modulename, "parallel restore is not supported with archives made by pre-8.0 pg_dump\n");
 
+       /*
+        * It's also not gonna work if we can't reopen the input file, so let's
+        * try that immediately.
+        */
+       (AH->ReopenPtr) (AH);
+
        slots = (ParallelSlot *) calloc(sizeof(ParallelSlot), n_slots);
 
        /* Adjust dependency information */

diff --git a/src/bin/pg_dump/pg_backup_custom.c b/src/bin/pg_dump/pg_backup_custom.c
index e233e68e025844ce985b08fbbefed309f46a39a8..caa2c836bbe88033829ee2349c98ad9321e2d2d1 100644 (file)
--- a/src/bin/pg_dump/pg_backup_custom.c
+++ b/src/bin/pg_dump/pg_backup_custom.c
@@ -866,10 +866,15 @@ _ReopenArchive(ArchiveHandle *AH)
 
        if (AH->mode == archModeWrite)
                die_horribly(AH, modulename, "can only reopen input archives\n");
+
+       /*
+        * These two cases are user-facing errors since they represent unsupported
+        * (but not invalid) use-cases.  Word the error messages appropriately.
+        */
        if (AH->fSpec == NULL || strcmp(AH->fSpec, "") == 0)
-               die_horribly(AH, modulename, "cannot reopen stdin\n");
+               die_horribly(AH, modulename, "parallel restore from stdin is not supported\n");
        if (!ctx->hasSeek)
-               die_horribly(AH, modulename, "cannot reopen non-seekable file\n");
+               die_horribly(AH, modulename, "parallel restore from non-seekable file is not supported\n");
 
        errno = 0;
        tpos = ftello(AH->FH);