pg_dump -j against a standby server returns a pretty bad error message when
pointed at a standby node:
pg_dump: [archiver (db)] query failed: ERROR: cannot assign TransactionIds
during recovery
pg_dump: [archiver (db)] query was: SELECT pg_export_snapshot()
That looks quite scary to the user, and also throws errors in the server
log which monitoring tools or DBAs will react to.
PFA a patch that changes this to:
pg_dump: Synchronized snapshots are not supported on standby servers.
Run with --no-synchronized-snapshots instead if you do not need
synchronized snapshots.
which is a message similar (the hint identical) the one you get if you
point it at a version older than 9.2 which doesn't have sync snapshots.
I think the cleanest way to do it is to just track if it's a standby in the
AH struct as written.
Comments?
--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/
diff --git a/src/bin/pg_dump/pg_backup.h b/src/bin/pg_dump/pg_backup.h
index 83f6029..f94caa3 100644
--- a/src/bin/pg_dump/pg_backup.h
+++ b/src/bin/pg_dump/pg_backup.h
@@ -173,6 +173,7 @@ typedef struct Archive
int verbose;
char *remoteVersionStr; /* server's version string */
int remoteVersion; /* same in numeric form */
+ bool isStandby; /* is server a standby node */
int minRemoteVersion; /* allowable range */
int maxRemoteVersion;
diff --git a/src/bin/pg_dump/pg_backup_db.c b/src/bin/pg_dump/pg_backup_db.c
index 35ce945..dc073a6 100644
--- a/src/bin/pg_dump/pg_backup_db.c
+++ b/src/bin/pg_dump/pg_backup_db.c
@@ -37,6 +37,7 @@ _check_database_version(ArchiveHandle *AH)
{
const char *remoteversion_str;
int remoteversion;
+ PGresult *res;
remoteversion_str = PQparameterStatus(AH->connection, "server_version");
remoteversion = PQserverVersion(AH->connection);
@@ -56,6 +57,12 @@ _check_database_version(ArchiveHandle *AH)
remoteversion_str, progname, PG_VERSION);
exit_horribly(NULL, "aborting because of server version mismatch\n");
}
+
+ /* Identify if this is a standby node */
+ res = ExecuteSqlQuery((Archive *) AH, "SELECT pg_catalog.pg_is_in_recovery()", PGRES_TUPLES_OK);
+
+ AH->public.isStandby = (strcmp(PQgetvalue(res, 0, 0), "t") == 0);
+ PQclear(res);
}
/*
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 1267afb..e0c64cf 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -651,19 +651,13 @@ main(int argc, char **argv)
* When running against 9.0 or later, check if we are in recovery mode,
* which means we are on a hot standby.
*/
- if (fout->remoteVersion >= 90000)
+ if (fout->remoteVersion >= 90000 && fout->isStandby)
{
- PGresult *res = ExecuteSqlQueryForSingleRow(fout, "SELECT pg_catalog.pg_is_in_recovery()");
-
- if (strcmp(PQgetvalue(res, 0, 0), "t") == 0)
- {
- /*
- * On hot standby slaves, never try to dump unlogged table data,
- * since it will just throw an error.
- */
- dopt.no_unlogged_table_data = true;
- }
- PQclear(res);
+ /*
+ * On hot standby slaves, never try to dump unlogged table data, since
+ * it will just throw an error.
+ */
+ dopt.no_unlogged_table_data = true;
}
/* Select the appropriate subquery to convert user IDs to names */
@@ -1096,7 +1090,16 @@ setup_connection(Archive *AH, const char *dumpencoding,
else if (AH->numWorkers > 1 &&
AH->remoteVersion >= 90200 &&
!dopt->no_synchronized_snapshots)
+ {
+ if (!dopt->no_synchronized_snapshots && AH->isStandby)
+ exit_horribly(NULL,
+ "Synchronized snapshots are not supported on standby servers.\n"
+ "Run with --no-synchronized-snapshots instead if you do not need\n"
+ "synchronized snapshots.\n");
+
+
AH->sync_snapshot_id = get_synchronized_snapshot(AH);
+ }
}
static void
--
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