Refactor one use of IDENTIFY_SYSTEM in WAL streaming code of pg_basebackup

0c013e0 has done a large refactoring to unify all the code paths using
replication commands, but forgot one code path doing WAL streaming that
checks the validity of a cluster connecting to with IDENTIFY_SYSTEM.
There is a generic routine able to handle that, so make use of it in
this code path.  This impacts pg_receivewal and pg_basebackup.

Author: Bharath Rupireddy
Discussion: https://postgr.es/m/CALj2ACVKKYUMC8GE72Y7BP9g1batrrq3sEwUh+1_i2krWZC_2Q@mail.gmail.com

diff --git a/src/bin/pg_basebackup/receivelog.c b/src/bin/pg_basebackup/receivelog.c
index ec53b6837e787e76440cec16e16fcf73ecd853e3..9601fd8d9cf9e5145df1cf54d9555734b1104b6a 100644 (file)
--- a/src/bin/pg_basebackup/receivelog.c
+++ b/src/bin/pg_basebackup/receivelog.c
@@ -482,36 +482,32 @@ ReceiveXlogStream(PGconn *conn, StreamCtl *stream)
 
    if (stream->sysidentifier != NULL)
    {
-       /* Validate system identifier hasn't changed */
-       res = PQexec(conn, "IDENTIFY_SYSTEM");
-       if (PQresultStatus(res) != PGRES_TUPLES_OK)
-       {
-           pg_log_error("could not send replication command \"%s\": %s",
-                        "IDENTIFY_SYSTEM", PQerrorMessage(conn));
-           PQclear(res);
-           return false;
-       }
-       if (PQntuples(res) != 1 || PQnfields(res) < 3)
+       char       *sysidentifier = NULL;
+       TimeLineID  servertli;
+
+       /*
+        * Get the server system identifier and timeline, and validate them.
+        */
+       if (!RunIdentifySystem(conn, &sysidentifier, &servertli, NULL, NULL))
        {
-           pg_log_error("could not identify system: got %d rows and %d fields, expected %d rows and %d or more fields",
-                        PQntuples(res), PQnfields(res), 1, 3);
-           PQclear(res);
+           pg_free(sysidentifier);
            return false;
        }
-       if (strcmp(stream->sysidentifier, PQgetvalue(res, 0, 0)) != 0)
+
+       if (strcmp(stream->sysidentifier, sysidentifier) != 0)
        {
            pg_log_error("system identifier does not match between base backup and streaming connection");
-           PQclear(res);
+           pg_free(sysidentifier);
            return false;
        }
-       if (stream->timeline > atoi(PQgetvalue(res, 0, 1)))
+       pg_free(sysidentifier);
+
+       if (stream->timeline > servertli)
        {
            pg_log_error("starting timeline %u is not present in the server",
                         stream->timeline);
-           PQclear(res);
            return false;
        }
-       PQclear(res);
    }
 
    /*