Refactor replication connection code of various pg_basebackup utilities.

Move some more code to manage replication connection command to streamutil.c. A later patch will introduce replication slot via pg_receivexlog and this avoid duplicating relevant code between pg_receivexlog and pg_recvlogical. Author: Michael Paquier, with some editing by me.
2025-08-22 21:53:06 +03:00 · 2014-10-01 17:22:21 +02:00
parent fdf81c9a6c
commit 0c013e08cf
5 changed files with 223 additions and 142 deletions
--- a/src/bin/pg_basebackup/streamutil.c
+++ b/src/bin/pg_basebackup/streamutil.c
@@ -27,6 +27,7 @@
 #include "receivelog.h"
 #include "streamutil.h"

+#include "pqexpbuffer.h"
 #include "common/fe_memutils.h"
 #include "datatype/timestamp.h"

@@ -227,11 +228,183 @@ GetConnection(void)
 	return tmpconn;
 }

+/*
+ * Run IDENTIFY_SYSTEM through a given connection and give back to caller
+ * some result information if requested:
+ * - Start LSN position
+ * - Current timeline ID
+ * - System identifier
+ * - Plugin name
+ */
+bool
+RunIdentifySystem(PGconn *conn, char **sysid, TimeLineID *starttli,
+				  XLogRecPtr *startpos, char **db_name)
+{
+	PGresult   *res;
+	uint32		hi, lo;
+
+	/* Check connection existence */
+	Assert(conn != NULL);
+
+	res = PQexec(conn, "IDENTIFY_SYSTEM");
+	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+	{
+		fprintf(stderr, _("%s: could not send replication command \"%s\": %s"),
+				progname, "IDENTIFY_SYSTEM", PQerrorMessage(conn));
+		return false;
+	}
+	if (PQntuples(res) != 1 || PQnfields(res) < 3)
+	{
+		fprintf(stderr,
+				_("%s: could not identify system: got %d rows and %d fields, expected %d rows and %d or more fields\n"),
+				progname, PQntuples(res), PQnfields(res), 1, 3);
+		return false;
+	}
+
+	/* Get system identifier */
+	if (sysid != NULL)
+		*sysid = pg_strdup(PQgetvalue(res, 0, 0));
+
+	/* Get timeline ID to start streaming from */
+	if (starttli != NULL)
+		*starttli = atoi(PQgetvalue(res, 0, 1));
+
+	/* Get LSN start position if necessary */
+	if (startpos != NULL)
+	{
+		if (sscanf(PQgetvalue(res, 0, 2), "%X/%X", &hi, &lo) != 2)
+		{
+			fprintf(stderr,
+					_("%s: could not parse transaction log location \"%s\"\n"),
+					progname, PQgetvalue(res, 0, 2));
+			return false;
+		}
+		*startpos = ((uint64) hi) << 32 | lo;
+	}
+
+	/* Get database name, only available in 9.4 and newer versions */
+	if  (db_name != NULL)
+	{
+		if (PQnfields(res) < 4)
+			fprintf(stderr,
+					_("%s: could not identify system: got %d rows and %d fields, expected %d rows and %d or more fields\n"),
+					progname, PQntuples(res), PQnfields(res), 1, 4);
+
+		if (PQgetisnull(res, 0, 3))
+			*db_name =  NULL;
+		else
+			*db_name = pg_strdup(PQgetvalue(res, 0, 3));
+	}
+
+	PQclear(res);
+	return true;
+}
+
+/*
+ * Create a replication slot for the given connection. This function
+ * returns true in case of success as well as the start position
+ * obtained after the slot creation.
+ */
+bool
+CreateReplicationSlot(PGconn *conn, const char *slot_name, const char *plugin,
+					  XLogRecPtr *startpos, bool is_physical)
+{
+	PQExpBuffer query;
+	PGresult   *res;
+
+	query = createPQExpBuffer();
+
+	Assert((is_physical && plugin == NULL) ||
+		   (!is_physical && plugin != NULL));
+	Assert(slot_name != NULL);
+
+	/* Build query */
+	if (is_physical)
+		appendPQExpBuffer(query, "CREATE_REPLICATION_SLOT \"%s\" PHYSICAL",
+						  slot_name);
+	else
+		appendPQExpBuffer(query, "CREATE_REPLICATION_SLOT \"%s\" LOGICAL \"%s\"",
+						  slot_name, plugin);
+
+	res = PQexec(conn, query->data);
+	if (PQresultStatus(res) != PGRES_TUPLES_OK)
+	{
+		fprintf(stderr, _("%s: could not send replication command \"%s\": %s"),
+				progname, query->data, PQerrorMessage(conn));
+		return false;
+	}
+
+	if (PQntuples(res) != 1 || PQnfields(res) != 4)
+	{
+		fprintf(stderr,
+				_("%s: could not create replication slot \"%s\": got %d rows and %d fields, expected %d rows and %d fields\n"),
+				progname, slot_name,
+				PQntuples(res), PQnfields(res), 1, 4);
+		return false;
+	}
+
+	/* Get LSN start position if necessary */
+	if (startpos != NULL)
+	{
+		uint32		hi, lo;
+
+		if (sscanf(PQgetvalue(res, 0, 1), "%X/%X", &hi, &lo) != 2)
+		{
+			fprintf(stderr,
+					_("%s: could not parse transaction log location \"%s\"\n"),
+					progname, PQgetvalue(res, 0, 1));
+			return false;
+		}
+		*startpos = ((uint64) hi) << 32 | lo;
+	}
+
+	PQclear(res);
+	return true;
+}
+
+/*
+ * Drop a replication slot for the given connection. This function
+ * returns true in case of success.
+ */
+bool
+DropReplicationSlot(PGconn *conn, const char *slot_name)
+{
+	PQExpBuffer query;
+	PGresult   *res;
+
+	Assert(slot_name != NULL);
+
+	query = createPQExpBuffer();
+
+	/* Build query */
+	appendPQExpBuffer(query, "DROP_REPLICATION_SLOT \"%s\"",
+					  slot_name);
+	res = PQexec(conn, query->data);
+	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+	{
+		fprintf(stderr, _("%s: could not send replication command \"%s\": %s"),
+				progname, query->data, PQerrorMessage(conn));
+		return false;
+	}
+
+	if (PQntuples(res) != 0 || PQnfields(res) != 0)
+	{
+		fprintf(stderr,
+				_("%s: could not drop replication slot \"%s\": got %d rows and %d fields, expected %d rows and %d fields\n"),
+				progname, slot_name,
+				PQntuples(res), PQnfields(res), 0, 0);
+		return false;
+	}
+
+	PQclear(res);
+	return true;
+}
+

 /*
 * Frontend version of GetCurrentTimestamp(), since we are not linked with
- * backend code. The protocol always uses integer timestamps, regardless of
- * server setting.
+ * backend code. The replication protocol always uses integer timestamps,
+ * regardless of the server setting.
 */
 int64
 feGetCurrentTimestamp(void)