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Add function get_current_lsn()

Browse Source 
This is a somewhat convoluted attempt to retrieve the current LSN
of any node, regardless of whether in recovery or not, and if in
recovery, independent of whether streaming or recovering from
archive.
This commit is contained in:
Ian Barwick
2018-11-22 19:29:56 +09:00
parent 80a280cbf4
commit 0f4e04e61e
2 changed files with 129 additions and 1 deletions
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129
dbutils.c
View File

@@ -4787,7 +4787,6 @@ get_last_wal_receive_location(PGconn *conn)
PGresult *res = NULL;
XLogRecPtr ptr = InvalidXLogRecPtr;
if (server_version_num >= 100000)
{
res = PQexec(conn, "SELECT pg_catalog.pg_last_wal_receive_lsn()");
@@ -4807,6 +4806,134 @@ get_last_wal_receive_location(PGconn *conn)
return ptr;
}
XLogRecPtr
get_current_lsn(PGconn *conn)
{
PQExpBufferData query;
PGresult *res = NULL;
XLogRecPtr ptr = InvalidXLogRecPtr;
initPQExpBuffer(&query);
if (server_version_num == UNKNOWN_SERVER_VERSION_NUM)
server_version_num = get_server_version(conn, NULL);
/*
WITH lsn_states AS (
SELECT
CASE WHEN pg_catalog.pg_is_in_recovery() IS FALSE
THEN pg_catalog.pg_current_wal_lsn()
ELSE NULL
END
AS current_wal_lsn,
CASE WHEN pg_catalog.pg_is_in_recovery() IS TRUE
THEN pg_catalog.pg_last_wal_receive_lsn()
ELSE NULL
END
AS last_wal_receive_lsn,
CASE WHEN pg_catalog.pg_is_in_recovery() IS TRUE
THEN pg_catalog.pg_last_wal_replay_lsn()
ELSE NULL
END
AS last_wal_replay_lsn
)
SELECT
CASE WHEN pg_catalog.pg_is_in_recovery() IS FALSE
THEN current_wal_lsn
ELSE
CASE WHEN last_wal_receive_lsn IS NULL
THEN last_wal_replay_lsn
ELSE
CASE WHEN last_wal_replay_lsn > last_wal_receive_lsn
THEN last_wal_replay_lsn
ELSE last_wal_receive_lsn
END
END
END
AS current_lsn
FROM lsn_states
*/
if (server_version_num >= 100000)
{
appendPQExpBufferStr(&query,
" WITH lsn_states AS ( "
" SELECT "
" CASE WHEN pg_catalog.pg_is_in_recovery() IS FALSE "
" THEN pg_catalog.pg_current_wal_lsn() "
" ELSE NULL "
" END "
" AS current_wal_lsn, "
" CASE WHEN pg_catalog.pg_is_in_recovery() IS TRUE "
" THEN pg_catalog.pg_last_wal_receive_lsn() "
" ELSE NULL "
" END "
" AS last_wal_receive_lsn, "
" CASE WHEN pg_catalog.pg_is_in_recovery() IS TRUE "
" THEN pg_catalog.pg_last_wal_replay_lsn() "
" ELSE NULL "
" END "
" AS last_wal_replay_lsn "
" ) ");
}
else
{
appendPQExpBufferStr(&query,
" WITH lsn_states AS ( "
" SELECT "
" CASE WHEN pg_catalog.pg_is_in_recovery() IS FALSE "
" THEN pg_catalog.pg_current_xlog_location() "
" ELSE NULL "
" END "
" AS current_wal_lsn, "
" CASE WHEN pg_catalog.pg_is_in_recovery() IS TRUE "
" THEN pg_catalog.pg_last_xlog_receive_location() "
" ELSE NULL "
" END "
" AS last_wal_receive_lsn, "
" CASE WHEN pg_catalog.pg_is_in_recovery() IS TRUE "
" THEN pg_catalog.pg_last_xlog_replay_location()) "
" ELSE NULL "
" END "
" AS last_wal_replay_lsn "
" ) ");
}
appendPQExpBufferStr(&query,
" SELECT "
" CASE WHEN pg_catalog.pg_is_in_recovery() IS FALSE "
" THEN current_wal_lsn "
" ELSE "
" CASE WHEN last_wal_receive_lsn IS NULL "
" THEN last_wal_replay_lsn "
" ELSE "
" CASE WHEN last_wal_replay_lsn > last_wal_receive_lsn "
" THEN last_wal_replay_lsn "
" ELSE last_wal_receive_lsn "
" END "
" END "
" END "
" AS current_lsn "
" FROM lsn_states ");
res = PQexec(conn, query.data);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
{
log_db_error(conn, query.data, _("unable to execute get_current_lsn()"));
}
else if (!PQgetisnull(res, 0, 0))
{
ptr = parse_lsn(PQgetvalue(res, 0, 0));
}
termPQExpBuffer(&query);
PQclear(res);
return ptr;
}
/* ============= */
/* BDR functions */
/* ============= */

1
dbutils.h
View File

@@ -545,6 +545,7 @@ void reset_voting_status(PGconn *conn);
/* replication status functions */
XLogRecPtr get_current_wal_lsn(PGconn *conn);
XLogRecPtr get_last_wal_receive_location(PGconn *conn);
XLogRecPtr get_current_lsn(PGconn *conn);
bool get_replication_info(PGconn *conn, ReplInfo *replication_info);
int get_replication_lag_seconds(PGconn *conn);
void get_node_replication_stats(PGconn *conn, int server_version_num, t_node_info *node_info);