doc: Recommend pg_stat_io rather than pg_stat_wal in WAL configuration

Since a051e71e28a1, pg_stat_io is able to track statistics for the WAL
activity, providing an equivalent of pg_stat_wal with more granularity
for the fsyncs/writes counts and timings, as the data is split across
backend types.

This commit now recommends pg_stat_io rather than pg_stat_wal in the
section "WAL configuration", some of the latter's attributes being
candidate for removal in a follow-up commit.

Extracted from a larger patch by the same author.

Author: Bertrand Drouvot 
Discussion: https://postgr.es/m/Z7RkQ0EfYaqqjgz/@ip-10-97-1-34.eu-west-3.compute.internal

diff --git a/doc/src/sgml/wal.sgml b/doc/src/sgml/wal.sgml
index b908720adea2656bea2ed77d1354447fe9160c80..4c0bf710ddaff96c547137c49709fd637d56af74 100644 (file)
--- a/doc/src/sgml/wal.sgml
+++ b/doc/src/sgml/wal.sgml
@@ -810,11 +810,12 @@
   
    There are two internal functions to write WAL data to disk:
    XLogWrite and issue_xlog_fsync.
-   When wal-io-timing"/> is enabled, the total
+   When  is enabled, the total
    amounts of time XLogWrite writes and
    issue_xlog_fsync syncs WAL data to disk are counted as
-   wal_write_time and wal_sync_time in
-   , respectively.
+   write_time and sync_time in
+    for the object
+   wal, respectively.
    XLogWrite is normally called by
    XLogInsertRecord (when there is no space for the new
    record in WAL buffers), XLogFlush and the WAL writer,
@@ -829,11 +830,12 @@
    fsync, or fsync_writethrough,
    the write operation moves WAL buffers to kernel cache and
    issue_xlog_fsync syncs them to disk. Regardless
-   of the setting of track_wal_io_timing, the number
+   of the setting of track_io_timing, the number
    of times XLogWrite writes and
    issue_xlog_fsync syncs WAL data to disk are also
-   counted as wal_write and wal_sync
-   in pg_stat_wal, respectively.
+   counted as writes and fsyncs
+   in pg_stat_io for the object
+   wal, respectively.