Update commit_delay documentation.

Commit 13fe298ca06f5390df5edf073cf401f9f0b67458 changed this GUC to be
PGC_SUSET, but neglected to update the documentation to match.

While at it, edit and rearrange the text a little for clarity.

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 95de86441e4254a98f8c2265d33dcd02faff2dca..6e1b084f71d5b229a1fbca20f621e00a281ca23b 100644 (file)
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1949,7 +1949,7 @@ include 'filename'
       
       
        
-        commit_delay adds a time delay, set in
+        commit_delay adds a time delay, measured in
         microseconds, before a WAL flush is initiated.  This can improve
         group commit throughput by allowing a larger number of transactions
         to commit via a single WAL flush, if system load is high enough
@@ -1959,7 +1959,12 @@ include 'filename'
         flush.  Because the delay is just wasted if no other transactions
         become ready to commit, a delay is only performed if at least
         commit_siblings other transactions are active
-        immediately before a flush would otherwise have been initiated.
+        when a flush is about to be initiated.  Also, no delays are
+        performed if fsync is disabled.
+        The default commit_delay is zero (no delay).
+        Only superusers can change this setting.
+       
+       
         In PostgreSQL releases prior to 9.3,
         commit_delay behaved differently and was much
         less effective: it affected only commits, rather than all WAL flushes,
@@ -1967,9 +1972,7 @@ include 'filename'
         was completed sooner.  Beginning in PostgreSQL 9.3,
         the first process that becomes ready to flush waits for the configured
         interval, while subsequent processes wait only until the leader
-        completes the flush.  The default commit_delay is zero
-        (no delay).  No delays are performed unless fsync
-        is enabled.
+        completes the flush operation.