Remove zero_damaged_pages from postgresql.conf.sample; the only way to

find out about it is to read the documentation that tells you how
dangerous it is.  Add default_transaction_read_only to documentation;
seems to have been overlooked in patch that added read-only transactions.
Clean up check_guc comparison script, which has been suffering bit rot.

src/backend/utils/misc/check_guc

@@ -1,21 +1,24 @@
 #!/bin/sh
 
 ## currently, this script makes a lot of assumptions:
-## 1) the valid config settings may be preceded by a '#', but NOT '# '
-##    (we use this to skip comments)
-## 2) the valid config settings will be followed immediately by  ' =' 
-##    (at least one space preceding the '=' for guc.c)
-## 3) the options have PGC_ on the same line as the option
-## 4) the options have '{ ' on the same line as the option
+## in postgresql.conf.sample:
+##   1) the valid config settings may be preceded by a '#', but NOT '# '
+##      (we use this to skip comments)
+##   2) the valid config settings will be followed immediately by  ' =' 
+##      (at least one space preceding the '=')
+## in guc.c:
+##   3) the options have PGC_ on the same line as the option
+##   4) the options have '{' on the same line as the option
 
 ##  Problems
 ## 1) Don't know what to do with TRANSACTION ISOLATION LEVEL
 
-## if an option is valid but shows up in only one file (guc.c or 
-## postgresql.conf.sample, it should be listed here so that it 
+## if an option is valid but shows up in only one file (guc.c but not
+## postgresql.conf.sample), it should be listed here so that it 
 ## can be ignored
 INTENTIONALLY_NOT_INCLUDED="pre_auth_delay lc_messages lc_monetary \
-lc_time lc_numeric server_encoding session_authorization"
+lc_numeric lc_time seed server_encoding session_authorization \
+transaction_isolation transaction_read_only zero_damaged_pages"
 
 ### What options are listed in postgresql.conf.sample, but don't appear 
 ### in guc.c?
@@ -26,19 +29,19 @@ grep -v '^# ' | # strip comments
 sed -e 's/^#//' | 
 awk '{print $1}'`
 
-SETTINGS=`echo "$SETTINGS" | 
-tr 'A-Z' 'a-z' # lowercase`
+SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
 
 for i in $SETTINGS ; do 
   hidden=0
   ## it sure would be nice to replace this with an sql "not in" statement
-  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-    if [ "$hidethis" = "$i" ] ; then 
-      hidden=1
-    fi
-  done
+  ## it doesn't seem to make sense to have things in .sample and not in guc.c
+#  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
+#    if [ "$hidethis" = "$i" ] ; then 
+#      hidden=1
+#    fi
+#  done
   if [ "$hidden" -eq 0 ] ; then
-    grep -i $i guc.c > /dev/null
+    grep -i '"'$i'"' guc.c > /dev/null
     if [ $? -ne 0 ] ; then 
       echo "$i seems to be missing from guc.c"; 
     fi; 
@@ -50,19 +53,21 @@ done
 
 # grab everything that looks like a setting and convert it to lower case
 
-SETTINGS=`grep '{ .*PGC_' guc.c | awk '{print $2}' | \
-          sed -e 's/"//g' -e 's/,//'`
+SETTINGS=`grep '{.* PGC_' guc.c | awk '{print $1}' | \
+          sed -e 's/{//g' -e 's/"//g' -e 's/,//'`
+
 SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
 
 for i in $SETTINGS ; do
   hidden=0
+  ## it sure would be nice to replace this with an sql "not in" statement
   for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
     if [ "$hidethis" = "$i" ] ; then
       hidden=1
     fi
   done
   if [ "$hidden" -eq 0 ] ; then
-    grep -i $i postgresql.conf.sample > /dev/null
+    grep -i '#'$i' ' postgresql.conf.sample > /dev/null
     if [ $? -ne 0 ] ; then
       echo "$i seems to be missing from postgresql.conf.sample";
     fi

src/backend/utils/misc/postgresql.conf.sample

@@ -205,6 +205,7 @@
 #authentication_timeout = 60	# 1-600, in seconds
 #deadlock_timeout = 1000	# in milliseconds
 #default_transaction_isolation = 'read committed'
+#default_transaction_read_only = false
 #extra_float_digits = 0		# min -15, max 2
 #max_expr_depth = 10000		# min 10
 #max_files_per_process = 1000	# min 25
@@ -213,6 +214,5 @@
 #sql_inheritance = true
 #transform_null_equals = false
 #statement_timeout = 0		# 0 is disabled, in milliseconds
-#zero_damaged_pages = false     # set this true only for disaster recovery
 #db_user_namespace = false
 #preload_libraries = ''