Further fixes for quoted-list GUC values in pg_dump and ruleutils.c.

Commits 742869946 et al turn out to be a couple bricks shy of a load.
We were dumping the stored values of GUC_LIST_QUOTE variables as they
appear in proconfig or setconfig catalog columns.  However, although that
quoting rule looks a lot like SQL-identifier double quotes, there are two
critical differences: empty strings ("") are legal, and depending on which
variable you're considering, values longer than NAMEDATALEN might be valid
too.  So the current technique fails altogether on empty-string list
entries (as reported by Steven Winfield in bug #15248) and it also risks
truncating file pathnames during dump/reload of GUC values that are lists
of pathnames.

To fix, split the stored value without any downcasing or truncation,
and then emit each element as a SQL string literal.

This is a tad annoying, because we now have three copies of the
comma-separated-string splitting logic in varlena.c as well as a fourth
one in dumputils.c.  (Not to mention the randomly-different-from-those
splitting logic in libpq...)  I looked at unifying these, but it would
be rather a mess unless we're willing to tweak the API definitions of
SplitIdentifierString, SplitDirectoriesString, or both.  That might be
worth doing in future; but it seems pretty unsafe for a back-patched
bug fix, so for now accept the duplication.

Back-patch to all supported branches, as the previous fix was.

Discussion: https://postgr.es/m/7585.1529435872@sss.pgh.pa.us

2 files changed, 14 insertions, 14 deletions

diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 744d501e319..078129f251b 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -3160,21 +3160,21 @@ CREATE FUNCTION func_with_set_params() RETURNS integer
     SET extra_float_digits TO 2
     SET work_mem TO '4MB'
     SET datestyle to iso, mdy
-    SET local_preload_libraries TO "Mixed/Case", 'c:/"a"/path'
+    SET local_preload_libraries TO "Mixed/Case", 'c:/''a"/path', '', '0123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789'
     IMMUTABLE STRICT;
 SELECT pg_get_functiondef('func_with_set_params()'::regprocedure);
-                      pg_get_functiondef                       
----------------------------------------------------------------
- CREATE OR REPLACE FUNCTION public.func_with_set_params()     +
-  RETURNS integer                                             +
-  LANGUAGE sql                                                +
-  IMMUTABLE STRICT                                            +
-  SET search_path TO pg_catalog                               +
-  SET extra_float_digits TO '2'                               +
-  SET work_mem TO '4MB'                                       +
-  SET "DateStyle" TO 'iso, mdy'                               +
-  SET local_preload_libraries TO "Mixed/Case", "c:/""a""/path"+
- AS $function$select 1;$function$                             +
+                                                                            pg_get_functiondef                                                                            
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------
+ CREATE OR REPLACE FUNCTION public.func_with_set_params()                                                                                                                +
+  RETURNS integer                                                                                                                                                        +
+  LANGUAGE sql                                                                                                                                                           +
+  IMMUTABLE STRICT                                                                                                                                                       +
+  SET search_path TO 'pg_catalog'                                                                                                                                        +
+  SET extra_float_digits TO '2'                                                                                                                                          +
+  SET work_mem TO '4MB'                                                                                                                                                  +
+  SET "DateStyle" TO 'iso, mdy'                                                                                                                                          +
+  SET local_preload_libraries TO 'Mixed/Case', 'c:/''a"/path', '', '0123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789'+
+ AS $function$select 1;$function$                                                                                                                                        +
  
 (1 row)
 
diff --git a/src/test/regress/sql/rules.sql b/src/test/regress/sql/rules.sql
index 3ca4c073565..f4ee30ec8f4 100644
--- a/src/test/regress/sql/rules.sql
+++ b/src/test/regress/sql/rules.sql
@@ -1164,7 +1164,7 @@ CREATE FUNCTION func_with_set_params() RETURNS integer
     SET extra_float_digits TO 2
     SET work_mem TO '4MB'
     SET datestyle to iso, mdy
-    SET local_preload_libraries TO "Mixed/Case", 'c:/"a"/path'
+    SET local_preload_libraries TO "Mixed/Case", 'c:/''a"/path', '', '0123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789'
     IMMUTABLE STRICT;
 SELECT pg_get_functiondef('func_with_set_params()'::regprocedure);