Fix pg_dump's heuristic for deciding which casts to dump.

Back in 2003 we had a discussion about how to decide which casts to dump.
At the time pg_dump really only considered an object's containing schema
to decide what to dump (ie, dump whatever's not in pg_catalog), and so
we chose a complicated idea involving whether the underlying types were to
be dumped (cf commit a6790ce).  But users
are allowed to create casts between built-in types, and we failed to dump
such casts.  Let's get rid of that heuristic, which has accreted even more
ugliness since then, in favor of just looking at the cast's OID to decide
if it's a built-in cast or not.

In passing, also fix some really ancient code that supposed that it had to
manufacture a dependency for the cast on its cast function; that's only
true when dumping from a pre-7.3 server.  This just resulted in some wasted
cycles and duplicate dependency-list entries with newer servers, but we
might as well improve it.

Per gripes from a number of people, most recently Greg Sabino Mullane.
Back-patch to all supported branches.

Author: tglsfdc

src/bin/pg_dump/pg_dump.c

@@ -1342,6 +1342,24 @@ selectDumpableDefaultACL(DefaultACLInfo *dinfo)
 		dinfo->dobj.dump = include_everything;
 }
 
+/*
+ * selectDumpableCast: policy-setting subroutine
+ *		Mark a cast as to be dumped or not
+ *
+ * Casts do not belong to any particular namespace (since they haven't got
+ * names), nor do they have identifiable owners.  To distinguish user-defined
+ * casts from built-in ones, we must resort to checking whether the cast's
+ * OID is in the range reserved for initdb.
+ */
+static void
+selectDumpableCast(CastInfo *cast)
+{
+	if (cast->dobj.catId.oid < (Oid) FirstNormalObjectId)
+		cast->dobj.dump = false;
+	else
+		cast->dobj.dump = include_everything;
+}
+
 /*
  * selectDumpableExtension: policy-setting subroutine
  *		Mark an extension as to be dumped or not
@@ -6258,12 +6276,13 @@ getCasts(Archive *fout, int *numCasts)
 							  sTypeInfo->dobj.name, tTypeInfo->dobj.name);
 		castinfo[i].dobj.name = namebuf.data;
 
-		if (OidIsValid(castinfo[i].castfunc))
+		if (fout->remoteVersion < 70300 &&
+			OidIsValid(castinfo[i].castfunc))
 		{
 			/*
 			 * We need to make a dependency to ensure the function will be
 			 * dumped first.  (In 7.3 and later the regular dependency
-			 * mechanism will handle this for us.)
+			 * mechanism handles this for us.)
 			 */
 			FuncInfo   *funcInfo;
 
@@ -6272,6 +6291,9 @@ getCasts(Archive *fout, int *numCasts)
 				addObjectDependency(&castinfo[i].dobj,
 									funcInfo->dobj.dumpId);
 		}
+
+		/* Decide whether we want to dump it */
+		selectDumpableCast(&(castinfo[i]));
 	}
 
 	PQclear(res);
@@ -10154,55 +10176,9 @@ dumpCast(Archive *fout, CastInfo *cast)
 	}
 
 	/*
-	 * As per discussion we dump casts if one or more of the underlying
-	 * objects (the conversion function and the two data types) are not
-	 * builtin AND if all of the non-builtin objects are included in the dump.
-	 * Builtin meaning, the namespace name does not start with "pg_".
-	 *
-	 * However, for a cast that belongs to an extension, we must not use this
-	 * heuristic, but just dump the cast iff we're told to (via dobj.dump).
+	 * Make sure we are in proper schema (needed for getFormattedTypeName).
+	 * Casts don't have a schema of their own, so use pg_catalog.
 	 */
-	if (!cast->dobj.ext_member)
-	{
-		TypeInfo   *sourceInfo = findTypeByOid(cast->castsource);
-		TypeInfo   *targetInfo = findTypeByOid(cast->casttarget);
-
-		if (sourceInfo == NULL || targetInfo == NULL)
-			return;
-
-		/*
-		 * Skip this cast if all objects are from pg_
-		 */
-		if ((funcInfo == NULL ||
-			 strncmp(funcInfo->dobj.namespace->dobj.name, "pg_", 3) == 0) &&
-			strncmp(sourceInfo->dobj.namespace->dobj.name, "pg_", 3) == 0 &&
-			strncmp(targetInfo->dobj.namespace->dobj.name, "pg_", 3) == 0)
-			return;
-
-		/*
-		 * Skip cast if function isn't from pg_ and is not to be dumped.
-		 */
-		if (funcInfo &&
-			strncmp(funcInfo->dobj.namespace->dobj.name, "pg_", 3) != 0 &&
-			!funcInfo->dobj.dump)
-			return;
-
-		/*
-		 * Same for the source type
-		 */
-		if (strncmp(sourceInfo->dobj.namespace->dobj.name, "pg_", 3) != 0 &&
-			!sourceInfo->dobj.dump)
-			return;
-
-		/*
-		 * and the target type.
-		 */
-		if (strncmp(targetInfo->dobj.namespace->dobj.name, "pg_", 3) != 0 &&
-			!targetInfo->dobj.dump)
-			return;
-	}
-
-	/* Make sure we are in proper schema (needed for getFormattedTypeName) */
 	selectSourceSchema(fout, "pg_catalog");
 
 	defqry = createPQExpBuffer();