From: Paul Ramsey <pramsey@cleverelephant.ca>
Date: Tue, 18 Aug 2015 20:59:00 +0000 (+0000)
Subject: #3238, handle case of "placeholder" GUC as well as real GUC conflicts
X-Git-Tag: 2.2.0rc1~148
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=794aad0e3008be4872829afb261ff1a61ab23dc1;p=postgis

#3238, handle case of "placeholder" GUC as well as real GUC conflicts


git-svn-id: http://svn.osgeo.org/postgis/trunk@13937 b70326c6-7e19-0410-871a-916f4a2858ee
---

diff --git a/postgis/lwgeom_backend_api.c b/postgis/lwgeom_backend_api.c
index 5fbfa54af..9da26bf4d 100644
--- a/postgis/lwgeom_backend_api.c
+++ b/postgis/lwgeom_backend_api.c
@@ -102,6 +102,88 @@ static void lwgeom_backend_switch( const char* newvalue, void* extra )
     lwpgerror("Can't find %s geometry backend", newvalue );
 }
 
+
+#include "utils/guc.h"
+#include "utils/guc_tables.h"
+
+
+/*
+ * the bare comparison function for GUC names
+ */
+static int
+guc_name_compare(const char *namea, const char *nameb)
+{
+	/*
+	 * The temptation to use strcasecmp() here must be resisted, because the
+	 * array ordering has to remain stable across setlocale() calls. So, build
+	 * our own with a simple ASCII-only downcasing.
+	 */
+	while (*namea && *nameb)
+	{
+		char		cha = *namea++;
+		char		chb = *nameb++;
+
+		if (cha >= 'A' && cha <= 'Z')
+			cha += 'a' - 'A';
+		if (chb >= 'A' && chb <= 'Z')
+			chb += 'a' - 'A';
+		if (cha != chb)
+			return cha - chb;
+	}
+	if (*namea)
+		return 1;				/* a is longer */
+	if (*nameb)
+		return -1;				/* b is longer */
+	return 0;
+}
+
+/*
+ * comparator for qsorting and bsearching guc_variables array
+ */
+static int
+guc_var_compare(const void *a, const void *b)
+{
+	const struct config_generic *confa = *(struct config_generic * const *) a;
+	const struct config_generic *confb = *(struct config_generic * const *) b;
+
+	return guc_name_compare(confa->name, confb->name);
+}
+
+/* 
+* This is copied from the top half of the find_option function 
+* in postgresql's guc.c. We search the guc_variables for our option.
+* Then we make sure it's not a placeholder. Only then are we sure 
+* we have a potential conflict, of the sort experienced during an 
+* extension upgrade.
+*/
+static int
+guc_find_option(const char *name)
+{
+	const char **key = &name;
+	struct config_generic **res;
+
+	/*
+	 * By equating const char ** with struct config_generic *, we are assuming
+	 * the name field is first in config_generic.
+	 */
+	res = (struct config_generic **) bsearch((void *) &key,
+											 (void *) get_guc_variables(),
+											 GetNumConfigOptions(),
+											 sizeof(struct config_generic *),
+											 guc_var_compare);
+	
+	/* Found nothing? Good */
+	if ( ! res ) return 0;
+	 
+	/* Hm, you found something, but maybe it's just a placeholder? */
+	/* We'll consider a placehold a "not found" */
+	if ( (*res)->flags & GUC_CUSTOM_PLACEHOLDER )
+		return 0;
+		
+	return 1;
+}
+
+
 void lwgeom_init_backend()
 {
 	/* #2382 Before trying to create a user GUC, make sure */
@@ -110,19 +192,19 @@ void lwgeom_init_backend()
 	/* already be loaded in memory and the GUC already defined. We */
 	/* can skip GUC definition in this case, so we just return. */
 	static const char *guc_name = "postgis.backend";
-	const char *guc_installed = GetConfigOption(guc_name, TRUE, FALSE);
-
+	// const char *guc_installed = GetConfigOption(guc_name, TRUE, FALSE);
+		
 	/* Uh oh, this GUC name already exists. Ordinarily we could just go on */
 	/* our way, but the way the postgis.backend works is by using the "assign" */
 	/* callback to change which backend is in use by flipping a global variable */
 	/* over. This saves the overhead of looking up the engine every time, at */
 	/* the expense of the extra complexity. */
-	if ( guc_installed )
+	if ( guc_find_option(guc_name) )
 	{
 		/* In this narrow case the previously installed GUC is tied to the callback in */
 		/* the previously loaded library. Probably this is happening during an */
 		/* upgrade, so the old library is where the callback ties to. */
-		elog(WARNING, "'%s' is currently set to '%s' and cannot be changed until you reconnect", guc_name, guc_installed);
+		elog(WARNING, "'%s' is already set and cannot be changed until you reconnect", guc_name);
 		return;
 	}
 
@@ -143,6 +225,19 @@ void lwgeom_init_backend()
 				);
 }
 
+#if 0
+
+backend/utils/misc/guc.h
+int GetNumConfigOptions(void) returns num_guc_variables
+
+backend/utils/misc/guc_tables.h
+struct config_generic ** get_guc_variables(void)
+
+
+
+
+#endif
+
 PG_FUNCTION_INFO_V1(intersects);
 Datum intersects(PG_FUNCTION_ARGS)
 {