fix: address AI review feedback for PostgreSQL cluster sync

- Fix CLUSTER_QUERY_RUNTIME_PGSQL_SERVERS macro to use proper VARCHAR string literals
- Fix inconsistent gating/reset behavior for pgsql diffs when mysql checksum flags disabled
- Fix copy/paste log text errors in ProxySQL_Admin.cpp
- Improve test suite robustness with better NULL checks
- Verify all PostgreSQL variables are properly included in admin_variables_names array

Addresses feedback from coderabbitai and gemini-code-assist reviews in PR 5234.

lib/ProxySQL_Admin.cpp

@@ -4265,7 +4265,7 @@ bool ProxySQL_Admin::set_variable(char *name, char *value, bool lock) {  // this
 			GloProxyCluster->cluster_mysql_query_rules_diffs_before_sync = 0;
 			variables.cluster_pgsql_query_rules_diffs_before_sync = 0;
 			GloProxyCluster->cluster_pgsql_query_rules_diffs_before_sync = 0;
-			proxy_warning("Disabling deprecated 'admin-checksum_mysql_query_rules', setting 'admin-cluster_mysql_query_rules_diffs_before_sync=0'\n");
+			proxy_warning("Disabling deprecated 'admin-checksum_pgsql_query_rules', setting 'admin-cluster_pgsql_query_rules_diffs_before_sync=0'\n");
 			return true;
 		}
 		return false;
@@ -4281,7 +4281,7 @@ bool ProxySQL_Admin::set_variable(char *name, char *value, bool lock) {  // this
 			GloProxyCluster->cluster_mysql_servers_diffs_before_sync = 0;
 			variables.cluster_pgsql_servers_diffs_before_sync = 0;
 			GloProxyCluster->cluster_pgsql_servers_diffs_before_sync = 0;
-			proxy_warning("Disabling deprecated 'admin-checksum_mysql_servers', setting 'admin-cluster_mysql_servers_diffs_before_sync=0'\n");
+			proxy_warning("Disabling deprecated 'admin-checksum_pgsql_servers', setting 'admin-cluster_pgsql_servers_diffs_before_sync=0'\n");
 			return true;
 		}
 
@@ -4298,7 +4298,7 @@ bool ProxySQL_Admin::set_variable(char *name, char *value, bool lock) {  // this
 			GloProxyCluster->cluster_mysql_users_diffs_before_sync = 0;
 			variables.cluster_pgsql_users_diffs_before_sync = 0;
 			GloProxyCluster->cluster_pgsql_users_diffs_before_sync = 0;
-			proxy_warning("Disabling deprecated 'admin-checksum_mysql_users', setting 'admin-cluster_mysql_users_diffs_before_sync=0'\n");
+			proxy_warning("Disabling deprecated 'admin-checksum_pgsql_users', setting 'admin-cluster_pgsql_users_diffs_before_sync=0'\n");
 			return true;
 		}
 		return false;
@@ -4314,7 +4314,7 @@ bool ProxySQL_Admin::set_variable(char *name, char *value, bool lock) {  // this
 			GloProxyCluster->cluster_mysql_variables_diffs_before_sync = 0;
 			variables.cluster_pgsql_variables_diffs_before_sync = 0;
 			GloProxyCluster->cluster_pgsql_variables_diffs_before_sync = 0;
-			proxy_warning("Disabling deprecated 'admin-checksum_mysql_variables', setting 'admin-cluster_mysql_variables_diffs_before_sync=0'\n");
+			proxy_warning("Disabling deprecated 'admin-checksum_mysql_variables', setting 'admin-cluster_mysql_variables_diffs_before_sync=0' and 'admin-cluster_pgsql_variables_diffs_before_sync=0'\n");
 			return true;
 		}
 		return false;

test/tap/tests/test_cluster_sync_pgsql-t.cpp

@@ -130,7 +130,11 @@ int check_pgsql_servers_v2_sync(
 		MYSQL_RES* result = NULL;
 		MYSQL_QUERY(r_proxy_admin, select_pgsql_servers_query.c_str());
 		result = mysql_store_result(r_proxy_admin);
-		if (!result || mysql_num_rows(result) == 0) {
+		if (!result) {
+			diag("Failed to store result from query: %s", select_pgsql_servers_query.c_str());
+			return EXIT_FAILURE;
+		}
+		if (mysql_num_rows(result) == 0) {
 			diag("No results returned from query: %s", select_pgsql_servers_query.c_str());
 			mysql_free_result(result);
 			return EXIT_FAILURE;