Add error message when prefix search is performed

Author: maksm90

expected/rum.out

@@ -304,3 +304,4 @@ SELECT a <=> to_tsquery('pg_catalog.english', 'w:*'), *
 	FROM test_rum
 	WHERE a @@ to_tsquery('pg_catalog.english', 'w:*')
 	ORDER BY a <=> to_tsquery('pg_catalog.english', 'w:*');
+ERROR:  Compare with prefix expressions isn't supported

rum--1.0.sql

@@ -89,7 +89,6 @@ AS
         FUNCTION        2       rum_extract_tsvector(tsvector,internal,internal,internal,internal),
         FUNCTION        3       rum_extract_tsquery(tsquery,internal,smallint,internal,internal,internal,internal),
         FUNCTION        4       rum_tsquery_consistent(internal,smallint,tsvector,int,internal,internal,internal,internal),
-        FUNCTION        5       gin_cmp_prefix(text,text,smallint,internal),
         FUNCTION        6       rum_tsvector_config(internal),
         FUNCTION        7       rum_tsquery_pre_consistent(internal,smallint,tsvector,int,internal,internal,internal,internal),
         FUNCTION        8       rum_tsquery_distance(internal,smallint,tsvector,int,internal,internal,internal,internal,internal),

rumscan.c

@@ -207,9 +207,16 @@ rumFillScanKey(RumScanOpaque so, OffsetNumber attnum,
 			/* set up normal entry using extractQueryFn's outputs */
 			queryKey = queryValues[i];
 			queryCategory = queryCategories[i];
-			isPartialMatch =
-				(rumstate->canPartialMatch[attnum - 1] && partial_matches)
-				? partial_matches[i] : false;
+
+			/*
+			 * check inconsistence related to impossibility to do partial match
+			 * and existance of prefix expression in tsquery
+			 */
+			if (partial_matches && partial_matches[i] &&
+					!rumstate->canPartialMatch[attnum - 1])
+				elog(ERROR, "Compare with prefix expressions isn't supported");
+
+			isPartialMatch = (partial_matches) ? partial_matches[i] : false;
 			this_extra = (extra_data) ? extra_data[i] : NULL;
 		}
 		else