Fix broken collation-aware searches in SP-GiST text opclass.

tglsfdc · tglsfdc · commit 608d1f97114d · 2018-04-16T16:06:47.000-04:00
spg_text_leaf_consistent() supposed that it should compare only Min(querylen, entrylen) bytes of the two strings, and then deal with any excess bytes in one string or the other by assuming the longer string is greater if the prefixes are equal. Quite aside from the fact that that's just wrong in some locales (e.g., 'ch' is not less than 'd' in cs_CZ), it also risked passing incomplete multibyte characters to strcoll(), with ensuing bad results. Instead, just pass the full strings to varstr_cmp, and let it decide what to do about unequal-length strings. Fortunately, this error doesn't imply any index corruption, it's just that searches might return the wrong set of entries. Per report from Emre Hasegeli, though this is not his patch. Thanks to Peter Geoghegan for review and discussion. This code was born broken, so back-patch to all supported branches. In HEAD, I failed to resist the temptation to do a bit of cosmetic cleanup/pgindent'ing on 710d90d, too. Discussion: https://postgr.es/m/CAE2gYzzb6K51VnTq5i5p52z+j9p2duEa-K1T3RrC_GQEynAKEg@mail.gmail.com
diff --git a/src/backend/access/spgist/spgtextproc.c b/src/backend/access/spgist/spgtextproc.c
@@ -603,22 +603,22 @@ spg_text_leaf_consistent(PG_FUNCTION_ARGS)
 			/* If asserts enabled, verify encoding of reconstructed string */
 			Assert(pg_verifymbstr(fullValue, fullLen, false));
 
-			r = varstr_cmp(fullValue, Min(queryLen, fullLen),
-						   VARDATA_ANY(query), Min(queryLen, fullLen),
+			r = varstr_cmp(fullValue, fullLen,
+						   VARDATA_ANY(query), queryLen,
 						   PG_GET_COLLATION());
 		}
 		else
 		{
 			/* Non-collation-aware comparison */
 			r = memcmp(fullValue, VARDATA_ANY(query), Min(queryLen, fullLen));
-		}
 
-		if (r == 0)
-		{
-			if (queryLen > fullLen)
-				r = -1;
-			else if (queryLen < fullLen)
-				r = 1;
+			if (r == 0)
+			{
+				if (queryLen > fullLen)
+					r = -1;
+				else if (queryLen < fullLen)
+					r = 1;
+			}
 		}
 
 		switch (strategy)
