Fix end-of-loop optimization in pglz_find_match() function.

After the recent pglz optimization patch, the next/prev pointers in the
hash table are never NULL, INVALID_ENTRY_PTR is used to represent invalid
entries instead. The end-of-loop check in pglz_find_match() function didn't
get the memo. The result was the same from a correctness point of view, but
because the NULL-check would never fail, the tiny optimization turned into
a pessimization.

Reported by Stephen Frost, using Coverity scanner.

diff --git a/src/backend/utils/adt/pg_lzcompress.c b/src/backend/utils/adt/pg_lzcompress.c
index ae6751929e3d98a96ce3b456af625d9b48ec8389..1c129b800b3b1a6622111f0edeeec5d63bb176ae 100644 (file)
--- a/src/backend/utils/adt/pg_lzcompress.c
+++ b/src/backend/utils/adt/pg_lzcompress.c
@@ -466,7 +466,7 @@ pglz_find_match(int16 *hstart, const char *input, const char *end,
         * Be happy with lesser good matches the more entries we visited. But
         * no point in doing calculation if we're at end of list.
         */
-       if (hent)
+       if (hent != INVALID_ENTRY_PTR)
        {
            if (len >= good_match)
                break;