Move the guts of our Levenshtein implementation into core.

The hope is that we can use this to produce better diagnostics in
some cases.

Peter Geoghegan, reviewed by Michael Paquier, with some further
changes by me.

1 files changed, 21 insertions, 1 deletions

diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index c3171b549a6..b3f397e9595 100644
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -1546,7 +1546,6 @@ varstr_cmp(char *arg1, int len1, char *arg2, int len2, Oid collid)
 	return result;
 }
 
-
 /* text_cmp()
  * Internal comparison function for text strings.
  * Returns -1, 0 or 1
@@ -4747,3 +4746,24 @@ text_format_nv(PG_FUNCTION_ARGS)
 {
 	return text_format(fcinfo);
 }
+
+/*
+ * Helper function for Levenshtein distance functions. Faster than memcmp(),
+ * for this use case.
+ */
+static inline bool
+rest_of_char_same(const char *s1, const char *s2, int len)
+{
+	while (len > 0)
+	{
+		len--;
+		if (s1[len] != s2[len])
+			return false;
+	}
+	return true;
+}
+
+/* Expand each Levenshtein distance variant */
+#include "levenshtein.c"
+#define LEVENSHTEIN_LESS_EQUAL
+#include "levenshtein.c"