1 files changed, 69 insertions, 3 deletions
diff --git a/src/backend/utils/adt/jsonpath_exec.c b/src/backend/utils/adt/jsonpath_exec.c
index 293d6da027c..4a0de4fe95a 100644
--- a/src/backend/utils/adt/jsonpath_exec.c
+++ b/src/backend/utils/adt/jsonpath_exec.c
@@ -1981,6 +1981,73 @@ executeComparison(JsonPathItem *cmp, JsonbValue *lv, JsonbValue *rv, void *p)
 }
 
 /*
+ * Perform per-byte comparison of two strings.
+ */
+static int
+binaryCompareStrings(const char *s1, int len1,
+					 const char *s2, int len2)
+{
+	int			cmp;
+
+	cmp = memcmp(s1, s2, Min(len1, len2));
+
+	if (cmp != 0)
+		return cmp;
+
+	if (len1 == len2)
+		return 0;
+
+	return len1 < len2 ? -1 : 1;
+}
+
+/*
+ * Compare two strings in the current server encoding using Unicode codepoint
+ * collation.
+ */
+static int
+compareStrings(const char *mbstr1, int mblen1,
+			   const char *mbstr2, int mblen2)
+{
+	if (GetDatabaseEncoding() == PG_SQL_ASCII ||
+		GetDatabaseEncoding() == PG_UTF8)
+	{
+		/*
+		 * It's known property of UTF-8 strings that their per-byte comparison
+		 * result matches codepoints comparison result.  ASCII can be
+		 * considered as special case of UTF-8.
+		 */
+		return binaryCompareStrings(mbstr1, mblen1, mbstr2, mblen2);
+	}
+	else
+	{
+		/* We have to convert other encodings to UTF-8 first, then compare. */
+		char	   *utf8str1 = pg_server_to_any(mbstr1, mblen1, PG_UTF8),
+				   *utf8str2 = pg_server_to_any(mbstr2, mblen2, PG_UTF8);
+		int			cmp;
+
+		cmp = binaryCompareStrings(utf8str1, strlen(utf8str1),
+								   utf8str2, strlen(utf8str2));
+
+		pfree(utf8str1);
+		pfree(utf8str2);
+
+		/*
+		 * When all Unicode codepoints are equal, return result of binary
+		 * comparison.  In some edge cases, same characters may have different
+		 * representations in encoding.  Then our behavior could diverge from
+		 * standard.  However, that allow us to do simple binary comparison
+		 * for "==" operator, which is performance critical in typical cases.
+		 * In future to implement strict standard conformance, we can do
+		 * normalization of input JSON strings.
+		 */
+		if (cmp == 0)
+			return binaryCompareStrings(mbstr1, mblen1, mbstr2, mblen2);
+		else
+			return cmp;
+	}
+}
+
+/*
  * Compare two SQL/JSON items using comparison operation 'op'.
  */
 static JsonPathBool
@@ -2022,9 +2089,8 @@ compareItems(int32 op, JsonbValue *jb1, JsonbValue *jb2)
 						   jb2->val.string.val,
 						   jb1->val.string.len) ? jpbFalse : jpbTrue;
 
-			cmp = varstr_cmp(jb1->val.string.val, jb1->val.string.len,
-							 jb2->val.string.val, jb2->val.string.len,
-							 DEFAULT_COLLATION_OID);
+			cmp = compareStrings(jb1->val.string.val, jb1->val.string.len,
+								 jb2->val.string.val, jb2->val.string.len);
 			break;
 
 		case jbvBinary: