Fix string comparison in jsonpath

Take into account pg_server_to_any() may return input string "as is".

Reported-by: Andrew Dunstan, Thomas Munro
Discussion: https://postgr.es/m/0ed83a33-d900-466a-880a-70ef456c721f%402ndQuadrant.com
Author: Alexander Korotkov, Thomas Munro
Backpatch-through: 12

diff --git a/src/backend/utils/adt/jsonpath_exec.c b/src/backend/utils/adt/jsonpath_exec.c
index 4a0de4fe95a616ee6f61d0719f539f2f96ff9d09..72bc5eab6cb09374fb49138b5d3b6c33b2286457 100644 (file)
--- a/src/backend/utils/adt/jsonpath_exec.c
+++ b/src/backend/utils/adt/jsonpath_exec.c
@@ -2020,16 +2020,37 @@ compareStrings(const char *mbstr1, int mblen1,
    }
    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;
+       char       *utf8str1,
+                  *utf8str2;
+       int         cmp,
+                   utf8len1,
+                   utf8len2;
 
-       cmp = binaryCompareStrings(utf8str1, strlen(utf8str1),
-                                  utf8str2, strlen(utf8str2));
+       /*
+        * We have to convert other encodings to UTF-8 first, then compare.
+        * Input strings may be not null-terminated and pg_server_to_any() may
+        * return them "as is".  So, use strlen() only if there is real
+        * conversion.
+        */
+       utf8str1 = pg_server_to_any(mbstr1, mblen1, PG_UTF8);
+       utf8str2 = pg_server_to_any(mbstr2, mblen2, PG_UTF8);
+       utf8len1 = (mbstr1 == utf8str1) ? mblen1 : strlen(utf8str1);
+       utf8len2 = (mbstr2 == utf8str2) ? mblen2 : strlen(utf8str2);
+
+       cmp = binaryCompareStrings(utf8str1, utf8len1, utf8str2, utf8len2);
+
+       /*
+        * If pg_server_to_any() did no real conversion, then we actually
+        * compared original strings.  So, we already done.
+        */
+       if (mbstr1 == utf8str1 && mbstr2 == utf8str2)
+           return cmp;
 
-       pfree(utf8str1);
-       pfree(utf8str2);
+       /* Free memory if needed */
+       if (mbstr1 != utf8str1)
+           pfree(utf8str1);
+       if (mbstr2 != utf8str2)
+           pfree(utf8str2);
 
        /*
         * When all Unicode codepoints are equal, return result of binary