bugfix: xpath encoding issue

Hi

When I tested XMLTABLE function I found a bug of XPATH function -
xpath_internal

There xmltype is not correctly encoded to xmlChar due possible invalid
encoding info in header. It is possible when XML was loaded with recv
function and has not UTF8 encoding.

The functions based on xml_parse function works well.

The fix is simple

diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index f81cf489d2..89aae48cb3 100644
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -3874,9 +3874,11 @@ xpath_internal(text *xpath_expr_text, xmltype *data,
ArrayType *namespaces,
ns_count = 0;
}

- datastr = VARDATA(data);
- len = VARSIZE(data) - VARHDRSZ;
+ datastr = xml_out_internal(data, 0);
+ len = strlen(datastr);
+
xpath_len = VARSIZE(xpath_expr_text) - VARHDRSZ;
+
if (xpath_len == 0)
ereport(ERROR,
(errcode(ERRCODE_DATA_EXCEPTION),

Regards

Pavel