Github user traflm commented on a diff in the pull request:
https://github.com/apache/incubator-trafodion/pull/642#discussion_r73778733
--- Diff: core/sql/common/CharType.cpp ---
@@ -1217,7 +1217,7 @@ void CharType::minMaxRepresentableValue(void* bufPtr,
if (stringLiteral)
{
NABoolean isNull = FALSE;
- NABoolean res = createSQLLiteral((const char *) bufPtr,
*stringLiteral, isNull, h);
+ NABoolean res = createSQLLiteral((const char *) bufPtr -
getSQLnullHdrSize(), *stringLiteral, isNull, h);
--- End diff --
The calling to type->minRepresentableValue should pass the buf address that
take null indicator buffer into account, good examples are in:
-EncodedValue::minMaxValue()
-ConstValue::ConstValue()
As you can see in above two functions, the buffer ptr is set to the postion:
buffer_start + null_header_len
a buffer should like
[nullHeader][VCHARLEN]Data
inside minRepresentableValue , it will treat the VCHARLEN, so it seems the
agreement is the nullHeader is already bypassed.
So the starting position of bufPtr is
[nullHeader][VCHARLEN]Data
^
However, in the createSQLLiteral() , it will again bypass the nullHeader:
const char *valPtr = buf + getSQLnullHdrSize();
So I did this change. As you correctly pointed out, this is dangerous...
A better way is to change createSQLLiteral, but there are some other places
call createSQLLiteral() which has different assumption of the starting
position of the buffer ptr, ConstValue::getConstStr() for example, so I choose
the simplest way, I am more nervous to change many other code which I don't
understand where will be invoked. But yes, it is not good.
A better change is to fix in createSQLLiteral semantics, the input buffer
ptr will be the position after nullHeader, but that will involve more changes
which I feel not confident, but I will try.
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