Github user nonstop-qfchen commented on a diff in the pull request:
https://github.com/apache/incubator-trafodion/pull/132#discussion_r42519468
--- Diff: core/sql/optimizer/ItemExpr.cpp ---
@@ -14906,3 +14906,80 @@ NABoolean LOBoper::isCovered
return FALSE;
}
+// Compute the exprssion at compile time. Assume all operands are
constants.
+// Return NULL if the computation fails and CmpCommon::diags() may be
side-affected.
+ConstValue* ItemExpr::compute(CollHeap* heap)
+{
+ ValueIdList exprs;
+ exprs.insert(getValueId());
+
+ const NAType& dataType = getValueId().getType();
+
+ Lng32 decodedValueLen = dataType.getNominalSize() +
dataType.getSQLnullHdrSize();
+
+ char staticDecodeBuf[200];
+ Lng32 staticDecodeBufLen = 200;
+
+ char* decodeBuf = staticDecodeBuf;
+ Lng32 decodeBufLen = staticDecodeBufLen;
+
+ // For character types, multiplying by 8 to deal with conversions between
--- End diff --
Yes, it looks like multiplying by 8 (or 6 after change) is generic. I think
it is safe to multiplying by 6 because the max # of bytes in UTF8 is 6
which can encode code points up to 7FFFFFFF.
On Tue, Oct 20, 2015 at 10:41 AM, Hans Zeller <[email protected]>
wrote:
> In core/sql/optimizer/ItemExpr.cpp
>
<https://github.com/apache/incubator-trafodion/pull/132#discussion_r42512787>
> :
>
> > +ConstValue* ItemExpr::compute(CollHeap* heap)
> > +{
> > + ValueIdList exprs;
> > + exprs.insert(getValueId());
> > +
> > + const NAType& dataType = getValueId().getType();
> > +
> > + Lng32 decodedValueLen = dataType.getNominalSize() +
dataType.getSQLnullHdrSize();
> > +
> > + char staticDecodeBuf[200];
> > + Lng32 staticDecodeBufLen = 200;
> > +
> > + char* decodeBuf = staticDecodeBuf;
> > + Lng32 decodeBufLen = staticDecodeBufLen;
> > +
> > + // For character types, multiplying by 8 to deal with conversions
between
>
> There is actually a method to compute this length,
> CharInfo::getMaxConvertedLenInBytes() (file common/charinfo.h) but it may
> be inconvenient and overkill in this situation.
>
> â
> Reply to this email directly or view it on GitHub
> <https://github.com/apache/incubator-trafodion/pull/132/files#r42512787>.
>
--
Regards, --Qifan
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