/**
* Replace the query with its query descriptor text.
* The MVQR_LOG_QUERY_DESCRIPTORS CQD was set to 'DUMP', so instead of running
* this query, we are going to replace it with something that, when executed,
* will produce the XML text of the query descriptor as its output. This
* 'something' is a TupleList node that has the text lines of the descriptor
* as its tuples.
*
* @param rootExpr The RelExpr tree of the existing query
* @param xmlText The XML text of the query descriptor
*/
RelRoot* MvQueryRewriteHandler::handleAnalyzeOnlyQuery(RelRoot* rootExpr, NAString* xmlText)
{
static NAString empty("No descriptor generated.");
if (xmlText==NULL)
xmlText = ∅
CollHeap *heap = CmpCommon::statementHeap();
Int32 maxLen=xmlText->length();
Int32 pos=0;
Int32 lastPos=-1;
ItemExpr* tupleExpr = NULL;
while (pos<maxLen-1)
{
// Find the next CR character
pos = xmlText->index("\n", 1, pos+1, NAString::exact);
if (pos==-1) // If this is the last line with no CR.
pos=maxLen;
// The next line if from the last CR to this one.
NASubString line=(*xmlText)(lastPos+1, pos-lastPos-1);
lastPos=pos;
// Make a constant character string from it.
ItemExpr* tuple = new (heap)
Convert(new(heap) SystemLiteral(line));
// Collect the tuples in a list
if (tupleExpr==NULL)
tupleExpr = tuple;
else
tupleExpr = new(heap) ItemList(tuple, tupleExpr);
}
// Construct the TupleList node
TupleList* tupleListNode = new(heap) TupleList(tupleExpr->reverseTree(), heap);
RelRoot* newRoot = new(heap) RelRoot(tupleListNode);
// A RenameTable above it to give a name to the column of text.
ItemExpr *renExpr = new(heap)
RenameCol(NULL, new(heap) ColRefName("Query Descriptor", heap));
NAString tableName("Descriptor table");
RelExpr* renameNode = new(heap)
RenameTable(TRUE, newRoot, tableName, renExpr, heap);
// And a final RelRoot on top with a SELECT *.
ItemExpr *starExpr = new(heap) ColReference(new(heap) ColRefName(1));
RelRoot* topRoot = new(heap) RelRoot(renameNode, REL_ROOT, starExpr);
topRoot->setRootFlag(TRUE);
// Now bind the new query tree
BindWA* bindWA = rootExpr->getRETDesc()->getBindWA();
RelExpr* boundRoot = topRoot->bindNode(bindWA);
// Transform it. This will eliminate the Rename node and the extraneous root.
NormWA normWA(CmpCommon::context());
ExprGroupId eg(boundRoot);
boundRoot->transformNode(normWA, eg);
// And Normalize it.
RelRoot *normRoot = (RelRoot *)eg.getPtr();
normRoot->normalizeNode(normWA);
return normRoot;
}
