//*****************************************************************************
// thisSubgraph and otherSubGraph are equivalent subgraphs (from the MV and
// query join graphs). This method checks if they will continue to match
// if an extra-hub table is added. It checks that ALL predicates connecting
// this table to the subgraph match those of the other table/subgraph.
// The assumption is that this is the MV table/subgraph, while the other
// is the query table/subgraph, so the query can have additional join
// predicates over those in the MV. Those extra predicates are returned as
// rewrite instructions.
//*****************************************************************************
NABoolean MVCandidate::matchPredsFromTableToSubGraph(const QRJoinSubGraphPtr mvSubGraph,
const QRJoinSubGraphPtr querySubGraph,
const JoinGraphTablePtr mvGraphTable,
const JoinGraphTablePtr queryGraphTable)
{
// For each join pred on this table
CollIndex maxEntries = mvGraphTable->getEqualitySets().entries();
for (CollIndex i=0; i<maxEntries; i++)
{
// Find the column its using
const JoinGraphEqualitySetPtr mvEqSet = mvGraphTable->getEqualitySets()[i];
const JoinGraphHalfPredicatePtr mvHalfPred = mvEqSet->findHalfPredTo(mvGraphTable);
// Get the corresponding eqSet from the other join graph
const JoinGraphEqualitySetPtr queryEqSet = queryGraphTable->getEqSetUsing(mvHalfPred);
if (queryEqSet == NULL)
{
// Corresponding eqSet not found - match failed.
return FALSE;
}
// Verify that the half-pred to the EQ set matches.
const JoinGraphHalfPredicatePtr queryHalfPred = queryEqSet->findHalfPredTo(queryGraphTable);
if (mvHalfPred->match(queryHalfPred) == FALSE)
return FALSE;
// Let the JoinPredMatching object continue with the matching from the EQ set to the subgraph.
if (matchPredsFromEQSetToSubGraph(mvSubGraph,
querySubGraph,
mvEqSet,
queryEqSet,
mvHalfPred->getID()) == FALSE)
return FALSE;
}
return TRUE;
} // matchPredsFromTableToSubGraph()
