//---------------------------------------------------------------------------
// @function:
// CJoinOrderDP::PexprBuildPred
//
// @doc:
// Build predicate connecting the two given sets
//
//---------------------------------------------------------------------------
CExpression *
CJoinOrderDP::PexprBuildPred
(
CBitSet *pbsFst,
CBitSet *pbsSnd
)
{
// collect edges connecting the given sets
CBitSet *pbsEdges = GPOS_NEW(m_mp) CBitSet(m_mp);
CBitSet *pbs = GPOS_NEW(m_mp) CBitSet(m_mp, *pbsFst);
pbs->Union(pbsSnd);
for (ULONG ul = 0; ul < m_ulEdges; ul++)
{
SEdge *pedge = m_rgpedge[ul];
if (
pbs->ContainsAll(pedge->m_pbs) &&
!pbsFst->IsDisjoint(pedge->m_pbs) &&
!pbsSnd->IsDisjoint(pedge->m_pbs)
)
{
#ifdef GPOS_DEBUG
BOOL fSet =
#endif // GPOS_DEBUG
pbsEdges->ExchangeSet(ul);
GPOS_ASSERT(!fSet);
}
}
pbs->Release();
CExpression *pexprPred = NULL;
if (0 < pbsEdges->Size())
{
CExpressionArray *pdrgpexpr = GPOS_NEW(m_mp) CExpressionArray(m_mp);
CBitSetIter bsi(*pbsEdges);
while (bsi.Advance())
{
ULONG ul = bsi.Bit();
SEdge *pedge = m_rgpedge[ul];
pedge->m_pexpr->AddRef();
pdrgpexpr->Append(pedge->m_pexpr);
}
pexprPred = CPredicateUtils::PexprConjunction(m_mp, pdrgpexpr);
}
pbsEdges->Release();
return pexprPred;
}
//---------------------------------------------------------------------------
// @function:
// CPhysical::PppsRequiredPushThruNAry
//
// @doc:
// Helper for pushing required partition propagation to the children of
// an n-ary operator
//
//---------------------------------------------------------------------------
CPartitionPropagationSpec *
CPhysical::PppsRequiredPushThruNAry
(
IMemoryPool *mp,
CExpressionHandle &exprhdl,
CPartitionPropagationSpec *pppsReqd,
ULONG child_index
)
{
GPOS_ASSERT(NULL != pppsReqd);
CPartIndexMap *ppimReqd = pppsReqd->Ppim();
CPartFilterMap *ppfmReqd = pppsReqd->Ppfm();
ULongPtrArray *pdrgpul = ppimReqd->PdrgpulScanIds(mp);
CPartIndexMap *ppimResult = GPOS_NEW(mp) CPartIndexMap(mp);
CPartFilterMap *ppfmResult = GPOS_NEW(mp) CPartFilterMap(mp);
const ULONG ulPartIndexIds = pdrgpul->Size();
const ULONG arity = exprhdl.UlNonScalarChildren();
// iterate over required part index ids and decide which ones to push to the outer
// and which to the inner side of the n-ary op
for (ULONG ul = 0; ul < ulPartIndexIds; ul++)
{
ULONG part_idx_id = *((*pdrgpul)[ul]);
GPOS_ASSERT(ppimReqd->Contains(part_idx_id));
CBitSet *pbsPartConsumer = GPOS_NEW(mp) CBitSet(mp);
for (ULONG ulChildIdx = 0; ulChildIdx < arity; ulChildIdx++)
{
if (exprhdl.GetRelationalProperties(ulChildIdx)->Ppartinfo()->FContainsScanId(part_idx_id))
{
(void) pbsPartConsumer->ExchangeSet(ulChildIdx);
}
}
if (arity == pbsPartConsumer->Size() &&
COperator::EopPhysicalSequence == exprhdl.Pop()->Eopid() &&
(*(exprhdl.Pgexpr()))[0]->FHasCTEProducer())
{
GPOS_ASSERT(2 == arity);
// this is a part index id that comes from both sides of a sequence
// with a CTE producer on the outer side, so pretend that part index
// id is not defined the inner sides
pbsPartConsumer->ExchangeClear(1);
}
if (!FCanPushPartReqToChild(pbsPartConsumer, child_index))
{
// clean up
pbsPartConsumer->Release();
continue;
}
// clean up
pbsPartConsumer->Release();
CPartKeysArray *pdrgppartkeys = exprhdl.GetRelationalProperties(child_index)->Ppartinfo()->PdrgppartkeysByScanId(part_idx_id);
GPOS_ASSERT(NULL != pdrgppartkeys);
pdrgppartkeys->AddRef();
// push requirements to child node
ppimResult->AddRequiredPartPropagation(ppimReqd, part_idx_id, CPartIndexMap::EppraPreservePropagators, pdrgppartkeys);
// check if there is a filter on the part index id and propagate that further down
if (ppfmReqd->FContainsScanId(part_idx_id))
{
CExpression *pexpr = ppfmReqd->Pexpr(part_idx_id);
// if the current child is inner child and the predicate is IsNull check and the parent is outer join,
// don't push IsNull check predicate to the partition filter.
// for all the other cases, push the filter down.
if (!(1 == child_index &&
CUtils::FScalarNullTest(pexpr) &&
CUtils::FPhysicalOuterJoin(exprhdl.Pop()))
)
{
pexpr->AddRef();
ppfmResult->AddPartFilter(mp, part_idx_id, pexpr, NULL /*stats */);
}
}
}
pdrgpul->Release();
return GPOS_NEW(mp) CPartitionPropagationSpec(ppimResult, ppfmResult);
}
//---------------------------------------------------------------------------
// @function:
// CJoinOrderDP::PexprBestJoinOrder
//
// @doc:
// find best join order for a given set of elements;
//
//---------------------------------------------------------------------------
CExpression *
CJoinOrderDP::PexprBestJoinOrder
(
CBitSet *pbs
)
{
GPOS_CHECK_STACK_SIZE;
GPOS_CHECK_ABORT;
GPOS_ASSERT(NULL != pbs);
// start by looking-up cost in the DP map
CExpression *pexpr = PexprLookup(pbs);
if (pexpr == m_pexprDummy)
{
// no join order could be created
return NULL;
}
if (NULL != pexpr)
{
// join order is found by looking up map
return pexpr;
}
// find maximal covered subset
CBitSet *pbsCovered = PbsCovered(pbs);
if (0 == pbsCovered->Size())
{
// set is not covered, return a cross product
pbsCovered->Release();
return PexprCross(pbs);
}
if (!pbsCovered->Equals(pbs))
{
// create a cross product for uncovered subset
CBitSet *pbsUncovered = GPOS_NEW(m_mp) CBitSet(m_mp, *pbs);
pbsUncovered->Difference(pbsCovered);
CExpression *pexprResult =
PexprJoinCoveredSubsetWithUncoveredSubset(pbs, pbsCovered, pbsUncovered);
pbsCovered->Release();
pbsUncovered->Release();
return pexprResult;
}
pbsCovered->Release();
// if set has size 2, there is only one possible solution
if (2 == pbs->Size())
{
return PexprJoin(pbs);
}
// otherwise, compute best join order using dynamic programming
CExpression *pexprBestJoinOrder = PexprBestJoinOrderDP(pbs);
if (pexprBestJoinOrder == m_pexprDummy)
{
// no join order could be created
return NULL;
}
return pexprBestJoinOrder;
}