//---------------------------------------------------------------------------
// @function:
// CBinding::PexprExtract
//
// @doc:
// Extract a binding according to a given pattern;
// Keep root node fixed;
//
//---------------------------------------------------------------------------
CExpression *
CBinding::PexprExtract
(
IMemoryPool *pmp,
CGroupExpression *pgexpr,
CExpression *pexprPattern,
CExpression *pexprLast
)
{
GPOS_CHECK_ABORT;
if (!pexprPattern->FMatchPattern(pgexpr))
{
// shallow matching fails
return NULL;
}
// the previously extracted pattern must have the same root
GPOS_ASSERT_IMP(NULL != pexprLast, pexprLast->Pgexpr() == pgexpr);
COperator *popPattern = pexprPattern->Pop();
if (popPattern->FPattern() && CPattern::PopConvert(popPattern)->FLeaf())
{
// return immediately; no deep extraction for leaf patterns
pgexpr->Pop()->AddRef();
return GPOS_NEW(pmp) CExpression(pmp, pgexpr->Pop(), pgexpr);
}
DrgPexpr *pdrgpexpr = NULL;
ULONG ulArity = pgexpr->UlArity();
if (0 == ulArity && NULL != pexprLast)
{
// no more bindings
return NULL;
}
else
{
// attempt binding to children
pdrgpexpr = GPOS_NEW(pmp) DrgPexpr(pmp);
if (!FExtractChildren(pmp, pgexpr, pexprPattern, pexprLast, pdrgpexpr))
{
pdrgpexpr->Release();
return NULL;
}
}
CExpression *pexpr = PexprFinalize(pmp, pgexpr, pdrgpexpr);
GPOS_ASSERT(NULL != pexpr);
return pexpr;
}
//---------------------------------------------------------------------------
// @function:
// CBinding::PexprExtract
//
// @doc:
// Extract a binding according to a given pattern;
// If no appropriate child pattern can be matched advance the root node
// until group is exhausted;
//
//---------------------------------------------------------------------------
CExpression *
CBinding::PexprExtract
(
IMemoryPool *pmp,
CGroup *pgroup,
CExpression *pexprPattern,
CExpression *pexprLast
)
{
GPOS_CHECK_STACK_SIZE;
GPOS_CHECK_ABORT;
GPOS_ASSERT(NULL != pgroup);
GPOS_ASSERT(NULL != pexprPattern);
CGroupExpression *pgexpr = NULL;
if (NULL != pexprLast)
{
pgexpr = pexprLast->Pgexpr();
}
else
{
// init cursor
pgexpr = PgexprNext(pgroup, NULL);
}
GPOS_ASSERT(NULL != pgexpr);
COperator *popPattern = pexprPattern->Pop();
if (popPattern->FPattern() && CPattern::PopConvert(popPattern)->FLeaf())
{
// for leaf patterns, we do not iterate on group expressions
if (NULL != pexprLast)
{
// if a leaf was extracted before, then group is exhausted
return NULL;
}
return PexprExtract(pmp, pgexpr, pexprPattern, pexprLast);
}
// start position for next binding
CExpression *pexprStart = pexprLast;
do
{
if (pexprPattern->FMatchPattern(pgexpr))
{
CExpression *pexprResult =
PexprExtract(pmp, pgexpr, pexprPattern, pexprStart);
if (NULL != pexprResult)
{
return pexprResult;
}
}
// move cursor and reset start position
pgexpr = PgexprNext(pgroup, pgexpr);
pexprStart = NULL;
GPOS_CHECK_ABORT;
}
while (NULL != pgexpr);
// group exhausted
return NULL;
}
