// is this entire expression cacheable after this phase?
NABoolean Scan::isCacheableExpr(CacheWA& cwa)
{
if (cwa.getPhase() >= CmpMain::BIND) {
// save scan's TableDesc
cwa.incNofScans(tabId_);
// native hbase access is not cacheable for now.
if ((getTableDesc()->getNATable()->isHbaseRowTable()) ||
(getTableDesc()->getNATable()->isHbaseCellTable()))
return FALSE;
if (stream_) { // pub-sub streams are not cacheable
return FALSE;
}
// mpalias SELECT is not cacheable unless explicitly requested
if (getTableDesc()->getNATable()->isAnMPTableWithAnsiName() &&
CmpCommon::getDefault(QUERY_CACHE_MPALIAS) == DF_OFF) {
return FALSE;
}
cwa.setConditionallyCacheable();
if (CmpCommon::getDefaultLong(MVQR_REWRITE_LEVEL) >= 1 &&
QRDescGenerator::hasRewriteEnabledMVs(getTableDesc())) {
cwa.setRewriteEnabledMV();
}
return RelExpr::isCacheableExpr(cwa);
}
return FALSE;
}
// is this entire expression cacheable after this phase?
NABoolean Join::isCacheableExpr(CacheWA& cwa)
{
if (cwa.getPhase() >= CmpMain::BIND) {
// must first descend to scans to get cwa.numberOfScans_
if (!RelExpr::isCacheableExpr(cwa)) {
return FALSE;
}
if (isCacheableNode(cwa.getPhase())) {
cwa.setConditionallyCacheable();
}
// if we allow joins of views to be cached, query caching cannot
// distinguish between (see note at bottom of cachewa.h)
// select avg(f.a) from v f, v s group by f.b;
// select avg(s.a) from v f, v s group by f.b;
// select avg(t.a) from v f, t group by f.b;
// assuming v is "create view v from select * from t". We avoid
// false cache hits by detecting the possible occurrence of such
// view joins here and later using cwa.isViewJoin_ to include
// their query texts into their cache keys.
//
// A view is repsented by a renamed table with isView() returnning
// TRUE.
RelExpr *c0 = child(0);
RelExpr *c1 = child(1);
if ((c0->getOperatorType() == REL_RENAME_TABLE &&
((RenameTable *)c0)->isView() == TRUE)
||
(c1->getOperatorType() == REL_RENAME_TABLE &&
((RenameTable *)c1)->isView() == TRUE)) {
cwa.foundViewJoin();
}
// check its join predicate
ItemExpr *pred = joinPredTree_ ? joinPredTree_ :
joinPred_.rebuildExprTree();
if (pred) {
cwa.setHasPredicate();
// is join predicate cacheable?
if (pred->hasNoLiterals(cwa)) {
// predicate with no literals is cacheable
}
else {
cwa.setPredHasNoLit(FALSE);
if (!pred->isCacheableExpr(cwa)) {
// a non-cacheable predicate renders Join non-cacheable.
setNonCacheable();
return FALSE;
}
}
}
return TRUE; // join may be cacheable
}
return FALSE;
}
// is this entire expression cacheable after this phase?
NABoolean RelExpr::isCacheableExpr(CacheWA& cwa)
{
switch (cwa.getPhase()) {
case CmpMain::PARSE:
case CmpMain::BIND: {
// does query have too many ExprNodes?
if (cwa.inc_N_check_still_cacheable() == FALSE) {
// yes. query with too many ExprNodes is not cacheable.
return FALSE;
}
if (isNonCacheable()) { // this node is not cacheable
return FALSE; // so the entire expression is not cacheable
// don't mark this node non-cacheable because this
// RelExpr may be cacheable after the next phase.
}
if (isCacheableNode(cwa.getPhase())) {
// must be an INSERT, UPDATE, DELETE, or SELECT node;
// so, mark this expression as conditionally cacheable.
cwa.setConditionallyCacheable();
}
// must descend to scans to get cwa.numberOfScans_
if (!cacheableKids(cwa)) {
return FALSE;
}
// this node is either cacheable or maybecacheable
// check its selection predicate
ItemExpr *pred = selPredTree() ? selPredTree() :
getSelectionPred().rebuildExprTree();
if (pred) {
cwa.setHasPredicate();
// is selection predicate cacheable?
if (pred->hasNoLiterals(cwa)) {
// predicate with no literals is cacheable
}
else {
cwa.setPredHasNoLit(FALSE);
if (!pred->isCacheableExpr(cwa)) {
// a non-cacheable selection predicate
// renders entire RelExpr non-cacheable.
setNonCacheable();
return FALSE;
}
}
}
return TRUE; // RelExpr may be cacheable
}
default: { const NABoolean notYetImplemented = FALSE;
CMPASSERT(notYetImplemented);
return FALSE;
}
}
}