// 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;
}
}
}
// return true if ItemExpr & its descendants have no constants & noncacheables
NABoolean ItemExpr::hasNoLiterals(CacheWA& cwa)
{
if (isNonCacheable()) {
return FALSE;
}
OperatorTypeEnum opTyp = getOperatorType();
switch (opTyp) {
case ITM_CONSTANT:
case ITM_HOSTVAR:
case ITM_DYN_PARAM:
case ITM_CACHE_PARAM:
return FALSE;
default: // fall thru
break;
}
NABoolean result = TRUE;
Int32 arity = getArity();
for (Int32 x = 0; x < arity && result; x++) {
if (child(x)) {
result = child(x)->hasNoLiterals(cwa);
}
}
return result;
}
// does this entire ItemExpr qualify query to be cacheable after this phase?
NABoolean ItemExpr::isCacheableExpr(CacheWA& cwa)
{
switch (cwa.getPhase()) {
default: { const NABoolean notYetImplemented = FALSE;
CMPASSERT(notYetImplemented);
break;
}
case CmpMain::PARSE:
// ItemExpr::isCacheableExpr is used by Tuple::isCacheable to
// determine whether a tuple-insert or a tuplelist-insert is
// cacheable after parse. It traverses a tuple's values list
// looking for non-cacheable ItemExprs such as HostVar,
// DynamicParam, Subquery, etc.
// determine cacheability of tuple INSERT's itemexprs here
if (isNonCacheable() || !cwa.isConditionallyCacheable()) {
return FALSE;
}
else { // we're either cacheable or maybecacheable
Int32 arity = getArity();
if (arity <= 0) { // we have no kids & we're conditionally cacheable
return TRUE; // we're cacheable
}
// cacheability of child(ren) determine our cacheability
for (Int32 x = 0; x < arity; x++) {
if (!child(x) || child(x)->isNonCacheable()) {
// the 1st noncacheable child makes us noncacheable
setNonCacheable();
return FALSE;
}
else if (!child(x)->isCacheableExpr(cwa)) {
// noncacheable child
return FALSE;
}
else { // cacheable child
continue; // look at next child
}
}
// all children are cacheable, so we're cacheable too
setCacheableNode(cwa.getPhase());
return TRUE;
}
break;
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;
}
// ItemExpr::isCacheableExpr is used in "after BIND" cases to
// visit all operands of an ItemExpr looking for noncacheable
// expressions. For example, it discovers that
// SELECT (SELECT a FROM t2 WHERE MAX(o.c)>1) FROM t1 o;
// is noncacheable only after it visits the outer query's select list.
if (isNonCacheable()) {
return FALSE;
}
else if (isCacheableNode(cwa.getPhase())) {
return TRUE;
}
else { // we're either cacheable or maybecacheable
// Assume this ItemExpr is an operand of a function or a list. In
// this case, a single noncacheable child renders us noncacheable.
Int32 arity = getArity();
for (Int32 x = 0; x < arity; x++) {
if (!child(x) || !child(x)->isCacheableExpr(cwa)) {
// noncacheable child
return FALSE;
}
else { // cacheable child
continue; // look at next child
}
}
// all children are cacheable, so we're cacheable too
setCacheableNode(cwa.getPhase());
return TRUE;
}
break;
}
return FALSE;
}
