// is this entire expression cacheable after this phase?
NABoolean Tuple::isCacheableExpr(CacheWA& cwa)
{
// we do not call RelExpr::isCacheableExpr here because it's redundant
// -- Tuple is a leaf node and has no predicates.
ItemExpr *tExpr = tupleExprTree() ? tupleExprTree() :
tupleExpr_.rebuildExprTree();
return tExpr->isCacheableExpr(cwa);
}
// 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;
}
}
}
// is this entire expression cacheable after this phase?
NABoolean GroupByAgg::isCacheableExpr(CacheWA& cwa)
{
// descend to scans early to get cwa.numberOfScans_
if (!RelExpr::isCacheableExpr(cwa)) {
return FALSE;
}
// is the group by col/expr cacheable?
ItemExpr *grpExpr = groupExprTree_ ? groupExprTree_ :
groupExpr_.rebuildExprTree(ITM_ITEM_LIST);
if (grpExpr && !grpExpr->isCacheableExpr(cwa)) {
return FALSE;
}
return TRUE; // may be cacheable
}
// is any literal in this expr safely coercible to its target type?
NABoolean Assign::isSafelyCoercible(CacheWA &cwa) const
{
if (cwa.getPhase() >= CmpMain::BIND) {
// we have to disallow caching of the following types of updates:
// update t set col = overlylongliteral
ItemExpr *src = getSource().getItemExpr();
if (src->getOperatorType() == ITM_CONSTANT) {
// source is a literal; make sure this update is cacheable only if
// literal can be safely coerced into its target type.
return ((ConstValue*)src)->canBeSafelyCoercedTo(getTarget().getType());
}
else { // source is not a literal
// we need to descend into this expr to verify that no
// errors can occur during backpatching. For example,
// update t set i = i + 123456789012345678901234567890
// should not be cacheable if i is a smallint.
// reject "update t set c=(subquery)" as noncacheable
// as part of a fix to CR 10-020108-8401.
return src->isSafelyCoercible(cwa) && src->isCacheableExpr(cwa);
}
}
return FALSE;
}
// is this entire expression cacheable after this phase?
NABoolean GenericUpdate::isCacheableExpr(CacheWA& cwa)
{
// descend to scans early to get cwa.numberOfScans_
if (!RelExpr::isCacheableExpr(cwa)) {
return FALSE;
}
// Make "{update|delete} ... where current of cursor" non-cacheable
// so that stale cache will not lead to timestamp mismatch error at
// runtime. AQR attempts to handle this error, but only after the
// referenced cursor is closed due to transaction rollback. This is
// Solution 10-100425-9755.
if (currOfCursorName()) {
return FALSE;
}
if (cwa.getPhase() >= CmpMain::BIND) {
// make sure any literals in the assignment clause can be safely
// cast and assigned to their target types at plan-backpatch-time
ItemExpr *newExpr = newRecExprTree_ ? newRecExprTree_ :
newRecExpr_.rebuildExprTree(ITM_ITEM_LIST);
if (newExpr && !newExpr->isSafelyCoercible(cwa)) {
return FALSE;
}
// reject as non-cacheable queries such as
// prepare s from select * from (update t042qT8 set b=7
// set on rollback c=12345678901234567890 where a=2) as t;
ItemExpr *setOnRollback;
if (newRecBeforeExpr_.entries() > 0 &&
(setOnRollback=newRecBeforeExpr_.rebuildExprTree(ITM_ITEM_LIST))
&& !setOnRollback->isSafelyCoercible(cwa)) {
return FALSE;
}
// make sure any executor predicate is cacheable
ItemExpr *execPred = executorPredTree_ ? executorPredTree_ :
executorPred_.rebuildExprTree();
if (execPred) {
cwa.setHasPredicate();
if (execPred->hasNoLiterals(cwa)) {
// predicate with no literals is cacheable
}
else {
cwa.setPredHasNoLit(FALSE);
return execPred->isCacheableExpr(cwa);
}
}
// at this time, not cacheable if subquery is specified in
// UPDATE SET clause.
// This could be enabled later.
if (subqInUpdateAssign()) {
return FALSE;
}
}
else {
if ((getTableName().isPartitionNameSpecified()) ||
(getTableName().isLocationNameSpecified()) ||
(getTableName().isPartitionRangeSpecified()))
return FALSE; // If PartnClause is used no cache hit before bind stage.
}
return TRUE; // may be cacheable
}
