@Override
public boolean has(final Flag flag) {
for (final Expr pred : preds) {
if (flag == Flag.FCS && pred.seqType().mayBeNumber() || pred.has(flag)) return true;
}
return false;
}
/**
* Checks if the predicates are successful for the specified item.
*
* @param it item to be checked
* @param qc query context
* @return result of check
* @throws QueryException query exception
*/
protected final boolean preds(final Item it, final QueryContext qc) throws QueryException {
if (preds.length == 0) return true;
// set context value and position
final Value cv = qc.value;
try {
if (qc.scoring) {
double s = 0;
for (final Expr p : preds) {
qc.value = it;
final Item i = p.test(qc, info);
if (i == null) return false;
s += i.score();
}
it.score(Scoring.avg(s, preds.length));
} else {
for (final Expr p : preds) {
qc.value = it;
if (p.test(qc, info) == null) return false;
}
}
return true;
} finally {
qc.value = cv;
}
}
@Override
public Expr optimize(final QueryContext qc, final VarScope scp) throws QueryException {
final Expr c = super.optimize(qc, scp);
if (c != this) return c;
final int es = exprs.length;
final ExprList list = new ExprList(es);
for (int i = 0; i < es; i++) {
Expr e = exprs[i];
if (e instanceof CmpG) {
// merge adjacent comparisons
while (i + 1 < es && exprs[i + 1] instanceof CmpG) {
final Expr tmp = ((CmpG) e).union((CmpG) exprs[i + 1], qc, scp);
if (tmp != null) {
e = tmp;
i++;
} else {
break;
}
}
}
// expression will always return true
if (e == Bln.TRUE) return optPre(Bln.TRUE, qc);
// skip expression yielding false
if (e != Bln.FALSE) list.add(e);
}
// all arguments return false
if (list.isEmpty()) return optPre(Bln.FALSE, qc);
if (es != list.size()) {
qc.compInfo(OPTREWRITE_X, this);
exprs = list.finish();
}
compFlatten(qc);
boolean not = true;
for (final Expr expr : exprs) {
if (!expr.isFunction(Function.NOT)) {
not = false;
break;
}
}
if (not) {
qc.compInfo(OPTREWRITE_X, this);
final int el = exprs.length;
final Expr[] inner = new Expr[el];
for (int e = 0; e < el; e++) inner[e] = ((Arr) exprs[e]).exprs[0];
final Expr ex = new And(info, inner).optimize(qc, scp);
return Function.NOT.get(null, info, ex).optimize(qc, scp);
}
// return single expression if it yields a boolean
return exprs.length == 1 ? compBln(exprs[0], info) : this;
}
/**
* Prepares this expression for iterative evaluation. The expression can be iteratively evaluated
* if no predicate or only the first is positional.
*
* @return result of check
*/
protected final boolean posIterator() {
// check if first predicate is numeric
if (preds.length == 1) {
Expr p = preds[0];
if (p instanceof Int) p = Pos.get(((Int) p).itr(), info);
pos = p instanceof Pos ? (Pos) p : null;
last = p.isFunction(Function.LAST);
preds[0] = p;
}
return pos != null || last;
}
/**
* Merges a single predicate with the root expression and returns the resulting expression, or
* returns a self reference if the expression cannot be merged. This function is e.g. called by
* {@link Where#optimize}.
*
* @param qc query context
* @param scp variable scope
* @param root root expression
* @return expression
* @throws QueryException query exception
*/
public Expr merge(final Expr root, final QueryContext qc, final VarScope scp)
throws QueryException {
// only one predicate can be rewritten; root expression must yield nodes
if (preds.length != 1 || !(root.seqType().type instanceof NodeType)) return this;
final Expr pred = preds[0];
// a[.] -> a
if (pred instanceof Context) return root;
if (!pred.seqType().mayBeNumber()) {
// a[b] -> a/b
if (pred instanceof Path) return Path.get(info, root, pred).optimize(qc, scp);
if (pred instanceof CmpG) {
final CmpG cmp = (CmpG) pred;
final Expr expr1 = cmp.exprs[0], expr2 = cmp.exprs[1];
// only first operand can depend on context
if (!expr2.has(Flag.CTX)) {
Expr path = null;
// a[. = 'x'] -> a = 'x'
if (expr1 instanceof Context) path = root;
// a[text() = 'x'] -> a/text() = 'x'
if (expr1 instanceof Path) path = Path.get(info, root, expr1).optimize(qc, scp);
if (path != null) return new CmpG(path, expr2, cmp.op, cmp.coll, cmp.sc, cmp.info);
}
}
if (pred instanceof FTContains) {
final FTContains cmp = (FTContains) pred;
final FTExpr ftexpr = cmp.ftexpr;
// only first operand can depend on context
if (!ftexpr.has(Flag.CTX)) {
final Expr expr = cmp.expr;
Expr path = null;
// a[. contains text 'x'] -> a contains text 'x'
if (expr instanceof Context) path = root;
// [text() contains text 'x'] -> a/text() contains text 'x'
if (expr instanceof Path) path = Path.get(info, root, expr).optimize(qc, scp);
if (path != null) return new FTContains(path, ftexpr, cmp.info);
}
}
}
return this;
}
@Override
public boolean indexAccessible(final IndexInfo ii) throws QueryException {
int costs = 0;
final ExprList el = new ExprList(exprs.length);
for (final Expr expr : exprs) {
// check if expression can be rewritten, and if access is not sequential
if (!expr.indexAccessible(ii)) return false;
// skip expressions without results
if (ii.costs == 0) continue;
costs += ii.costs;
el.add(ii.expr);
}
// use summarized costs for estimation
ii.costs = costs;
// no expressions means no costs: expression will later be ignored
ii.expr = el.size() == 1 ? el.get(0) : new Union(info, el.finish());
return true;
}
@Override
public Expr optimize(final QueryContext qc, final VarScope scp) throws QueryException {
// number of predicates may change in loop
for (int p = 0; p < preds.length; p++) {
final Expr pred = preds[p];
if (pred instanceof CmpG || pred instanceof CmpV) {
final Cmp cmp = (Cmp) pred;
if (cmp.exprs[0].isFunction(Function.POSITION)) {
final Expr e2 = cmp.exprs[1];
final SeqType st2 = e2.seqType();
// position() = last() -> last()
// position() = $n (numeric) -> $n
if (e2.isFunction(Function.LAST) || st2.one() && st2.type.isNumber()) {
if (cmp instanceof CmpG && ((CmpG) cmp).op == OpG.EQ
|| cmp instanceof CmpV && ((CmpV) cmp).op == OpV.EQ) {
qc.compInfo(OPTWRITE, pred);
preds[p] = e2;
}
}
}
} else if (pred instanceof And) {
if (!pred.has(Flag.FCS)) {
// replace AND expression with predicates (don't swap position tests)
qc.compInfo(OPTPRED, pred);
final Expr[] and = ((Arr) pred).exprs;
final int m = and.length - 1;
final ExprList el = new ExprList(preds.length + m);
for (final Expr e : Arrays.asList(preds).subList(0, p)) el.add(e);
for (final Expr a : and) {
// wrap test with boolean() if the result is numeric
el.add(Function.BOOLEAN.get(null, info, a).optimizeEbv(qc, scp));
}
for (final Expr e : Arrays.asList(preds).subList(p + 1, preds.length)) el.add(e);
preds = el.finish();
}
} else if (pred instanceof ANum) {
final ANum it = (ANum) pred;
final long i = it.itr();
if (i == it.dbl()) {
preds[p] = Pos.get(i, info);
} else {
qc.compInfo(OPTREMOVE, this, pred);
return Empty.SEQ;
}
} else if (pred.isValue()) {
if (pred.ebv(qc, info).bool(info)) {
qc.compInfo(OPTREMOVE, this, pred);
preds = Array.delete(preds, p--);
} else {
// handle statically known predicates
qc.compInfo(OPTREMOVE, this, pred);
return Empty.SEQ;
}
}
}
return this;
}
@Override
public Item item(final QueryContext qc, final InputInfo ii) throws QueryException {
// compute scoring
if (qc.scoring) {
double s = 0;
boolean f = false;
for (final Expr expr : exprs) {
final Item it = expr.ebv(qc, info);
f |= it.bool(ii);
s += it.score();
}
return Bln.get(f, Scoring.avg(s, exprs.length));
}
// standard evaluation
for (final Expr expr : exprs) {
if (expr.ebv(qc, info).bool(ii)) return Bln.TRUE;
}
return Bln.FALSE;
}
@Override
public Expr optimize(final QueryContext qc, final VarScope scp) throws QueryException {
super.optimize(qc, scp);
final ExprList el = new ExprList(exprs.length);
for (final Expr ex : exprs) {
if (ex.isEmpty()) {
// remove empty operands (return empty sequence if first value is empty)
if (el.isEmpty()) return optPre(qc);
qc.compInfo(OPTREMOVE_X_X, this, ex);
} else {
el.add(ex);
}
}
// ensure that results are always sorted
if (el.size() == 1 && iterable) return el.get(0);
// replace expressions with optimized list
exprs = el.finish();
return this;
}
@Override
public void plan(final FElem plan) {
for (final Expr p : preds) p.plan(plan);
}
@Override
public boolean removable(final Var var) {
for (final Expr p : preds) if (p.uses(var)) return false;
return true;
}