@Override
public boolean indexAccessible(final IndexInfo ii) throws QueryException {
final int es = exprs.length;
final boolean[] ng = new boolean[es];
int costs = 0;
for (final FTExpr expr : exprs) {
if (!expr.indexAccessible(ii)) return false;
// use worst costs for estimation, as all index results may need to be scanned
if (costs < ii.costs) costs = ii.costs;
}
ii.costs = costs;
negated = ng;
return true;
}
/**
* 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 FTExpr compile(final CompileContext cc) throws QueryException {
super.compile(cc);
boolean not = true;
for (final FTExpr expr : exprs) not &= expr instanceof FTNot;
if (not) {
// convert (!A and !B and ...) to !(A or B or ...)
final int es = exprs.length;
for (int e = 0; e < es; ++e) exprs[e] = exprs[e].exprs[0];
return new FTNot(info, new FTOr(info, exprs));
}
return this;
}
@Override
public boolean has(final Flag flag) {
for (final FTExpr e : exprs) if (e.has(flag)) return true;
return false;
}
/**
* Checks if sub expressions of a mild not operator violate the grammar.
*
* @return result of check
*/
boolean usesExclude() {
for (final FTExpr e : exprs) if (e.usesExclude()) return true;
return false;
}
