@Override
public boolean accept(final ASTVisitor visitor) {
if (!visitAll(visitor, specs)) return false;
for (final Expr ng : preExpr) if (!ng.accept(visitor)) return false;
for (final Var ng : post) if (!visitor.declared(ng)) return false;
return true;
}
@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;
}
@Override
public final Expr optimize(final QueryContext qc, final VarScope scp) throws QueryException {
final Value v = initial(qc);
if (v != null && v.isEmpty() || emptyPath(v)) return optPre(qc);
// merge descendant steps
Expr e = mergeSteps(qc);
if (e == this && v != null && v.type == NodeType.DOC) {
// check index access
e = index(qc, v);
// rewrite descendant to child steps
if (e == this) e = children(qc, v);
}
// recompile path if it has changed
if (e != this) return e.compile(qc, scp);
// set atomic type for single attribute steps to speed up predicate tests
if (root == null && steps.length == 1 && steps[0] instanceof Step) {
final Step curr = (Step) steps[0];
if (curr.axis == ATTR && curr.test.kind == Kind.URI_NAME) curr.seqType(SeqType.NOD_ZO);
}
// choose best path implementation and set type information
final Path path = get(info, root, steps);
path.size = path.size(qc);
path.seqType = SeqType.get(steps[steps.length - 1].seqType().type, size);
return path;
}
/**
* 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 final boolean has(final Flag flag) {
// first step or root expression will be used as context
if (flag == Flag.CTX) return root == null || root.has(flag);
for (final Expr s : steps) if (s.has(flag)) return true;
return root != null && root.has(flag);
}
@Override
public Expr comp(final QueryContext ctx) throws QueryException {
ts = checkUp(ts, ctx).comp(ctx);
final Expr[] tmp = new Expr[cases.length];
for (int i = 0; i < cases.length; ++i) tmp[i] = cases[i].expr;
checkUp(ctx, tmp);
// static condition: return branch in question
if (ts.isValue()) {
for (final TypeCase c : cases) {
if (c.var.type == null || c.var.type.instance(ts.value(ctx)))
return optPre(c.comp(ctx, (Value) ts).expr, ctx);
}
}
// compile branches
for (final TypeCase c : cases) c.comp(ctx);
// return result if all branches are equal (e.g., empty)
boolean eq = true;
for (int i = 1; i < cases.length; ++i) {
eq &= cases[i - 1].expr.sameAs(cases[i].expr);
}
if (eq) return optPre(null, ctx);
// evaluate return type
type = cases[0].type();
for (int c = 1; c < cases.length; ++c) {
type = type.intersect(cases[c].type());
}
return this;
}
@Override
public int exprSize() {
int sz = 1;
for (final Let lt : copies) sz += lt.exprSize();
for (final Expr e : expr) sz += e.exprSize();
return sz;
}
@Override
public int exprSize() {
int sz = 1;
if (occ != null) for (final Expr o : occ) sz += o.exprSize();
for (final Expr e : exprs) sz += e.exprSize();
return sz + query.exprSize();
}
/**
* Ensures that none of the specified expressions performs an update. Otherwise, throws an
* exception.
*
* @param exprs expressions (may be {@code null}, and may contain {@code null} references)
* @throws QueryException query exception
*/
protected final void checkNoneUp(final Expr... exprs) throws QueryException {
if (exprs == null) return;
checkAllUp(exprs);
for (final Expr expr : exprs) {
if (expr != null && expr.has(Flag.UPD)) throw UPNOT_X.get(info, description());
}
}
@Override
public boolean uses(final Use u) {
for (final Expr p : pred) {
if (u == Use.POS && p.type().mayBeNum() || p.uses(u)) return true;
}
return false;
}
@Override
public int exprSize() {
int sz = 0;
for (final Expr e : preExpr) sz += e.exprSize();
for (final Expr e : specs) sz += e.exprSize();
return sz;
}
@Override
public final Expr compile(final QueryContext qc, final VarScope scp) throws QueryException {
if (root != null) root = root.compile(qc, scp);
// no steps
if (steps.length == 0) return root == null ? new Context(info) : root;
final Value init = qc.value, cv = initial(qc);
final boolean doc = cv != null && cv.type == NodeType.DOC;
qc.value = cv;
try {
final int sl = steps.length;
for (int s = 0; s < sl; s++) {
Expr e = steps[s];
// axis step: if input is a document, its type is temporarily generalized
final boolean as = e instanceof Step;
if (as && s == 0 && doc) cv.type = NodeType.NOD;
e = e.compile(qc, scp);
if (e.isEmpty()) return optPre(qc);
steps[s] = e;
// no axis step: invalidate context value
if (!as) qc.value = null;
}
} finally {
if (doc) cv.type = NodeType.DOC;
qc.value = init;
}
// optimize path
return optimize(qc, scp);
}
@Override
public void checkUp() throws QueryException {
for (final Let c : copies) c.checkUp();
final Expr m = expr[0];
m.checkUp();
if (!m.isVacuous() && !m.has(Flag.UPD)) throw UPMODIFY.get(info);
checkNoUp(expr[1]);
}
@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;
}
/**
* Ensures that all specified expressions are vacuous or either updating or non-updating.
* Otherwise, throws an exception.
*
* @param exprs expressions to be checked
* @throws QueryException query exception
*/
void checkAllUp(final Expr... exprs) throws QueryException {
// updating state: 0 = initial state, 1 = updating, -1 = non-updating
int s = 0;
for (final Expr expr : exprs) {
expr.checkUp();
if (expr.isVacuous()) continue;
final boolean u = expr.has(Flag.UPD);
if (u && s == -1 || !u && s == 1) throw UPALL.get(info, description());
s = u ? 1 : -1;
}
}
/**
* Tests if the specified expressions are updating or vacuous.
*
* @param ctx query context
* @param expr expression array
* @throws QueryException query exception
*/
public void checkUp(final QueryContext ctx, final Expr... expr) throws QueryException {
if (!ctx.updating) return;
int s = 0;
for (final Expr e : expr) {
if (e.vacuous()) continue;
final boolean u = e.uses(Use.UPD);
if (u && s == 2 || !u && s == 1) UPNOT.thrw(input, desc());
s = u ? 1 : 2;
}
}
/**
* Checks if the predicates are successful for the specified item.
*
* @param it item to be checked
* @param ctx query context
* @return result of check
* @throws QueryException query exception
*/
public boolean preds(final Item it, final QueryContext ctx) throws QueryException {
// set context item and position
ctx.value = it;
for (final Expr p : pred) {
final Item i = p.test(ctx, input);
if (i == null) return false;
// item accepted.. adopt last scoring value
it.score(i.score());
}
return true;
}
@Override
public Expr optimize(final QueryContext ctx, final VarScope scp) throws QueryException {
if (root instanceof Context) {
ctx.compInfo(OPTREMCTX);
root = null;
}
for (final Expr e : steps) {
// check for empty steps
if (e.isEmpty()) return optPre(null, ctx);
}
return this;
}
/**
* Returns the initial context value of a path or {@code null}.
*
* @param qc query context (may be @code null)
* @return root
*/
private Value initial(final QueryContext qc) {
// current context value
final Value v = qc != null ? qc.value : null;
// no root or context expression: return context
if (root == null || root instanceof Context) return v;
// root reference
if (root instanceof Root) return v != null && v instanceof Item ? Root.root(v) : v;
// root is value: return root
if (root.isValue()) return (Value) root;
// data reference
final Data d = root.data();
if (d != null) return new DBNode(d, 0, Data.ELEM);
// otherwise, return null
return null;
}
@Override
public Expr compile(final QueryContext qc, final VarScope scp) throws QueryException {
ts = ts.compile(qc, scp);
// static condition: return branch in question
if (ts.isValue()) {
final Value val = ts.value(qc);
for (final TypeCase tc : cases) {
if (tc.matches(val)) return optPre(tc.compile(qc, scp, (Value) ts).expr, qc);
}
}
// compile branches
for (final TypeCase tc : cases) tc.compile(qc, scp);
return optimize(qc, scp);
}
/**
* Checks if the path can be rewritten for iterative evaluation.
*
* @param root root expression; can be a {@code null} reference
* @param steps path steps
* @return result of check
*/
private static boolean iterative(final Expr root, final Expr... steps) {
if (root == null || !root.iterable()) return false;
final int sl = steps.length;
for (int s = 0; s < sl; ++s) {
switch (((Step) steps[s]).axis) {
// reverse axes - don't iterate
case ANC:
case ANCORSELF:
case PREC:
case PRECSIBL:
return false;
// multiple, unsorted results - only iterate at last step,
// or if last step uses attribute axis
case DESC:
case DESCORSELF:
case FOLL:
case FOLLSIBL:
return s + 1 == sl || s + 2 == sl && ((Step) steps[s + 1]).axis == Axis.ATTR;
// allow iteration for CHILD, ATTR, PARENT and SELF axes
default:
}
}
return true;
}
@Override
public void plan(final Serializer ser) throws IOException {
ser.openElement(this);
for (final TypeCase c : cases) c.plan(ser);
ts.plan(ser);
ser.closeElement();
}
@Override
public final Expr inline(final QueryContext ctx, final VarScope scp, final Var v, final Expr e)
throws QueryException {
final Value oldVal = ctx.value;
try {
ctx.value = root(ctx);
final Expr rt = root == null ? null : root.inline(ctx, scp, v, e);
if (rt != null) {
setRoot(ctx, rt);
ctx.value = oldVal;
ctx.value = root(ctx);
}
boolean change = rt != null;
for (int i = 0; i < steps.length; i++) {
final Expr nw = steps[i].inline(ctx, scp, v, e);
if (nw != null) {
steps[i] = nw;
change = true;
}
}
return change ? optimize(ctx, scp) : null;
} finally {
ctx.value = oldVal;
}
}
@Override
public FTWords compile(final QueryContext qc, final VarScope scp) throws QueryException {
if (occ != null) {
final int ol = occ.length;
for (int o = 0; o < ol; ++o) occ[o] = occ[o].compile(qc, scp);
}
// compile only once
if (tokens == null) {
query = query.compile(qc, scp);
if (query.isValue()) tokens = tokens(qc);
// choose fast evaluation for default settings
fast = mode == FTMode.ANY && tokens != null && occ == null;
if (ftt == null) ftt = new FTTokenizer(this, qc);
}
return this;
}
/**
* Merges expensive descendant-or-self::node() steps.
*
* @param qc query context
* @return original or new expression
*/
private Expr mergeSteps(final QueryContext qc) {
boolean opt = false;
final int sl = steps.length;
final ExprList stps = new ExprList(sl);
for (int s = 0; s < sl; s++) {
final Expr step = steps[s];
// check for simple descendants-or-self step with succeeding step
if (s < sl - 1 && step instanceof Step) {
final Step curr = (Step) step;
if (curr.simple(DESCORSELF, false)) {
// check succeeding step
final Expr next = steps[s + 1];
// descendant-or-self::node()/child::X -> descendant::X
if (simpleChild(next)) {
((Step) next).axis = DESC;
opt = true;
continue;
}
// descendant-or-self::node()/(X, Y) -> (descendant::X | descendant::Y)
Expr e = mergeList(next);
if (e != null) {
steps[s + 1] = e;
opt = true;
continue;
}
// //(X, Y)[text()] -> (/descendant::X | /descendant::Y)[text()]
if (next instanceof Filter && !next.has(Flag.FCS)) {
final Filter f = (Filter) next;
e = mergeList(f.root);
if (e != null) {
f.root = e;
opt = true;
continue;
}
}
}
}
stps.add(step);
}
if (opt) {
qc.compInfo(OPTDESC);
return get(info, root, stps.finish());
}
return this;
}
/**
* 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;
}
