@Override
protected Expr opt(final QueryContext qc, final VarScope scp) {
final Expr e = exprs[0];
final SeqType st = e.seqType();
if (!st.mayBeZero()) return e;
seqType = SeqType.get(st.type, seqType.occ);
return this;
}
@Override
public GroupBy optimize(final QueryContext qc, final VarScope scp) throws QueryException {
final int pl = preExpr.length;
for (int p = 0; p < pl; p++) {
final SeqType it = preExpr[p].seqType();
post[p].refineType(it.withOcc(it.mayBeZero() ? Occ.ZERO_MORE : Occ.ONE_MORE), qc);
}
return this;
}
@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 Expr compile(final QueryContext ctx) throws QueryException {
for (int e = 0; e < expr.length; e++) expr[e] = expr[e].compile(ctx);
// compute number of results
size = 0;
for (final Expr e : expr) {
final long c = e.size();
if (c == -1) {
size = c;
break;
}
size += c;
}
// evaluate sequence type
type = SeqType.EMP;
Value[] val = new Value[expr.length];
for (int v = 0; v < expr.length; v++) {
final Expr e = expr[v];
// check if all expressions are values
if (val != null) {
if (e.isValue()) val[v] = (Value) e;
else val = null;
}
// skip expression that will not add any results
if (e.isEmpty()) continue;
// evaluate sequence type
final SeqType et = e.type();
type =
type == SeqType.EMP
? et
: SeqType.get(
et.type == type.type ? et.type : AtomType.ITEM,
et.mayBeZero() && type.mayBeZero() ? Occ.ZERO_MORE : Occ.ONE_MORE);
}
// return cached integer sequence, cached values or self reference
Expr e = this;
final int s = (int) size;
if (val != null && size <= Integer.MAX_VALUE) {
if (type.type == AtomType.STR) e = StrSeq.get(val, s);
else if (type.type == AtomType.BLN) e = BlnSeq.get(val, s);
else if (type.type == AtomType.FLT) e = FltSeq.get(val, s);
else if (type.type == AtomType.DBL) e = DblSeq.get(val, s);
else if (type.type == AtomType.DEC) e = DecSeq.get(val, s);
else if (type.type == AtomType.BYT) e = BytSeq.get(val, s);
else if (type.type.instanceOf(AtomType.ITR)) e = IntSeq.get(val, s, type.type);
else {
final ValueBuilder vb = new ValueBuilder(s);
for (final Value v : val) vb.add(v);
e = vb.value();
}
}
return optPre(e, ctx);
}
@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;
}
/**
* Compiles the filter expression, excluding the root node.
*
* @param ctx query context
* @return compiled expression
*/
private Expr opt(final QueryContext ctx) {
// evaluate return type
final SeqType t = root.type();
// determine number of results and type
final long s = root.size();
if (s != -1) {
if (pos != null) {
size = Math.max(0, s + 1 - pos.min) - Math.max(0, s - pos.max);
} else if (last) {
size = s > 0 ? 1 : 0;
}
// no results will remain: return empty sequence
if (size == 0) return optPre(null, ctx);
type = SeqType.get(t.type, size);
} else {
type = SeqType.get(t.type, t.zeroOrOne() ? Occ.ZERO_ONE : Occ.ZERO_MORE);
}
// no numeric predicates.. use simple iterator
if (!super.has(Flag.FCS)) return new IterFilter(this);
// one single position() or last() function specified: return single value
if (preds.length == 1
&& (last || pos != null)
&& root.isValue()
&& t.one()
&& (last || pos.min == 1 && pos.max == 1)) return optPre(root, ctx);
// only choose deterministic and context-independent offsets; e.g., skip:
// (1 to 10)[random:integer(10)] or (1 to 10)[.]
boolean off = false;
if (preds.length == 1) {
final Expr p = preds[0];
final SeqType st = p.type();
off = st.type.isNumber() && st.zeroOrOne() && !p.has(Flag.CTX) && !p.has(Flag.NDT);
if (off) type = SeqType.get(type.type, Occ.ZERO_ONE);
}
// iterator for simple numeric predicate
return off || useIterator() ? new IterPosFilter(this, off) : this;
}