/**
* Flattens the tree by pushing down the field name. For example, if the tree looks like this:
*
* <pre>
* EQ
* / \
* VALUE EQ
* / \ / \
* TEXT field GLOBAL (N)
* </pre>
*
* Then we will output tree that looks like this:
*
* <pre>
* EQ
* / \
* VALUE (N)
* / \
* TEXT field
* </pre>
*
* Here <code>(N)</code> is an arbitrary node. We also drop EQ if it is in front of conjunction or
* disjunction. We do not drop it for other comparators, as we want parsing to fail for foo <
* (1 2).
*/
private static Tree flatten(Tree tree, Tree restriction) throws QueryTreeException {
if (tree.getType() == QueryLexer.VALUE) {
return tree;
}
if (tree.getType() == QueryLexer.HAS || tree.getType() == QueryLexer.EQ) {
Tree lhs = tree.getChild(0);
if (lhs.getType() == QueryLexer.VALUE) {
String myField = lhs.getChild(1).getText();
if (restriction == null) {
restriction = lhs;
} else {
String otherField = restriction.getChild(1).getText();
if (!myField.equals(otherField)) {
throw new QueryTreeException(
String.format("Restriction on %s and %s", otherField, myField),
lhs.getChild(1).getCharPositionInLine());
}
}
}
Tree rhs = tree.getChild(1);
Tree flattened = flatten(rhs, restriction);
if (flattened.getType() == QueryLexer.HAS
|| flattened.getType() == QueryLexer.EQ
|| flattened.getType() == QueryLexer.CONJUNCTION
|| flattened.getType() == QueryLexer.DISJUNCTION
|| flattened.getType() == QueryLexer.SEQUENCE) {
return flattened;
}
if (flattened != rhs) {
tree.setChild(1, flattened);
}
if (restriction != lhs) {
tree.setChild(0, restriction);
}
return tree;
}
for (int i = 0; i < tree.getChildCount(); ++i) {
Tree original = tree.getChild(i);
Tree flattened = flatten(tree.getChild(i), restriction);
if (original != flattened) {
tree.setChild(i, flattened);
}
}
return tree;
}
public static Tree simplify(Tree tree) {
for (int i = 0; i < tree.getChildCount(); ++i) {
Tree child = tree.getChild(i);
Tree optimized = simplify(child);
if (child != optimized) {
tree.setChild(i, optimized);
}
}
switch (tree.getType()) {
case QueryLexer.CONJUNCTION:
case QueryLexer.DISJUNCTION:
case QueryLexer.SEQUENCE:
if (tree.getChildCount() == 1) {
return tree.getChild(0);
}
break;
}
return tree;
}
