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package uk.ac.ox.cs.pagoda.util;
import java.util.Collection;
import java.util.HashSet;
import java.util.LinkedList;
public class ConjunctiveQueryHelper {
public static String[][] getAnswerVariables(String queryText) {
Collection<String> disVars = new LinkedList<String>(), undisVars = new LinkedList<String>();
for (String var: getAllVariables(queryText))
if (var.startsWith("?")) disVars.add(var.substring(1));
else undisVars.add(var.substring(2));
String[] distinguishedVariables = disVars.toArray(new String[0]);
String[] undistinguishedVariables = undisVars.toArray(new String[0]);
String[] answerVariables = null;
String uppercase = queryText.toUpperCase();
int selectIndex = uppercase.indexOf("SELECT");
int whereIndex = uppercase.indexOf("WHERE");
String selectClause = queryText.substring(selectIndex + 6, whereIndex);
if (selectClause.contains("*")) answerVariables = distinguishedVariables;
else {
String[] terms = selectClause.split(" ");
int num = 0;
for (int i = 0; i < terms.length; ++i)
if (terms[i].startsWith("?")) ++num;
answerVariables = new String[num];
for (int i = 0, j = 0; i < terms.length; ++i)
if (terms[i].startsWith("?"))
answerVariables[j++] = terms[i].substring(1);
}
if (answerVariables != distinguishedVariables) {
int index = 0;
for (; index < answerVariables.length; ++index) {
distinguishedVariables[index] = answerVariables[index];
disVars.remove(answerVariables[index]);
}
for (String var: disVars)
distinguishedVariables[index++] = var;
}
return new String[][] { answerVariables, distinguishedVariables, undistinguishedVariables };
}
private static Collection<String> getAllVariables(String queryText) {
Collection<String> vars = new HashSet<String>();
int start, end = 0;
char ch;
while ((start = queryText.indexOf("?", end)) != -1) {
end = start + 1;
while (end + 1 < queryText.length() && (ch = queryText.charAt(end + 1)) != '\n' && ch != ' ')
++end;
vars.add(queryText.substring(start, end + 1));
}
end = 0;
while ((start = queryText.indexOf("_:", end)) != -1) {
end = start + 1;
while (end + 1 < queryText.length() && (ch = queryText.charAt(end + 1)) != '\n' && ch != ' ')
++end;
vars.add(queryText.substring(start, end + 1));
}
return vars;
}
}
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