Metacat

/**

 *  '$RCSfile$'

 *    Purpose: A Class that represents a structured query, and can be

 *             constructed from an XML serialization conforming to

 *             pathquery.dtd. The printSQL() method can be used to print

 *             a SQL serialization of the query.

 *  Copyright: 2000 Regents of the University of California and the

 *             National Center for Ecological Analysis and Synthesis

 *    Authors: Matt Jones

 *

 *   '$Author: daigle $'

 *     '$Date: 2010-01-28 12:35:59 -0800 (Thu, 28 Jan 2010) $'

 * '$Revision: 5204 $'

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 2 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 */

package edu.ucsb.nceas.metacat;

import java.io.IOException;

import java.io.Reader;

import java.io.StringReader;

import java.util.Enumeration;

import java.util.Stack;

import java.util.Vector;

import edu.ucsb.nceas.metacat.shared.MetacatUtilException;

import edu.ucsb.nceas.metacat.util.MetacatUtil;

import edu.ucsb.nceas.metacat.util.SystemUtil;

//import edu.ucsb.nceas.utilities.UtilException;

import org.apache.log4j.Logger;

import org.xml.sax.Attributes;

import org.xml.sax.InputSource;

import org.xml.sax.SAXException;

import org.xml.sax.XMLReader;

import org.xml.sax.helpers.DefaultHandler;

import org.xml.sax.helpers.XMLReaderFactory;

import java.util.Iterator;

/**

 * A Class that represents a structured query, and can be constructed from an

 * XML serialization conforming to

 *

 * @see pathquery.dtd. The printSQL() method can be used to print a SQL

 *      serialization of the query.

 */

public class QuerySpecification extends DefaultHandler

{

    /** flag determining whether extended query terms are present */

    private boolean containsExtendedSQL = false;

    /** flag determining whether predicates are present */

    private boolean containsPredicates = false;

    /** Identifier for this query document */

    private String meta_file_id;

    /** Title of this query */

    private String queryTitle;

    /** List of document types to be returned using package back tracing */

    private Vector returnDocList;

    /** List of document types to be searched */

    private Vector filterDocList;

    /** List of fields to be returned in result set */

    private Vector returnFieldList;

    /** List of fields with "[" and "]" in result set. This is a subset of returnFieldList.

     *   If some of return fields have [,  those fields will be stored this vector (we have different query for those return fields */

    private Vector returnFieldListWithPredicates;

    /** List of users owning documents to be searched */

    private Vector ownerList;

    /** The root query group that contains the recursive query constraints */

    private QueryGroup query = null;

    /** A string buffer to stored normalized query (Sometimes, the query have 

     * a value like "&", it will cause problem in html transform). So we need a

     * normalized query xml string.

     */

    private StringBuffer xml = new StringBuffer();

    // Query data structures used temporarily during XML parsing

    private Stack elementStack;

    private Stack queryStack;

    private String currentValue;

    private String currentPathexpr;

    private String parserName = null;

    private String accNumberSeparator = null;

    private boolean percentageSearch = false;

    private String userName = null;

    private static final String PUBLIC = "public";

    private String[] group = null;

    public static final String ATTRIBUTESYMBOL = "@";

    public static final char PREDICATE_START = '[';

    public static final char PREDICATE_END = ']';

    //private boolean hasAttributeReturnField = false;

    //private Hashtable attributeReturnList = new Hashtable();

    //private int countAttributeReturnField = 0;

    private StringBuffer textBuffer = new StringBuffer();

    private static Logger logMetacat = Logger.getLogger(QuerySpecification.class);

    /**

     * construct an instance of the QuerySpecification class

     *

     * @param queryspec

     *            the XML representation of the query (should conform to

     *            pathquery.dtd) as a Reader

     * @param parserName

     *            the fully qualified name of a Java Class implementing the

     *            org.xml.sax.XMLReader interface

     */

    public QuerySpecification(Reader queryspec, String parserName,

            String accNumberSeparator) throws IOException

    {

        super();

        // Initialize the class variables

        returnDocList = new Vector();

        filterDocList = new Vector();

        elementStack = new Stack();

        queryStack = new Stack();

        returnFieldList = new Vector();

        returnFieldListWithPredicates = new Vector();

        ownerList = new Vector();

        this.parserName = parserName;

        this.accNumberSeparator = accNumberSeparator;

        // Initialize the parser and read the queryspec

        XMLReader parser = initializeParser();

        if (parser == null) {

            System.err.println("SAX parser not instantiated properly.");

        }

        try {

            parser.parse(new InputSource(queryspec));

        } catch (SAXException e) {

            System.err.println("error parsing data in "

                    + "QuerySpecification.QuerySpecification");

            System.err.println(e.getMessage());

        }

    }

    /**

     * construct an instance of the QuerySpecification class

     *

     * @param queryspec

     *            the XML representation of the query (should conform to

     *            pathquery.dtd) as a String

     * @param parserName

     *            the fully qualified name of a Java Class implementing the

     *            org.xml.sax.Parser interface

     */

    public QuerySpecification(String queryspec, String parserName,

            String accNumberSeparator) throws IOException

    {

        this(new StringReader(queryspec), parserName, accNumberSeparator);

    }

    /**

     * construct an instance of the QuerySpecification class which don't need

     * to parser a xml document

     *

     * @param accNumberSeparator

     *            the separator between doc version

     */

    public QuerySpecification(String accNumberSeparator) throws IOException

    {

        // Initialize the class variables

        returnDocList = new Vector();

        filterDocList = new Vector();

        elementStack = new Stack();

        queryStack = new Stack();

        returnFieldList = new Vector();

        returnFieldListWithPredicates = new Vector();

        ownerList = new Vector();

        this.accNumberSeparator = accNumberSeparator;

    }

    /**

     * Method to set user name

     *

     * @param myName

     *            the user name

     */

    public void setUserName(String myName)

    {

        //to lower case

        if (myName != null) {

            this.userName = myName.toLowerCase();

        } else {

            this.userName = myName;

        }

    }

    /**

     * Method to set user group

     *

     * @param myGroup

     *            the user group

     */

    public void setGroup(String[] myGroup)

    {

        this.group = myGroup;

    }

    /**

     * Method to indicate this query is a percentage search

     */

    public boolean isPercentageSearch()

    {

        return percentageSearch;

    }

    /*

     * Method to get owner query. If it is owner it has all permission

     */

    private String createOwerQuery()

    {

        String ownerQuery = null;

        //if user is public, we don't need to run owner query

        if (userName != null && !userName.equalsIgnoreCase(PUBLIC))

        {

	        ownerQuery = "SELECT docid FROM xml_documents WHERE ";

	        if (userName != null && !userName.equals("")) {

	            ownerQuery = ownerQuery + "lower(user_owner) ='" + userName + "'";

	        }

        }

        logMetacat.info("OwnerQuery: " + ownerQuery);

        return ownerQuery;

    }

    /*

     * Method to create query for xml_access, this part is to get docid list

     * which have a allow rule for a given user

     */

    private String createAllowRuleQuery()

    {

        String allowQuery = null;

        String allowString = constructAllowString();

        allowQuery = "SELECT docid from xml_access WHERE( " + allowString;

        allowQuery = allowQuery + ")";

        logMetacat.info("allow query is: " + allowQuery);

        return allowQuery;

    }

    /* Method to construct a allow rule string */

    private String constructAllowString()

    {

        String allowQuery = "";

       // add public

        allowQuery = "(lower(principal_name) = '" + PUBLIC

                + "'";

        // add user name

        if (userName != null && !userName.equals("") && !userName.equalsIgnoreCase(PUBLIC)) {

            allowQuery = allowQuery + "OR lower(principal_name) = '" + userName +"'";

        }

        // add  group

        if (group != null) {

            for (int i = 0; i < group.length; i++) {

                String groupUint = group[i];

                if (groupUint != null && !groupUint.equals("")) {

                    groupUint = groupUint.toLowerCase();

                    allowQuery = allowQuery + " OR lower(principal_name) = '"

                            + groupUint + "'";

                }//if

            }//for

        }//if

        // add allow rule

        allowQuery = allowQuery + ") AND perm_type = 'allow'" + " AND permission > 3";

        logMetacat.info("allow string is: " + allowQuery);

        return allowQuery;

    }

    /*

     * Method to create query for xml_access, this part is to get docid list

     * which have a deny rule and perm_order is allowFirst for a given user.

     * This means the user will be denied to read

     */

    private String createDenyRuleQuery()

    {

        String denyQuery = null;

        String denyString = constructDenyString();

        denyQuery = "SELECT docid from xml_access WHERE( " + denyString;

        denyQuery = denyQuery + ") ";

        logMetacat.info("denyquery is: " + denyQuery);

        return denyQuery;

    }

    /* Construct deny string */

    private String constructDenyString()

    {

        String denyQuery = "";

        // add public

        denyQuery = "(lower(principal_name) = '" + PUBLIC

                 + "'";

         // add user name

         if (userName != null && !userName.equals("") && !userName.equalsIgnoreCase(PUBLIC)) {

        	 denyQuery = denyQuery + "OR lower(principal_name) = '" + userName +"'";

         }

         // add  groups

         if (group != null) {

             for (int i = 0; i < group.length; i++) {

                 String groupUint = group[i];

                 if (groupUint != null && !groupUint.equals("")) {

                     groupUint = groupUint.toLowerCase();

                     denyQuery = denyQuery + " OR lower(principal_name) = '"

                             + groupUint + "'";

                 }//if

             }//for

         }//if

         // add deny rules

         denyQuery = denyQuery + ") AND perm_type = 'deny'" +  " AND perm_order ='allowFirst'" +" AND permission > 3";

         logMetacat.info("allow string is: " + denyQuery);

         return denyQuery;

    }

    /**

     * Method to append a access control query to SQL. So in DBQuery class, we

     * can get docid from both user specified query and access control query.

     * We don't need to checking permission after we get the doclist. It will

     * be good to performance

     *

     */

    public String getAccessQuery()

    {

        String accessQuery = null;

        String onwer = createOwerQuery();

        String allow = createAllowRuleQuery();

        String deny = createDenyRuleQuery();

        //logMetacat.warn("onwer " +onwer);

        //logMetacat.warn("allow "+allow);

        //logMetacat.warn("deny "+deny);

        if (onwer != null)

        {

          accessQuery = " AND (docid IN(" + onwer + ")";

          accessQuery = accessQuery + " OR (docid IN (" + allow + ")"

                + " AND docid NOT IN (" + deny + ")))";

        }

        else

        {

        	accessQuery = " AND (docid IN (" + allow + ")"

                + " AND docid NOT IN (" + deny + "))";

        }

        logMetacat.warn("accessquery is: " + accessQuery);

        return accessQuery;

    }

    /**

     * Returns true if the parsed query contains and extended xml query (i.e.

     * there is at least one <returnfield> in the pathquery document)

     */

    public boolean containsExtendedSQL()

    {

        if (containsExtendedSQL) {

            return true;

        } else {

            return false;

        }

    }

    /**

     * Accessor method to return the identifier of this Query

     */

    public String getIdentifier()

    {

        return meta_file_id;

    }

    /**

     * method to set the identifier of this query

     */

    public void setIdentifier(String id)

    {

        this.meta_file_id = id;

    }

    /**

     * Accessor method to return the title of this Query

     */

    public String getQueryTitle()

    {

        return queryTitle;

    }

    /**

     * method to set the title of this query

     */

    public void setQueryTitle(String title)

    {

        this.queryTitle = title;

    }

    /**

     * Accessor method to return a vector of the return document types as

     * defined in the <returndoctype> tag in the pathquery dtd.

     */

    public Vector getReturnDocList()

    {

        return this.returnDocList;

    }

    /**

     * method to set the list of return docs of this query

     */

    public void setReturnDocList(Vector returnDocList)

    {

        this.returnDocList = returnDocList;

    }

    /**

     * Accessor method to return a vector of the filter doc types as defined in

     * the <filterdoctype> tag in the pathquery dtd.

     */

    public Vector getFilterDocList()

    {

        return this.filterDocList;

    }

    /**

     * method to set the list of filter docs of this query

     */

    public void setFilterDocList(Vector filterDocList)

    {

        this.filterDocList = filterDocList;

    }

    /**

     * Accessor method to return a vector of the extended return fields as

     * defined in the <returnfield> tag in the pathquery dtd.

     */

    public Vector getReturnFieldList()

    {

        return this.returnFieldList;

    }

    /**

     * method to set the list of fields to be returned by this query

     */

    public void setReturnFieldList(Vector returnFieldList)

    {

        this.returnFieldList = returnFieldList;

    }

    /**

     * Accessor method to return a vector of the owner fields as defined in the

     * <owner> tag in the pathquery dtd.

     */

    public Vector getOwnerList()

    {

        return this.ownerList;

    }

    /**

     * method to set the list of owners used to constrain this query

     */

    public void setOwnerList(Vector ownerList)

    {

        this.ownerList = ownerList;

    }

    /**

     * get the QueryGroup used to express query constraints

     */

    public QueryGroup getQueryGroup()

    {

        return query;

    }

    /**

     * set the querygroup

     */

    public void setQueryGroup(QueryGroup group)

    {

        query = group;

    }

    /**

     * set if this query sepcification has extendQuery(has return doc type or

     * not)

     */

    public void setContainsExtenedSQL(boolean hasExtenedQuery)

    {

        containsExtendedSQL = hasExtenedQuery;

    }

    /**

     * Set up the SAX parser for reading the XML serialized query

     */

    private XMLReader initializeParser()

    {

        XMLReader parser = null;

        // Set up the SAX document handlers for parsing

        try {

            // Get an instance of the parser

            parser = XMLReaderFactory.createXMLReader(parserName);

            // Set the ContentHandler to this instance

            parser.setContentHandler(this);

            // Set the error Handler to this instance

            parser.setErrorHandler(this);

        } catch (Exception e) {

            System.err.println("Error in QuerySpcecification.initializeParser "

                    + e.toString());

        }

        return parser;

    }

    /**

     * callback method used by the SAX Parser when the start tag of an element

     * is detected. Used in this context to parse and store the query

     * information in class variables.

     */

    public void startElement(String uri, String localName, String qName,

            Attributes atts) throws SAXException

    {

        logMetacat.debug("start at startElement "+localName);

        BasicNode currentNode = new BasicNode(localName);

        //write element name into xml buffer.

        xml.append("<");

        xml.append(localName);

        // add attributes to BasicNode here

        if (atts != null) {

            int len = atts.getLength();

            for (int i = 0; i < len; i++) {

                currentNode

                        .setAttribute(atts.getLocalName(i), atts.getValue(i));

                xml.append(" ");

                xml.append(atts.getLocalName(i));

                xml.append("=\"");

                xml.append(atts.getValue(i));

                xml.append("\"");

            }

        }

        xml.append(">");

        elementStack.push(currentNode);

        if (currentNode.getTagName().equals("querygroup")) {

            QueryGroup currentGroup = new QueryGroup(currentNode

                    .getAttribute("operator"));

            if (query == null) {

                query = currentGroup;

            } else {

                QueryGroup parentGroup = (QueryGroup) queryStack.peek();

                parentGroup.addChild(currentGroup);

            }

            queryStack.push(currentGroup);

        }

        logMetacat.debug("end in startElement "+localName);

    }

    /**

     * callback method used by the SAX Parser when the end tag of an element is

     * detected. Used in this context to parse and store the query information

     * in class variables.

     */

    public void endElement(String uri, String localName, String qName)

            throws SAXException

    {

    	 logMetacat.debug("start in endElement "+localName);

        BasicNode leaving = (BasicNode) elementStack.pop();

        if (leaving.getTagName().equals("queryterm")) {

            boolean isCaseSensitive = (new Boolean(leaving

                    .getAttribute("casesensitive"))).booleanValue();

            QueryTerm currentTerm = null;

            if (currentPathexpr == null) {

                currentTerm = new QueryTerm(isCaseSensitive, leaving

                        .getAttribute("searchmode"), currentValue);

            } else {

                currentTerm = new QueryTerm(isCaseSensitive, leaving

                        .getAttribute("searchmode"), currentValue,

                        currentPathexpr);

            }

            QueryGroup currentGroup = (QueryGroup) queryStack.peek();

            currentGroup.addChild(currentTerm);

            currentValue = null;

            currentPathexpr = null;

        } else if (leaving.getTagName().equals("querygroup")) {

            QueryGroup leavingGroup = (QueryGroup) queryStack.pop();

        } else if (leaving.getTagName().equals("meta_file_id")) {

              meta_file_id = textBuffer.toString().trim();

        } else if (leaving.getTagName().equals("querytitle")) {

              queryTitle = textBuffer.toString().trim();

        } else if (leaving.getTagName().equals("value")) {

              currentValue = textBuffer.toString().trim();

              currentValue = MetacatUtil.normalize(currentValue);

        } else if (leaving.getTagName().equals("pathexpr")) {

              currentPathexpr = textBuffer.toString().trim();

        } else if (leaving.getTagName().equals("returndoctype")) {

              returnDocList.add(textBuffer.toString().trim());

        } else if (leaving.getTagName().equals("filterdoctype")) {

              filterDocList.add(textBuffer.toString().trim());

        } else if (leaving.getTagName().equals("returnfield")) {

              handleReturnField(textBuffer.toString().trim());

        } else if (leaving.getTagName().equals("filterdoctype")) {

              filterDocList.add(textBuffer.toString().trim());

        } else if (leaving.getTagName().equals("owner")) {

              ownerList.add(textBuffer.toString().trim());

        }

        String normalizedXML = textBuffer.toString().trim();

        logMetacat.debug("================before normailze "+normalizedXML);

        normalizedXML =  MetacatUtil.normalize(normalizedXML);

        logMetacat.debug("================after normailze "+normalizedXML);

        xml.append(normalizedXML);

        xml.append("</");

        xml.append(localName);

        xml.append(">");

        //rest textBuffer

        textBuffer = new StringBuffer();

    }

    /**

     * Gets normailized query string in xml format, which can be transformed

     * to html

     */

    public String getNormalizedXMLQuery()

    {

    	//System.out.println("normailized xml \n"+xml.toString());

    	return xml.toString();

    }

    /**

     * callback method used by the SAX Parser when the text sequences of an xml

     * stream are detected. Used in this context to parse and store the query

     * information in class variables.

     */

    public void characters(char ch[], int start, int length)

    {

      // buffer all text nodes for same element. This is for text was splited

      // into different nodes

      String text = new String(ch, start, length);

      logMetacat.debug("the text in characters "+text);

      textBuffer.append(text);

    }

   /**

    * Method to handle return field. It will be callied in ecogrid part

    * @param inputString

    */

    public void handleReturnField(String inputString)

    {

        int attributePos = inputString.indexOf(ATTRIBUTESYMBOL);

        int predicateStart = -1;

        int predicateEnd;

        boolean hasPredicate = false;

        while (true)

        {

            predicateStart = inputString.indexOf(PREDICATE_START, predicateStart + 1);

            if (attributePos == -1)

                break;

            if (predicateStart == -1)

                break;

            hasPredicate = true;

            if (attributePos < predicateStart)

                break;

            predicateEnd = inputString.indexOf(PREDICATE_END, predicateStart);

            if (predicateEnd == -1)

            {

                logMetacat.warn("handleReturnField(): ");

                logMetacat.warn("    Invalid path: " + inputString);

                return;

            }

            while (attributePos < predicateEnd)

            {

                attributePos = inputString.indexOf(ATTRIBUTESYMBOL, attributePos + 1);

                if (attributePos == -1)

                    break;

            }

        }

        if (hasPredicate)

        {

            containsPredicates = true;

            returnFieldListWithPredicates.add(inputString);

        }

        containsExtendedSQL = true;

        // no attribute value will be returned

        logMetacat.info("QuerySpecification.handleReturnField(): " );

        logMetacat.info("  there are no attributes in the XPATH statement" );

        returnFieldList.add(inputString);

    }

    /**

     * create a SQL serialization of the query that this instance represents

     */

    public String printSQL(boolean useXMLIndex)

    {

        StringBuffer self = new StringBuffer();

        StringBuffer queryString = new StringBuffer();

        queryString.append("SELECT docid,docname,doctype,");

        queryString.append("date_created, date_updated, rev ");

        queryString.append("FROM xml_documents WHERE");

        // Get the query from the QueryGroup and check

        // if no query has been returned

        String queryFromQueryGroup;

        if (query != null) {

        	queryFromQueryGroup = query.printSQL(useXMLIndex);

        } else {

        	queryFromQueryGroup = "";

        }

        logMetacat.info("Query from query in QuerySpec.printSQL: " 

        		+ queryFromQueryGroup);

        if(!queryFromQueryGroup.trim().equals("")){

            self.append(" docid IN (");

            self.append(queryFromQueryGroup);

            self.append(") ");

        }

        // Add SQL to filter for doctypes requested in the query

        // This is an implicit OR for the list of doctypes. Only doctypes in

        // this

        // list will be searched if the tag is present

        if (!filterDocList.isEmpty()) {

            boolean firstdoctype = true;

            boolean emptyString = true;

            if(!self.toString().equals("")){

                self.append(" AND (");

                emptyString = false;

            }

            Enumeration en = filterDocList.elements();

            while (en.hasMoreElements()) {

                String currentDoctype = (String) en.nextElement();

                if (firstdoctype) {

                    firstdoctype = false;

                    self.append(" doctype = '" + currentDoctype + "'");

                } else {

                    self.append(" OR doctype = '" + currentDoctype + "'");

                }

            }

            if(!emptyString){

                self.append(") ");

            }

        }

        // Add SQL to filter for owners requested in the query

        // This is an implicit OR for the list of owners

        if (!ownerList.isEmpty()) {

            boolean first = true;

            boolean emptyString = true;

            if(!self.toString().equals("")){

                self.append(" AND (");

                emptyString = false;

            }

            Enumeration en = ownerList.elements();

            while (en.hasMoreElements()) {

                String current = (String) en.nextElement();

                if (current != null) {

                    current = current.toLowerCase();

                }

                if (first) {

                    first = false;

                    self.append(" lower(user_owner) = '" + current + "'");

                } else {

                    self.append(" OR lower(user_owner) = '" + current + "'");

                }

            }

            if(!emptyString){

                self.append(") ");

            }

        }

        // if there is only one percentage search item, this query is a

        // percentage

        // search query

        logMetacat.info("percentage number: "

                + query.getPercentageSymbolCount());

        if (query.getPercentageSymbolCount() == 1) {

            logMetacat.info("It is a percentage search");

            percentageSearch = true;

        }

        queryString.append(self.toString());

        return queryString.toString();

    }

    /**

     * This method prints sql based upon the <returnfield> tag in the

     * pathquery document. This allows for customization of the returned fields.

     * If the boolean useXMLIndex paramter is false, it uses a recursive query on

     * xml_nodes to find the fields to be included by their path expression, and

     * avoids the use of the xml_index table.

     *

     * @param doclist the list of document ids to search

     * @param unaccessableNodePair the node pairs (start id and end id) which

     *            this user should not access

     * @param useXMLIndex a boolean flag indicating whether to search using

     *            xml_index

     */

    public String printExtendedSQL(String doclist, boolean useXMLIndex)

    {

        if (useXMLIndex && !containsPredicates)

        {

            return printExtendedSQL(doclist);

        }

        else

        {

            StringBuffer self = new StringBuffer();

            boolean firstfield = true;

            // first part comes from fields without  predicates 

            String queryFromWithoutPrecidates = printExtendedSQL(doclist);

             if (queryFromWithoutPrecidates != null)

             {

            	 // it has return fields without predicate

            	 self.append(queryFromWithoutPrecidates);

            	 firstfield = false;

             }

            //put the returnfields into the query

            //the for loop allows for multiple fields

            for (int i = 0; i <   returnFieldListWithPredicates.size(); i++)

            {

                if (firstfield)

                {

                    firstfield = false;

                }

                else

                {

                    self.append(" UNION ");

                }

                String path  = (String)  returnFieldListWithPredicates.elementAt(i);

                self.append("select xml_nodes.docid, ");

                self.append("'"+ path.replaceAll("'", "''") + "' as path, ");

                self.append("xml_nodes.nodedata, ");

                self.append("xml_nodes.parentnodeid, ");

                self.append("xml_nodes.nodetype ");

                //self.append("from xml_nodes, xml_documents ");

                self.append("from xml_nodes ");

                self.append("where ");

                self.append(QueryTerm.useNestedStatements(path));

                self.append(" AND xml_nodes.docid in (");

                self.append(doclist);

                if (returnFieldIsAttribute(path))

                {

                    self.append(")");

                }

                else

                {

                     self.append(") AND xml_nodes.nodetype = 'TEXT'");

                }

                //self.append(" AND xml_nodes.rootnodeid = xml_documents.rootnodeid");

                //addAccessRestrictionSQL(unaccessableNodePair, self);

            }

            return self.toString();

        }

    }

    /*

     * Determines the returnfield is an attribute of not. 

     * For given returnfield, this programm will cut the part of path after last slash.

     * If no slash in the path, the original string will be considered as last part.

     * If first character of last part is @ it will retrun true. 

     */

    private boolean returnFieldIsAttribute(String path)

    {

    	boolean isAttribute = false;

    	if (path != null)

    	{

    	    int slashIndex = path.lastIndexOf("/");

    	    if (slashIndex !=-1)

    	    {

    	    	// if there is slash in the path, path should be replace by the last part

    	    	path = path.substring(slashIndex+1);

    	    }

    	    logMetacat.debug("In QuerySpecification.returnFieldIsAttribute method, final path is "+path);

    	    // if first of character of path is @, the path is attribute

    	    if (path.charAt(0) == '@')

    	    {

    	    	logMetacat.debug("it is attribute");

    	    	isAttribute = true;

    	    }

    	}

    	return isAttribute;

    }

    /**

     * This method prints sql based upon the <returnfield> tag in the

     * pathquery document. This allows for customization of the returned fields.

     * It uses the xml_index table and so assumes that this table has been

     * built.

     *

     * @param doclist the list of document ids to search

     * @param unaccessableNodePair the node pairs (start id and end id)

     *            which this user should not access