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package lux;
import java.io.IOException;
import java.io.StringReader;
import java.util.Map;
import javax.xml.transform.stream.StreamSource;
import lux.exception.LuxException;
import lux.index.FieldName;
import lux.index.IndexConfiguration;
import lux.index.field.TinyBinaryField;
import lux.xml.tinybin.TinyBinary;
import net.sf.saxon.Configuration;
import net.sf.saxon.s9api.DocumentBuilder;
import net.sf.saxon.s9api.SaxonApiException;
import net.sf.saxon.s9api.XdmNode;
import net.sf.saxon.tree.tiny.TinyDocumentImpl;
import net.sf.saxon.tree.tiny.TinyTree;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.DocumentStoredFieldVisitor;
import org.apache.lucene.index.AtomicReaderContext;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.util.BytesRef;
import org.slf4j.LoggerFactory;
/**
* Reads, parses and caches XML documents from a Lucene index. Assigns Lucene
* docIDs as Saxon document numbers. This reader and its cache are intended to survive for a
* single query only, and is *not thread-safe*.
*/
public class CachingDocReader {
// the (inverse of the) portion of heap to allocate to each per-request document cache.
// This should really rely on the number of clients
private final static int CACHE_RATIO = 100;
private final NodeCache cache = new NodeCache(java.lang.Runtime.getRuntime().maxMemory() / CACHE_RATIO);
private final String xmlFieldName;
private final String uriFieldName;
private final DocumentBuilder builder;
private final Configuration config;
private int cacheHits = 0;
private int cacheMisses = 0;
private long buildTime = 0;
/**
* Create a CachingDocReader that will use the provided objects to read and
* parse XML documents.
*
* @param builder
* will be used to construct XML documents as XdmNodes
* @param config
* assigns the proper document ID to each constructed document
* @param indexConfig
* supplies the names of the xml storage and uri fields
*/
public CachingDocReader(DocumentBuilder builder, Configuration config, IndexConfiguration indexConfig) {
this.builder = builder;
this.config = config;
this.xmlFieldName = indexConfig.getFieldName(FieldName.XML_STORE);
this.uriFieldName = indexConfig.getFieldName(FieldName.URI);
}
/**
* Reads the document with the given relative id from an atomic reader.
* If cached, the cached copy is returned. Otherwise the document is read from the index.
* If the document does not exist in the index, or has been deleted, results are not
* well-defined: see {@link IndexReader}.
*
* @param leafDocID the relative docid of the document to read
* @param context an atomic Lucene index reader context (a leaf of the segmented index tree)
* @return the document, as a Saxon XdmNode
* @throws IOException if there is some sort of low-level problem with the index
* @throws LuxException if there is an error building the document that has been retrieved
*/
public XdmNode get(int leafDocID, AtomicReaderContext context) throws IOException {
long docID = leafDocID + context.docBase;
XdmNode node= cache.get(docID);
if (node != null) {
++cacheHits;
return node;
}
DocumentStoredFieldVisitor fieldSelector = new DocumentStoredFieldVisitor();
context.reader().document(leafDocID, fieldSelector);
Document document = fieldSelector.getDocument();
return getXdmNode(docID, document);
}
/**
* Reads the document with the given id. If cached, the cached copy is
* returned. Otherwise the document is read from the index. If the document
* does not exist in the index, or has been deleted, results are not
* well-defined: see {@link IndexReader}.
*
* @param docID the absolute docid of the document to read
* @param reader the Lucene index reader
* @return the document, as a Saxon XdmNode
* @throws IOException if there is some sort of low-level problem with the index
* @throws LuxException if there is an error building the document that has been retrieved
*/
public XdmNode get(int docID, IndexReader reader) throws IOException {
XdmNode node = cache.get(docID);
if (node != null) {
++cacheHits;
return node;
}
DocumentStoredFieldVisitor fieldSelector = new DocumentStoredFieldVisitor();
reader.document(docID, fieldSelector);
Document document = fieldSelector.getDocument();
return getXdmNode(docID, document);
}
/**
* @param docID
* @return a document from the cache, or null if no document matching the docID is in the cache
*/
public XdmNode get(long docID) {
return cache.get(docID);
}
private XdmNode getXdmNode(long docID, Document document) throws IOException {
String xml = document.get(xmlFieldName);
String uri = document.get(uriFieldName);
BytesRef binaryValue = document.getBinaryValue(xmlFieldName);
byte[] bytes;
if (binaryValue != null) {
bytes = binaryValue.bytes;
} else {
bytes = null;
}
XdmNode node = createXdmNode (docID, uri, xml, bytes);
document.removeField(xmlFieldName);
node.getUnderlyingNode().getDocumentRoot().setUserData (Document.class.getName(), document);
return node;
}
/**
* Either the xml or the bytes parameter carries the document contents. If the xml is non-null, it is assumed to be a serialized
* XML document, and is parsed. If the bytes is non-null and begins with a tinybin signature, it is interpreted as
* tiny binary. Otherwise, the bytes are treated as a binary (non-XML) document. If both xml and bytes are null, a
* warning is logged and an empty binary document created.
*
* @param docID The Solr/Lucene docid; or a shard/docid combo under Solr Cloud
* @param uri The uri path (no scheme) of the document to create
* @param xml The contents of the document, if an XML document
* @param bytes The contents of the document
* @return a new document made from the arguments
*/
public XdmNode createXdmNode (long docID, String uri, String xml, byte[] bytes) {
uri = "lux:/" + uri;
DocIDNumberAllocator docIdAllocator = (DocIDNumberAllocator) config.getDocumentNumberAllocator();
docIdAllocator.setNextDocID(docID);
long t0 = System.nanoTime();
XdmNode node = null;
if (xml == null) {
if (bytes == null) {
// This is a document without the expected fields, as will happen, eg if we just connect to
// some random database.
LoggerFactory.getLogger(CachingDocReader.class).warn ("Document {} has no XML content", docID);
bytes = new byte[0];
}
if (bytes.length > 4 && bytes[0] == 'T' && bytes[1] == 'I' && bytes[2] == 'N') {
// An XML document stored in tiny binary format
TinyBinary tb = new TinyBinary(bytes, TinyBinaryField.UTF8);
node = new XdmNode (tb.getTinyDocument(config));
} else {
xml = "";
}
}
if (node == null) {
StreamSource source = new StreamSource(new StringReader(xml));
source.setSystemId(uri);
try {
node = builder.build(source);
} catch (SaxonApiException e) {
// shouldn't normally happen since the document would generally have
// been parsed when indexed.
throw new LuxException(e);
}
}
// associate the bytes with the xml stub (for all non-XML content)
if (bytes != null && xml == null) {
((TinyDocumentImpl)node.getUnderlyingNode()).setUserData("_binaryDocument", bytes);
}
// doesn't seem to do what one might think:
// ((TinyDocumentImpl) node.getUnderlyingNode()).setBaseURI(uri);
((TinyDocumentImpl) node.getUnderlyingNode()).setSystemId(uri);
buildTime += (System.nanoTime() - t0);
cache.put(docID, node);
++cacheMisses;
return node;
}
/**
* @return the number of items retrieved from the cache
*/
public int getCacheHits() {
return cacheHits;
}
/**
* @return the number of items retrieved and added to the cache
*/
public int getCacheMisses() {
return cacheMisses;
}
/**
* @return the total time spent building documents (in nanoseconds). This
* includes time spent parsing and constructing a Saxon
* NodeInfo/XdmNode.
*/
public long getBuildTime() {
return buildTime;
}
/**
* Clears all cached documents.
*/
public void clear() {
cache.clear();
}
static class NodeCache extends java.util.LinkedHashMap {
private long bytes;
private final long maxbytes;
public NodeCache (long maxbytes) {
super((int) ((maxbytes / 100) * 4 / 3 + 1), 0.75f, true);
this.maxbytes = maxbytes;
this.bytes = 0;
}
@Override
public XdmNode put (Long key, XdmNode value) {
bytes += calculateSize (value);
return super.put(key, value);
}
@Override
protected boolean removeEldestEntry(Map.Entry eldest) {
while (bytes > maxbytes) {
remove(eldest.getKey());
bytes -= calculateSize (eldest.getValue());
for (Map.Entry entry : entrySet()) {
// get the next eldest
eldest = entry;
break;
}
}
return false;
}
/**
* @param value a document whose size is to be calculated
* @return the size of a TinyBinary representation of the document, which should be pretty close to the actual
* heap size used.
*/
private long calculateSize(XdmNode value) {
TinyTree tree = ((TinyDocumentImpl)value.getUnderlyingNode()).getTree();
int nodeCount = tree.getNumberOfNodes();
int attCount = tree.getNumberOfAttributes();
int nsCount = tree.getNumberOfNamespaces();
byte[] binary = (byte[]) ((TinyDocumentImpl)value.getUnderlyingNode()).getUserData("_binaryDocument");
int binSize = binary == null ? 0 : binary.length;
// gross estimate of the number of string pointers
// Note: we don't count the size of the names in the name pool, on the assumption they will be shared
// by a lot of documents.
int stringLen = 12 + 2 * nodeCount + 2 * attCount + 2 * nsCount;
// actually count the lengths of all the attributes
CharSequence[] attValueArray = tree.getAttributeValueArray();
for (int i = 0; i < attCount; i++) {
stringLen += attValueArray[i].length();
}
return 36
+ binSize
+ nodeCount * 19
+ attCount * 8
+ nsCount * 8
+ tree.getCharacterBuffer().length() * 2
+ (tree.getCommentBuffer() == null ? 0 : tree.getCommentBuffer().length() * 2)
+ stringLen;
}
}
}
/*
* This Source Code Form is subject to the terms of the Mozilla Public License,
* v. 2.0. If a copy of the MPL was not distributed with this file, You can
* obtain one at http://mozilla.org/MPL/2.0/.
*/
