index.rb in sup-0.11

- old
+ new

@@ -1,7 +1,9 @@
-## Index interface, subclassed by Ferret indexer.
+ENV["XAPIAN_FLUSH_THRESHOLD"] = "1000"
 
+require 'xapian'
+require 'set'
 require 'fileutils'
 
 begin
   require 'chronic'
   $have_chronic = true
@@ -10,30 +12,48 @@
   $have_chronic = false
 end
 
 module Redwood
 
-class BaseIndex
+# This index implementation uses Xapian for searching and storage. It
+# tends to be slightly faster than Ferret for indexing and significantly faster
+# for searching due to precomputing thread membership.
+class Index
   include InteractiveLock
 
+  STEM_LANGUAGE = "english"
+  INDEX_VERSION = '2'
+
+  ## dates are converted to integers for xapian, and are used for document ids,
+  ## so we must ensure they're reasonably valid. this typically only affect
+  ## spam.
+  MIN_DATE = Time.at 0
+  MAX_DATE = Time.at(2**31-1)
+
+  HookManager.register "custom-search", <<EOS
+Executes before a string search is applied to the index,
+returning a new search string.
+Variables:
+  subs: The string being searched.
+EOS
+
   class LockError < StandardError
     def initialize h
       @h = h
     end
 
     def method_missing m; @h[m.to_s] end
   end
 
-  def is_a_deprecated_ferret_index?; false end
-
   include Singleton
 
   def initialize dir=BASE_DIR
     @dir = dir
     @lock = Lockfile.new lockfile, :retries => 0, :max_age => nil
     @sync_worker = nil
     @sync_queue = Queue.new
+    @index_mutex = Monitor.new
   end
 
   def lockfile; File.join @dir, "lock" end
 
   def lock
@@ -77,44 +97,64 @@
     SourceManager.save_sources
     save_index
   end
 
   def load_index
-    unimplemented
+    path = File.join(@dir, 'xapian')
+    if File.exists? path
+      @xapian = Xapian::WritableDatabase.new(path, Xapian::DB_OPEN)
+      db_version = @xapian.get_metadata 'version'
+      db_version = '0' if db_version.empty?
+      if db_version == '1'
+        info "Upgrading index format 1 to 2"
+        @xapian.set_metadata 'version', INDEX_VERSION
+      elsif db_version != INDEX_VERSION
+        fail "This Sup version expects a v#{INDEX_VERSION} index, but you have an existing v#{db_version} index. Please downgrade to your previous version and dump your labels before upgrading to this version (then run sup-sync --restore)."
+      end
+    else
+      @xapian = Xapian::WritableDatabase.new(path, Xapian::DB_CREATE)
+      @xapian.set_metadata 'version', INDEX_VERSION
+    end
+    @enquire = Xapian::Enquire.new @xapian
+    @enquire.weighting_scheme = Xapian::BoolWeight.new
+    @enquire.docid_order = Xapian::Enquire::ASCENDING
   end
 
-  def add_message m; unimplemented end
-  def update_message m; unimplemented end
-  def update_message_state m; unimplemented end
+  def add_message m; sync_message m, true end
+  def update_message m; sync_message m, true end
+  def update_message_state m; sync_message m, false end
 
-  def save_index fn
-    unimplemented
+  def save_index
+    info "Flushing Xapian updates to disk. This may take a while..."
+    @xapian.flush
   end
 
   def contains_id? id
-    unimplemented
+    synchronize { find_docid(id) && true }
   end
 
   def contains? m; contains_id? m.id end
 
   def size
-    unimplemented
+    synchronize { @xapian.doccount }
   end
 
   def empty?; size == 0 end
 
   ## Yields a message-id and message-building lambda for each
   ## message that matches the given query, in descending date order.
   ## You should probably not call this on a block that doesn't break
   ## rather quickly because the results can be very large.
   def each_id_by_date query={}
-    unimplemented
+    each_id(query) { |id| yield id, lambda { build_message id } }
   end
 
   ## Return the number of matches for query in the index
   def num_results_for query={}
-    unimplemented
+    xapian_query = build_xapian_query query
+    matchset = run_query xapian_query, 0, 0, 100
+    matchset.matches_estimated
   end
 
   ## yield all messages in the thread containing 'm' by repeatedly
   ## querying the index. yields pairs of message ids and
   ## message-building lambdas, so that building an unwanted message
@@ -122,61 +162,238 @@
   ##
   ## only two options, :limit and :skip_killed. if :skip_killed is
   ## true, stops loading any thread if a message with a :killed flag
   ## is found.
   def each_message_in_thread_for m, opts={}
-    unimplemented
+    # TODO thread by subject
+    return unless doc = find_doc(m.id)
+    queue = doc.value(THREAD_VALUENO).split(',')
+    msgids = [m.id]
+    seen_threads = Set.new
+    seen_messages = Set.new [m.id]
+    while not queue.empty?
+      thread_id = queue.pop
+      next if seen_threads.member? thread_id
+      return false if opts[:skip_killed] && thread_killed?(thread_id)
+      seen_threads << thread_id
+      docs = term_docids(mkterm(:thread, thread_id)).map { |x| @xapian.document x }
+      docs.each do |doc|
+        msgid = doc.value MSGID_VALUENO
+        next if seen_messages.member? msgid
+        msgids << msgid
+        seen_messages << msgid
+        queue.concat doc.value(THREAD_VALUENO).split(',')
+      end
+    end
+    msgids.each { |id| yield id, lambda { build_message id } }
+    true
   end
 
   ## Load message with the given message-id from the index
   def build_message id
-    unimplemented
+    entry = synchronize { get_entry id }
+    return unless entry
+
+    source = SourceManager[entry[:source_id]]
+    raise "invalid source #{entry[:source_id]}" unless source
+
+    m = Message.new :source => source, :source_info => entry[:source_info],
+                    :labels => entry[:labels], :snippet => entry[:snippet]
+
+    mk_person = lambda { |x| Person.new(*x.reverse!) }
+    entry[:from] = mk_person[entry[:from]]
+    entry[:to].map!(&mk_person)
+    entry[:cc].map!(&mk_person)
+    entry[:bcc].map!(&mk_person)
+
+    m.load_from_index! entry
+    m
   end
 
   ## Delete message with the given message-id from the index
   def delete id
-    unimplemented
+    synchronize { @xapian.delete_document mkterm(:msgid, id) }
   end
 
   ## Given an array of email addresses, return an array of Person objects that
   ## have sent mail to or received mail from any of the given addresses.
-  def load_contacts email_addresses, h={}
-    unimplemented
+  def load_contacts email_addresses, opts={}
+    contacts = Set.new
+    num = opts[:num] || 20
+    each_id_by_date :participants => email_addresses do |id,b|
+      break if contacts.size >= num
+      m = b.call
+      ([m.from]+m.to+m.cc+m.bcc).compact.each { |p| contacts << [p.name, p.email] }
+    end
+    contacts.to_a.compact.map { |n,e| Person.new n, e }[0...num]
   end
 
   ## Yield each message-id matching query
+  EACH_ID_PAGE = 100
   def each_id query={}
-    unimplemented
+    offset = 0
+    page = EACH_ID_PAGE
+
+    xapian_query = build_xapian_query query
+    while true
+      ids = run_query_ids xapian_query, offset, (offset+page)
+      ids.each { |id| yield id }
+      break if ids.size < page
+      offset += page
+    end
   end
 
   ## Yield each message matching query
   def each_message query={}, &b
     each_id query do |id|
       yield build_message(id)
     end
   end
 
-  ## Implementation-specific optimization step
+  ## xapian-compact takes too long, so this is a no-op
+  ## until we think of something better
   def optimize
-    unimplemented
   end
 
   ## Return the id source of the source the message with the given message-id
   ## was synced from
   def source_for_id id
-    unimplemented
+    synchronize { get_entry(id)[:source_id] }
   end
 
   class ParseError < StandardError; end
 
   ## parse a query string from the user. returns a query object
   ## that can be passed to any index method with a 'query'
   ## argument.
   ##
   ## raises a ParseError if something went wrong.
   def parse_query s
-    unimplemented
+    query = {}
+
+    subs = HookManager.run("custom-search", :subs => s) || s
+    begin
+      subs = SearchManager.expand subs
+    rescue SearchManager::ExpansionError => e
+      raise ParseError, e.message
+    end
+    subs = subs.gsub(/\b(to|from):(\S+)\b/) do
+      field, value = $1, $2
+      email_field, name_field = %w(email name).map { |x| "#{field}_#{x}" }
+      if(p = ContactManager.contact_for(value))
+        "#{email_field}:#{p.email}"
+      elsif value == "me"
+        '(' + AccountManager.user_emails.map { |e| "#{email_field}:#{e}" }.join(' OR ') + ')'
+      else
+        "(#{email_field}:#{value} OR #{name_field}:#{value})"
+      end
+    end
+
+    ## if we see a label:deleted or a label:spam term anywhere in the query
+    ## string, we set the extra load_spam or load_deleted options to true.
+    ## bizarre? well, because the query allows arbitrary parenthesized boolean
+    ## expressions, without fully parsing the query, we can't tell whether
+    ## the user is explicitly directing us to search spam messages or not.
+    ## e.g. if the string is -(-(-(-(-label:spam)))), does the user want to
+    ## search spam messages or not?
+    ##
+    ## so, we rely on the fact that turning these extra options ON turns OFF
+    ## the adding of "-label:deleted" or "-label:spam" terms at the very
+    ## final stage of query processing. if the user wants to search spam
+    ## messages, not adding that is the right thing; if he doesn't want to
+    ## search spam messages, then not adding it won't have any effect.
+    query[:load_spam] = true if subs =~ /\blabel:spam\b/
+    query[:load_deleted] = true if subs =~ /\blabel:deleted\b/
+
+    ## gmail style "is" operator
+    subs = subs.gsub(/\b(is|has):(\S+)\b/) do
+      field, label = $1, $2
+      case label
+      when "read"
+        "-label:unread"
+      when "spam"
+        query[:load_spam] = true
+        "label:spam"
+      when "deleted"
+        query[:load_deleted] = true
+        "label:deleted"
+      else
+        "label:#{$2}"
+      end
+    end
+
+    ## gmail style attachments "filename" and "filetype" searches
+    subs = subs.gsub(/\b(filename|filetype):(\((.+?)\)\B|(\S+)\b)/) do
+      field, name = $1, ($3 || $4)
+      case field
+      when "filename"
+        debug "filename: translated #{field}:#{name} to attachment:\"#{name.downcase}\""
+        "attachment:\"#{name.downcase}\""
+      when "filetype"
+        debug "filetype: translated #{field}:#{name} to attachment_extension:#{name.downcase}"
+        "attachment_extension:#{name.downcase}"
+      end
+    end
+
+    if $have_chronic
+      lastdate = 2<<32 - 1
+      firstdate = 0
+      subs = subs.gsub(/\b(before|on|in|during|after):(\((.+?)\)\B|(\S+)\b)/) do
+        field, datestr = $1, ($3 || $4)
+        realdate = Chronic.parse datestr, :guess => false, :context => :past
+        if realdate
+          case field
+          when "after"
+            debug "chronic: translated #{field}:#{datestr} to #{realdate.end}"
+            "date:#{realdate.end.to_i}..#{lastdate}"
+          when "before"
+            debug "chronic: translated #{field}:#{datestr} to #{realdate.begin}"
+            "date:#{firstdate}..#{realdate.end.to_i}"
+          else
+            debug "chronic: translated #{field}:#{datestr} to #{realdate}"
+            "date:#{realdate.begin.to_i}..#{realdate.end.to_i}"
+          end
+        else
+          raise ParseError, "can't understand date #{datestr.inspect}"
+        end
+      end
+    end
+
+    ## limit:42 restrict the search to 42 results
+    subs = subs.gsub(/\blimit:(\S+)\b/) do
+      lim = $1
+      if lim =~ /^\d+$/
+        query[:limit] = lim.to_i
+        ''
+      else
+        raise ParseError, "non-numeric limit #{lim.inspect}"
+      end
+    end
+
+    debug "translated query: #{subs.inspect}"
+
+    qp = Xapian::QueryParser.new
+    qp.database = @xapian
+    qp.stemmer = Xapian::Stem.new(STEM_LANGUAGE)
+    qp.stemming_strategy = Xapian::QueryParser::STEM_SOME
+    qp.default_op = Xapian::Query::OP_AND
+    qp.add_valuerangeprocessor(Xapian::NumberValueRangeProcessor.new(DATE_VALUENO, 'date:', true))
+    NORMAL_PREFIX.each { |k,vs| vs.each { |v| qp.add_prefix k, v } }
+    BOOLEAN_PREFIX.each { |k,vs| vs.each { |v| qp.add_boolean_prefix k, v } }
+
+    begin
+      xapian_query = qp.parse_query(subs, Xapian::QueryParser::FLAG_PHRASE|Xapian::QueryParser::FLAG_BOOLEAN|Xapian::QueryParser::FLAG_LOVEHATE|Xapian::QueryParser::FLAG_WILDCARD)
+    rescue RuntimeError => e
+      raise ParseError, "xapian query parser error: #{e}"
+    end
+
+    debug "parsed xapian query: #{xapian_query.description}"
+
+    raise ParseError if xapian_query.nil? or xapian_query.empty?
+    query[:qobj] = xapian_query
+    query[:text] = s
+    query
   end
 
   def save_thread t
     t.each_dirty_message do |m|
       if @sync_worker
@@ -205,36 +422,334 @@
       update_message_state m
       # Necessary to keep Xapian calls from lagging the UI too much.
       sleep 0.03
     end
   end
-end
 
-## just to make the backtraces even more insane, here we engage in yet more
-## method_missing metaprogramming so that Index.init(index_type_name) will
-## magically make Index act like the correct Index class.
-class Index
-  def self.init type=nil
-    ## determine the index type from the many possible ways of setting it
-    type = (type == "auto" ? nil : type) ||
-      ENV['SUP_INDEX'] ||
-      $config[:index] ||
-      (File.exist?(File.join(BASE_DIR, "xapian")) && "xapian") || ## PRIORITIZE THIS
-      (File.exist?(File.join(BASE_DIR, "ferret")) && "ferret") || ## deprioritize this
-      DEFAULT_NEW_INDEX_TYPE
+  private
+
+  # Stemmed
+  NORMAL_PREFIX = {
+    'subject' => 'S',
+    'body' => 'B',
+    'from_name' => 'FN',
+    'to_name' => 'TN',
+    'name' => %w(FN TN),
+    'attachment' => 'A',
+    'email_text' => 'E',
+    '' => %w(S B FN TN A E),
+  }
+
+  # Unstemmed
+  BOOLEAN_PREFIX = {
+    'type' => 'K',
+    'from_email' => 'FE',
+    'to_email' => 'TE',
+    'email' => %w(FE TE),
+    'date' => 'D',
+    'label' => 'L',
+    'source_id' => 'I',
+    'attachment_extension' => 'O',
+    'msgid' => 'Q',
+    'id' => 'Q',
+    'thread' => 'H',
+    'ref' => 'R',
+  }
+
+  PREFIX = NORMAL_PREFIX.merge BOOLEAN_PREFIX
+
+  MSGID_VALUENO = 0
+  THREAD_VALUENO = 1
+  DATE_VALUENO = 2
+
+  MAX_TERM_LENGTH = 245
+
+  # Xapian can very efficiently sort in ascending docid order. Sup always wants
+  # to sort by descending date, so this method maps between them. In order to
+  # handle multiple messages per second, we use a logistic curve centered
+  # around MIDDLE_DATE so that the slope (docid/s) is greatest in this time
+  # period. A docid collision is not an error - the code will pick the next
+  # smallest unused one.
+  DOCID_SCALE = 2.0**32
+  TIME_SCALE = 2.0**27
+  MIDDLE_DATE = Time.gm(2011)
+  def assign_docid m, truncated_date
+    t = (truncated_date.to_i - MIDDLE_DATE.to_i).to_f
+    docid = (DOCID_SCALE - DOCID_SCALE/(Math::E**(-(t/TIME_SCALE)) + 1)).to_i
+    while docid > 0 and docid_exists? docid
+      docid -= 1
+    end
+    docid > 0 ? docid : nil
+  end
+
+  # XXX is there a better way?
+  def docid_exists? docid
     begin
-      require "sup/#{type}_index"
-      @klass = Redwood.const_get "#{type.capitalize}Index"
-      @obj = @klass.init
-    rescue LoadError, NameError => e
-      raise "unknown index type #{type.inspect}: #{e.message}"
+      @xapian.doclength docid
+      true
+    rescue RuntimeError #Xapian::DocNotFoundError
+      raise unless $!.message =~ /DocNotFoundError/
+      false
     end
-    debug "using #{type} index"
-    @obj
   end
 
-  def self.instance; @obj end
-  def self.method_missing m, *a, &b; @obj.send(m, *a, &b) end
-  def self.const_missing x; @obj.class.const_get(x) end
+  def term_docids term
+    @xapian.postlist(term).map { |x| x.docid }
+  end
+
+  def find_docid id
+    docids = term_docids(mkterm(:msgid,id))
+    fail unless docids.size <= 1
+    docids.first
+  end
+
+  def find_doc id
+    return unless docid = find_docid(id)
+    @xapian.document docid
+  end
+
+  def get_id docid
+    return unless doc = @xapian.document(docid)
+    doc.value MSGID_VALUENO
+  end
+
+  def get_entry id
+    return unless doc = find_doc(id)
+    Marshal.load doc.data
+  end
+
+  def thread_killed? thread_id
+    not run_query(Q.new(Q::OP_AND, mkterm(:thread, thread_id), mkterm(:label, :Killed)), 0, 1).empty?
+  end
+
+  def synchronize &b
+    @index_mutex.synchronize &b
+  end
+
+  def run_query xapian_query, offset, limit, checkatleast=0
+    synchronize do
+      @enquire.query = xapian_query
+      @enquire.mset(offset, limit-offset, checkatleast)
+    end
+  end
+
+  def run_query_ids xapian_query, offset, limit
+    matchset = run_query xapian_query, offset, limit
+    matchset.matches.map { |r| r.document.value MSGID_VALUENO }
+  end
+
+  Q = Xapian::Query
+  def build_xapian_query opts
+    labels = ([opts[:label]] + (opts[:labels] || [])).compact
+    neglabels = [:spam, :deleted, :killed].reject { |l| (labels.include? l) || opts.member?("load_#{l}".intern) }
+    pos_terms, neg_terms = [], []
+
+    pos_terms << mkterm(:type, 'mail')
+    pos_terms.concat(labels.map { |l| mkterm(:label,l) })
+    pos_terms << opts[:qobj] if opts[:qobj]
+    pos_terms << mkterm(:source_id, opts[:source_id]) if opts[:source_id]
+
+    if opts[:participants]
+      participant_terms = opts[:participants].map { |p| [:from,:to].map { |d| mkterm(:email, d, (Redwood::Person === p) ? p.email : p) } }.flatten
+      pos_terms << Q.new(Q::OP_OR, participant_terms)
+    end
+
+    neg_terms.concat(neglabels.map { |l| mkterm(:label,l) })
+
+    pos_query = Q.new(Q::OP_AND, pos_terms)
+    neg_query = Q.new(Q::OP_OR, neg_terms)
+
+    if neg_query.empty?
+      pos_query
+    else
+      Q.new(Q::OP_AND_NOT, [pos_query, neg_query])
+    end
+  end
+
+  def sync_message m, overwrite
+    doc = synchronize { find_doc(m.id) }
+    existed = doc != nil
+    doc ||= Xapian::Document.new
+    do_index_static = overwrite || !existed
+    old_entry = !do_index_static && doc.entry
+    snippet = do_index_static ? m.snippet : old_entry[:snippet]
+
+    entry = {
+      :message_id => m.id,
+      :source_id => m.source.id,
+      :source_info => m.source_info,
+      :date => truncate_date(m.date),
+      :snippet => snippet,
+      :labels => m.labels.to_a,
+      :from => [m.from.email, m.from.name],
+      :to => m.to.map { |p| [p.email, p.name] },
+      :cc => m.cc.map { |p| [p.email, p.name] },
+      :bcc => m.bcc.map { |p| [p.email, p.name] },
+      :subject => m.subj,
+      :refs => m.refs.to_a,
+      :replytos => m.replytos.to_a,
+    }
+
+    if do_index_static
+      doc.clear_terms
+      doc.clear_values
+      index_message_static m, doc, entry
+    end
+
+    index_message_threading doc, entry, old_entry
+    index_message_labels doc, entry[:labels], (do_index_static ? [] : old_entry[:labels])
+    doc.entry = entry
+
+    synchronize do
+      unless docid = existed ? doc.docid : assign_docid(m, truncate_date(m.date))
+        # Could be triggered by spam
+        warn "docid underflow, dropping #{m.id.inspect}"
+        return
+      end
+      @xapian.replace_document docid, doc
+    end
+
+    m.labels.each { |l| LabelManager << l }
+    true
+  end
+
+  ## Index content that can't be changed by the user
+  def index_message_static m, doc, entry
+    # Person names are indexed with several prefixes
+    person_termer = lambda do |d|
+      lambda do |p|
+        doc.index_text p.name, PREFIX["#{d}_name"] if p.name
+        doc.index_text p.email, PREFIX['email_text']
+        doc.add_term mkterm(:email, d, p.email)
+      end
+    end
+
+    person_termer[:from][m.from] if m.from
+    (m.to+m.cc+m.bcc).each(&(person_termer[:to]))
+
+    # Full text search content
+    subject_text = m.indexable_subject
+    body_text = m.indexable_body
+    doc.index_text subject_text, PREFIX['subject']
+    doc.index_text body_text, PREFIX['body']
+    m.attachments.each { |a| doc.index_text a, PREFIX['attachment'] }
+
+    # Miscellaneous terms
+    doc.add_term mkterm(:date, m.date) if m.date
+    doc.add_term mkterm(:type, 'mail')
+    doc.add_term mkterm(:msgid, m.id)
+    doc.add_term mkterm(:source_id, m.source.id)
+    m.attachments.each do |a|
+      a =~ /\.(\w+)$/ or next
+      doc.add_term mkterm(:attachment_extension, $1)
+    end
+
+    # Date value for range queries
+    date_value = begin
+      Xapian.sortable_serialise m.date.to_i
+    rescue TypeError
+      Xapian.sortable_serialise 0
+    end
+
+    doc.add_value MSGID_VALUENO, m.id
+    doc.add_value DATE_VALUENO, date_value
+  end
+
+  def index_message_labels doc, new_labels, old_labels
+    return if new_labels == old_labels
+    added = new_labels.to_a - old_labels.to_a
+    removed = old_labels.to_a - new_labels.to_a
+    added.each { |t| doc.add_term mkterm(:label,t) }
+    removed.each { |t| doc.remove_term mkterm(:label,t) }
+  end
+
+  ## Assign a set of thread ids to the document. This is a hybrid of the runtime
+  ## search done by the Ferret index and the index-time union done by previous
+  ## versions of the Xapian index. We first find the thread ids of all messages
+  ## with a reference to or from us. If that set is empty, we use our own
+  ## message id. Otherwise, we use all the thread ids we previously found. In
+  ## the common case there's only one member in that set, but if we're the
+  ## missing link between multiple previously unrelated threads we can have
+  ## more. XapianIndex#each_message_in_thread_for follows the thread ids when
+  ## searching so the user sees a single unified thread.
+  def index_message_threading doc, entry, old_entry
+    return if old_entry && (entry[:refs] == old_entry[:refs]) && (entry[:replytos] == old_entry[:replytos])
+    children = term_docids(mkterm(:ref, entry[:message_id])).map { |docid| @xapian.document docid }
+    parent_ids = entry[:refs] + entry[:replytos]
+    parents = parent_ids.map { |id| find_doc id }.compact
+    thread_members = SavingHash.new { [] }
+    (children + parents).each do |doc2|
+      thread_ids = doc2.value(THREAD_VALUENO).split ','
+      thread_ids.each { |thread_id| thread_members[thread_id] << doc2 }
+    end
+    thread_ids = thread_members.empty? ? [entry[:message_id]] : thread_members.keys
+    thread_ids.each { |thread_id| doc.add_term mkterm(:thread, thread_id) }
+    parent_ids.each { |ref| doc.add_term mkterm(:ref, ref) }
+    doc.add_value THREAD_VALUENO, (thread_ids * ',')
+  end
+
+  def truncate_date date
+    if date < MIN_DATE
+      debug "warning: adjusting too-low date #{date} for indexing"
+      MIN_DATE
+    elsif date > MAX_DATE
+      debug "warning: adjusting too-high date #{date} for indexing"
+      MAX_DATE
+    else
+      date
+    end
+  end
+
+  # Construct a Xapian term
+  def mkterm type, *args
+    case type
+    when :label
+      PREFIX['label'] + args[0].to_s.downcase
+    when :type
+      PREFIX['type'] + args[0].to_s.downcase
+    when :date
+      PREFIX['date'] + args[0].getutc.strftime("%Y%m%d%H%M%S")
+    when :email
+      case args[0]
+      when :from then PREFIX['from_email']
+      when :to then PREFIX['to_email']
+      else raise "Invalid email term type #{args[0]}"
+      end + args[1].to_s.downcase
+    when :source_id
+      PREFIX['source_id'] + args[0].to_s.downcase
+    when :attachment_extension
+      PREFIX['attachment_extension'] + args[0].to_s.downcase
+    when :msgid, :ref, :thread
+      PREFIX[type.to_s] + args[0][0...(MAX_TERM_LENGTH-1)]
+    else
+      raise "Invalid term type #{type}"
+    end
+  end
 end
 
+end
+
+class Xapian::Document
+  def entry
+    Marshal.load data
+  end
+
+  def entry=(x)
+    self.data = Marshal.dump x
+  end
+
+  def index_text text, prefix, weight=1
+    term_generator = Xapian::TermGenerator.new
+    term_generator.stemmer = Xapian::Stem.new(Redwood::Index::STEM_LANGUAGE)
+    term_generator.document = self
+    term_generator.index_text text, weight, prefix
+  end
+
+  alias old_add_term add_term
+  def add_term term
+    if term.length <= Redwood::Index::MAX_TERM_LENGTH
+      old_add_term term, 0
+    else
+      warn "dropping excessively long term #{term}"
+    end
+  end
 end