diff --git a/CHANGES.txt b/CHANGES.txt
index ea906fba604..c4932d2b2b9 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -139,6 +139,10 @@ New Features
 26. SOLR-334L Pluggable query parsers.  Allows specification of query
     type and arguments as a prefix on a query string. (yonik)
 
+27. SOLR-351L External Value Source.  An external file may be used
+     to specify the values of a field, currently usable as
+     a ValueSource in a FunctionQuery. (yonik)
+
 Changes in runtime behavior
 
 Optimizations
diff --git a/src/java/org/apache/solr/schema/ExternalFileField.java b/src/java/org/apache/solr/schema/ExternalFileField.java
new file mode 100755
index 00000000000..59c31426b08
--- /dev/null
+++ b/src/java/org/apache/solr/schema/ExternalFileField.java
@@ -0,0 +1,98 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.solr.schema;
+
+import org.apache.lucene.search.SortField;
+import org.apache.lucene.document.Fieldable;
+import org.apache.solr.search.function.ValueSource;
+import org.apache.solr.search.function.FloatFieldSource;
+import org.apache.solr.search.function.FileFloatSource;
+import org.apache.solr.search.QParser;
+import org.apache.solr.request.XMLWriter;
+import org.apache.solr.request.TextResponseWriter;
+import org.apache.solr.common.SolrException;
+
+import java.util.Map;
+import java.io.IOException;
+
+/** Get values from an external file instead of the index.
+ *
+ * <p/><code>keyField</code> will normally be the unique key field, but it doesn't have to be.
+ * <ul><li> It's OK to have a keyField value that can't be found in the index</li>
+ * <li>It's OK to have some documents without a keyField in the file (defVal is used as the default)</li>
+ * <li>It's OK for a keyField value to point to multiple documents (no uniqueness requirement)</li>
+ * </ul>
+ * <code>valType</code> is a reference to another fieldType to define the value type of this field (must currently be FloatField (float))
+ *
+ * The format of the external file is simply newline separated keyFieldValue=floatValue.
+ * <br/>Example:
+ * <br/><code>doc33=1.414</code>
+ * <br/><code>doc34=3.14159</code>
+ * <br/><code>doc40=42</code>
+ *
+ * <p/>Solr looks for the external file in the index directory under the name of
+ * external_&lt;fieldname&gt; or external_&lt;fieldname&gt;.*
+ *
+ * <p/>If any files of the latter pattern appear, the last (after being sorted by name) will be used and previous versions will be deleted.
+ * This is to help support systems where one may not be able to overwrite a file (like Windows, if the file is in use).
+ * <p/>If the external file has already been loaded, and it is changed, those changes will not be visible until a commit has been done.
+ * <p/>The external file may be sorted or unsorted by the key field, but it will be substantially slower (untested) if it isn't sorted.
+ * <p/>Fields of this type may currently only be used as a ValueSource in a FunctionQuery.
+ *
+ * @version $Id$
+ */
+public class ExternalFileField extends FieldType {
+  private FieldType ftype;
+  private String keyFieldName;
+  private IndexSchema schema;
+  private float defVal;
+
+  protected void init(IndexSchema schema, Map<String,String> args) {
+    restrictProps(SORT_MISSING_FIRST | SORT_MISSING_LAST);
+    String ftypeS = getArg("valType", args);
+    if (ftypeS!=null) {
+      ftype = schema.getFieldTypes().get(ftypeS);
+      if (ftype==null || !(ftype instanceof FloatField)) {
+        throw new SolrException(SolrException.ErrorCode.SERVER_ERROR, "Only float (FloatField) is currently supported as external field type.  got " + ftypeS);
+      }
+    }   
+    keyFieldName = args.remove("keyField");
+    String defValS = args.remove("defVal");
+    defVal = defValS==null ? 0 : Float.parseFloat(defValS);
+    this.schema = schema;
+  }
+
+  public void write(XMLWriter xmlWriter, String name, Fieldable f) throws IOException {
+    throw new UnsupportedOperationException();
+  }
+
+  public void write(TextResponseWriter writer, String name, Fieldable f) throws IOException {
+    throw new UnsupportedOperationException();
+  }
+
+  public SortField getSortField(SchemaField field,boolean reverse) {
+    throw new UnsupportedOperationException();
+  }
+
+  public ValueSource getValueSource(SchemaField field, QParser parser) {
+    // default key field to unique key
+    SchemaField keyField = keyFieldName==null ? schema.getUniqueKeyField() : schema.getField(keyFieldName);
+    return new FileFloatSource(field, keyField, defVal, parser);
+  }
+
+
+}
diff --git a/src/java/org/apache/solr/search/function/FileFloatSource.java b/src/java/org/apache/solr/search/function/FileFloatSource.java
new file mode 100755
index 00000000000..f8dbb70804c
--- /dev/null
+++ b/src/java/org/apache/solr/search/function/FileFloatSource.java
@@ -0,0 +1,417 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.solr.search.function;
+
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.TermDocs;
+import org.apache.lucene.index.TermEnum;
+import org.apache.lucene.index.Term;
+import org.apache.solr.core.SolrCore;
+import org.apache.solr.schema.SchemaField;
+import org.apache.solr.schema.FieldType;
+import org.apache.solr.search.QParser;
+
+import java.io.*;
+import java.util.*;
+
+/**
+ * Obtains float field values from an external file.
+ * @version $Id$
+ */
+
+public class FileFloatSource extends ValueSource {
+  private SchemaField field;
+  private final SchemaField keyField;
+  private final float defVal;
+
+  private final String indexDir;
+
+  public FileFloatSource(SchemaField field, SchemaField keyField, float defVal, QParser parser) {
+    this.field = field;
+    this.keyField = keyField;
+    this.defVal = defVal;
+    this.indexDir = parser.getReq().getCore().getIndexDir();
+  }
+
+  public String description() {
+    return "float(" + field + ')';
+  }
+
+  public DocValues getValues(IndexReader reader) throws IOException {
+    final float[] arr = getCachedFloats(reader);
+    return new DocValues() {
+      public float floatVal(int doc) {
+        return arr[doc];
+      }
+
+      public int intVal(int doc) {
+        return (int)arr[doc];
+      }
+
+      public long longVal(int doc) {
+        return (long)arr[doc];
+      }
+
+      public double doubleVal(int doc) {
+        return (double)arr[doc];
+      }
+
+      public String strVal(int doc) {
+        return Float.toString(arr[doc]);
+      }
+
+      public String toString(int doc) {
+        return description() + '=' + floatVal(doc);
+      }
+    };
+  }
+
+  public boolean equals(Object o) {
+    if (o.getClass() !=  FileFloatSource.class) return false;
+    FileFloatSource other = (FileFloatSource)o;
+    return this.field.getName().equals(other.field.getName())
+            && this.keyField.getName().equals(other.keyField.getName())
+            && this.defVal == other.defVal
+            && this.indexDir.equals(other.indexDir);
+  }
+
+  public int hashCode() {
+    return FileFloatSource.class.hashCode() + field.getName().hashCode();
+  };
+
+  public String toString() {
+    return "FileFloatSource(field="+field.getName()+",keyField="+keyField.getName()
+            + ",defVal="+defVal+",indexDir="+indexDir+")";
+
+  }
+
+  private final float[] getCachedFloats(IndexReader reader) {
+    return (float[])floatCache.get(reader, new Entry(this));
+  }
+
+  static Cache floatCache = new Cache() {
+    protected Object createValue(IndexReader reader, Object key) {
+      return getFloats(((Entry)key).ffs, reader);
+    }
+  };
+
+  /** Internal cache. (from lucene FieldCache) */
+  abstract static class Cache {
+    private final Map readerCache = new WeakHashMap();
+
+    protected abstract Object createValue(IndexReader reader, Object key);
+
+    public Object get(IndexReader reader, Object key) {
+      Map innerCache;
+      Object value;
+      synchronized (readerCache) {
+        innerCache = (Map) readerCache.get(reader);
+        if (innerCache == null) {
+          innerCache = new HashMap();
+          readerCache.put(reader, innerCache);
+          value = null;
+        } else {
+          value = innerCache.get(key);
+        }
+        if (value == null) {
+          value = new CreationPlaceholder();
+          innerCache.put(key, value);
+        }
+      }
+      if (value instanceof CreationPlaceholder) {
+        synchronized (value) {
+          CreationPlaceholder progress = (CreationPlaceholder) value;
+          if (progress.value == null) {
+            progress.value = createValue(reader, key);
+            synchronized (readerCache) {
+              innerCache.put(key, progress.value);
+              onlyForTesting = progress.value;
+            }
+          }
+          return progress.value;
+        }
+      }
+
+      return value;
+    }
+  }
+
+  static Object onlyForTesting; // set to the last value
+
+  static final class CreationPlaceholder {
+    Object value;
+  }
+
+    /** Expert: Every composite-key in the internal cache is of this type. */
+  private static class Entry {
+    final FileFloatSource ffs;
+    public Entry(FileFloatSource ffs) {
+      this.ffs = ffs;
+    }
+
+    public boolean equals(Object o) {
+      if (!(o instanceof Entry)) return false;
+      Entry other = (Entry)o;
+      return ffs.equals(other.ffs);
+    }
+
+    public int hashCode() {
+      return ffs.hashCode();
+    }
+  }
+
+
+
+  private static float[] getFloats(FileFloatSource ffs, IndexReader reader) {
+    float[] vals = new float[reader.maxDoc()];
+    if (ffs.defVal != 0) {
+      Arrays.fill(vals, ffs.defVal);
+    }
+    InputStream is;
+    String fname = "external_" + ffs.field.getName();
+    try {
+      is = getLatestFile(ffs.indexDir, fname);
+    } catch (IOException e) {
+      // log, use defaults
+      SolrCore.log.severe("Error opening external value source file: " +e);
+      return vals;
+    }
+
+    BufferedReader r = new BufferedReader(new InputStreamReader(is));
+
+    String idName = ffs.keyField.getName().intern();
+    FieldType idType = ffs.keyField.getType();
+    boolean sorted=true;   // assume sorted until we discover it's not
+
+
+    // warning: lucene's termEnum.skipTo() is not optimized... it simply does a next()
+    // because of this, simply ask the reader for a new termEnum rather than
+    // trying to use skipTo()
+
+    List<String> notFound = new ArrayList<String>();
+    int notFoundCount=0;
+    int otherErrors=0;
+
+    TermDocs termDocs = null;
+    Term protoTerm = new Term(idName, "");
+    TermEnum termEnum = null;
+    // Number of times to try termEnum.next() before resorting to skip
+    int numTimesNext = 10;
+
+    char delimiter='=';
+    String termVal;
+    boolean hasNext=true;
+    String prevKey="";
+
+    String lastVal="\uFFFF\uFFFF\uFFFF\uFFFF\uFFFF\uFFFF\uFFFF\uFFFF";
+
+    try {
+      termDocs = reader.termDocs();
+      termEnum = reader.terms(protoTerm);
+      Term t = termEnum.term();
+      if (t != null && t.field() == idName) { // intern'd comparison
+        termVal = t.text();
+      } else {
+        termVal = lastVal;
+      }
+
+
+      for (String line; (line=r.readLine())!=null;) {
+        int delimIndex = line.indexOf(delimiter);
+        if (delimIndex < 0) continue;
+
+        int endIndex = line.length();
+        /* EOLs should already be removed for BufferedReader.readLine()
+        for(int endIndex = line.length();endIndex>delimIndex+1; endIndex--) {
+          char ch = line.charAt(endIndex-1);
+          if (ch!='\n' && ch!='\r') break;
+        }
+        */
+        String key = line.substring(0, delimIndex);
+        String val = line.substring(delimIndex+1, endIndex);
+
+        String internalKey = idType.toInternal(key);
+        float fval;
+        try {
+          fval=Float.parseFloat(val);
+        } catch (Exception e) {
+          if (++otherErrors<=10) {
+            SolrCore.log.severe( "Error loading external value source + fileName + " + e
+              + (otherErrors<10 ? "" : "\tSkipping future errors for this file.")                    
+            );
+          }
+          continue;  // go to next line in file.. leave values as default.
+        }
+
+        if (sorted) {
+          // make sure this key is greater than the previous key
+          sorted = internalKey.compareTo(prevKey) >= 0;
+          prevKey = internalKey;
+
+          if (sorted) {
+            int countNext = 0;
+            for(;;) {
+              int cmp = internalKey.compareTo(termVal);
+              if (cmp == 0) {
+                termDocs.seek(termEnum);
+                while (termDocs.next()) {
+                  vals[termDocs.doc()] = fval;
+                }
+                break;
+              } else if (cmp < 0) {
+                // term enum has already advanced past current key... we didn't find it.
+                if (notFoundCount<10) {  // collect first 10 not found for logging
+                  notFound.add(key);
+                }
+                notFoundCount++;
+                break;
+              } else {
+                // termEnum is less than our current key, so skip ahead
+
+                // try next() a few times to see if we hit or pass the target.
+                // Lucene's termEnum.skipTo() is currently unoptimized (it just does next())
+                // so the best thing is to simply ask the reader for a new termEnum(target)
+                // if we really need to skip.
+                if (++countNext > numTimesNext) {
+                  termEnum = reader.terms(protoTerm.createTerm(internalKey));
+                  t = termEnum.term();
+                } else {
+                  hasNext = termEnum.next();
+                  t = hasNext ? termEnum.term() : null;
+                }
+
+                if (t != null && t.field() == idName) { // intern'd comparison
+                  termVal = t.text();
+                } else {
+                  termVal = lastVal;
+                }
+              }
+            } // end for(;;)
+          }
+        }
+
+        if (!sorted) {
+          termEnum = reader.terms(protoTerm.createTerm(internalKey));
+          t = termEnum.term();
+          if (t != null && t.field() == idName  // intern'd comparison
+                  && internalKey.equals(t.text()))
+          {
+            termDocs.seek (termEnum);
+            while (termDocs.next()) {
+              vals[termDocs.doc()] = fval;
+            }
+          } else {
+            if (notFoundCount<10) {  // collect first 10 not found for logging
+              notFound.add(key);
+            }
+            notFoundCount++;
+          }
+        }
+      }
+    } catch (IOException e) {
+      // log, use defaults
+      SolrCore.log.severe("Error loading external value source: " +e);
+    } finally {
+      // swallow exceptions on close so we don't override any
+      // exceptions that happened in the loop
+      if (termDocs!=null) try{termDocs.close();}catch(Exception e){}
+      if (termEnum!=null) try{termEnum.close();}catch(Exception e){}
+      try{r.close();}catch(Exception e){}
+    }
+
+    SolrCore.log.info("Loaded external value source " + fname
+      + (notFoundCount==0 ? "" : " :"+notFoundCount+" missing keys "+notFound)
+    );
+
+    return vals;
+  }
+
+
+  // Future: refactor/pull out into VersionedFile class
+
+  /* Open the latest version of a file... fileName if that exists, or
+   * the last fileName.* after being sorted lexicographically.
+   * Older versions of the file are deleted (and queued for deletion if
+   * that fails).
+   */
+  private static InputStream getLatestFile(String dirName, String fileName) throws FileNotFoundException {
+    Collection<File> oldFiles=null;
+    final String prefix = fileName+'.';
+    File f = new File(dirName, fileName);
+    InputStream is = null;
+
+    // there can be a race between checking for a file and opening it...
+    // the user may have just put a new version in and deleted an old version.
+    // try multiple times in a row.
+    for (int retry=0; retry<10; retry++) {
+      try {
+        if (!f.exists()) {
+          File dir = new File(dirName);
+          String[] names = dir.list(new FilenameFilter() {
+            public boolean accept(File dir, String name) {
+              return name.startsWith(prefix);
+            }
+          });
+          Arrays.sort(names);
+          f = new File(dir, names[names.length-1]);
+          oldFiles = new ArrayList<File>();
+          for (int i=0; i<names.length-1; i++) {
+            oldFiles.add(new File(dir, names[i]));
+          }
+        }
+
+        is = new FileInputStream(f);
+      } catch (Exception e) {
+        // swallow exception for now
+      }
+    }
+
+    // allow exception to be thrown from the final try.
+    is = new FileInputStream(f);
+
+    // delete old files only after we have successfuly opened the newest
+    if (oldFiles != null) {
+      delete(oldFiles);
+    }
+
+    return is;
+  }
+
+
+
+  private static final Set<File> deleteList = new HashSet<File>();
+  private static synchronized void delete(Collection<File> files) {
+    synchronized (deleteList) {
+      deleteList.addAll(files);
+      List<File> deleted = new ArrayList<File>();
+      for (File df : deleteList) {
+        try {
+          df.delete();
+          // deleteList.remove(df);
+          deleted.add(df);
+        } catch (SecurityException e) {
+          if (!df.exists()) {
+            deleted.add(df);
+          }
+        }
+      }
+      deleteList.removeAll(deleted);
+    }
+  }
+
+
+}
diff --git a/src/test/org/apache/solr/search/function/TestFunctionQuery.java b/src/test/org/apache/solr/search/function/TestFunctionQuery.java
index 157597b458f..739f24b8cf5 100755
--- a/src/test/org/apache/solr/search/function/TestFunctionQuery.java
+++ b/src/test/org/apache/solr/search/function/TestFunctionQuery.java
@@ -18,9 +18,16 @@
 package org.apache.solr.search.function;
 
 import org.apache.solr.util.AbstractSolrTestCase;
+import org.apache.solr.core.SolrCore;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Random;
+import java.util.Arrays;
+import java.io.File;
+import java.io.Writer;
+import java.io.OutputStreamWriter;
+import java.io.FileOutputStream;
 
 /**
  * Tests some basic functionality of Solr while demonstrating good
@@ -43,12 +50,27 @@ public class TestFunctionQuery extends AbstractSolrTestCase {
     super.tearDown();
   }
 
+  String base = "external_foo_extf";
+  void makeExternalFile(String field, String contents, String charset) {
+    String dir = h.getCore().getIndexDir();
+    String filename = dir + "/external_" + field + "." + System.currentTimeMillis();
+    try {
+      Writer out = new OutputStreamWriter(new FileOutputStream(filename), charset);
+      out.write(contents);
+      out.close();
+    } catch (Exception e) {
+      throw new RuntimeException(e);
+    }
+  }
+
+
   void createIndex(String field, float... values) {
     // lrf.args.put("version","2.0");
     for (float val : values) {
       String s = Float.toString(val);
-      assertU(adoc("id", s, field, s));
-      System.out.println("added doc for " + val);
+      if (field!=null) assertU(adoc("id", s, field, s));
+      else assertU(adoc("id", s));
+      // System.out.println("added doc for " + val);
     }
     assertU(optimize()); // squeeze out any possible deleted docs
   }
@@ -77,14 +99,14 @@ public class TestFunctionQuery extends AbstractSolrTestCase {
     // "//doc[./float[@name='foo_pf']='10.0' and ./float[@name='score']='10.0']"
 
     for (int i=0; i<results.length; i+=2) {
-      String xpath = "//doc[./float[@name='" + field + "']='"
+      String xpath = "//doc[./float[@name='" + "id" + "']='"
               + results[i] + "' and ./float[@name='score']='"
               + results[i+1] + "']";
       tests.add(xpath);
     }
 
     assertQ(req("q", parseableQuery
-                ,"fl", "*,score"
+                ,"fl", "*,score","indent","on","rows","100"
                 )
             , tests.toArray(new String[tests.size()])
             );
@@ -137,4 +159,78 @@ public class TestFunctionQuery extends AbstractSolrTestCase {
     doTest("foo_pf");  // a plain float field
     doTest("foo_f");  // a sortable float field
   }
-}
+
+  public void testExternalField() {
+    String field = "foo_extf";
+
+    float[] ids = {100,-4,0,10,25,5,77,23,55,-78,-45,-24,63,78,94,22,34,54321,261,-627};
+
+    createIndex(null,ids);
+
+    // Unsorted field, largest first
+    makeExternalFile(field, "54321=543210\n0=-999\n25=250","UTF-8");
+    // test identity (straight field value)
+    singleTest(field, "\0", 54321, 543210, 0,-999, 25,250, 100, 1);
+    Object orig = FileFloatSource.onlyForTesting;
+    singleTest(field, "log(\0)");
+    // make sure the values were cached
+    assertTrue(orig == FileFloatSource.onlyForTesting);
+    singleTest(field, "sqrt(\0)");
+    assertTrue(orig == FileFloatSource.onlyForTesting);
+
+    makeExternalFile(field, "0=1","UTF-8");
+    assertU(commit());
+    assertTrue(orig != FileFloatSource.onlyForTesting);
+
+
+    Random r = new Random();
+    for (int i=0; i<10; i++) {   // do more iterations for a thorough test
+      int len = r.nextInt(ids.length+1);
+      boolean sorted = r.nextBoolean();
+      // shuffle ids
+      for (int j=0; j<ids.length; j++) {
+        int other=r.nextInt(ids.length);
+        float v=ids[0];
+        ids[0] = ids[other];
+        ids[other] = v;
+      }
+
+      if (sorted) {
+        // sort only the first elements
+        Arrays.sort(ids,0,len);
+      }
+
+      // make random values
+      float[] vals = new float[len];
+      for (int j=0; j<len; j++) {
+        vals[j] = r.nextInt(200)-100;
+      }
+
+      // make and write the external file
+      StringBuilder sb = new StringBuilder();
+      for (int j=0; j<len; j++) {
+        sb.append("" + ids[j] + "=" + vals[j]+"\n");        
+      }
+      makeExternalFile(field, sb.toString(),"UTF-8");
+
+      // make it visible
+      assertU(commit());
+
+      // test it
+      float[] answers = new float[ids.length*2];
+      for (int j=0; j<len; j++) {
+        answers[j*2] = ids[j];
+        answers[j*2+1] = vals[j];
+      }
+      for (int j=len; j<ids.length; j++) {
+        answers[j*2] = ids[j];
+        answers[j*2+1] = 1;  // the default values
+      }
+
+      singleTest(field, "\0", answers);
+      System.out.println("Done test "+i);
+    }
+
+  }
+
+}
\ No newline at end of file
diff --git a/src/test/test-files/solr/conf/schema11.xml b/src/test/test-files/solr/conf/schema11.xml
index d8264ef1b4c..f8de198749a 100755
--- a/src/test/test-files/solr/conf/schema11.xml
+++ b/src/test/test-files/solr/conf/schema11.xml
@@ -232,7 +232,10 @@
     <!-- since fields of this type are by default not stored or indexed, any data added to 
          them will be ignored outright 
      --> 
-    <fieldtype name="ignored" stored="false" indexed="false" class="solr.StrField" /> 
+    <fieldType name="ignored" stored="false" indexed="false" class="solr.StrField" /> 
+
+    <fieldType name="file" keyField="id" defVal="1" stored="false" indexed="false" class="solr.ExternalFileField" valType="float"/>
+
 
  </types>
 
@@ -282,6 +285,8 @@
    <dynamicField name="*_b"  type="boolean" indexed="true"  stored="true"/>
    <dynamicField name="*_dt" type="date"    indexed="true"  stored="true"/>
 
+   <dynamicField name="*_extf" type="file"/>
+
    <dynamicField name="*_random" type="random" />
 
    <!-- uncomment the following to ignore any fields that don't already match an existing