diff --git a/java/com/android/dialer/constants/Constants.java b/java/com/android/dialer/constants/Constants.java
index 644dd6b..fb1aa2a 100644
--- a/java/com/android/dialer/constants/Constants.java
+++ b/java/com/android/dialer/constants/Constants.java
@@ -60,6 +60,9 @@
   @NonNull
   public abstract String getPhoneLookupHistoryProviderAuthority();
 
+  @NonNull
+  public abstract String getPreferredSimFallbackProviderAuthority();
+
   public abstract String getUserAgent(Context context);
 
   @NonNull
diff --git a/java/com/android/dialer/constants/aospdialer/ConstantsImpl.java b/java/com/android/dialer/constants/aospdialer/ConstantsImpl.java
index e7eab68..312b3f5 100644
--- a/java/com/android/dialer/constants/aospdialer/ConstantsImpl.java
+++ b/java/com/android/dialer/constants/aospdialer/ConstantsImpl.java
@@ -48,6 +48,12 @@
     return "com.android.dialer.phonelookuphistory";
   }
 
+  @NonNull
+  @Override
+  public String getPreferredSimFallbackProviderAuthority() {
+    return "com.android.dialer.preferredsimfallback";
+  }
+
   @Override
   public String getUserAgent(Context context) {
     return null;
diff --git a/java/com/android/dialer/constants/googledialer/ConstantsImpl.java b/java/com/android/dialer/constants/googledialer/ConstantsImpl.java
index 8580fce..e4a96fe 100644
--- a/java/com/android/dialer/constants/googledialer/ConstantsImpl.java
+++ b/java/com/android/dialer/constants/googledialer/ConstantsImpl.java
@@ -50,6 +50,12 @@
     return "com.google.android.dialer.phonelookuphistory";
   }
 
+  @NonNull
+  @Override
+  public String getPreferredSimFallbackProviderAuthority() {
+    return "com.google.android.dialer.preferredsimfallback";
+  }
+
   @Override
   public String getUserAgent(Context context) {
     StringBuilder userAgent = new StringBuilder("GoogleDialer ");
diff --git a/java/com/android/dialer/phonelookup/composite/CompositePhoneLookup.java b/java/com/android/dialer/phonelookup/composite/CompositePhoneLookup.java
index f85b357..59a8457 100644
--- a/java/com/android/dialer/phonelookup/composite/CompositePhoneLookup.java
+++ b/java/com/android/dialer/phonelookup/composite/CompositePhoneLookup.java
@@ -23,7 +23,6 @@
 import com.android.dialer.common.concurrent.DialerFutures;
 import com.android.dialer.phonelookup.PhoneLookup;
 import com.android.dialer.phonelookup.PhoneLookupInfo;
-import com.google.common.base.Function;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
@@ -60,15 +59,12 @@
     }
     return Futures.transform(
         Futures.allAsList(futures),
-        new Function<List<PhoneLookupInfo>, PhoneLookupInfo>() {
-          @Override
-          public PhoneLookupInfo apply(List<PhoneLookupInfo> infos) {
-            PhoneLookupInfo.Builder mergedInfo = PhoneLookupInfo.newBuilder();
-            for (PhoneLookupInfo info : infos) {
-              mergedInfo.mergeFrom(info);
-            }
-            return mergedInfo.build();
+        infos -> {
+          PhoneLookupInfo.Builder mergedInfo = PhoneLookupInfo.newBuilder();
+          for (PhoneLookupInfo info : infos) {
+            mergedInfo.mergeFrom(info);
           }
+          return mergedInfo.build();
         },
         MoreExecutors.directExecutor());
   }
@@ -102,30 +98,23 @@
     }
     return Futures.transform(
         Futures.allAsList(futures),
-        new Function<
-            List<ImmutableMap<DialerPhoneNumber, PhoneLookupInfo>>,
-            ImmutableMap<DialerPhoneNumber, PhoneLookupInfo>>() {
-          @Override
-          public ImmutableMap<DialerPhoneNumber, PhoneLookupInfo> apply(
-              List<ImmutableMap<DialerPhoneNumber, PhoneLookupInfo>> allMaps) {
-            ImmutableMap.Builder<DialerPhoneNumber, PhoneLookupInfo> combinedMap =
-                ImmutableMap.builder();
-            for (DialerPhoneNumber dialerPhoneNumber : existingInfoMap.keySet()) {
-              PhoneLookupInfo.Builder combinedInfo = PhoneLookupInfo.newBuilder();
-              for (ImmutableMap<DialerPhoneNumber, PhoneLookupInfo> map : allMaps) {
-                PhoneLookupInfo subInfo = map.get(dialerPhoneNumber);
-                if (subInfo == null) {
-                  throw new IllegalStateException(
-                      "A sublookup didn't return an info for number: "
-                          + LogUtil.sanitizePhoneNumber(
-                              dialerPhoneNumber.getRawInput().getNumber()));
-                }
-                combinedInfo.mergeFrom(subInfo);
+        (allMaps) -> {
+          ImmutableMap.Builder<DialerPhoneNumber, PhoneLookupInfo> combinedMap =
+              ImmutableMap.builder();
+          for (DialerPhoneNumber dialerPhoneNumber : existingInfoMap.keySet()) {
+            PhoneLookupInfo.Builder combinedInfo = PhoneLookupInfo.newBuilder();
+            for (ImmutableMap<DialerPhoneNumber, PhoneLookupInfo> map : allMaps) {
+              PhoneLookupInfo subInfo = map.get(dialerPhoneNumber);
+              if (subInfo == null) {
+                throw new IllegalStateException(
+                    "A sublookup didn't return an info for number: "
+                        + LogUtil.sanitizePhoneNumber(dialerPhoneNumber.getRawInput().getNumber()));
               }
-              combinedMap.put(dialerPhoneNumber, combinedInfo.build());
+              combinedInfo.mergeFrom(subInfo);
             }
-            return combinedMap.build();
+            combinedMap.put(dialerPhoneNumber, combinedInfo.build());
           }
+          return combinedMap.build();
         },
         MoreExecutors.directExecutor());
   }
diff --git a/java/com/android/dialer/preferredsim/PreferredSimFallbackContract.java b/java/com/android/dialer/preferredsim/PreferredSimFallbackContract.java
new file mode 100644
index 0000000..79e097c
--- /dev/null
+++ b/java/com/android/dialer/preferredsim/PreferredSimFallbackContract.java
@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed 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 com.android.dialer.preferredsim;
+
+import android.content.ComponentName;
+import android.net.Uri;
+import android.provider.ContactsContract.CommonDataKinds;
+import android.telecom.PhoneAccountHandle;
+import com.android.dialer.constants.Constants;
+
+/**
+ * Extend fields for preferred SIM that is not available in {@link
+ * android.provider.ContactsContract.Data} before P. Only query and update is supported for this
+ * provider, and the update selection must be {@link PreferredSim#UPDATE_ID_SELECTION}. Caller must
+ * have {@link android.Manifest.permission#READ_CONTACTS} to read or {@link
+ * android.Manifest.permission#WRITE_CONTACTS} to write.
+ */
+public final class PreferredSimFallbackContract {
+
+  /**
+   * Check the meta-data "com.android.dialer.PREFERRED_SIM_FALLBACK_AUTHORITY" to get the authority
+   * of the default dialer if it support it.
+   */
+  public static final String AUTHORITY = Constants.get().getPreferredSimFallbackProviderAuthority();
+
+  public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY);
+
+  /** Columns for preferred SIM. */
+  public static final class PreferredSim {
+
+    /**
+     * Unique key that should match {@link
+     * android.provider.ContactsContract.CommonDataKinds.Phone#_ID} of the data row it is associated
+     * with.
+     */
+    public static final String DATA_ID = "data_id";
+
+    /**
+     * The flattened {@link android.content.ComponentName} of a {@link PhoneAccountHandle} that is
+     * the preferred {@code PhoneAccountHandle} to call the contact with. Used by {@link
+     * CommonDataKinds.Phone}.
+     *
+     * @see PhoneAccountHandle#getComponentName()
+     * @see ComponentName#flattenToString()
+     */
+    public static final String PREFERRED_PHONE_ACCOUNT_COMPONENT_NAME =
+        "preferred_phone_account_component_name";
+
+    /**
+     * The ID of a {@link PhoneAccountHandle} that is the preferred {@code PhoneAccountHandle} to
+     * call the contact with. Used by {@link CommonDataKinds.Phone}.
+     *
+     * @see PhoneAccountHandle#getId() ()
+     * @see ComponentName#flattenToString()
+     */
+    public static final String PREFERRED_PHONE_ACCOUNT_ID = "preferred_phone_account_id";
+  }
+}
diff --git a/java/com/android/dialer/preferredsim/impl/AndroidManifest.xml b/java/com/android/dialer/preferredsim/impl/AndroidManifest.xml
new file mode 100644
index 0000000..e21598f
--- /dev/null
+++ b/java/com/android/dialer/preferredsim/impl/AndroidManifest.xml
@@ -0,0 +1,36 @@
+<!--
+ ~ Copyright (C) 2017 The Android Open Source Project
+ ~
+ ~ Licensed 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
+ -->
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.android.dialer.preferredsim">
+
+  <application>
+
+    <provider
+        android:authorities="com.android.dialer.preferredsimfallback"
+        android:exported="true"
+        android:multiprocess="false"
+        android:name=".impl.PreferredSimFallbackProvider"
+        android:readPermission="android.permission.READ_CONTACTS"
+        android:writePermission="android.permission.WRITE_CONTACTS"/>
+
+    <meta-data
+        android:name="com.android.dialer.SUPPORTS_PREFERRED_SIM"
+        android:value="true"/>
+    <meta-data
+        android:name="com.android.dialer.PREFERRED_SIM_FALLBACK_AUTHORITY"
+        android:value="com.android.dialer.preferredsimfallback"/>
+  </application>
+</manifest>
diff --git a/java/com/android/dialer/preferredsim/impl/PreferredSimDatabaseHelper.java b/java/com/android/dialer/preferredsim/impl/PreferredSimDatabaseHelper.java
new file mode 100644
index 0000000..4795ea4
--- /dev/null
+++ b/java/com/android/dialer/preferredsim/impl/PreferredSimDatabaseHelper.java
@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed 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 com.android.dialer.preferredsim.impl;
+
+import android.content.Context;
+import android.database.sqlite.SQLiteDatabase;
+import android.database.sqlite.SQLiteOpenHelper;
+import com.android.dialer.common.LogUtil;
+import com.android.dialer.preferredsim.PreferredSimFallbackContract.PreferredSim;
+
+/** Database helper class for preferred SIM. */
+public class PreferredSimDatabaseHelper extends SQLiteOpenHelper {
+
+  static final String TABLE = "preferred_sim";
+
+  private static final String CREATE_TABLE_SQL =
+      "create table if not exists "
+          + TABLE
+          + " ("
+          + (PreferredSim.DATA_ID + " integer primary key, ")
+          + (PreferredSim.PREFERRED_PHONE_ACCOUNT_COMPONENT_NAME + " text, ")
+          + (PreferredSim.PREFERRED_PHONE_ACCOUNT_ID + " text")
+          + ");";
+
+  PreferredSimDatabaseHelper(Context appContext) {
+    super(appContext, "preferred_sim.db", null, 1);
+  }
+
+  @Override
+  public void onCreate(SQLiteDatabase db) {
+    LogUtil.enterBlock("PreferredSimDatabaseHelper.onCreate");
+    long startTime = System.currentTimeMillis();
+    db.execSQL(CREATE_TABLE_SQL);
+    LogUtil.i(
+        "PreferredSimDatabaseHelper.onCreate",
+        "took: %dms",
+        System.currentTimeMillis() - startTime);
+  }
+
+  @Override
+  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}
+}
diff --git a/java/com/android/dialer/preferredsim/impl/PreferredSimFallbackProvider.java b/java/com/android/dialer/preferredsim/impl/PreferredSimFallbackProvider.java
new file mode 100644
index 0000000..322baa2
--- /dev/null
+++ b/java/com/android/dialer/preferredsim/impl/PreferredSimFallbackProvider.java
@@ -0,0 +1,150 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed 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 com.android.dialer.preferredsim.impl;
+
+import android.Manifest.permission;
+import android.content.ContentProvider;
+import android.content.ContentValues;
+import android.content.pm.PackageManager;
+import android.database.Cursor;
+import android.net.Uri;
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
+import android.text.TextUtils;
+import com.android.dialer.preferredsim.PreferredSimFallbackContract;
+import com.android.dialer.preferredsim.PreferredSimFallbackContract.PreferredSim;
+
+/**
+ * Content provider for preferred SIM columns that is only available in ContactsProvider after P.
+ * Only supports {@link PreferredSimFallbackContract#CONTENT_URI} without id. Insert and delete not
+ * supported because there are no current use case.
+ *
+ * @see PreferredSimFallbackContract
+ */
+public class PreferredSimFallbackProvider extends ContentProvider {
+
+  private static final String UPDATE_ID_SELECTION = PreferredSim.DATA_ID + " = ?";
+
+  private PreferredSimDatabaseHelper databaseHelper;
+
+  @Override
+  public boolean onCreate() {
+    databaseHelper = new PreferredSimDatabaseHelper(getContext());
+    return true;
+  }
+
+  @Nullable
+  @Override
+  public Cursor query(
+      @NonNull Uri uri,
+      @Nullable String[] projection,
+      @Nullable String selection,
+      @Nullable String[] selectionArgs,
+      @Nullable String sortOrder) {
+    checkReadContactsPermission();
+    return databaseHelper
+        .getReadableDatabase()
+        .query(
+            PreferredSimDatabaseHelper.TABLE,
+            projection,
+            selection,
+            selectionArgs,
+            null,
+            null,
+            sortOrder);
+  }
+
+  @Nullable
+  @Override
+  public String getType(@NonNull Uri uri) {
+    return null;
+  }
+
+  @Nullable
+  @Override
+  public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
+    throw new IllegalArgumentException("Unsupported operation");
+  }
+
+  /**
+   * A row should only be deleted through {@link android.provider.ContactsContract.Data}. Since
+   * {@link android.provider.ContactsContract.Data#_ID} is AUTOINCREMENT and could not be reused,
+   * rows in this database will simply be orphaned and not cleaned up. To unset preference, update
+   * {@link PreferredSim#PREFERRED_PHONE_ACCOUNT_COMPONENT_NAME} and {@link
+   * PreferredSim#PREFERRED_PHONE_ACCOUNT_ID} to {@code null}. Delete is only allowed from dialer so
+   * simulator can wipe all preference.
+   */
+  @Override
+  public int delete(
+      @NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
+    if (!TextUtils.equals(getContext().getPackageName(), getCallingPackage())) {
+      throw new IllegalArgumentException("Unsupported operation");
+    }
+
+    return databaseHelper
+        .getWritableDatabase()
+        .delete(PreferredSimDatabaseHelper.TABLE, selection, selectionArgs);
+  }
+
+  /**
+   * Data will be inserted if {@link PreferredSim#DATA_ID} does not already exist in the database.
+   * During update the whole row will be replaced.
+   *
+   * @param uri must be {@link PreferredSimFallbackContract#CONTENT_URI}
+   * @param values must contains exactly the keys {@link
+   *     PreferredSim#PREFERRED_PHONE_ACCOUNT_COMPONENT_NAME} {@link
+   *     PreferredSim#PREFERRED_PHONE_ACCOUNT_ID}. The value may be {@code null}
+   * @param selection must equals "data_id = ?"
+   * @param selectionArgs must contains exactly the {@link PreferredSim#DATA_ID}
+   */
+  @Override
+  public int update(
+      @NonNull Uri uri,
+      @Nullable ContentValues values,
+      @Nullable String selection,
+      @Nullable String[] selectionArgs) {
+    checkWriteContactsPermission();
+    if (values == null) {
+      return 0;
+    }
+    if (!UPDATE_ID_SELECTION.equals(selection)
+        || selectionArgs == null
+        || selectionArgs.length != 1) {
+      throw new IllegalArgumentException("Unsupported operation");
+    }
+    values.put(PreferredSim.DATA_ID, selectionArgs[0]);
+    if (databaseHelper.getWritableDatabase().replace(PreferredSimDatabaseHelper.TABLE, null, values)
+        == -1) {
+      throw new IllegalStateException("update failed");
+    }
+    return 1;
+  }
+
+  private void checkReadContactsPermission() {
+    if (getContext().checkCallingOrSelfPermission(permission.READ_CONTACTS)
+        == PackageManager.PERMISSION_DENIED) {
+      throw new SecurityException("READ_CONTACTS required");
+    }
+  }
+
+  private void checkWriteContactsPermission() {
+    if (getContext().checkCallingOrSelfPermission(permission.WRITE_CONTACTS)
+        == PackageManager.PERMISSION_DENIED) {
+      throw new SecurityException("WRITE_CONTACTS required");
+    }
+  }
+}
diff --git a/packages.mk b/packages.mk
index c8a1ee5..2cce8c6 100644
--- a/packages.mk
+++ b/packages.mk
@@ -41,6 +41,7 @@
 	com.android.dialer.phonenumberutil \
 	com.android.dialer.postcall \
 	com.android.dialer.precall.impl \
+	com.android.dialer.preferredsim.impl \
 	com.android.dialer.searchfragment.common \
 	com.android.dialer.searchfragment.cp2 \
 	com.android.dialer.searchfragment.list \