From 5f0ecb5d596b1dc64701ba2b616e42e1e43f0195 Mon Sep 17 00:00:00 2001
From: Martin Fietz <Martin.Fietz@gmail.com>
Date: Wed, 2 Dec 2015 12:34:01 +0100
Subject: Use MergeCursor for high number of images

---
 .../danoeh/antennapod/core/storage/DBReader.java   | 18 ++++++----
 .../antennapod/core/storage/PodDBAdapter.java      | 40 ++++++++++++++++++----
 2 files changed, 44 insertions(+), 14 deletions(-)

diff --git a/core/src/main/java/de/danoeh/antennapod/core/storage/DBReader.java b/core/src/main/java/de/danoeh/antennapod/core/storage/DBReader.java
index c0a30f740..c34515118 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/storage/DBReader.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/storage/DBReader.java
@@ -225,12 +225,12 @@ public final class DBReader {
     private static Map<Long,FeedMedia> getFeedMedia(PodDBAdapter adapter,
                                                     long... itemIds) {
 
-        ArrayList<String> ids = new ArrayList<>(itemIds.length);
-        for(long itemId : itemIds) {
-            ids.add(String.valueOf(itemId));
+        String[] ids = new String[itemIds.length];
+        for(int i=0, len=itemIds.length; i < len; i++) {
+            ids[i] = String.valueOf(itemIds[i]);
         }
         Map<Long,FeedMedia> result = new HashMap<>(itemIds.length);
-        Cursor cursor = adapter.getFeedMediaCursor(ids.toArray(new String[0]));
+        Cursor cursor = adapter.getFeedMediaCursor(ids);
         try {
             if (cursor.moveToFirst()) {
                 do {
@@ -862,10 +862,14 @@ public final class DBReader {
     /**
      * Searches the DB for a FeedImage of the given id.
      *
-     * @param ids The id of the object
-     * @return The found object
+     * @param imageIds The ids of the images
+     * @return Map that associates the id of an image with the image itself
      */
-    private static Map<Long,FeedImage> getFeedImages(PodDBAdapter adapter, final long... ids) {
+    private static Map<Long,FeedImage> getFeedImages(PodDBAdapter adapter, final long... imageIds) {
+        String[] ids = new String[imageIds.length];
+        for(int i=0, len=imageIds.length; i < len; i++) {
+            ids[i] = String.valueOf(imageIds[i]);
+        }
         Cursor cursor = adapter.getImageCursor(ids);
         Map<Long, FeedImage> result = new HashMap<>(cursor.getCount());
         try {
diff --git a/core/src/main/java/de/danoeh/antennapod/core/storage/PodDBAdapter.java b/core/src/main/java/de/danoeh/antennapod/core/storage/PodDBAdapter.java
index bf324c9d1..05af9303f 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/storage/PodDBAdapter.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/storage/PodDBAdapter.java
@@ -14,7 +14,6 @@ import android.os.Build;
 import android.text.TextUtils;
 import android.util.Log;
 
-import org.apache.commons.lang3.StringUtils;
 import org.apache.commons.lang3.Validate;
 
 import java.util.Arrays;
@@ -1018,15 +1017,42 @@ public class PodDBAdapter {
     /**
      * Returns a cursor for a DB query in the FeedImages table for given IDs.
      *
-     * @param ids IDs of the FeedImages
+     * @param imageIds IDs of the images
      * @return The cursor of the query
      */
-    public final Cursor getImageCursor(long... ids) {
-        String sql = "SELECT * FROM " + TABLE_NAME_FEED_IMAGES +
-                " WHERE " + KEY_ID + " IN (" + StringUtils.join(ids, ',') + ")";
-        Cursor c = db.rawQuery(sql, null);
+    public final Cursor getImageCursor(String... imageIds) {
+        int length = imageIds.length;
+        if (length > IN_OPERATOR_MAXIMUM) {
+            Log.w(TAG, "Length of id array is larger than "
+                    + IN_OPERATOR_MAXIMUM + ". Creating multiple cursors");
+            int numCursors = (int) (((double) length) / (IN_OPERATOR_MAXIMUM)) + 1;
+            Cursor[] cursors = new Cursor[numCursors];
+            for (int i = 0; i < numCursors; i++) {
+                int neededLength;
+                String[] parts;
+                final int elementsLeft = length - i * IN_OPERATOR_MAXIMUM;
 
-        return c;
+                if (elementsLeft >= IN_OPERATOR_MAXIMUM) {
+                    neededLength = IN_OPERATOR_MAXIMUM;
+                    parts = Arrays.copyOfRange(imageIds, i
+                            * IN_OPERATOR_MAXIMUM, (i + 1)
+                            * IN_OPERATOR_MAXIMUM);
+                } else {
+                    neededLength = elementsLeft;
+                    parts = Arrays.copyOfRange(imageIds, i
+                            * IN_OPERATOR_MAXIMUM, (i * IN_OPERATOR_MAXIMUM)
+                            + neededLength);
+                }
+
+                cursors[i] = db.rawQuery("SELECT * FROM "
+                        + TABLE_NAME_FEED_IMAGES + " WHERE " + KEY_ID + " IN "
+                        + buildInOperator(neededLength), parts);
+            }
+            return new MergeCursor(cursors);
+        } else {
+            return db.query(TABLE_NAME_FEED_IMAGES, null, KEY_ID + " IN "
+                    + buildInOperator(length), imageIds, null, null, null);
+        }
     }
 
     public final Cursor getSimpleChaptersOfFeedItemCursor(final FeedItem item) {
-- 
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