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Optimize fillWindow to improve reverse-seek performance.

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Bug: 5520301

When an application requests a row from a SQLiteCursor that
is not in the window, instead of filling from the requested
row position onwards, fill from a little bit ahead of the
requested row position.

This fixes a problem with applications that seek backwards
in large cursor windows.  Previously the application could
end up refilling the window every time it moved back
one position.

We try to fill about 1/3 before the requested position and
2/3 after which substantially improves scrolling responsiveness
when the list is bound to a data set that does not fit
entirely within one cursor window.

Change-Id: I168ff1d3aed1a41ac96267be34a026c108590e52
This commit is contained in:
Jeff Brown
2011-10-27 14:52:28 -07:00
parent 4257e3b181
commit 650de3dcfc
10 changed files with 240 additions and 125 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
core/java/android/database/BulkCursorNative.java
View File

@@ -180,13 +180,13 @@ final class BulkCursorProxy implements IBulkCursor {
return mRemote;
}
public CursorWindow getWindow(int startPos) throws RemoteException
public CursorWindow getWindow(int position) throws RemoteException
{
Parcel data = Parcel.obtain();
Parcel reply = Parcel.obtain();
try {
data.writeInterfaceToken(IBulkCursor.descriptor);
data.writeInt(startPos);
data.writeInt(position);
mRemote.transact(GET_CURSOR_WINDOW_TRANSACTION, data, reply, 0);
DatabaseUtils.readExceptionFromParcel(reply);

11
core/java/android/database/CursorToBulkCursorAdaptor.java
View File

@@ -132,11 +132,11 @@ public final class CursorToBulkCursorAdaptor extends BulkCursorNative
}
@Override
public CursorWindow getWindow(int startPos) {
public CursorWindow getWindow(int position) {
synchronized (mLock) {
throwIfCursorIsClosed();
if (!mCursor.moveToPosition(startPos)) {
if (!mCursor.moveToPosition(position)) {
closeFilledWindowLocked();
return null;
}
@@ -149,12 +149,11 @@ public final class CursorToBulkCursorAdaptor extends BulkCursorNative
if (window == null) {
mFilledWindow = new CursorWindow(mProviderName);
window = mFilledWindow;
mCursor.fillWindow(startPos, window);
} else if (startPos < window.getStartPosition()
|| startPos >= window.getStartPosition() + window.getNumRows()) {
} else if (position < window.getStartPosition()
|| position >= window.getStartPosition() + window.getNumRows()) {
window.clear();
mCursor.fillWindow(startPos, window);
}
mCursor.fillWindow(position, window);
}
// Acquire a reference before returning from this RPC.

18
core/java/android/database/CursorWindow.java
View File

@@ -55,6 +55,7 @@ public class CursorWindow extends SQLiteClosable implements Parcelable {
public int mWindowPtr;
private int mStartPos;
private final String mName;
private final CloseGuard mCloseGuard = CloseGuard.get();
@@ -84,6 +85,8 @@ public class CursorWindow extends SQLiteClosable implements Parcelable {
private static native boolean nativePutDouble(int windowPtr, double value, int row, int column);
private static native boolean nativePutNull(int windowPtr, int row, int column);
private static native String nativeGetName(int windowPtr);
/**
* Creates a new empty cursor window and gives it a name.
* <p>
@@ -95,6 +98,7 @@ public class CursorWindow extends SQLiteClosable implements Parcelable {
*/
public CursorWindow(String name) {
mStartPos = 0;
mName = name;
mWindowPtr = nativeCreate(name, sCursorWindowSize);
if (mWindowPtr == 0) {
throw new CursorWindowAllocationException("Cursor window allocation of " +
@@ -129,6 +133,7 @@ public class CursorWindow extends SQLiteClosable implements Parcelable {
throw new CursorWindowAllocationException("Cursor window could not be "
+ "created from binder.");
}
mName = nativeGetName(mWindowPtr);
mCloseGuard.open("close");
}
@@ -155,6 +160,14 @@ public class CursorWindow extends SQLiteClosable implements Parcelable {
}
}
/**
* Gets the name of this cursor window.
* @hide
*/
public String getName() {
return mName;
}
/**
* Closes the cursor window and frees its underlying resources when all other
* remaining references have been released.
@@ -758,4 +771,9 @@ public class CursorWindow extends SQLiteClosable implements Parcelable {
String s = (buff.length() > 980) ? buff.substring(0, 980) : buff.toString();
return "# Open Cursors=" + total + s;
}
@Override
public String toString() {
return getName() + " {" + Integer.toHexString(mWindowPtr) + "}";
}
}

26
core/java/android/database/DatabaseUtils.java
View File

@@ -725,6 +725,32 @@ public class DatabaseUtils {
}
}
/**
* Picks a start position for {@link Cursor#fillWindow} such that the
* window will contain the requested row and a useful range of rows
* around it.
*
* When the data set is too large to fit in a cursor window, seeking the
* cursor can become a very expensive operation since we have to run the
* query again when we move outside the bounds of the current window.
*
* We try to choose a start position for the cursor window such that
* 1/3 of the window's capacity is used to hold rows before the requested
* position and 2/3 of the window's capacity is used to hold rows after the
* requested position.
*
* @param cursorPosition The row index of the row we want to get.
* @param cursorWindowCapacity The estimated number of rows that can fit in
* a cursor window, or 0 if unknown.
* @return The recommended start position, always less than or equal to
* the requested row.
* @hide
*/
public static int cursorPickFillWindowStartPosition(
int cursorPosition, int cursorWindowCapacity) {
return Math.max(cursorPosition - cursorWindowCapacity / 3, 0);
}
/**
* Query the table for the number of rows in the table.
* @param db the database the table is in

12
core/java/android/database/IBulkCursor.java
View File

@@ -30,11 +30,17 @@ import android.os.RemoteException;
*/
public interface IBulkCursor extends IInterface {
/**
* Returns a BulkCursorWindow, which either has a reference to a shared
* memory segment with the rows, or an array of JSON strings.
* Gets a cursor window that contains the specified position.
* The window will contain a range of rows around the specified position.
*/
public CursorWindow getWindow(int startPos) throws RemoteException;
public CursorWindow getWindow(int position) throws RemoteException;
/**
* Notifies the cursor that the position has changed.
* Only called when {@link #getWantsAllOnMoveCalls()} returns true.
*
* @param position The new position
*/
public void onMove(int position) throws RemoteException;
/**

26
core/java/android/database/sqlite/SQLiteCursor.java
View File

@@ -18,6 +18,7 @@ package android.database.sqlite;
import android.database.AbstractWindowedCursor;
import android.database.CursorWindow;
import android.database.DatabaseUtils;
import android.os.StrictMode;
import android.util.Log;
@@ -48,7 +49,10 @@ public class SQLiteCursor extends AbstractWindowedCursor {
private final SQLiteCursorDriver mDriver;
/** The number of rows in the cursor */
private volatile int mCount = NO_COUNT;
private int mCount = NO_COUNT;
/** The number of rows that can fit in the cursor window, 0 if unknown */
private int mCursorWindowCapacity;
/** A mapping of column names to column indices, to speed up lookups */
private Map<String, Integer> mColumnNameMap;
@@ -158,18 +162,20 @@ public class SQLiteCursor extends AbstractWindowedCursor {
return mCount;
}
private void fillWindow(int startPos) {
private void fillWindow(int requiredPos) {
clearOrCreateWindow(getDatabase().getPath());
mWindow.setStartPosition(startPos);
int count = getQuery().fillWindow(mWindow);
if (startPos == 0) { // fillWindow returns count(*) only for startPos = 0
if (mCount == NO_COUNT) {
int startPos = DatabaseUtils.cursorPickFillWindowStartPosition(requiredPos, 0);
mCount = getQuery().fillWindow(mWindow, startPos, requiredPos, true);
mCursorWindowCapacity = mWindow.getNumRows();
if (Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG, "received count(*) from native_fill_window: " + count);
Log.d(TAG, "received count(*) from native_fill_window: " + mCount);
}
mCount = count;
} else if (mCount <= 0) {
throw new IllegalStateException("Row count should never be zero or negative "
+ "when the start position is non-zero");
} else {
int startPos = DatabaseUtils.cursorPickFillWindowStartPosition(requiredPos,
mCursorWindowCapacity);
getQuery().fillWindow(mWindow, startPos, requiredPos, false);
}
}

36
core/java/android/database/sqlite/SQLiteQuery.java
View File

@@ -30,8 +30,10 @@ import android.util.Log;
public class SQLiteQuery extends SQLiteProgram {
private static final String TAG = "SQLiteQuery";
private static native int nativeFillWindow(int databasePtr, int statementPtr, int windowPtr,
int startPos, int offsetParam);
private static final boolean DEBUG_FILL_WINDOW_PERFORMANCE = false;
private static native long nativeFillWindow(int databasePtr, int statementPtr, int windowPtr,
int offsetParam, int startPos, int requiredPos, boolean countAllRows);
private static native int nativeColumnCount(int statementPtr);
private static native String nativeColumnName(int statementPtr, int columnIndex);
@@ -71,19 +73,39 @@ public class SQLiteQuery extends SQLiteProgram {
* Reads rows into a buffer. This method acquires the database lock.
*
* @param window The window to fill into
* @return number of total rows in the query
* @param startPos The start position for filling the window.
* @param requiredPos The position of a row that MUST be in the window.
* If it won't fit, then the query should discard part of what it filled.
* @param countAllRows True to count all rows that the query would
* return regardless of whether they fit in the window.
* @return Number of rows that were enumerated. Might not be all rows
* unless countAllRows is true.
*/
/* package */ int fillWindow(CursorWindow window) {
/* package */ int fillWindow(CursorWindow window,
int startPos, int requiredPos, boolean countAllRows) {
mDatabase.lock(mSql);
long timeStart = SystemClock.uptimeMillis();
try {
acquireReference();
try {
window.acquireReference();
int numRows = nativeFillWindow(nHandle, nStatement, window.mWindowPtr,
window.getStartPosition(), mOffsetIndex);
long result = nativeFillWindow(nHandle, nStatement, window.mWindowPtr,
mOffsetIndex, startPos, requiredPos, countAllRows);
int actualPos = (int)(result >> 32);
int countedRows = (int)result;
window.setStartPosition(actualPos);
if (DEBUG_FILL_WINDOW_PERFORMANCE) {
Log.d(TAG, "fillWindow: window=\"" + window
+ "\", startPos=" + startPos + ", requiredPos=" + requiredPos
+ ", countAllRows=" + countAllRows
+ ", offset=" + mOffsetIndex
+ ", actualPos=" + actualPos + ", filledRows=" + window.getNumRows()
+ ", countedRows=" + countedRows
+ ", took " + (SystemClock.uptimeMillis() - timeStart)
+ " ms, query=\"" + mSql + "\"");
}
mDatabase.logTimeStat(mSql, timeStart);
return numRows;
return countedRows;
} catch (IllegalStateException e){
// simply ignore it
return 0;