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...
private void open() {
mConnectionPtr = nativeOpen(mConfiguration.path, mConfiguration.openFlags,
mConfiguration.label,
SQLiteDebug.DEBUG_SQL_STATEMENTS, SQLiteDebug.DEBUG_SQL_TIME);
setPageSize();
setForeignKeyModeFromConfiguration();
setWalModeFromConfiguration();
setJournalSizeLimit();
setAutoCheckpointInterval();
setLocaleFromConfiguration();
// Register custom functions.
final int functionCount = mConfiguration.customFunctions.size();
for (
int i = 0; i < functionCount; i++) {
SQLiteCustomFunction function = mConfiguration.customFunctions.get(i);
nativeRegisterCustomFunction(mConnectionPtr, function);
}
}
...
private void setWalModeFromConfiguration() {
if (!mConfiguration.isInMemoryDb() && !mIsReadOnlyConnection) {
if ((mConfiguration.openFlags & SQLiteDatabase.ENABLE_WRITE_AHEAD_LOGGING) != 0) {
setJournalMode("
WAL");
setSyncMode(SQLiteGlobal.getWALSyncMode());
}
else {
setJournalMode(SQLiteGlobal.getDefaultJournalMode());
setSyncMode(SQLiteGlobal.getDefaultSyncMode());
}
}
}
...
private void setJournalMode(String newValue) {
String value = executeForString("
PRAGMA journal_mode",
null,
null);
if (!value.equalsIgnoreCase(newValue)) {
try {
String result = executeForString("PRAGMA journal_mode=" + newValue, null, null);
if (result.equalsIgnoreCase(newValue)) {
return;
}
// PRAGMA journal_mode silently fails and returns the original journal
// mode in some cases if the journal mode could not be changed.
}
catch (SQLiteDatabaseLockedException ex) {
// This error (SQLITE_BUSY) occurs if one connection has the database
// open in WAL mode and another tries to change it to non-WAL.
}
// Because we always disable WAL mode when a database is first opened
// (even if we intend to re-enable it), we can encounter problems if
// there is another open connection to the database somewhere.
// This can happen for a variety of reasons such as an application opening
// the same database in multiple processes at the same time or if there is a
// crashing content provider service that the ActivityManager has
// removed from its registry but whose process hasn't quite died yet
// by the time it is restarted in a new process.
//
// If we don't change the journal mode, nothing really bad happens.
// In the worst case, an application that enables WAL might not actually
// get it, although it can still use connection pooling.
Log.w(TAG, "
Could not change the database journal mode of '"
+ mConfiguration.label + "
' from '" + value + "
' to '" + newValue
+ "
' because the database is locked. This usually means that "
+ "
there are other open connections to the database which prevents "
+ "
the database from enabling or disabling write-ahead logging mode. "
+ "
Proceeding without changing the journal mode.");
}
}
...
/**
* Executes a statement that returns a single {@link String} result.
*
* @param sql The SQL statement to execute.
* @param bindArgs The arguments to bind, or null if none.
* @param cancellationSignal A signal to cancel the operation in progress, or null if none.
* @return The value of the first column in the first row of the result set
* as a <code>String</code>, or null if none.
*
* @throws SQLiteException if an error occurs, such as a syntax error
* or invalid number of bind arguments.
* @throws OperationCanceledException if the operation was canceled.
*/
public String executeForString(String sql, Object[] bindArgs,
CancellationSignal cancellationSignal) {
if (sql ==
null) {
throw new IllegalArgumentException("
sql must not be null.");
}
final int cookie = mRecentOperations.beginOperation("
executeForString", sql, bindArgs);
try {
final PreparedStatement statement = acquirePreparedStatement(sql);
try {
throwIfStatementForbidden(statement);
bindArguments(statement, bindArgs);
applyBlockGuardPolicy(statement);
attachCancellationSignal(cancellationSignal);
try {
return nativeExecuteForString(mConnectionPtr, statement.mStatementPtr);
}
finally {
detachCancellationSignal(cancellationSignal);
}
}
finally {
releasePreparedStatement(statement);
}
}
catch (RuntimeException ex) {
mRecentOperations.failOperation(cookie, ex);
throw ex;
}
finally {
mRecentOperations.endOperation(cookie);
}
}