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Code Issues Releases Activity

SERVER-595 be sure to release mutex in corner case when scan from beginning

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This commit is contained in:
Aaron 2010-02-06 14:56:48 -08:00
parent 7c48eed652
commit 1d562aeb9b
1 changed files with 5 additions and 13 deletions
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18
db/query.cpp
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@ -504,14 +504,6 @@ namespace mongo {
virtual void init() {
b_.skip( sizeof( QueryResult ) );
// findingStart mode is used to find the first operation of interest when
// we are scanning through a repl log. For efficiency in the common case,
// where the first operation of interest is closer to the tail than the head,
// we start from the tail of the log and work backwards until we find the
// first operation of interest. Then we scan forward from that first operation,
// actually returning results to the client. During the findingStart phase,
// we release the db mutex occasionally to avoid blocking the db process for
// an extended period of time.
if ( findingStart_ ) {
// Use a ClientCursor here so we can release db mutex while scanning
// oplog (can take quite a while with large oplogs).
@ -553,7 +545,7 @@ namespace mongo {
return DiskLoc(); // reached beginning of collection
}
void createClientCursor( const DiskLoc &startLoc ) {
void createClientCursor( const DiskLoc &startLoc = DiskLoc() ) {
auto_ptr<Cursor> c = qp().newCursor( startLoc );
findingStartCursor_ = new ClientCursor(c, qp().ns(), false);
}
@ -579,7 +571,7 @@ namespace mongo {
switch( findingStartMode_ ) {
case Initial: {
if ( !matcher_->matches( findingStartCursor_->c->currKey(), findingStartCursor_->c->currLoc() ) ) {
findingStart_ = false; // found first recort out of query range, so scan normally
findingStart_ = false; // found first record out of query range, so scan normally
c_ = qp().newCursor( findingStartCursor_->c->currLoc() );
return;
}
@ -600,9 +592,9 @@ namespace mongo {
return;
}
DiskLoc prev = prevLoc( findingStartCursor_->c->currLoc() );
if ( prev.isNull() ) { // no previous extent, just start a regular scan from beginning
findingStart_ = false;
c_ = qp().newCursor();
if ( prev.isNull() ) { // hit beginning, so start scanning from here
createClientCursor();
findingStartMode_ = InExtent;
return;
}
// There might be a more efficient implementation than creating new cursor & client cursor each time,