Query ConfigDiffTracker<ValType, ShardType>::configDiffQuery() const {
_assertAttached();
// Basic idea behind the query is to find all the chunks $gte the current max version.
// Currently, any splits and merges will increment the current max version.
BSONObjBuilder queryB;
queryB.append(ChunkType::ns(), _ns);
{
BSONObjBuilder tsBuilder(queryB.subobjStart(ChunkType::DEPRECATED_lastmod()));
tsBuilder.appendTimestamp("$gte", _maxVersion->toLong());
tsBuilder.done();
}
// NOTE: IT IS IMPORTANT FOR CONSISTENCY THAT WE SORT BY ASC VERSION, IN ORDER TO HANDLE
// CURSOR YIELDING BETWEEN CHUNKS BEING MIGRATED.
//
// This ensures that changes to chunk version (which will always be higher) will always
// come *after* our current position in the chunk cursor.
Query queryObj(queryB.obj());
queryObj.sort(BSON("lastmod" << 1));
LOG(2) << "major version query from " << *_maxVersion << " and over "
<< _maxShardVersions->size() << " shards is " << queryObj;
return queryObj;
}
Query ConfigDiffTracker<ValType,ShardType>::
configDiffQuery( const set<ChunkVersion>& extraMinorVersions ) const
{
verifyAttached();
//
// Basic idea behind the query is to find all the chunks $gt the current max version, and
// then also update chunks that we need minor versions - splits and (2.0) max chunks on
// shards
//
static const int maxMinorVersionClauses = 50;
BSONObjBuilder queryB;
int numStaleMinorClauses = extraMinorVersions.size() + _maxShardVersions->size();
#ifdef _DEBUG
// In debug builds, randomly trigger full reloads to exercise both codepaths
if( rand() % 2 ) numStaleMinorClauses = maxMinorVersionClauses;
#endif
queryB.append(ChunkType::ns(), _ns);
//
// If we have only a few minor versions to refresh, we can be more selective in our query
//
if( numStaleMinorClauses < maxMinorVersionClauses ) {
//
// Get any version changes higher than we know currently
//
BSONArrayBuilder queryOrB( queryB.subarrayStart( "$or" ) );
{
BSONObjBuilder queryNewB( queryOrB.subobjStart() );
{
BSONObjBuilder ts(queryNewB.subobjStart(ChunkType::DEPRECATED_lastmod()));
// We should *always* pull at least a single chunk back, this lets us quickly
// detect if our collection was unsharded (and most of the time if it was
// resharded) in the meantime
ts.appendTimestamp( "$gte", _maxVersion->toLong() );
ts.done();
}
queryNewB.done();
}
// Get any shard version changes higher than we know currently
// Needed since there could have been a split of the max version chunk of any shard
// TODO: Ideally, we shouldn't care about these
for( typename map<ShardType, ChunkVersion>::const_iterator it = _maxShardVersions->begin(); it != _maxShardVersions->end(); it++ ) {
BSONObjBuilder queryShardB( queryOrB.subobjStart() );
queryShardB.append(ChunkType::shard(), nameFrom( it->first ) );
{
BSONObjBuilder ts(queryShardB.subobjStart(ChunkType::DEPRECATED_lastmod()));
ts.appendTimestamp( "$gt", it->second.toLong() );
ts.done();
}
queryShardB.done();
}
// Get any minor version changes we've marked as interesting
// TODO: Ideally we shouldn't care about these
for( set<ChunkVersion>::const_iterator it = extraMinorVersions.begin(); it != extraMinorVersions.end(); it++ ) {
BSONObjBuilder queryShardB( queryOrB.subobjStart() );
{
BSONObjBuilder ts(queryShardB.subobjStart(ChunkType::DEPRECATED_lastmod()));
ts.appendTimestamp( "$gt", it->toLong() );
ts.appendTimestamp( "$lt",
ChunkVersion( it->majorVersion() + 1, 0, OID() ).toLong() );
ts.done();
}
queryShardB.done();
}
queryOrB.done();
}
BSONObj query = queryB.obj();
LOG(2) << "major version query from " << *_maxVersion << " and over "
<< _maxShardVersions->size() << " shards is " << query << endl;
//
// NOTE: IT IS IMPORTANT FOR CONSISTENCY THAT WE SORT BY ASC VERSION, TO HANDLE
// CURSOR YIELDING BETWEEN CHUNKS BEING MIGRATED.
//
// This ensures that changes to chunk version (which will always be higher) will always
// come *after* our current position in the chunk cursor.
//
Query queryObj(query);
queryObj.sort(BSON( "lastmod" << 1 ));
return Query( query );
}