/**
* Reloads a table's metadata, reusing any existing cached metadata to speed up the operation.
* Returns the updated Table object or null if no table with this name exists in the catalog. If
* the existing table is dropped or modified (indicated by the catalog version changing) while the
* reload is in progress, the loaded value will be discarded and the current cached value will be
* returned. This may mean that a missing table (not yet loaded table) will be returned.
*/
public Table reloadTable(TTableName tblName) throws CatalogException {
LOG.debug(
String.format(
"Refreshing table metadata: %s.%s", tblName.getDb_name(), tblName.getTable_name()));
long previousCatalogVersion;
TableLoadingMgr.LoadRequest loadReq;
catalogLock_.readLock().lock();
try {
Table tbl = getTable(tblName.getDb_name(), tblName.getTable_name());
if (tbl == null) return null;
previousCatalogVersion = tbl.getCatalogVersion();
loadReq = tableLoadingMgr_.loadAsync(tblName, tbl);
} finally {
catalogLock_.readLock().unlock();
}
Preconditions.checkNotNull(loadReq);
try {
return replaceTableIfUnchanged(loadReq.get(), previousCatalogVersion);
} finally {
loadReq.close();
}
}
/**
* Gets the table with the given name, loading it if needed (if the existing catalog object is not
* yet loaded). Returns the matching Table or null if no table with this name exists in the
* catalog. If the existing table is dropped or modified (indicated by the catalog version
* changing) while the load is in progress, the loaded value will be discarded and the current
* cached value will be returned. This may mean that a missing table (not yet loaded table) will
* be returned.
*/
public Table getOrLoadTable(String dbName, String tblName) throws CatalogException {
TTableName tableName = new TTableName(dbName.toLowerCase(), tblName.toLowerCase());
TableLoadingMgr.LoadRequest loadReq;
long previousCatalogVersion;
// Return the table if it is already loaded or submit a new load request.
catalogLock_.readLock().lock();
try {
Table tbl = getTable(dbName, tblName);
if (tbl == null || tbl.isLoaded()) return tbl;
previousCatalogVersion = tbl.getCatalogVersion();
loadReq = tableLoadingMgr_.loadAsync(tableName, null);
} finally {
catalogLock_.readLock().unlock();
}
Preconditions.checkNotNull(loadReq);
try {
// The table may have been dropped/modified while the load was in progress, so only
// apply the update if the existing table hasn't changed.
return replaceTableIfUnchanged(loadReq.get(), previousCatalogVersion);
} finally {
loadReq.close();
}
}
