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dbms: lazy opening of files [#CONV-2944].

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This commit is contained in:
Alexey Milovidov 2012-06-21 16:16:58 +00:00
parent c9f9913ef5
commit 3482ab7686
1 changed files with 16 additions and 3 deletions
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19
dbms/src/Storages/StorageLog.cpp
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@ -24,8 +24,6 @@ using Poco::SharedPtr;
LogBlockInputStream::LogBlockInputStream(size_t block_size_, const Names & column_names_, StorageLog & storage_, size_t mark_number_, size_t rows_limit_)
: block_size(block_size_), column_names(column_names_), storage(storage_), mark_number(mark_number_), rows_limit(rows_limit_), rows_read(0)
{
for (Names::const_iterator it = column_names.begin(); it != column_names.end(); ++it)
streams.insert(std::make_pair(*it, new Stream(storage.files[*it].data_file.path(), storage.files[*it].marks[mark_number].offset)));
}
@ -33,6 +31,13 @@ Block LogBlockInputStream::readImpl()
{
Block res;
/// Если файлы не открыты, то открываем их.
if (streams.empty())
for (Names::const_iterator it = column_names.begin(); it != column_names.end(); ++it)
streams.insert(std::make_pair(*it, new Stream(
storage.files[*it].data_file.path(),
storage.files[*it].marks[mark_number].offset)));
for (Names::const_iterator it = column_names.begin(); it != column_names.end(); ++it)
{
ColumnWithNameAndType column;
@ -47,7 +52,15 @@ Block LogBlockInputStream::readImpl()
if (res)
rows_read += res.getByPosition(0).column->size();
else
{
/** Закрываем файлы (ещё до уничтожения объекта).
* Чтобы при создании многих источников, но одновременном чтении только из нескольких,
* буферы не висели в памяти.
*/
streams.clear();
}
return res;
}