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#pragma once
#include <Storages/LiveView/StorageLiveView.h>
#include <Processors/ISource.h>
namespace DB
{
/** Implements LIVE VIEW table WATCH input stream.
* Keeps stream alive by outputting blocks with no rows
* based on period specified by the heartbeat interval.
*/
class LiveViewSource : public ISource
{
using NonBlockingResult = std::pair<Block, bool>;
public:
LiveViewSource(std::shared_ptr<StorageLiveView> storage_,
std::shared_ptr<BlocksPtr> blocks_ptr_,
std::shared_ptr<BlocksMetadataPtr> blocks_metadata_ptr_,
std::shared_ptr<bool> active_ptr_,
const bool has_limit_, const UInt64 limit_,
const UInt64 heartbeat_interval_sec_)
: ISource(storage_->getHeader())
, storage(std::move(storage_)), blocks_ptr(std::move(blocks_ptr_)),
blocks_metadata_ptr(std::move(blocks_metadata_ptr_)),
active_ptr(active_ptr_),
has_limit(has_limit_), limit(limit_),
heartbeat_interval_usec(heartbeat_interval_sec_ * 1000000)
{
/// grab active pointer
active = active_ptr.lock();
}
String getName() const override { return "LiveViewSource"; }
void onCancel() override
{
if (storage->shutdown_called)
return;
std::lock_guard lock(storage->mutex);
storage->condition.notify_all();
}
void refresh()
{
if (active && blocks && it == end)
it = blocks->begin();
}
void suspend()
{
active.reset();
}
void resume()
{
active = active_ptr.lock();
{
if (!blocks || blocks.get() != (*blocks_ptr).get())
blocks = (*blocks_ptr);
}
it = blocks->begin();
begin = blocks->begin();
end = blocks->end();
}
NonBlockingResult tryRead()
{
return tryReadImpl(false);
}
protected:
Chunk generate() override
{
/// try reading
auto block = tryReadImpl(true).first;
return Chunk(block.getColumns(), block.rows());
}
/** tryRead method attempts to read a block in either blocking
* or non-blocking mode. If blocking is set to false
* then method return empty block with flag set to false
* to indicate that method would block to get the next block.
*/
NonBlockingResult tryReadImpl(bool blocking)
{
Block res;
if (has_limit && num_updates == static_cast<Int64>(limit))
{
return { Block(), true };
}
/// If blocks were never assigned get blocks
if (!blocks)
{
std::lock_guard lock(storage->mutex);
if (!active)
return { Block(), false };
blocks = (*blocks_ptr);
it = blocks->begin();
begin = blocks->begin();
end = blocks->end();
}
if (isCancelled() || storage->shutdown_called)
{
return { Block(), true };
}
if (it == end)
{
{
std::unique_lock lock(storage->mutex);
if (!active)
return { Block(), false };
/// If we are done iterating over our blocks
/// and there are new blocks available then get them
if (blocks.get() != (*blocks_ptr).get())
{
blocks = (*blocks_ptr);
it = blocks->begin();
begin = blocks->begin();
end = blocks->end();
}
/// No new blocks available wait for new ones
else
{
if (!blocking)
{
return { Block(), false };
}
if (!end_of_blocks)
{
end_of_blocks = true;
return { getPort().getHeader(), true };
}
while (true)
{
UInt64 timestamp_usec = static_cast<UInt64>(Poco::Timestamp().epochMicroseconds());
/// Or spurious wakeup.
bool signaled = std::cv_status::no_timeout == storage->condition.wait_for(lock,
std::chrono::microseconds(std::max(UInt64(0), heartbeat_interval_usec - (timestamp_usec - last_event_timestamp_usec))));
if (isCancelled() || storage->shutdown_called)
{
return { Block(), true };
}
if (signaled)
{
break;
}
else
{
// heartbeat
last_event_timestamp_usec = static_cast<UInt64>(Poco::Timestamp().epochMicroseconds());
return { getPort().getHeader(), true };
}
}
}
}
return tryReadImpl(blocking);
}
res = *it;
++it;
if (it == end)
{
end_of_blocks = false;
num_updates += 1;
}
last_event_timestamp_usec = static_cast<UInt64>(Poco::Timestamp().epochMicroseconds());
return { res, true };
}
private:
std::shared_ptr<StorageLiveView> storage;
std::shared_ptr<BlocksPtr> blocks_ptr;
std::shared_ptr<BlocksMetadataPtr> blocks_metadata_ptr;
std::weak_ptr<bool> active_ptr;
std::shared_ptr<bool> active;
BlocksPtr blocks;
BlocksMetadataPtr blocks_metadata;
Blocks::iterator it;
Blocks::iterator end;
Blocks::iterator begin;
const bool has_limit;
const UInt64 limit;
Int64 num_updates = -1;
bool end_of_blocks = false;
UInt64 heartbeat_interval_usec;
UInt64 last_event_timestamp_usec = 0;
};
}
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