/**
* Iterate through the table blocks until all the active tuples have been found. Skip dirty tuples
* and mark them as clean so that they can be copied during the next snapshot.
*/
bool CopyOnWriteIterator::next(TableTuple &out) {
assert(m_currentBlock != NULL);
while (true) {
if (m_blockOffset >= m_currentBlock->unusedTupleBoundry()) {
if (m_blockIterator == m_end) {
m_table->snapshotFinishedScanningBlock(m_currentBlock, TBPtr());
break;
}
m_table->snapshotFinishedScanningBlock(m_currentBlock, m_blockIterator.data());
m_location = m_blockIterator.key();
m_currentBlock = m_blockIterator.data();
assert(m_currentBlock->address() == m_location);
m_blockIterator.data() = TBPtr();
m_blockOffset = 0;
m_blockIterator++;
}
assert(m_location < m_currentBlock.get()->address() + m_table->m_tableAllocationSize);
assert(m_location < m_currentBlock.get()->address() + (m_table->m_tupleLength * m_table->m_tuplesPerBlock));
assert (out.sizeInValues() == m_table->columnCount());
m_blockOffset++;
out.move(m_location);
const bool active = out.isActive();
const bool dirty = out.isDirty();
// Return this tuple only when this tuple is not marked as deleted and isn't dirty
if (active && !dirty) {
out.setDirtyFalse();
m_location += m_tupleLength;
return true;
} else {
out.setDirtyFalse();
m_location += m_tupleLength;
}
}
return false;
}
/**
* Iterate through the table blocks until all the active tuples have been found. Skip dirty tuples
* and mark them as clean so that they can be copied during the next snapshot.
*/
bool CopyOnWriteIterator::next(TableTuple &out) {
if (m_currentBlock == NULL) {
return false;
}
while (true) {
if (m_blockOffset >= m_currentBlock->unusedTupleBoundary()) {
if (m_blockIterator == m_end) {
m_surgeon->snapshotFinishedScanningBlock(m_currentBlock, TBPtr());
break;
}
m_surgeon->snapshotFinishedScanningBlock(m_currentBlock, m_blockIterator.data());
char *finishedBlock = m_currentBlock->address();
m_location = m_blockIterator.key();
m_currentBlock = m_blockIterator.data();
assert(m_currentBlock->address() == m_location);
m_blockOffset = 0;
// Remove the finished block from the map so that it can be released
// back to the OS if all tuples in the block is deleted.
//
// This invalidates the iterators, so we have to get new iterators
// using the current block's start address. m_blockIterator has to
// point to the next block, hence the upper_bound() call.
m_blocks.erase(finishedBlock);
m_blockIterator = m_blocks.upper_bound(m_currentBlock->address());
m_end = m_blocks.end();
}
assert(m_location < m_currentBlock.get()->address() + m_table->getTableAllocationSize());
assert(m_location < m_currentBlock.get()->address() + (m_table->getTupleLength() * m_table->getTuplesPerBlock()));
assert (out.columnCount() == m_table->columnCount());
m_blockOffset++;
out.move(m_location);
const bool active = out.isActive();
const bool dirty = out.isDirty();
if (dirty) m_skippedDirtyRows++;
if (!active) m_skippedInactiveRows++;
// Return this tuple only when this tuple is not marked as deleted and isn't dirty
if (active && !dirty) {
out.setDirtyFalse();
m_location += m_tupleLength;
return true;
} else {
out.setDirtyFalse();
m_location += m_tupleLength;
}
}
return false;
}
CopyOnWriteIterator::CopyOnWriteIterator(
PersistentTable *table,
TBMapI start,
TBMapI end) :
m_table(table), m_blockIterator(start), m_end(end),
m_tupleLength(table->m_tupleLength),
m_location(NULL),
m_blockOffset(0),
m_currentBlock(NULL) {
//Prime the pump
m_table->snapshotFinishedScanningBlock(m_currentBlock, m_blockIterator.data());
m_location = m_blockIterator.key();
m_currentBlock = m_blockIterator.data();
m_blockIterator.data() = TBPtr();
m_blockOffset = 0;
m_blockIterator++;
}
/**
* Internal method that handles transitions between blocks and
* returns true as long as tuples are available.
*/
bool ElasticScanner::continueScan() {
if (!m_scanComplete) {
// First block or end of block?
if (m_currentBlockPtr == NULL || m_tupleIndex >= m_currentBlockPtr->unusedTupleBoundry()) {
// No more blocks?
m_scanComplete = (m_blockIterator == m_blockEnd);
if (!m_scanComplete) {
// Shift to the next block.
m_tuplePtr = m_blockIterator.key();
m_currentBlockPtr = m_blockIterator.data();
m_scannedBlocks.insert(m_currentBlockPtr);
assert(m_currentBlockPtr->address() == m_tuplePtr);
m_blockIterator.data() = TBPtr();
m_tupleIndex = 0;
m_blockIterator++;
}
}
}
return !m_scanComplete;
}
