Method iterateScan

src/storage/table/update_info.cpp:245–296

}

void UpdateInfo::iterateScan(const Transaction* transaction, uint64_t startOffsetToScan,
    uint64_t numRowsToScan, uint64_t startPosInOutput,
    const iterate_read_from_row_func_t& readFromRowFunc) const {
    if (!isSet()) {
        return;
    }
    auto [startVectorIdx, startOffsetInVector] =
        StorageUtils::getQuotientRemainder(startOffsetToScan, DEFAULT_VECTOR_CAPACITY);
    auto [endVectorIdx, endOffsetInVector] = StorageUtils::getQuotientRemainder(
        startOffsetToScan + numRowsToScan, DEFAULT_VECTOR_CAPACITY);
    idx_t idx = startVectorIdx;
    sel_t posInVector = startPosInOutput;
    while (idx <= endVectorIdx) {
        const auto startOffsetInclusively = idx == startVectorIdx ? startOffsetInVector : 0;
        const auto endOffsetExclusively =
            idx == endVectorIdx ? endOffsetInVector : DEFAULT_VECTOR_CAPACITY;
        const auto numRowsInVector = endOffsetExclusively - startOffsetInclusively;
        // We keep track of the rows that have been applied with updates from updateInfo. The update
        // version chain is maintained with the newest version at the head and the oldest version at
        // the tail. For each tuple, we iterate through the chain to merge the updates from latest
        // visible version. If a row has been updated in the current vectorInfo, we should skip it
        // in older versions.
        std::bitset<DEFAULT_VECTOR_CAPACITY> rowsUpdated;
        iterateVectorInfo(transaction, idx, [&](const VectorUpdateInfo& vecUpdateInfo) -> void {
            if (vecUpdateInfo.numRowsUpdated == 0) {
                return;
            }
            if (rowsUpdated.count() == numRowsInVector) {
                // All rows in this vector have been updated with a newer visible version already.
                return;
            }
            // TODO(Guodong): Ideally we should make sure vecUpdateInfo.rowsInVector is sorted to
            // simplify the checks here.
            for (auto i = 0u; i < vecUpdateInfo.numRowsUpdated; i++) {
                if (vecUpdateInfo.rowsInVector[i] < startOffsetInclusively ||
                    vecUpdateInfo.rowsInVector[i] >= endOffsetExclusively) {
                    // Continue if the row is out of the current scan range.
                    continue;
                }
                auto updatedRowIdx = vecUpdateInfo.rowsInVector[i] - startOffsetInclusively;
                if (rowsUpdated[updatedRowIdx]) {
                    // Skip the rows that have been updated with a newer visible version already.
                    continue;
                }
                readFromRowFunc(vecUpdateInfo, i, posInVector + updatedRowIdx);
                rowsUpdated[updatedRowIdx] = true;
            }
        });
        posInVector += numRowsInVector;
        idx++;
    }
}

} // namespace storage
} // namespace lbug