14、COPS和COPS - GT系统的深入解析

COPS和COPS - GT系统的深入解析

1. get_trans算法介绍

get_trans算法用于获取数据存储的一致视图，以下是其伪代码：

# @param
# keys
# list of keys
# @param
# ctx_id
# context id
# @return values
# list of values
function get_trans(keys, ctx_id):
    # Get keys in parallel (first round)
    for k in keys
        results[k] = get_by_version(k, LATEST)
    # Calculate causally correct versions (ccv)
    for k in keys
        ccv[k] = max(ccv[k], results[k].vers)
        for dep in results[k].deps
            if dep.key in keys
                ccv[dep.key] = max(ccv[dep.key], dep.vers)
    # Get needed ccvs in parallel (second round)
    for k in keys
        if ccv[k] > results[k].vers
            results[k] = get_by_version(k, ccv[k])
    # Update the metadata st