Coordinated Hash Indexes for Database Reconfiguration
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Solution Overview
Problem
Database reconfiguration, which involves scanning millions of locks during server node changes, leads to prolonged downtime due to the time-consuming process of freezing and scanning every lock, affecting high availability requirements in modern global businesses.
Innovation Solution
Implementing coordinated hash indexes that allow for optimized lock master reconfiguration by indexing into both master and local hash tables, reducing the need to scan entire local hash tables and minimizing CPU cycles stalled due to cache misses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If database reconfiguration scans every lock maintained for the database, then it ensures complete lock master reconfiguration, but it causes prolonged downtime and affects high availability requirements
Solution Approach 1:
The patent segments the lock table into multiple partitions, each maintained by a different server node. During reconfiguration, only the specific partition containing the affected lock master needs to be scanned and updated, rather than scanning every lock in the entire database. This segmentation reduces the scope of work from O(n) to O(1) or O(k) where k is the number of partitions, significantly reducing downtime while maintaining reconfiguration completeness.
2Stability of the object's composition
If database reconfiguration freezes access to the database, then it ensures data consistency during reconfiguration, but it causes complete unavailability of database services
Solution Approach 1:
The patent implements local quality by allowing database access to continue on all server nodes except the specific node undergoing reconfiguration. Each node independently manages its local lock partition, enabling localized reconfiguration without global freezing. This maintains data consistency at the affected partition while preserving overall database availability and productivity.
3Loss of time
If coordinated hash indexes are implemented to index into both master and local hash tables, then it reduces the need to scan entire local hash tables, but it increases the complexity of the indexing structure
Solution Approach 1:
The patent merges the master hash index and local hash index into a coordinated unified indexing structure. The hash index simultaneously provides routing information for both the master lock table and the local lock partitions, eliminating the need for separate scanning operations. While the index structure becomes more complex, this merging reduces reconfiguration time by enabling direct access to relevant lock partitions without full-table scans.
Data Source
AI summary
According to embodiments, reconfiguration of lock masters for a cluster of nodes is optimized using coordinated hash indexes to index into the master hash table and into local hash tables stored on the nodes of the cluster. A DBMS uses a hybrid hash index, a portion of which represents a corresponding master hash index, to index into both the master hash table and into a local hash table for a given lock. The hash index used to store lock metadata in a particular local hash table bucket, on a particular node, encodes the lock master index, for a master hash table, to which the locks in the local hash table bucket correspond. Only the portions of the local hash table on the lock master that correspond to the index of the master hash table bucket need to be scanned in order to perform needed tasks for lock master reconfiguration.