NewCollector create an index usage collector.

NewSample creates a new data point for index usage.

NewStmtIndexUsageCollector creates a new StmtIndexUsageCollector.

Collector represents a data structure to record the index usage for the whole node.

GlobalIndexID is the key type for indexUsageMap.

Sample is the data structure to store index usage information.

SessionIndexUsageCollector collects index usage per-session.

StmtIndexUsageCollector removes the duplicates index for recording `QueryTotal` in session collector.