[IGNITE-10598] H2 ConnectionManager drop ThreadLocal logic

• Type: Task
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Affects Version/s: 2.7
• Component/s: sql
• Labels: h2-limitation
• Ignite Flags: Docs Required
• Assignee: Taras Ledkov
• Reporter: Taras Ledkov
• Created: 07/Dec/18 13:59
• Updated: 01/Oct/19 03:09
• Resolved: 06/Feb/19 10:22

Description

Looks like we have to change H2 connection management after the patch IGNITE-9171 is applied. Caching H2 connection in ThreadLocal doesn't make sense because connections are shared between thread in fact.

Drop ThreadLocal connection cache simplifies connection management. We haven't check thread state to close connection.

The solution needs in good performance analysis & benchmark to be sure that contention on concurrent collection of H2 connections doesn't affect query performance.

Issue Links

• duplicates: IGNITE-11211 SQL: Rework connection pool
• relates to: IGNITE-9171 Use lazy mode with results pre-fetch
• relates to: IGNITE-7526 SQL: Introduce memory region for reducer merge results with disk offload