[IGNITE-9256] SQL: make sure that fetched results are cleared from iterator when last element is fetched

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.6
• Fix Version/s: 2.7
• Component/s: sql
• Labels: sql-stability
• Assignee: Sergey Grimstad
• Reporter: Vladimir Ozerov
• Created: 13/Aug/18 10:48
• Updated: 02/Aug/19 11:23
• Resolved: 28/Aug/18 07:56

Description

In practice it is possible for user to forget to nullify Ignite's result set after iteration is finished. Or he may delay cleanup for some reason.
The problem is that we hold the whole H2's result set inside our iterator even after all results are delivered to the user.
We should forcibly close and then nullify all H2 objects once all results are returned.

Key code pieces:
IgniteH2Indexing.executeSqlQueryWithTimer - how we get result from H2
H2ResultSetIterator - base iterator with H2 objects inside

Issue Links

• relates to: IGNITE-9428 MVCC TX: MvccQueryTrackerImpl.onDone() semantic is broken.
• links to: GitHub Pull Request #4540
• links to: GitHub Pull Request #4540