[HIVE-25142] Rehashing in map join fast hash table causing corruption for large keys

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0.0-alpha-1
• Component/s: Hive
• Labels: pull-request-available
• Assignee: mahesh kumar behera
• Reporter: mahesh kumar behera
• Created: 20/May/21 05:04
• Updated: 06/Dec/23 14:23
• Resolved: 22/May/21 10:29

Description

In map join the hash table is created using the keys. To support rehashing, the keys are stored in write buffer. The hash table contains the offset of the keys along with the hash code. When rehashing is done, the offset is extracted from the hash table and then hash code is generated again. For large keys of size greater than 255, the key length is also stored along with the key. In case of fast hash table implementation the way key is extracted is not proper. There is a code bug and thats causing the wrong key to be extracted and causing wrong hash code generation. This is causing the corruption in the hash table.

Issue Links

• fixes: HIVE-26673 Incorrect row count when vectorisation is enabled
• links to: GitHub Pull Request #2300