[IMPALA-7121] Clean up partitionIds_ member from HdfsTable

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 2.12.0
• Fix Version/s: Impala 2.13.0, Impala 3.1.0
• Component/s: Catalog
• Epic Color: ghx-label-9
• Assignee: Gabor Kaszab
• Reporter: Gabor Kaszab
• Created: 05/Jun/18 08:09
• Updated: 24/Feb/19 02:40
• Resolved: 25/Jun/18 11:07

Description

HdfsTable already has a number of internal structures that meant to speed-up processes like partition pruning. partitionIds_ is a HashSet of partition IDs but apparently we already have this information in partitionMap_ that is a mapping between partition IDs and HdfsPartitions. As a result we can simply drop partitionsIds_ and modify getPartitionIds() to return partitionMap_.keySet().

This is not expected to introduce regression for the following reasons:

• HashMap.keySet() is O(1) complex as it returns a wrapper around an internal set of keys from the HashMap.
• We have to be careful not to modify this keySet() returned from getPartitionIds() because that would also alter the partitionMap_ member. This is safe as all callsites of getPartitionIds() immediately copies the items of the set to a separate set.