[IMPALA-12111] Speed up DATE to STRING conversion

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: Impala 4.3.0
• Component/s: Backend
• Epic Color: ghx-label-10
• Assignee: Unassigned
• Reporter: Csaba Ringhofer
• Created: 02/May/23 08:52
• Updated: 16/Jul/24 23:56
• Resolved: 08/May/23 14:35

Description

Converting DATE to STRING is slower than converting TIMESTAMP to STRING which is weird as TIMESTAMP handling should need more work. The culprit seems to be using stringstream in DateValue.ToString(): https://github.com/apache/impala/blob/14698c8b99b80db7e6fd99900e32b6742bef1662/be/src/runtime/date-value.cc#L433

As dates are returned as string to the client this also slow down the materialization of results on the coordinator.