[IMPALA-7613] Support round(DECIMAL) with non-constant second argument

• Type: Bug
• Status: In Progress
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: Impala 3.0, Impala 2.12.0
• Component/s: Frontend
• Labels: decimal ramp-up
• Epic Color: ghx-label-3
• Assignee: Abhishek Rawat
• Reporter: Tim Armstrong
• Created: 24/Sep/18 18:06
• Updated: 05/Nov/19 20:02

Description

Sometimes users want to round to a precision that is data-driven (e.g. using a lookup table). They can't currently do this with decimal. I think we could support this by just using the input decimal type as the output type when the second argument is non-constant.

select round(l_tax, l_linenumber) from tpch.lineitem limit 5;
Query: select round(l_tax, l_linenumber) from tpch.lineitem limit 5
Query submitted at: 2018-09-24 11:03:10 (Coordinator: http://tarmstrong-box:25000)
ERROR: AnalysisException: round() must be called with a constant second argument.

Motivated by a user trying to do something like this; http://community.cloudera.com/t5/Interactive-Short-cycle-SQL/Impala-round-function-does-not-return-expected-result/m-p/80200#M4906

Issue Links

• relates to: IMPALA-6230 The output type of a round() function should match the input type