[IMPALA-1788] Consider replacing constant exprs with literal equivalents

• Type: New Feature
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 2.1.1
• Fix Version/s: Impala 2.8.0
• Component/s: Frontend
• Labels: performance planner ramp-up
• Target Version: Product Backlog
• Assignee: Alexander Behm
• Reporter: Henry Robinson
• Created: 16/Feb/15 05:47
• Updated: 15/Mar/18 20:32
• Resolved: 23/Nov/16 21:55

Description

Evaluating expressions that are the same for every row can be very expensive (note these numbers are taken from the debug build, so maybe this is not an issue in release?):

(15:33:02@desktop) ~/src/cloudera/impala (cdh5-trunk) $ impala-shell.sh -q "SELECT 1.2345678 FROM tpch.lineitem" -B 2>&1 > /dev/null
...
Fetched 6001215 row(s) in 61.33s

(15:34:06@desktop) ~/src/cloudera/impala (cdh5-trunk) $ impala-shell.sh -q "SELECT CAST('1.2345678' AS DOUBLE) FROM tpch.lineitem" -B 2>&1 > /dev/null
...
Fetched 6001215 row(s) in 74.86s

Issue Links

• breaks: IMPALA-5594 Impala should not reference shaded classes from Kudu jar
• breaks: IMPALA-6435 Codegen crash when UNIONing CHAR(n) literals
• is related to: IMPALA-6114 Incorrect type deduction causing analysis exception to be thrown
• relates to: IMPALA-2095 from_unixtime(constant) is evaluated on every row -- slower than hive
• relates to: IMPALA-1861 Conditional functions with constant arguments should be simplified during analysis