Quanlong Huang created IMPALA-10349:
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Summary: Revisit constant folding on non-ASCII strings
Key: IMPALA-10349
URL: https://issues.apache.org/jira/browse/IMPALA-10349
Project: IMPALA
Issue Type: Improvement
Reporter: Quanlong Huang
Constant folding may produce non-ASCII strings. In such cases, we currently
abandon folding the constant. See commit message of IMPALA-1788 or codes here:
[https://github.com/apache/impala/blob/9672d945963e1ca3c8699340f92d7d6ce1d91c9f/fe/src/main/java/org/apache/impala/analysis/LiteralExpr.java#L274-L282]
I think we should allow folding non-ASCII strings if they are legal UTF-8
strings.
Example of constant folding work:
{code:java}
Query: explain select * from functional.alltypes where string_col =
substr('123', 1, 1)
+-------------------------------------------------------------+
| Explain String |
+-------------------------------------------------------------+
| Max Per-Host Resource Reservation: Memory=32.00KB Threads=3 |
| Per-Host Resource Estimates: Memory=160MB |
| Codegen disabled by planner |
| |
| PLAN-ROOT SINK |
| | |
| 01:EXCHANGE [UNPARTITIONED] |
| | |
| 00:SCAN HDFS [functional.alltypes] |
| HDFS partitions=24/24 files=24 size=478.45KB |
| predicates: string_col = '1' |
| row-size=89B cardinality=730 |
+-------------------------------------------------------------+
{code}
Example of constant folding doesn't work:
{code:java}
Query: explain select * from functional.alltypes where string_col =
substr('引擎', 1, 3)
+-------------------------------------------------------------+
| Explain String |
+-------------------------------------------------------------+
| Max Per-Host Resource Reservation: Memory=32.00KB Threads=3 |
| Per-Host Resource Estimates: Memory=160MB |
| Codegen disabled by planner |
| |
| PLAN-ROOT SINK |
| | |
| 01:EXCHANGE [UNPARTITIONED] |
| | |
| 00:SCAN HDFS [functional.alltypes] |
| HDFS partitions=24/24 files=24 size=478.45KB |
| predicates: string_col = substr('引擎', 1, 3) |
| row-size=89B cardinality=730 |
+-------------------------------------------------------------+
{code}
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