Details
Critical Description
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:
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 | +-------------------------------------------------------------+
Example of constant folding doesn't work:
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 | +-------------------------------------------------------------+
Attachments
Issue Links
- is related to
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IMPALA-5323 Support Kudu BINARY
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- Resolved
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