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https://issues.apache.org/jira/browse/IMPALA-10349?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17835825#comment-17835825
]
ASF subversion and git services commented on IMPALA-10349:
----------------------------------------------------------
Commit 8ff51fbf74b4572ce3d1e43389fc10d35a8dd576 in impala's branch
refs/heads/master from Csaba Ringhofer
[ https://gitbox.apache.org/repos/asf?p=impala.git;h=8ff51fbf7 ]
IMPALA-5323: Support BINARY columns in Kudu tables
The patch adds read and write support for BINARY columns in Kudu
tables.
Predicate push down is implemented, but is incomplete:
a constant binary argument will be only pushed down if
the constant folding never encounters non-ascii strings.
Examples:
- cast(unhex(hex("aa")) as binary) can be pushed down
- cast(hex(unhex("aa")) as binary) can't be pushed
down as unhex("aa") is not ascii (even though the
final result is ascii)
See IMPALA-10349 for more details on this limitation.
The patch also changes casting BINARY <-> STRING from noop
to calling an actual function. While this may add some small
overhead it allows the backend to know whether an expression
returns STRING or BINARY.
Change-Id: Iff701a4b3a09ce7b6982c5d238e65f3d4f3d1151
Reviewed-on: http://gerrit.cloudera.org:8080/18868
Reviewed-by: Impala Public Jenkins <impala-public-jenk...@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenk...@cloudera.com>
> Revisit constant folding on non-ASCII strings
> ---------------------------------------------
>
> Key: IMPALA-10349
> URL: https://issues.apache.org/jira/browse/IMPALA-10349
> Project: IMPALA
> Issue Type: Improvement
> Components: Frontend
> Reporter: Quanlong Huang
> Priority: Critical
>
> 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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