[
https://issues.apache.org/jira/browse/HIVE-13068?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15254505#comment-15254505
]
Jesus Camacho Rodriguez commented on HIVE-13068:
------------------------------------------------
I agree with you.
However, I think it is difficult because of the current limitations that I
outlined above.
- For instance, is there a way to specify that a given constant should be of a
certain type in HQL without using cast/udfto? I think there is not, that is why
I came with this solution.
I could try to add the logic to fold the expression to the SemanticAnalyzer,
thus not traversing the tree. But I think it will not make such a big
difference performance wise and we will end up adding more logic to
SemanticAnalyzer, which is already huge. Further, if return path is in place at
some point, it will be more difficult to detect/remove that unnecessary logic
too.
- The problem with {{power}} expression is that it was returning NaN when it
was folded, and I think we cannot convert that currently through AST? It was a
corner case and I did not explore it much further as the patch was so full of
small pieces. But I will explore it further.
- The filter removal for {{true}} predicates comes practically for free if we
need to execute SimpleConstantReduction, but I agree I could try to rewrite
that logic in SemanticAnalyzer.
The fact that we are not carrying constants all over the operator tree and
checking all the expressions to replace them, should make a performance
difference already. I agree with you that we need to take it a step further,
but without further integration work, I did not figure out a better solution
for some of these cases (specially the CAST, that is quite common because of
Calcite tight type system).
> Disable Hive ConstantPropagate optimizer when CBO has optimized the plan II
> ---------------------------------------------------------------------------
>
> Key: HIVE-13068
> URL: https://issues.apache.org/jira/browse/HIVE-13068
> Project: Hive
> Issue Type: Sub-task
> Components: CBO, Logical Optimizer
> Affects Versions: 2.1.0
> Reporter: Jesus Camacho Rodriguez
> Assignee: Jesus Camacho Rodriguez
> Attachments: HIVE-13068.01.patch, HIVE-13068.01.patch,
> HIVE-13068.patch
>
>
> After HIVE-12543 went in, we need follow-up work to disable the last call to
> ConstantPropagate in Hive. This probably implies work on extending the
> constant folding logic in Calcite.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
