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https://issues.apache.org/jira/browse/HIVE-1546?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12909318#action_12909318
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Ashutosh Chauhan commented on HIVE-1546:
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@Namit,
Continuing from discussion yesterday w.r.t new interface/hooks that you were
suggesting. As far as I understood you have two primary concerns:
* You do not want to have config variable enabled SemanticAnalyzer factory
producing different Analyzers. Rather, you want to have only one
HiveSemanticAnalyzer.
* You also dont want others to extend SemanticAnalyzer, DDLSemanticAnalyzer
and other Hive classes.
As a solution to this, there will be new hooks introduced. These pre and post
hooks will be called by Hive at different times during Semantic Analysis phase.
To me, it seems there are few potential problems:
* Hive will need to call these hooks from each and every method of its
Analyzer which opens up whole lot more integration points to external tools
(like Howl) and burden on those Analyzers then the current approach of factory
enabled instantiation and extending of those classes.
* Either there will be a one generic hook or many different hooks. If there is
only one generic hook, then passed in information also need to be generic and
as a result it will be a root of AST Node. If so, in any particular hook I am
using I need to traverse the whole AST to get the node I am interested in.
* If the hooks are more specific, then more specific information can be passed
in which is more useful, but then you will have long list of such hooks.
* Even if these concerns are taken care of, it seems that all of Howl's
requirements may not get satisfied (like getting hold of DDLTask and modifying
it, doing metadata operations etc.) I can elaborate on them further once I can
see what you are proposing.
Clearly from my description, you can see that I didnt get what you were
envisioning and how is it better then current design. I must be missing
something. Would you like to propose what you were suggesting? The attached
patch and Howl classes on this jira should be sufficient to spec out Howl's
requirements, if you need them.
> Ability to plug custom Semantic Analyzers for Hive Grammar
> ----------------------------------------------------------
>
> Key: HIVE-1546
> URL: https://issues.apache.org/jira/browse/HIVE-1546
> Project: Hadoop Hive
> Issue Type: Improvement
> Components: Metastore
> Affects Versions: 0.7.0
> Reporter: Ashutosh Chauhan
> Assignee: Ashutosh Chauhan
> Fix For: 0.7.0
>
> Attachments: hive-1546-3.patch, hive-1546-4.patch, hive-1546.patch,
> hive-1546_2.patch, Howl_Semantic_Analysis.txt
>
>
> It will be useful if Semantic Analysis phase is made pluggable such that
> other projects can do custom analysis of hive queries before doing metastore
> operations on them.
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