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https://issues.apache.org/jira/browse/HIVE-385?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12695952#action_12695952
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Neil Conway commented on HIVE-385:
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Yeah, using multiple Drivers might be the easiest in the short term. I think in
the long term, it might make sense to have an interface like:
* QueryPlan: the AST + output of the query optimizer, immutable
* QueryResult: the output of applying the query executor to a QueryPlan;
provides the Driver's GetResults() method.
* The driver just becomes a function that takes an (immutable) QueryPlan and
produces a QueryResult, which contains all the state associated with the query
execution
But for now, the candidate patch I attached just separates the existing code in
Driver into two methods, compile() and execute(). Review/feedback welcome.
One potential cause of error is that the order of some operations has changed
-- for example, the old code sets HiveConf.ConfVars.HIVEQUERYSTRING, sets a
QueryId and does SessionState.get().getHiveHistory().startQuery() before doing
parse+analyze, whereas we now do parse+analyze first. AFAICS that shouldn't
break anything, but let me know if that's incorrect.
> Split Driver.run() into compile() + exec()
> ------------------------------------------
>
> Key: HIVE-385
> URL: https://issues.apache.org/jira/browse/HIVE-385
> Project: Hadoop Hive
> Issue Type: Improvement
> Components: Query Processor
> Reporter: Neil Conway
> Assignee: Neil Conway
> Attachments: hive_driver_compile.patch
>
>
> Currently, Driver.run() parses, analyzes, and then executes a given query
> string. This isn't very flexible: it would be nice to be able to parse and
> analyze a query to get a query plan, and then execute that query plan at a
> later time (zero or more times). This would also be a necessary prerequisite
> for supporting server-side prepared statements.
> I'd like to change Driver as follows:
> * Add a new method Driver.compile(String), which parses and analyzes the
> given query string, and returns an object representing the planned query
> * Add a new method Driver.execute(Plan), which runs the given planned query
> * Reimplement run(String) as { p = compile(String); execute(p); }
> Comments welcome; I should have a candidate patch ready soon.
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